2005-04-16 15:20:36 -07:00
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2011-12-07 13:06:11 -05:00
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2006-01-11 12:17:46 -08:00
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2006-12-08 02:37:56 -08:00
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2012-07-26 21:08:32 -07:00
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2005-04-16 15:20:36 -07:00
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2008-03-26 22:11:34 +01:00
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2011-12-07 13:06:11 -05:00
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2013-09-11 14:26:10 -07:00
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2011-12-07 13:06:11 -05:00
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2013-04-12 01:50:06 +01:00
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2013-05-01 17:51:54 -07:00
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2005-11-07 17:19:07 -05:00
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2007-07-15 23:41:25 -07:00
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2005-04-16 15:20:36 -07:00
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2008-02-06 01:37:57 -08:00
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2005-11-07 17:15:49 -05:00
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2008-03-26 22:11:34 +01:00
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2008-03-27 13:06:23 +01:00
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fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
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2009-06-24 03:12:00 -04:00
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2005-04-16 15:20:36 -07:00
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2006-03-26 01:37:24 -08:00
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2013-03-15 10:53:28 -04:00
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2006-12-06 20:33:20 -08:00
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2013-09-16 21:34:53 -04:00
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2005-04-16 15:20:36 -07:00
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2006-01-16 22:14:23 -08:00
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2007-10-29 14:17:23 -06:00
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2006-01-16 22:14:23 -08:00
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fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
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2013-09-29 22:06:07 -04:00
|
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|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2008-02-06 01:37:57 -08:00
|
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2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
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2011-11-24 20:38:33 -05:00
|
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|
2008-03-26 22:11:34 +01:00
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2008-03-26 22:11:34 +01:00
|
|
|
|
|
|
|
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|
|
2011-11-24 20:38:33 -05:00
|
|
|
|
2008-03-26 22:11:34 +01:00
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2008-03-26 22:11:34 +01:00
|
|
|
|
|
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2011-11-24 19:54:23 -05:00
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
|
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
|
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
|
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
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|
|
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|
|
2011-11-24 19:54:23 -05:00
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
|
|
2011-11-25 00:50:41 -05:00
|
|
|
|
2009-06-24 03:12:00 -04:00
|
|
|
|
|
|
|
|
|
|
|
|
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|
2011-11-25 00:50:41 -05:00
|
|
|
|
2008-03-27 13:06:23 +01:00
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
2011-11-24 22:53:09 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
2011-11-24 22:53:09 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
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|
|
|
|
|
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
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2011-01-14 22:30:21 -05:00
|
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|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
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2011-11-24 22:53:09 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
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2011-11-24 22:53:09 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
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2011-11-24 20:38:33 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 02:35:16 -05:00
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2008-03-26 22:11:34 +01:00
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2011-11-25 02:35:16 -05:00
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2008-07-21 18:06:36 +08:00
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2011-11-25 02:35:16 -05:00
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2008-07-21 18:06:36 +08:00
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2008-03-26 22:11:34 +01:00
|
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|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2011-11-25 02:35:16 -05:00
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
2011-11-25 02:35:16 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2011-11-25 02:35:16 -05:00
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
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2011-11-25 02:35:16 -05:00
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2009-12-17 21:24:27 -05:00
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2009-04-26 20:25:54 +10:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 02:35:16 -05:00
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2008-07-21 18:06:36 +08:00
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2009-04-26 20:25:54 +10:00
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2011-11-25 02:35:16 -05:00
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2009-04-26 20:25:54 +10:00
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2008-07-21 18:06:36 +08:00
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2011-11-25 02:35:16 -05:00
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2008-07-21 18:06:36 +08:00
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2011-11-25 02:35:16 -05:00
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2008-07-21 18:06:36 +08:00
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2005-04-16 15:20:36 -07:00
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|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2008-02-15 14:38:00 -08:00
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|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
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|
|
|
|
|
|
|
|
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
|
|
|
2011-11-24 22:53:09 -05:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
2011-11-24 22:53:09 -05:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2011-11-24 22:37:54 -05:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2009-04-26 20:25:54 +10:00
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2011-11-24 22:53:09 -05:00
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2009-04-26 20:25:54 +10:00
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2011-11-24 22:53:09 -05:00
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2009-04-26 20:25:54 +10:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2011-11-24 22:37:54 -05:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2009-04-26 20:25:54 +10:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2011-11-24 22:53:09 -05:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2009-04-26 20:25:54 +10:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2011-11-21 12:11:31 +01:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2011-11-24 22:37:54 -05:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2011-11-24 22:37:54 -05:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2009-04-26 20:25:54 +10:00
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2011-01-07 17:50:10 +11:00
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2009-04-26 20:25:54 +10:00
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2011-01-07 17:50:10 +11:00
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2009-04-26 20:25:54 +10:00
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2012-11-16 17:23:50 +08:00
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2009-04-26 20:25:54 +10:00
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2011-11-21 12:11:31 +01:00
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2011-01-07 17:50:10 +11:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2009-04-26 20:25:54 +10:00
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2012-06-12 16:20:35 +02:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
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2008-02-15 14:37:30 -08:00
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2009-04-26 20:25:55 +10:00
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2011-11-24 22:37:54 -05:00
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2009-04-26 20:25:55 +10:00
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2012-06-12 16:20:35 +02:00
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2009-04-26 20:25:55 +10:00
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2012-06-12 16:20:35 +02:00
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2009-04-26 20:25:55 +10:00
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2012-06-12 16:20:35 +02:00
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2009-04-26 20:25:55 +10:00
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2013-01-23 17:07:38 -05:00
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2012-06-12 16:20:35 +02:00
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2009-08-06 15:07:39 -07:00
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2012-06-12 16:20:35 +02:00
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2009-04-26 20:25:55 +10:00
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2012-06-12 16:20:35 +02:00
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2009-04-26 20:25:55 +10:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2009-04-26 20:25:54 +10:00
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2011-11-24 22:37:54 -05:00
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2009-04-26 20:25:54 +10:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2008-02-15 14:37:30 -08:00
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2012-06-12 16:20:35 +02:00
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2011-12-09 08:06:57 -05:00
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2011-11-24 22:37:54 -05:00
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2008-02-15 14:37:30 -08:00
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[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
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|
2013-09-29 11:24:49 -04:00
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
|
|
|
2011-01-07 17:50:10 +11:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2009-04-26 20:25:54 +10:00
|
|
|
|
|
|
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|
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|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
[PATCH] r/o bind mounts: track numbers of writers to mounts
This is the real meat of the entire series. It actually
implements the tracking of the number of writers to a mount.
However, it causes scalability problems because there can be
hundreds of cpus doing open()/close() on files on the same mnt at
the same time. Even an atomic_t in the mnt has massive scalaing
problems because the cacheline gets so terribly contended.
This uses a statically-allocated percpu variable. All want/drop
operations are local to a cpu as long that cpu operates on the same
mount, and there are no writer count imbalances. Writer count
imbalances happen when a write is taken on one cpu, and released
on another, like when an open/close pair is performed on two
Upon a remount,ro request, all of the data from the percpu
variables is collected (expensive, but very rare) and we determine
if there are any outstanding writers to the mount.
