We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't need it since we can grab fs_info from the given space_info.
So remove the fs_info argument.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're computing a few values several times:
1) The current ordered extent's end offset inside the while loop, we have
computed it and stored it in the 'entry_end' variable but then we
compute it again later as the first argument to the min() macro;
2) The end file offset, open coded 3 times;
3) The current length (stored in variable 'len') computed 2 times, one
inside an assertion and the other when assigning to the 'len' variable.
So use existing variables and add new ones to prevent repeating these
expressions and reduce the source code.
We were also subtracting one from the result of min() macro call and
then adding 1 back in the next line, making both operations pointless.
So just remove the decrement and increment by 1.
This also reduces very slightly the object code.
Before:
$ size fs/btrfs/btrfs.ko
text data bss dec hex filename
1916576 161679 15592 2093847 1ff317 fs/btrfs/btrfs.ko
After:
$ size fs/btrfs/btrfs.ko
text data bss dec hex filename
1916556 161679 15592 2093827 1ff303 fs/btrfs/btrfs.ko
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We have the inode locked so no one can concurrently change its i_size and
neither do we change it ourselves, so there's no point in keep rounding
it in the while loop and setting it up in the control structure. That only
causes confusion when reading the code.
So move all the i_size setup and rounding out of the loop and assert the
inode is locked.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We're using different ways to round down the i_size by sector size, one
with a bitwise and with a negated mask and another with ALIGN_DOWN(), and
using ALIGN() to round up.
Replace these uses with the round_down() and round_up() macros which have
have names that make it clear the direction of the rounding (unlike the
ALIGN() macro) and getting rid of the bitwise and, negated mask and local
variable for the mask.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We don't expect to hit errors and log the error message, so add the
unlikely annotation to make it clear and to hint the compiler that it may
reorganize code to be more efficient.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
If the assertion fails we don't get to know which of the two expressions
failed and neither the values used in each expression.
So split the assertion into two, each for a single expression, so that
if any is triggered we see a line number reported in a stack trace that
points to which expression failed. Also make the assertions use the
verbose mode to print the values involved in the computations.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Instead of repeating the expression "start + len" multiple times, store it
in a variable and use it where needed.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
While running test case btrfs/192 from fstests with support for large
folios (needs CONFIG_BTRFS_EXPERIMENTAL=y) I ended up getting very sporadic
btrfs check failures reporting that csum items were missing. Looking into
the issue it turned out that btrfs check searches for csum items of a file
extent item with a range that spans beyond the i_size of a file and we
don't have any, because the kernel's writeback code skips submitting bios
for ranges beyond eof. It's not expected however to find a file extent item
that crosses the rounded up (by the sector size) i_size value, but there is
a short time window where we can end up with a transaction commit leaving
this small inconsistency between the i_size and the last file extent item.
Example btrfs check output when this happens:
$ btrfs check /dev/sdc
Opening filesystem to check...
Checking filesystem on /dev/sdc
UUID: 69642c61-5efb-4367-aa31-cdfd4067f713
[1/8] checking log skipped (none written)
[2/8] checking root items
[3/8] checking extents
[4/8] checking free space tree
[5/8] checking fs roots
root 5 inode 332 errors 1000, some csum missing
ERROR: errors found in fs roots
(...)
Looking at a tree dump of the fs tree (root 5) for inode 332 we have:
$ btrfs inspect-internal dump-tree -t 5 /dev/sdc
(...)
item 28 key (332 INODE_ITEM 0) itemoff 2006 itemsize 160
generation 17 transid 19 size 610969 nbytes 86016
block group 0 mode 100666 links 1 uid 0 gid 0 rdev 0
sequence 11 flags 0x0(none)
atime 1759851068.391327881 (2025-10-07 16:31:08)
ctime 1759851068.410098267 (2025-10-07 16:31:08)
mtime 1759851068.410098267 (2025-10-07 16:31:08)
otime 1759851068.391327881 (2025-10-07 16:31:08)
item 29 key (332 INODE_REF 340) itemoff 1993 itemsize 13
index 2 namelen 3 name: f1f
item 30 key (332 EXTENT_DATA 589824) itemoff 1940 itemsize 53
generation 19 type 1 (regular)
extent data disk byte 21745664 nr 65536
extent data offset 0 nr 65536 ram 65536
extent compression 0 (none)
(...)