I've written a little benchmark to sit in a loop for a couple of
seconds in several cpus in parallel doing open/write/close loops.
http://sr71.net/~dave/linux/openbench.c
The code in here is a a worst-possible case for this patch. It
does opens on a _pair_ of files in two different mounts in parallel.
This should cause my code to lose its "operate on the same mount"
optimization completely. This worst-case scenario causes a 3%
degredation in the benchmark.
I could probably get rid of even this 3%, but it would be more
complex than what I have here, and I think this is getting into
acceptable territory. In practice, I expect writing more than 3
bytes to a file, as well as disk I/O to mask any effects that this
has.
(To get rid of that 3%, we could have an #defined number of mounts
in the percpu variable. So, instead of a CPU getting operate only
on percpu data when it accesses only one mount, it could stay on
percpu data when it only accesses N or fewer mounts.)
[AV] merged fix for __clear_mnt_mount() stepping on freed vfsmount
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-02-15 14:37:59 -08:00
|
|
|
|
2008-02-15 14:37:30 -08:00
|
|
|
|
|
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2008-02-15 14:38:00 -08:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2008-02-15 14:38:00 -08:00
|
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2011-11-21 12:11:31 +01:00
|
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2011-11-21 12:11:33 +01:00
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2013-09-29 11:24:49 -04:00
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2011-11-21 12:11:31 +01:00
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2011-11-21 12:11:33 +01:00
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2011-11-21 12:11:31 +01:00
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2013-09-29 11:24:49 -04:00
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2011-11-21 12:11:31 +01:00
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2011-11-24 20:38:33 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 02:25:17 -05:00
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2008-03-26 22:11:34 +01:00
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2009-04-26 20:25:54 +10:00
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2011-11-24 22:53:09 -05:00
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2009-04-26 20:25:54 +10:00
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2011-11-24 20:38:33 -05:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 22:06:07 -04:00
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2005-04-16 15:20:36 -07:00
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2013-10-01 16:11:26 -04:00
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2013-09-29 22:06:07 -04:00
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2005-04-16 15:20:36 -07:00
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2013-10-01 16:11:26 -04:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2013-10-01 16:11:26 -04:00
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2013-09-29 22:06:07 -04:00
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2013-10-01 16:11:26 -04:00
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2013-09-29 22:06:07 -04:00
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2013-10-01 16:11:26 -04:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:20:17 -05:00
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2012-06-25 12:55:28 +01:00
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2005-11-07 17:20:17 -05:00
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2009-04-18 14:06:57 -04:00
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2005-11-07 17:20:17 -05:00
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2011-11-24 18:22:03 -05:00
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2013-09-29 22:06:07 -04:00
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fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
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2013-09-29 22:06:07 -04:00
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2005-11-07 17:20:17 -05:00
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2013-03-15 10:53:28 -04:00
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2013-09-05 14:39:11 +02:00
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2013-03-15 10:53:28 -04:00
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2013-09-05 14:39:11 +02:00
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2013-03-15 10:53:28 -04:00
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2013-09-05 14:39:11 +02:00
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2013-03-15 10:53:28 -04:00
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2013-09-05 14:39:11 +02:00
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2013-03-15 10:53:28 -04:00
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2011-11-25 00:46:35 -05:00
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2005-04-16 15:20:36 -07:00
|
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|
2006-12-08 02:37:56 -08:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
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2006-12-08 02:37:56 -08:00
|
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2005-11-07 17:15:49 -05:00
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
|
|
|
|
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|
|
|
2006-12-08 02:37:56 -08:00
|
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2005-11-07 17:15:49 -05:00
|
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2011-11-24 19:41:16 -05:00
|
|
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|
|
2011-11-24 22:25:07 -05:00
|
|
|
|
2011-11-24 22:19:58 -05:00
|
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|
|
2011-11-24 22:25:07 -05:00
|
|
|
|
2011-11-24 23:24:33 -05:00
|
|
|
|
2011-11-24 21:01:32 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
|
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
|
|
|
|
|
2011-11-24 21:28:22 -05:00
|
|
|
|
2005-11-07 17:19:50 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2011-11-25 03:19:09 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2011-11-25 03:19:09 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2005-11-07 17:19:50 -05:00
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
|
|
|
|
|
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|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
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|
|
|
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|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2011-11-24 21:01:32 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
|
|
|
|
|
2005-11-07 17:19:50 -05:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2005-11-07 17:19:50 -05:00
|
|
|
|
2011-11-24 19:47:15 -05:00
|
|
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|
2005-11-07 17:19:50 -05:00
|
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2011-11-24 22:19:58 -05:00
|
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2011-11-24 22:37:54 -05:00
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2005-11-07 17:19:50 -05:00
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2011-11-25 00:46:35 -05:00
|
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2005-11-07 17:19:50 -05:00
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2011-11-24 22:19:58 -05:00
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2005-11-07 17:19:50 -05:00
|
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2011-11-25 02:19:55 -05:00
|
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|
2012-06-09 00:59:08 -04:00
|
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2011-11-25 00:46:35 -05:00
|
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2011-01-14 22:30:21 -05:00
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2005-11-07 17:19:50 -05:00
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2011-11-24 21:01:32 -05:00
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2011-11-24 22:25:07 -05:00
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2011-11-24 23:24:33 -05:00
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2006-12-08 02:37:56 -08:00
|
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 23:24:33 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 23:24:33 -05:00
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2005-04-16 15:20:36 -07:00
|
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2011-11-24 22:19:58 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 23:24:33 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 18:57:30 -05:00
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2005-11-07 17:21:20 -05:00
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2011-11-24 23:24:33 -05:00
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2005-11-07 17:21:20 -05:00
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2011-03-17 22:08:28 -04:00
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2011-11-24 20:38:33 -05:00
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2011-03-17 22:08:28 -04:00
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2011-11-24 20:38:33 -05:00
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2011-03-17 22:08:28 -04:00
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2011-11-24 20:38:33 -05:00
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2011-11-24 22:25:07 -05:00
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2011-11-24 22:19:58 -05:00
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2013-09-29 11:24:49 -04:00
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2011-11-21 12:11:30 +01:00
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2013-09-29 11:24:49 -04:00
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2011-11-24 20:38:33 -05:00
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2011-03-17 22:08:28 -04:00
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2011-11-24 21:24:27 -05:00
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2005-11-07 17:17:22 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 21:24:27 -05:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2012-06-25 12:55:18 +01:00
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2008-03-27 13:06:23 +01:00
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2012-07-31 13:13:04 -07:00
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2012-06-25 12:55:18 +01:00
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2005-11-07 17:19:50 -05:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2012-06-25 12:55:18 +01:00
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2013-03-22 04:08:05 -07:00
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2013-03-29 21:04:39 -07:00
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2012-06-25 12:55:18 +01:00
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2013-09-29 11:24:49 -04:00
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2012-06-25 12:55:18 +01:00
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2013-09-29 11:24:49 -04:00
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2012-06-25 12:55:18 +01:00
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2012-07-31 13:13:04 -07:00
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2012-06-25 12:55:18 +01:00
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2011-11-24 20:55:08 -05:00
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2008-03-27 13:06:23 +01:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 22:06:07 -04:00
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2011-11-25 00:33:11 -05:00
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fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
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2013-09-29 22:06:07 -04:00
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2011-01-14 22:30:21 -05:00
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|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
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|
|
2013-09-29 11:24:49 -04:00
|
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|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
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|
2011-11-25 00:57:42 -05:00
|
|
|
|
|
|
|
|
|
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|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2011-11-25 00:33:11 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2005-11-07 17:13:39 -05:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
|
|
|
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|
|
2012-05-08 13:32:02 +09:30
|
|
|
|
2011-11-21 12:11:30 +01:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2013-09-28 12:41:25 -04:00
|
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|
2013-09-29 22:06:07 -04:00
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
|
|
|
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|
|
|
|
|
|
|
|
|
|
|
2011-11-25 00:57:42 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2011-11-25 00:57:42 -05:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
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|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
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|
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|
|
|
2005-11-07 17:13:39 -05:00
|
|
|
|
|
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2011-11-25 00:57:42 -05:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
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|
2005-11-07 17:13:39 -05:00
|
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2011-11-25 00:57:42 -05:00
|
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|
|
2005-11-07 17:13:39 -05:00
|
|
|
|
2011-11-25 00:57:42 -05:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
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|
2005-11-07 17:13:39 -05:00
|
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|
2011-11-25 00:57:42 -05:00
|
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|
2005-11-07 17:13:39 -05:00
|
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2013-09-29 11:24:49 -04:00
|
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|
2005-11-07 17:13:39 -05:00
|
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2005-04-16 15:20:36 -07:00
|
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2008-02-08 04:21:35 -08:00
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2011-12-08 21:32:45 -05:00
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2008-02-08 04:21:35 -08:00
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2009-05-08 16:05:57 -04:00
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2011-12-08 21:32:45 -05:00
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2008-02-08 04:21:35 -08:00
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2009-05-08 16:05:57 -04:00
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2008-02-08 04:21:35 -08:00
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2009-05-08 16:05:57 -04:00
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2008-02-08 04:21:35 -08:00
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2009-05-08 16:05:57 -04:00
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2008-03-27 13:06:24 +01:00
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2011-12-06 12:21:54 -05:00
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2005-04-16 15:20:36 -07:00
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2012-06-09 01:16:59 -04:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:17:51 -05:00
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2008-03-27 13:06:24 +01:00
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2005-04-16 15:20:36 -07:00
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2012-06-09 01:16:59 -04:00
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2007-07-15 23:39:55 -07:00
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2008-03-27 13:06:24 +01:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:17:51 -05:00
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2005-04-16 15:20:36 -07:00
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2011-12-06 12:21:54 -05:00
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2008-03-27 13:06:25 +01:00
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2012-06-09 01:16:59 -04:00
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2011-11-25 02:19:55 -05:00
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2011-12-06 12:21:54 -05:00
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2005-04-16 15:20:36 -07:00
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2008-03-27 13:06:24 +01:00
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2005-04-16 15:20:36 -07:00
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2011-12-06 12:21:54 -05:00
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2006-03-20 13:44:12 -05:00
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2008-03-27 13:06:24 +01:00
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2006-03-20 13:44:12 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2005-11-07 17:17:22 -05:00
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2011-11-24 18:57:30 -05:00
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2011-11-25 03:06:56 -05:00
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2005-04-16 15:20:36 -07:00
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fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
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|
2013-09-29 11:24:49 -04:00
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2011-11-25 03:06:56 -05:00
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2011-11-24 22:37:54 -05:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 11:24:49 -04:00
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2005-04-16 15:20:36 -07:00
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2006-03-27 01:14:51 -08:00
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2005-04-16 15:20:36 -07:00
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2006-03-27 01:14:51 -08:00
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2005-04-16 15:20:36 -07:00
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2006-03-27 01:14:51 -08:00
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2010-01-16 12:56:08 -05:00
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2013-09-29 11:24:49 -04:00
|
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2011-11-24 21:35:16 -05:00
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2006-03-27 01:14:51 -08:00
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2013-09-29 11:24:49 -04:00
|
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2010-01-16 12:56:08 -05:00
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2005-11-07 17:20:17 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-16 14:35:16 -04:00
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2013-03-16 15:12:40 -04:00
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2005-11-07 17:17:04 -05:00
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2011-11-24 20:58:57 -05:00
|
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2013-03-16 15:12:40 -04:00
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2013-09-29 22:06:07 -04:00
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2013-03-16 15:12:40 -04:00
|
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2011-11-24 21:01:32 -05:00
|
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|
2013-09-28 23:10:55 -04:00
|
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2011-11-24 20:58:57 -05:00
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2005-11-07 17:17:04 -05:00
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2013-03-16 15:12:40 -04:00
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2013-03-16 14:35:16 -04:00
|
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2013-03-16 15:12:40 -04:00
|
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2013-03-16 14:35:16 -04:00
|
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|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2011-01-15 20:08:44 -05:00
|
|
|
|
2011-11-24 18:57:30 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2011-11-25 03:06:56 -05:00
|
|
|
|
2011-11-24 21:01:32 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
2011-01-15 20:08:44 -05:00
|
|
|
|
2005-11-07 17:20:17 -05:00
|
|
|
|
2011-11-24 21:01:32 -05:00
|
|
|
|
2011-11-25 00:22:05 -05:00
|
|
|
|
2011-11-25 02:19:55 -05:00
|
|
|
|
2011-11-25 00:46:35 -05:00
|
|
|
|
|
|
|
|
|
2013-09-29 22:06:07 -04:00
|
|
|
|
|
|
|
|
|
2011-11-24 23:24:33 -05:00
|
|
|
|
2011-11-24 21:47:05 -05:00
|
|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2013-09-28 23:10:55 -04:00
|
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|
|
|
2013-03-15 10:53:28 -04:00
|
|
|
|
2008-03-21 23:59:49 -04:00
|
|
|
|
2011-11-24 20:43:10 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2013-03-16 14:49:45 -04:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
2013-03-16 14:39:34 -04:00
|
|
|
|
2008-03-22 00:46:23 -04:00
|
|
|
|
2011-11-24 21:35:16 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2011-11-24 21:35:16 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
2011-11-24 21:35:16 -05:00
|
|
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2005-04-16 15:20:36 -07:00
|
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2011-11-24 21:35:16 -05:00
|
|
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|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2011-11-24 22:37:54 -05:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
|
|
|
|
2013-09-29 11:24:49 -04:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
2011-11-25 00:57:42 -05:00
|
|
|
|
2005-04-16 15:20:36 -07:00
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2008-04-24 07:21:56 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 21:35:16 -05:00
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2005-04-16 15:20:36 -07:00
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2009-05-08 13:36:58 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-16 15:12:40 -04:00
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2013-09-29 11:24:49 -04:00
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2005-11-07 17:15:49 -05:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 22:06:07 -04:00
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2011-11-25 02:19:55 -05:00
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2013-09-29 22:06:07 -04:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 22:06:07 -04:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 11:24:49 -04:00
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2013-03-16 14:35:16 -04:00
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2005-04-16 15:20:36 -07:00
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2013-02-22 22:45:42 -05:00
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2005-04-16 15:20:36 -07:00
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2009-01-14 14:14:12 +01:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2011-11-25 00:33:11 -05:00
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2005-04-16 15:20:36 -07:00
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2010-02-10 12:15:53 +01:00
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2005-04-16 15:20:36 -07:00