We can see that the file extent item for file offset 589824 has a length of
64K and its number of bytes is 64K. Looking at the inode item we see that
its i_size is 610969 bytes which falls within the range of that file extent
item [589824, 655360[.
Looking into the csum tree:
$ btrfs inspect-internal dump-tree /dev/sdc
(...)
item 15 key (EXTENT_CSUM EXTENT_CSUM 21565440) itemoff 991 itemsize 200
range start 21565440 end 21770240 length 204800
item 16 key (EXTENT_CSUM EXTENT_CSUM 1104576512) itemoff 983 itemsize 8
range start 1104576512 end 1104584704 length 8192
(..)
We see that the csum item number 15 covers the first 24K of the file extent
item - it ends at offset 21770240 and the extent's disk_bytenr is 21745664,
so we have:
21770240 - 21745664 = 24K
We see that the next csum item (number 16) is completely outside the range,
so the remaining 40K of the extent doesn't have csum items in the tree.
If we round up the i_size to the sector size, we get:
round_up(610969, 4096) = 614400
If we subtract from that the file offset for the extent item we get:
614400 - 589824 = 24K
So the missing 40K corresponds to the end of the file extent item's range
minus the rounded up i_size:
655360 - 614400 = 40K
Normally we don't expect a file extent item to span over the rounded up
i_size of an inode, since when truncating, doing hole punching and other
operations that trim a file extent item, the number of bytes is adjusted.
There is however a short time window where the kernel can end up,
temporarily,persisting an inode with an i_size that falls in the middle of
the last file extent item and the file extent item was not yet trimmed (its
number of bytes reduced so that it doesn't cross i_size rounded up by the
sector size).
The steps (in the kernel) that lead to such scenario are the following:
1) We have inode I as an empty file, no allocated extents, i_size is 0;
2) A buffered write is done for file range [589824, 655360[ (length of
64K) and the i_size is updated to 655360. Note that we got a single
large folio for the range (64K);
3) A truncate operation starts that reduces the inode's i_size down to
610969 bytes. The truncate sets the inode's new i_size at
btrfs_setsize() by calling truncate_setsize() and before calling
btrfs_truncate();
4) At btrfs_truncate() we trigger writeback for the range starting at
610304 (which is the new i_size rounded down to the sector size) and
ending at (u64)-1;
5) During the writeback, at extent_write_cache_pages(), we get from the
call to filemap_get_folios_tag(), the 64K folio that starts at file
offset 589824 since it contains the start offset of the writeback
range (610304);
6) At writepage_delalloc() we find the whole range of the folio is dirty
and therefore we run delalloc for that 64K range ([589824, 655360[),
reserving a 64K extent, creating an ordered extent, etc;
7) At extent_writepage_io() we submit IO only for subrange [589824, 614400[
because the inode's i_size is 610969 bytes (rounded up by sector size
is 614400). There, in the while loop we intentionally skip IO beyond
i_size to avoid any unnecessay work and just call
btrfs_mark_ordered_io_finished() for the range [614400, 655360[ (which
has a 40K length);
8) Once the IO finishes we finish the ordered extent by ending up at
btrfs_finish_one_ordered(), join transaction N, insert a file extent
item in the inode's subvolume tree for file offset 589824 with a number
of bytes of 64K, and update the inode's delayed inode item or directly
the inode item with a call to btrfs_update_inode_fallback(), which
results in storing the new i_size of 610969 bytes;
9) Transaction N is committed either by the transaction kthread or some
other task committed it (in response to a sync or fsync for example).