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2010-02-10 12:15:53 +01:00
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2013-02-22 22:45:42 -05:00
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2010-02-10 12:15:53 +01:00
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2013-09-08 14:03:27 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:33:11 -05:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:46:35 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-29 21:04:39 -07:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:33:11 -05:00
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2005-04-16 15:20:36 -07:00
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2008-02-14 19:34:31 -08:00
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2008-07-22 09:59:21 -04:00
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2011-11-25 00:33:11 -05:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2005-04-16 15:20:36 -07:00
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2009-01-14 14:14:12 +01:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-30 01:35:18 -07:00
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2010-03-07 18:49:36 -08:00
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2013-03-30 01:35:18 -07:00
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2013-04-12 01:50:06 +01:00
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2010-03-07 18:49:36 -08:00
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2013-04-12 01:50:06 +01:00
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2010-03-07 18:49:36 -08:00
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2013-03-30 01:35:18 -07:00
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2010-03-07 18:49:36 -08:00
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2011-11-24 21:24:27 -05:00
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2005-11-07 17:17:22 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-30 01:35:18 -07:00
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2012-06-25 12:55:18 +01:00
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2005-11-07 17:21:20 -05:00
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2005-11-07 17:17:22 -05:00
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2012-06-25 12:55:18 +01:00
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2013-03-29 21:04:39 -07:00
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2011-11-24 22:25:07 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 23:24:33 -05:00
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2011-11-24 18:57:30 -05:00
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2008-04-29 00:59:40 -07:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2013-03-30 01:35:18 -07:00
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2005-11-07 17:21:20 -05:00
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2011-11-24 22:19:58 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 21:24:27 -05:00
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2013-03-15 10:53:28 -04:00
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2011-11-24 21:24:27 -05:00
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2012-06-25 12:55:18 +01:00
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2013-09-29 11:24:49 -04:00
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2011-11-25 02:19:55 -05:00
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2013-03-15 10:53:28 -04:00
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2013-09-29 11:24:49 -04:00
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2005-04-16 15:20:36 -07:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2013-09-29 11:24:49 -04:00
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2013-03-16 14:49:45 -04:00
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2013-09-29 11:24:49 -04:00
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2005-04-16 15:20:36 -07:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2012-06-25 12:55:18 +01:00
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2009-04-18 03:28:19 -04:00
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2007-06-07 12:20:32 -04:00
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2011-11-24 20:55:08 -05:00
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2013-03-16 15:12:40 -04:00
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2011-11-24 21:24:27 -05:00
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2013-03-16 14:49:45 -04:00
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2012-06-25 12:55:18 +01:00
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2013-08-14 12:44:39 +03:00
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2012-06-25 12:55:18 +01:00
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2007-06-07 12:20:32 -04:00
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2013-03-16 15:12:40 -04:00
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2013-03-16 14:49:45 -04:00
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2013-09-29 11:24:49 -04:00
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2013-03-16 14:42:19 -04:00
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2007-06-07 12:20:32 -04:00
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2010-01-30 22:51:25 -05:00
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2011-11-25 02:19:55 -05:00
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2010-01-30 22:51:25 -05:00
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2011-11-25 02:19:55 -05:00
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2010-01-30 22:51:25 -05:00
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2011-11-24 19:54:23 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-24 18:57:30 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-25 03:06:56 -05:00
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2011-11-25 01:05:37 -05:00
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2011-11-24 19:54:23 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-24 19:54:23 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-24 18:57:30 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-25 03:06:56 -05:00
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2011-11-25 01:05:37 -05:00
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2011-11-24 19:54:23 -05:00
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2008-03-27 13:06:23 +01:00
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2011-11-24 19:54:23 -05:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:50 -05:00
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2005-11-07 17:20:03 -05:00
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2005-11-07 17:19:50 -05:00
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2005-11-07 17:21:20 -05:00
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2005-11-07 17:19:50 -05:00
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2005-11-07 17:21:01 -05:00
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2005-11-07 17:21:20 -05:00
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2005-11-07 17:21:01 -05:00
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2005-11-07 17:20:03 -05:00
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2005-11-07 17:21:01 -05:00
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2005-11-07 17:19:50 -05:00
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2011-11-24 19:59:16 -05:00
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2013-03-15 10:53:28 -04:00
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2005-11-07 17:19:50 -05:00
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2011-11-24 18:57:30 -05:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:50 -05:00
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2011-11-25 01:05:37 -05:00
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2011-11-24 19:59:16 -05:00
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2008-03-27 13:06:23 +01:00
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2013-03-15 10:53:28 -04:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:50 -05:00
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2013-09-29 11:24:49 -04:00
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2010-01-16 12:57:40 -05:00
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2011-11-25 01:05:37 -05:00
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2011-11-25 03:06:56 -05:00
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2011-11-24 20:43:10 -05:00
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2005-11-07 17:19:50 -05:00
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2008-03-21 20:48:19 -04:00
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2011-11-24 19:59:16 -05:00
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2013-03-15 10:53:28 -04:00
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2011-11-25 00:46:35 -05:00
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2005-11-07 17:20:03 -05:00
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2013-03-15 10:53:28 -04:00
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2011-11-24 19:59:16 -05:00
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2005-11-07 17:20:03 -05:00
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2005-11-07 17:19:50 -05:00
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2011-11-24 21:01:32 -05:00
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2011-11-24 19:47:15 -05:00
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2005-11-07 17:19:50 -05:00
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2013-09-29 11:24:49 -04:00
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fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
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2008-03-27 13:06:23 +01:00
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2011-11-25 01:05:37 -05:00
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2011-11-24 19:59:16 -05:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:50 -05:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-16 15:12:40 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2013-03-16 15:12:40 -04:00
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2013-03-15 10:53:28 -04:00
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2013-03-16 15:12:40 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2013-03-16 14:49:45 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:30:56 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-15 10:53:28 -04:00
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2011-11-25 00:30:56 -05:00
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2005-04-16 15:20:36 -07:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2010-08-26 11:07:22 -07:00
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fs/namespace.c: bound mount propagation fix
This issue was discovered by users of busybox. And the bug is actual for
busybox users, I don't know how it affects others. Apparently, mount is
called with and without MS_SILENT, and this affects mount() behaviour.
But MS_SILENT is only supposed to affect kernel logging verbosity.
The following script was run in an empty test directory:
mkdir -p mount.dir mount.shared1 mount.shared2
touch mount.dir/a mount.dir/b
mount -vv --bind mount.shared1 mount.shared1
mount -vv --make-rshared mount.shared1
mount -vv --bind mount.shared2 mount.shared2
mount -vv --make-rshared mount.shared2
mount -vv --bind mount.shared2 mount.shared1
mount -vv --bind mount.dir mount.shared2
ls -R mount.dir mount.shared1 mount.shared2
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
rm -f mount.dir/a mount.dir/b mount.dir/c
rmdir mount.dir mount.shared1 mount.shared2
mount -vv was used to show the mount() call arguments and result.
Output shows that flag argument has 0x00008000 = MS_SILENT bit:
mount: mount('mount.shared1','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared1','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared2','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared2','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('mount.dir','mount.shared2','(null)',0x00009000,'(null)'):0
mount.dir:
a
b
mount.shared1:
mount.shared2:
a
b
After adding --loud option to remove MS_SILENT bit from just one mount cmd:
mkdir -p mount.dir mount.shared1 mount.shared2
touch mount.dir/a mount.dir/b
mount -vv --bind mount.shared1 mount.shared1 2>&1
mount -vv --make-rshared mount.shared1 2>&1
mount -vv --bind mount.shared2 mount.shared2 2>&1
mount -vv --loud --make-rshared mount.shared2 2>&1 # <-HERE
mount -vv --bind mount.shared2 mount.shared1 2>&1
mount -vv --bind mount.dir mount.shared2 2>&1
ls -R mount.dir mount.shared1 mount.shared2 2>&1
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
rm -f mount.dir/a mount.dir/b mount.dir/c
rmdir mount.dir mount.shared1 mount.shared2
The result is different now - look closely at mount.shared1 directory listing.
Now it does show files 'a' and 'b':
mount: mount('mount.shared1','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared1','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared2','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared2','',0x00104000,''):0
mount: mount('mount.shared2','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('mount.dir','mount.shared2','(null)',0x00009000,'(null)'):0
mount.dir:
a
b
mount.shared1:
a
b
mount.shared2:
a
b
The analysis shows that MS_SILENT flag which is ON by default in any
busybox-> mount operations cames to flags_to_propagation_type function and
causes the error return while is_power_of_2 checking because the function
expects only one bit set. This doesn't allow to do busybox->mount with
any --make-[r]shared, --make-[r]private etc options.
Moreover, the recently added flags_to_propagation_type() function doesn't
allow us to do such operations as --make-[r]private --make-[r]shared etc.
when MS_SILENT is on. The idea or clearing the MS_SILENT flag came from
to Denys Vlasenko.
Signed-off-by: Roman Borisov <ext-roman.borisov@nokia.com>
Reported-by: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Alexander Shishkin <virtuoso@slind.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-25 16:26:48 -07:00
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2010-08-26 11:07:22 -07:00
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2005-11-07 17:19:07 -05:00
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2008-08-02 00:55:27 -04:00
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2005-11-07 17:19:07 -05:00
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2011-11-24 18:57:30 -05:00
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2011-11-24 19:54:23 -05:00
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2005-11-07 17:19:07 -05:00
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2010-08-26 11:07:22 -07:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:07 -05:00
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2008-08-02 00:51:11 -04:00
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2005-11-07 17:19:07 -05:00
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2010-08-26 11:07:22 -07:00
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2008-03-27 13:06:23 +01:00
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2013-09-29 11:24:49 -04:00
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2011-11-25 03:06:56 -05:00
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2011-11-24 20:43:10 -05:00
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2013-09-29 11:24:49 -04:00
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2008-03-27 13:06:23 +01:00
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2013-03-16 15:12:40 -04:00
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2008-03-27 13:06:23 +01:00
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2005-11-07 17:19:07 -05:00
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2013-03-29 21:04:39 -07:00
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2005-04-16 15:20:36 -07:00
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2012-10-11 11:42:01 -04:00
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2008-02-08 04:22:12 -08:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2013-03-15 10:53:28 -04:00
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2013-02-22 22:49:10 -05:00
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2005-04-16 15:20:36 -07:00
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2011-09-26 20:36:09 -04:00
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2005-04-16 15:20:36 -07:00
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2010-03-07 18:49:36 -08:00
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2013-03-30 01:35:18 -07:00
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2010-03-07 18:49:36 -08:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2011-11-24 21:24:27 -05:00
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2013-03-15 10:53:28 -04:00
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2011-11-24 21:24:27 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 01:05:37 -05:00
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2011-03-18 08:55:38 -04:00
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2005-11-07 17:21:20 -05:00
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2011-03-18 08:55:38 -04:00
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2013-03-29 21:04:39 -07:00
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2005-11-07 17:15:04 -05:00
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2013-03-30 01:35:18 -07:00
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2005-11-07 17:15:04 -05:00
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2011-11-24 21:24:27 -05:00
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2005-11-07 17:15:04 -05:00
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2012-06-25 12:55:18 +01:00
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2013-04-09 17:33:29 +04:00
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2012-06-25 12:55:18 +01:00
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2005-11-07 17:15:04 -05:00
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2013-03-29 21:04:39 -07:00
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2013-03-15 10:53:28 -04:00
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2005-11-07 17:15:04 -05:00
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2013-09-29 11:24:49 -04:00
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2013-03-16 14:49:45 -04:00
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2013-09-29 11:24:49 -04:00
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2005-11-07 17:16:29 -05:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2005-11-07 17:15:04 -05:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2008-02-15 14:38:00 -08:00
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2013-03-22 03:10:15 -07:00
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2008-02-15 14:38:00 -08:00
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2011-11-24 22:37:54 -05:00
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2008-02-15 14:38:00 -08:00
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2011-11-24 22:37:54 -05:00
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2008-02-15 14:38:00 -08:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:55:27 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2011-11-25 00:46:35 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:46:35 -05:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2011-03-03 16:09:14 -05:00
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2005-04-16 15:20:36 -07:00
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2008-02-15 14:38:00 -08:00
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2008-08-02 00:51:11 -04:00
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2013-02-22 22:49:10 -05:00
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2009-05-08 13:36:58 -04:00
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2008-02-15 14:38:00 -08:00
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2010-01-16 13:01:26 -05:00
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2013-09-29 11:24:49 -04:00
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2011-11-25 00:46:35 -05:00
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2013-09-29 11:24:49 -04:00
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2008-09-26 19:01:20 -07:00
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2013-09-16 22:41:01 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 20:01:19 -05:00
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2005-11-07 17:21:20 -05:00
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2011-11-24 18:57:30 -05:00
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2011-11-25 03:06:56 -05:00
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2011-11-25 01:05:37 -05:00
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2005-11-07 17:21:20 -05:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2011-11-24 21:47:05 -05:00
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2011-11-24 19:59:16 -05:00
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2013-03-15 10:53:28 -04:00
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2013-02-22 22:49:10 -05:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2013-03-15 10:53:28 -04:00
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Add a dentry op to allow processes to be held during pathwalk transit
Add a dentry op (d_manage) to permit a filesystem to hold a process and make it
sleep when it tries to transit away from one of that filesystem's directories
during a pathwalk. The operation is keyed off a new dentry flag
(DCACHE_MANAGE_TRANSIT).
The filesystem is allowed to be selective about which processes it holds and
which it permits to continue on or prohibits from transiting from each flagged
directory. This will allow autofs to hold up client processes whilst letting
its userspace daemon through to maintain the directory or the stuff behind it
or mounted upon it.
The ->d_manage() dentry operation:
int (*d_manage)(struct path *path, bool mounting_here);
takes a pointer to the directory about to be transited away from and a flag
indicating whether the transit is undertaken by do_add_mount() or
do_move_mount() skipping through a pile of filesystems mounted on a mountpoint.
It should return 0 if successful and to let the process continue on its way;
-EISDIR to prohibit the caller from skipping to overmounted filesystems or
automounting, and to use this directory; or some other error code to return to
the user.