At this point we have inode I persisted with an i_size of 610969 bytes
and file extent item that starts at file offset 589824 and has a number
of bytes of 64K, ending at an offset of 655360 which is beyond the
i_size rounded up to the sector size (614400).
--> So after a crash or power failure here, the btrfs check program
reports that error about missing checksum items for this inode, as
it tries to lookup for checksums covering the whole range of the
extent;
10) Only after transaction N is committed that at btrfs_truncate() the
call to btrfs_start_transaction() starts a new transaction, N + 1,
instead of joining transaction N. And it's with transaction N + 1 that
it calls btrfs_truncate_inode_items() which updates the file extent
item at file offset 589824 to reduce its number of bytes from 64K down
to 24K, so that the file extent item's range ends at the i_size
rounded up to the sector size (614400 bytes).
Fix this by truncating the ordered extent at extent_writepage_io() when we
skip writeback because the current offset in the folio is beyond i_size.
This ensures we don't ever persist a file extent item with a number of
bytes beyond the rounded up (by sector size) value of the i_size.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
For the ->remove_bdev() callback, btrfs will:
- Mark the target device as missing
- Go degraded if the fs can afford it
- Return error other wise
Thus falls back to the shutdown callback
For the ->shutdown callback, btrfs will:
- Set the SHUTDOWN flag
Which will reject all new incoming operations, and make all writeback
to fail.
The behavior is the same as the NOLOGFLUSH behavior.
To support the lookup from bdev to a btrfs_device,
btrfs_dev_lookup_args is enhanced to have a new @devt member.
If set, we should be able to use that @devt member to uniquely locating a
btrfs device.
I know the shutdown can be a little overkilled, if one has a RAID1
metadata and RAID0 data, in that case one can still read data with 50%
chance to got some good data.
But a filesystem returning -EIO for half of the time is not really
considered usable.
Further it can also be as bad as the only device went missing for a single
device btrfs.
So here we go safe other than sorry when handling missing device.
And the remove_bdev callback will be hidden behind experimental features
for now, the reasons are:
- There are not enough btrfs specific bdev removal test cases
The existing test cases are all removing the only device, thus only
exercises the ->shutdown() behavior.
- Not yet determined what's the expected behavior
Although the current auto-degrade behavior is no worse than the old
behavior, it may not always be what the end users want.
Before there is a concrete interface, better hide the new feature
from end users.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Tested-by: Anand Jain <asj@kernel.org>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
The shutdown ioctl should follow the XFS one, which use magic number 'X',
and ioctl number 125, with a uint32 as flags.
For now btrfs don't distinguish DEFAULT and LOGFLUSH flags (just like
f2fs), both will freeze the fs first (implies committing the current
transaction), setting the SHUTDOWN flag and finally thaw the fs.
For NOLOGFLUSH flag, the freeze/thaw part is skipped thus the current
transaction is aborted.
The new shutdown ioctl is hidden behind experimental features for more
testing.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Tested-by: Anand Jain <asj@kernel.org>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
A new fs state EMERGENCY_SHUTDOWN is introduced, which is btrfs'
equivalent of XFS_IOC_GOINGDOWN or EXT4_IOC_SHUTDOWN, after entering
emergency shutdown state, all operations will return errors (-EIO), and
can not be bring back to normal state until unmouont.
The new state will reject the following file operations:
- read_iter()
- write_iter()
- mmap()
- open()
- remap_file_range()
- uring_cmd()
- splice_read()
This requires a small wrapper to do the extra shutdown check, then call
the regular filemap_splice_read() function
This should reject most of the file operations on a shutdown btrfs.
And for the existing dirty folios, extra shutdown checks are introduced
to the following functions:
- run_delalloc_nocow()
- run_delalloc_compressed()
- cow_file_range()
So that dirty ranges will still be properly cleaned without being
submitted.
Finally the shutdown state will also set the fs error, so that no new
transaction will be committed, protecting the metadata from any possible
further corruption.
And when the fs entered shutdown mode for the first time, a critical
level kernel message will show up to indicate the incident.