->d_manage() is called with namespace_sem writelocked if mounting_here is true
and no other locks held, so it may sleep. However, if mounting_here is true,
it may not initiate or wait for a mount or unmount upon the parameter
directory, even if the act is actually performed by userspace.
Within fs/namei.c, follow_managed() is extended to check with d_manage() first
on each managed directory, before transiting away from it or attempting to
automount upon it.
follow_down() is renamed follow_down_one() and should only be used where the
filesystem deliberately intends to avoid management steps (e.g. autofs).
A new follow_down() is added that incorporates the loop done by all other
callers of follow_down() (do_add/move_mount(), autofs and NFSD; whilst AFS, NFS
and CIFS do use it, their use is removed by converting them to use
d_automount()). The new follow_down() calls d_manage() as appropriate. It
also takes an extra parameter to indicate if it is being called from mount code
(with namespace_sem writelocked) which it passes to d_manage(). follow_down()
ignores automount points so that it can be used to mount on them.
__follow_mount_rcu() is made to abort rcu-walk mode if it hits a directory with
DCACHE_MANAGE_TRANSIT set on the basis that we're probably going to have to
sleep. It would be possible to enter d_manage() in rcu-walk mode too, and have
that determine whether to abort or not itself. That would allow the autofs
daemon to continue on in rcu-walk mode.
Note that DCACHE_MANAGE_TRANSIT on a directory should be cleared when it isn't
required as every tranist from that directory will cause d_manage() to be
invoked. It can always be set again when necessary.
==========================
WHAT THIS MEANS FOR AUTOFS
==========================
Autofs currently uses the lookup() inode op and the d_revalidate() dentry op to
trigger the automounting of indirect mounts, and both of these can be called
with i_mutex held.
autofs knows that the i_mutex will be held by the caller in lookup(), and so
can drop it before invoking the daemon - but this isn't so for d_revalidate(),
since the lock is only held on _some_ of the code paths that call it. This
means that autofs can't risk dropping i_mutex from its d_revalidate() function
before it calls the daemon.
The bug could manifest itself as, for example, a process that's trying to
validate an automount dentry that gets made to wait because that dentry is
expired and needs cleaning up:
mkdir S ffffffff8014e05a 0 32580 24956
Call Trace:
[<ffffffff885371fd>] :autofs4:autofs4_wait+0x674/0x897
[<ffffffff80127f7d>] avc_has_perm+0x46/0x58
[<ffffffff8009fdcf>] autoremove_wake_function+0x0/0x2e
[<ffffffff88537be6>] :autofs4:autofs4_expire_wait+0x41/0x6b
[<ffffffff88535cfc>] :autofs4:autofs4_revalidate+0x91/0x149
[<ffffffff80036d96>] __lookup_hash+0xa0/0x12f
[<ffffffff80057a2f>] lookup_create+0x46/0x80
[<ffffffff800e6e31>] sys_mkdirat+0x56/0xe4
versus the automount daemon which wants to remove that dentry, but can't
because the normal process is holding the i_mutex lock:
automount D ffffffff8014e05a 0 32581 1 32561
Call Trace:
[<ffffffff80063c3f>] __mutex_lock_slowpath+0x60/0x9b
[<ffffffff8000ccf1>] do_path_lookup+0x2ca/0x2f1
[<ffffffff80063c89>] .text.lock.mutex+0xf/0x14
[<ffffffff800e6d55>] do_rmdir+0x77/0xde
[<ffffffff8005d229>] tracesys+0x71/0xe0
[<ffffffff8005d28d>] tracesys+0xd5/0xe0
which means that the system is deadlocked.
This patch allows autofs to hold up normal processes whilst the daemon goes
ahead and does things to the dentry tree behind the automouter point without
risking a deadlock as almost no locks are held in d_manage() and none in
d_automount().
Signed-off-by: David Howells <dhowells@redhat.com>
Was-Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-14 18:45:26 +00:00
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fs: brlock vfsmount_lock
fs: brlock vfsmount_lock
Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.
A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.
The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).
The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 04:37:39 +10:00
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2013-03-16 14:39:34 -04:00
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2005-11-07 17:16:09 -05:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2005-04-16 15:20:36 -07:00
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fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
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2005-04-16 15:20:36 -07:00
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2012-10-11 11:42:01 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2009-10-04 21:49:49 +09:00
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2013-05-04 14:40:51 -04:00
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2009-10-04 21:49:49 +09:00
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2009-04-19 18:40:43 +02:00
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2009-03-26 17:53:14 +00:00
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2005-04-16 15:20:36 -07:00
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2006-01-09 20:52:17 -08:00
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2009-03-26 17:49:56 +00:00
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2008-02-15 14:38:00 -08:00
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2006-01-09 20:52:17 -08:00
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2010-08-09 12:05:43 -04:00
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2009-03-26 17:49:56 +00:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-11-07 17:21:20 -05:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2008-08-02 00:51:11 -04:00
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2005-04-16 15:20:36 -07:00
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2012-07-26 21:08:32 -07:00
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2011-06-15 10:21:48 -07:00
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2012-07-26 21:08:32 -07:00
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2010-03-07 18:49:36 -08:00
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2012-07-26 21:08:32 -07:00
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2009-06-22 15:09:13 -04:00
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2011-06-15 10:21:48 -07:00
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2009-06-22 15:09:13 -04:00
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2011-06-15 10:21:48 -07:00
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2010-03-07 18:49:36 -08:00
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2009-06-22 15:09:13 -04:00
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2012-07-26 21:08:32 -07:00
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2009-06-22 15:09:13 -04:00
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2013-09-28 20:47:57 -04:00
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2005-04-16 15:20:36 -07:00
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2006-12-08 02:37:56 -08:00
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2008-05-10 20:44:54 -04:00
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2011-11-24 18:57:30 -05:00
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2013-09-28 20:47:57 -04:00
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2011-11-24 20:55:08 -05:00
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2012-07-31 13:13:04 -07:00
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2005-04-16 15:20:36 -07:00
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2013-09-28 20:47:57 -04:00
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2012-07-26 21:08:32 -07:00
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2009-06-22 15:09:13 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-16 15:12:40 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-30 01:35:18 -07:00
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2013-09-28 20:47:57 -04:00
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2013-03-22 04:08:05 -07:00
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2012-07-31 13:13:04 -07:00
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2012-06-25 12:55:18 +01:00
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2013-03-16 14:49:45 -04:00
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2012-07-26 21:08:32 -07:00
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2012-06-25 12:55:18 +01:00
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2005-04-16 15:20:36 -07:00
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2011-12-06 13:32:36 -05:00
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2011-11-25 02:19:55 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2011-11-24 20:55:08 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 00:46:35 -05:00
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2013-09-28 20:47:57 -04:00
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2011-11-24 18:57:30 -05:00
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2005-04-16 15:20:36 -07:00
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2013-09-28 20:47:57 -04:00
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2011-11-24 18:57:30 -05:00
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2005-04-16 15:20:36 -07:00
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2011-11-25 03:06:56 -05:00
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2013-03-30 01:35:18 -07:00
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2005-04-16 15:20:36 -07:00
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2013-03-16 14:49:45 -04:00
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2005-04-16 15:20:36 -07:00
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2011-01-14 22:30:21 -05:00
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2005-04-16 15:20:36 -07:00
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2011-01-14 22:30:21 -05:00
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2005-04-16 15:20:36 -07:00
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2006-02-07 12:59:00 -08:00
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2005-04-16 15:20:36 -07:00
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2009-06-22 15:09:13 -04:00
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2011-11-25 02:19:55 -05:00
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2009-06-22 15:09:13 -04:00
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2012-07-26 21:08:32 -07:00
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2009-06-22 15:09:13 -04:00
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2011-11-25 02:19:55 -05:00
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2011-12-06 13:32:36 -05:00
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2013-05-04 15:18:53 -04:00
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2011-11-16 16:12:14 -05:00
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2011-11-25 02:19:55 -05:00
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2009-06-22 15:09:13 -04:00
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2011-11-16 21:43:59 -05:00
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2011-11-22 12:31:21 -05:00
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2011-11-16 21:43:59 -05:00
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2011-11-22 12:31:21 -05:00
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2011-11-16 21:43:59 -05:00
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2011-11-22 12:31:21 -05:00
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2011-11-16 21:43:59 -05:00
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2009-01-14 14:14:12 +01:00
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2005-04-16 15:20:36 -07:00
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|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
|
|
|
|
|
|
|
|
|
2012-10-10 15:25:28 -04:00
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
|
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
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2005-04-16 15:20:36 -07:00
|
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|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
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2005-04-16 15:20:36 -07:00
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
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|
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|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
|
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2005-04-16 15:20:36 -07:00
|
|
|
|
2012-10-10 15:25:28 -04:00
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
|
|
|
|
2005-04-16 15:20:36 -07:00
|
|
|
|
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When
do_mount_root() passes a kernel address that points to an object which is
smaller than a whole page, copy_mount_options() will happily go past this
memory object, possibly dereferencing "wild" pointers that could be in any
state (hence the kmemcheck warning, which shows that parts of the next
page are not even allocated).