That message will be important for end users as rejected delalloc ranges
will output error messages, hopefully that shutdown message and the fact
that all fs operations are returning error will prevent end users from
getting too confused about the delalloc error messages.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <asj@kernel.org>
Tested-by: Anand Jain <asj@kernel.org>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Enable GCC 16's coming "-fdiagnostics-show-context=N" option[1] to
provide enhanced diagnostic information for value-tracking warnings,
which displays the control flow chain leading to the diagnostic. This
covers our existing use of -Wrestrict and -Wstringop-overread, and
gets us closer to enabling -Warray-bounds, -Wstringop-overflow, and
-Wstringop-truncation, so we can track the rationale for the warning,
letting us more quickly identify actual issues vs what have looked in
the past like false positives. Fixes based on this work have already
been landing, e.g.:
4a6f18f286 ("net/mlx4_core: Avoid impossible mlx4_db_alloc() order value")
8a39f1c870 ("ovl: Check for NULL d_inode() in ovl_dentry_upper()")
e5f7e4e0a4 ("drm/amdgpu/atom: Work around vbios NULL offset false positive")
The context depth ("=N") provides the immediate decision path that led
to the problematic code location, showing conditional checks and branch
decisions that caused the warning. This will help us understand why
GCC's value-tracking analysis triggered the warning and makes it easier
to determine whether warnings are legitimate issues or false positives.
For example, an array bounds warning will now show the conditional
statements (like "if (i >= 4)") that established the out-of-bounds access
range, directly connecting the control flow to the warning location.
This is particularly valuable when GCC's interprocedural analysis can
generate warnings that are difficult to understand without seeing the
inferred control flow.
While my testing has shown that "=1" reports enough for finding
the origin of most bounds issues, I have used "=2" here just to be
conservative. Build time measurements with this option off, =1, and =2
are all with noise of each other, so there seems to be no harm in "turning
it up". If we need to, we can make this value configurable in the future.
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=6faa3cfe60ff9769d1bebfffdd2c7325217d7389 [1]
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20251121184342.it.626-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
While running kernel-doc validation on linux-next, warnings were emitted
for functions in include/linux/string.h due to missing return value
documentation:
Warning: include/linux/string.h:375 No description found for return value of 'kbasename'
Warning: include/linux/string.h:560 No description found for return value of 'strstarts'
This patch adds the missing return value descriptions for both functions
and clears the related kernel-doc warnings.
Signed-off-by: Kriish Sharma <kriish.sharma2006@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20251118184828.2621595-1-kriish.sharma2006@gmail.com
Signed-off-by: Kees Cook <kees@kernel.org>
In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)
The assigned type is "struct iris_inst *", but the returned type is
"struct iris_inst_hfi_gen2 *". The allocation is intentionally larger as
the first member of struct iris_inst_hfi_gen2 is struct iris_inst, so
this is by design. Cast the allocation type to match the assignment.
Link: https://patch.msgid.link/20250426061526.work.106-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)
The assigned type is "uint64_t *", but the returned type, while matching,
will be const qualified. As there is no general way to remove const
qualifiers, adjust the allocation type to match the assignment.
Link: https://patch.msgid.link/20250426061325.work.665-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
In preparation for making the kmalloc family of allocators type aware,
we need to make sure that the returned type from the allocation matches
the type of the variable being assigned. (Before, the allocator would
always return "void *", which can be implicitly cast to any pointer type.)
The returned type is "struct comedi_lrange **", but the assigned type,
while technically matching, is const qualified. Since there is no general
way to remove const qualifiers, switch the returned type to match the
assign type. No change in allocation size results.
Link: https://patch.msgid.link/20250426061015.work.971-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
We have a couple places doing the computation "pos + write_bytes" when we
already have it in the local variable "end_pos". Change then to use the
variable instead and make source code smaller. Also make the variable
const since it's not supposed to change.
This also has a very slight reduction in the module size.