(The likelihood of something going wrong here is pretty low -- first of
all this only applies to kernel calls to sys_mount(), which are mostly
found in the boot code. Secondly, I guess if the page was not mapped,
exact_copy_from_user() _would_ in fact handle it correctly because of its
access_ok(), etc. checks.)
But it is much nicer to avoid the dubious reads altogether, by stopping as
soon as we find a NUL byte. Is there a good reason why we can't do
something like this, using the already existing strndup_from_user()?
[akpm@linux-foundation.org: make copy_mount_string() static]
[AV: fix compat mount breakage, which involves undoing akpm's change above]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: al <al@dizzy.pdmi.ras.ru>
2009-09-18 13:05:45 -07:00
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2005-04-16 15:20:36 -07:00
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2011-11-23 19:34:49 -05:00
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2013-09-29 22:06:07 -04:00
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2011-11-23 19:34:49 -05:00
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2011-11-24 22:00:28 -05:00
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2011-11-23 19:34:49 -05:00
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2011-11-24 22:00:28 -05:00
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2011-11-24 22:25:07 -05:00
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2011-11-24 22:19:58 -05:00
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2011-11-23 19:34:49 -05:00
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2011-11-24 22:00:28 -05:00
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2011-11-23 19:34:49 -05:00
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2013-09-29 22:06:07 -04:00
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2011-11-24 22:00:28 -05:00
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2013-09-29 22:06:07 -04:00
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2011-11-23 19:34:49 -05:00
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2005-04-16 15:20:36 -07:00
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2006-01-08 01:03:18 -08:00
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2005-04-16 15:20:36 -07:00
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2009-01-14 14:14:16 +01:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2013-02-22 22:45:42 -05:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2011-03-18 08:55:38 -04:00
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2005-04-16 15:20:36 -07:00
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2010-08-10 11:41:36 +02:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2005-04-16 15:20:36 -07:00
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2011-11-24 19:41:16 -05:00
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2013-03-15 10:53:28 -04:00
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2011-11-25 01:05:37 -05:00
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2011-03-18 08:55:38 -04:00
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2011-11-25 00:46:35 -05:00
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2011-03-18 08:55:38 -04:00
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2013-03-29 21:04:39 -07:00
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2005-04-16 15:20:36 -07:00
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2009-05-04 03:32:03 +04:00
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2011-03-18 08:55:38 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2005-04-16 15:20:36 -07:00
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2008-03-22 18:00:39 -04:00
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2011-03-18 08:55:38 -04:00
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2011-11-24 21:47:05 -05:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2008-07-22 09:59:21 -04:00
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2011-03-18 08:55:38 -04:00
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2011-11-24 21:47:05 -05:00
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2011-03-18 08:55:38 -04:00
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2008-02-14 19:34:32 -08:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2013-09-29 11:24:49 -04:00
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2011-11-24 19:41:16 -05:00
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2013-03-29 21:04:39 -07:00
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2008-02-14 19:34:32 -08:00
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2013-03-15 10:53:28 -04:00
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2008-02-14 19:34:32 -08:00
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2013-03-15 10:53:28 -04:00
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2006-12-08 02:37:56 -08:00
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2013-09-29 11:24:49 -04:00
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2008-07-22 09:59:21 -04:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2011-03-18 08:55:38 -04:00
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2013-03-15 10:53:28 -04:00
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2011-03-18 08:55:38 -04:00
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2008-03-22 18:00:39 -04:00
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2011-03-18 08:55:38 -04:00
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2008-07-22 09:59:21 -04:00
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2005-04-16 15:20:36 -07:00
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2008-07-22 09:59:21 -04:00
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2005-04-16 15:20:36 -07:00
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2006-12-08 02:37:56 -08:00
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2008-02-14 19:34:39 -08:00
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2012-07-26 21:42:03 -07:00
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2005-04-16 15:20:36 -07:00
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2012-07-26 21:42:03 -07:00
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2005-04-16 15:20:36 -07:00
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fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.
The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.
We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.
- check the global sum once every interval (this will delay zero detection
for some interval, so it's probably a showstopper for vfsmounts).
- keep a local count and only taking the global sum when local reaches 0 (this
is difficult for vfsmounts, because we can't hold preempt off for the life of
a reference, so a counter would need to be per-thread or tied strongly to a
particular CPU which requires more locking).
- keep a local difference of increments and decrements, which allows us to sum
the total difference and hence find the refcount when summing all CPUs. Then,
keep a single integer "long" refcount for slow and long lasting references,
and only take the global sum of local counters when the long refcount is 0.
This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.
This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.
This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:11 +11:00
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2009-06-23 17:29:49 -04:00
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2005-04-16 15:20:36 -07:00
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2006-12-08 02:37:56 -08:00
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2011-12-06 13:32:36 -05:00
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2008-02-14 19:34:39 -08:00
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2005-04-16 15:20:36 -07:00
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2007-10-16 23:26:30 -07:00
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2005-04-16 15:20:36 -07:00
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2008-02-06 01:37:57 -08:00
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2006-09-29 01:58:57 -07:00
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2005-04-16 15:20:36 -07:00
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2011-11-23 12:14:10 -05:00
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2007-07-20 10:11:58 +09:00
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2005-04-16 15:20:36 -07:00
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2005-11-07 17:16:09 -05:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2011-03-22 16:33:54 -07:00
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2008-02-06 01:37:57 -08:00
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2013-03-15 10:53:28 -04:00
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2005-04-16 15:20:36 -07:00
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2006-09-29 01:58:57 -07:00
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2008-04-30 00:55:09 -07:00
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2007-10-29 14:17:23 -06:00
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2008-04-30 00:55:09 -07:00
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2005-04-16 15:20:36 -07:00
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2009-06-22 15:09:13 -04:00
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2005-04-16 15:20:36 -07:00
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2010-02-05 02:21:06 -05:00
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2009-06-22 15:09:13 -04:00
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2013-09-16 21:19:20 -04:00
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2012-07-26 21:08:32 -07:00
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2005-04-16 15:20:36 -07:00
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2011-03-17 22:08:28 -04:00
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2011-07-19 09:32:38 -07:00
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2012-06-09 00:59:08 -04:00
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2011-07-19 09:32:38 -07:00
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2011-03-17 22:08:28 -04:00
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2011-07-19 09:32:38 -07:00
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2012-06-09 00:59:08 -04:00
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2013-09-29 22:06:07 -04:00
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2011-07-19 09:32:38 -07:00
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fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API
__d_path() API is asking for trouble and in case of apparmor d_namespace_path()
getting just that. The root cause is that when __d_path() misses the root
it had been told to look for, it stores the location of the most remote ancestor
in *root. Without grabbing references. Sure, at the moment of call it had
been pinned down by what we have in *path. And if we raced with umount -l, we
could have very well stopped at vfsmount/dentry that got freed as soon as
prepend_path() dropped vfsmount_lock.
It is safe to compare these pointers with pre-existing (and known to be still
alive) vfsmount and dentry, as long as all we are asking is "is it the same
address?". Dereferencing is not safe and apparmor ended up stepping into
that. d_namespace_path() really wants to examine the place where we stopped,
even if it's not connected to our namespace. As the result, it looked
at ->d_sb->s_magic of a dentry that might've been already freed by that point.
All other callers had been careful enough to avoid that, but it's really
a bad interface - it invites that kind of trouble.
The fix is fairly straightforward, even though it's bigger than I'd like:
* prepend_path() root argument becomes const.
* __d_path() is never called with NULL/NULL root. It was a kludge
to start with. Instead, we have an explicit function - d_absolute_root().
Same as __d_path(), except that it doesn't get root passed and stops where
it stops. apparmor and tomoyo are using it.
* __d_path() returns NULL on path outside of root. The main
caller is show_mountinfo() and that's precisely what we pass root for - to
skip those outside chroot jail. Those who don't want that can (and do)
use d_path().
* __d_path() root argument becomes const. Everyone agrees, I hope.
* apparmor does *NOT* try to use __d_path() or any of its variants
when it sees that path->mnt is an internal vfsmount. In that case it's
definitely not mounted anywhere and dentry_path() is exactly what we want
there. Handling of sysctl()-triggered weirdness is moved to that place.
* if apparmor is asked to do pathname relative to chroot jail
and __d_path() tells it we it's not in that jail, the sucker just calls
d_absolute_path() instead. That's the other remaining caller of __d_path(),
BTW.
* seq_path_root() does _NOT_ return -ENAMETOOLONG (it's stupid anyway -
the normal seq_file logics will take care of growing the buffer and redoing
the call of ->show() just fine). However, if it gets path not reachable
from root, it returns SEQ_SKIP. The only caller adjusted (i.e. stopped
ignoring the return value as it used to do).
Reviewed-by: John Johansen <john.johansen@canonical.com>
ACKed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
2011-12-05 08:43:34 -05:00
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2011-11-25 00:46:35 -05:00
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fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API
__d_path() API is asking for trouble and in case of apparmor d_namespace_path()
getting just that. The root cause is that when __d_path() misses the root
it had been told to look for, it stores the location of the most remote ancestor
in *root. Without grabbing references. Sure, at the moment of call it had
been pinned down by what we have in *path. And if we raced with umount -l, we
could have very well stopped at vfsmount/dentry that got freed as soon as
prepend_path() dropped vfsmount_lock.
It is safe to compare these pointers with pre-existing (and known to be still
alive) vfsmount and dentry, as long as all we are asking is "is it the same
address?". Dereferencing is not safe and apparmor ended up stepping into
that. d_namespace_path() really wants to examine the place where we stopped,
even if it's not connected to our namespace. As the result, it looked
at ->d_sb->s_magic of a dentry that might've been already freed by that point.
All other callers had been careful enough to avoid that, but it's really
a bad interface - it invites that kind of trouble.
The fix is fairly straightforward, even though it's bigger than I'd like:
* prepend_path() root argument becomes const.
* __d_path() is never called with NULL/NULL root. It was a kludge
to start with. Instead, we have an explicit function - d_absolute_root().
Same as __d_path(), except that it doesn't get root passed and stops where
it stops. apparmor and tomoyo are using it.
* __d_path() returns NULL on path outside of root. The main
caller is show_mountinfo() and that's precisely what we pass root for - to
skip those outside chroot jail. Those who don't want that can (and do)
use d_path().
* __d_path() root argument becomes const. Everyone agrees, I hope.
* apparmor does *NOT* try to use __d_path() or any of its variants
when it sees that path->mnt is an internal vfsmount. In that case it's
definitely not mounted anywhere and dentry_path() is exactly what we want
there. Handling of sysctl()-triggered weirdness is moved to that place.
* if apparmor is asked to do pathname relative to chroot jail
and __d_path() tells it we it's not in that jail, the sucker just calls
d_absolute_path() instead. That's the other remaining caller of __d_path(),
BTW.
* seq_path_root() does _NOT_ return -ENAMETOOLONG (it's stupid anyway -
the normal seq_file logics will take care of growing the buffer and redoing
the call of ->show() just fine). However, if it gets path not reachable
from root, it returns SEQ_SKIP. The only caller adjusted (i.e. stopped
ignoring the return value as it used to do).
Reviewed-by: John Johansen <john.johansen@canonical.com>
ACKed-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
2011-12-05 08:43:34 -05:00
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2010-03-07 18:49:36 -08:00
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2013-03-15 01:45:51 -07:00
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2013-03-30 19:57:41 -07:00
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2013-03-24 14:28:27 -07:00
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2013-03-30 19:57:41 -07:00
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2013-03-24 14:28:27 -07:00
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2013-03-30 19:57:41 -07:00
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2013-09-16 21:37:36 -04:00
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2013-03-24 14:28:27 -07:00
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2013-03-30 19:57:41 -07:00
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2013-11-14 21:22:25 -08:00
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2013-03-30 19:57:41 -07:00
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2013-03-24 14:28:27 -07:00
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2013-03-30 19:57:41 -07:00
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2013-03-24 14:28:27 -07:00
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2013-03-30 19:57:41 -07:00
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2013-09-16 21:37:36 -04:00
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2013-03-30 19:57:41 -07:00
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2013-03-24 14:28:27 -07:00
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2010-03-07 18:49:36 -08:00
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2012-07-26 21:42:03 -07:00
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2013-03-20 12:49:49 -07:00
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2012-09-13 16:38:03 +08:00
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2010-03-07 18:49:36 -08:00
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2011-06-15 10:21:48 -07:00
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2010-03-07 18:49:36 -08:00
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2011-06-15 10:21:48 -07:00
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2010-03-07 18:49:36 -08:00
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