Before:
$ size fs/btrfs/btrfs.ko
text data bss dec hex filename
1915990 161647 15592 2093229 1ff0ad fs/btrfs/btrfs.ko
After:
$ size fs/btrfs/btrfs.ko
text data bss dec hex filename
1915974 161647 15592 2093213 1ff09d fs/btrfs/btrfs.ko
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
From the memory-barriers.txt document regarding memory barrier ordering
guarantees:
(*) These guarantees do not apply to bitfields, because compilers often
generate code to modify these using non-atomic read-modify-write
sequences. Do not attempt to use bitfields to synchronize parallel
algorithms.
(*) Even in cases where bitfields are protected by locks, all fields
in a given bitfield must be protected by one lock. If two fields
in a given bitfield are protected by different locks, the compiler's
non-atomic read-modify-write sequences can cause an update to one
field to corrupt the value of an adjacent field.
btrfs_space_info has a bitfield sharing an underlying word consisting of
the fields full, chunk_alloc, and flush:
struct btrfs_space_info {
struct btrfs_fs_info * fs_info; /* 0 8 */
struct btrfs_space_info * parent; /* 8 8 */
...
int clamp; /* 172 4 */
unsigned int full:1; /* 176: 0 4 */
unsigned int chunk_alloc:1; /* 176: 1 4 */
unsigned int flush:1; /* 176: 2 4 */
...
Therefore, to be safe from parallel read-modify-writes losing a write to
one of the bitfield members protected by a lock, all writes to all the
bitfields must use the lock. They almost universally do, except for
btrfs_clear_space_info_full() which iterates over the space_infos and
writes out found->full = 0 without a lock.
Imagine that we have one thread completing a transaction in which we
finished deleting a block_group and are thus calling
btrfs_clear_space_info_full() while simultaneously the data reclaim
ticket infrastructure is running do_async_reclaim_data_space():
T1 T2
btrfs_commit_transaction
btrfs_clear_space_info_full
data_sinfo->full = 0
READ: full:0, chunk_alloc:0, flush:1
do_async_reclaim_data_space(data_sinfo)
spin_lock(&space_info->lock);
if(list_empty(tickets))
space_info->flush = 0;
READ: full: 0, chunk_alloc:0, flush:1
MOD/WRITE: full: 0, chunk_alloc:0, flush:0
spin_unlock(&space_info->lock);
return;
MOD/WRITE: full:0, chunk_alloc:0, flush:1
and now data_sinfo->flush is 1 but the reclaim worker has exited. This
breaks the invariant that flush is 0 iff there is no work queued or
running. Once this invariant is violated, future allocations that go
into __reserve_bytes() will add tickets to space_info->tickets but will
see space_info->flush is set to 1 and not queue the work. After this,
they will block forever on the resulting ticket, as it is now impossible
to kick the worker again.
I also confirmed by looking at the assembly of the affected kernel that
it is doing RMW operations. For example, to set the flush (3rd) bit to 0,
the assembly is:
andb $0xfb,0x60(%rbx)
and similarly for setting the full (1st) bit to 0:
andb $0xfe,-0x20(%rax)
So I think this is really a bug on practical systems. I have observed
a number of systems in this exact state, but am currently unable to
reproduce it.
Rather than leaving this footgun lying around for the future, take
advantage of the fact that there is room in the struct anyway, and that
it is already quite large and simply change the three bitfield members to
bools. This avoids writes to space_info->full having any effect on
writes to space_info->flush, regardless of locking.
Fixes: 957780eb27 ("Btrfs: introduce ticketed enospc infrastructure")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
All callers of alloc_bitmap() hold a transaction handle, so GFP_NOFS is
needed to avoid deadlocks on recursion. Update the comment and drop the
stale TODO.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Rajeev Tapadia <rtapadia730@gmail.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In the previous code it was possible to incur into a double kfree()
scenario when calling add_delayed_ref_head(). This could happen if the
record was reported to already exist in the
btrfs_qgroup_trace_extent_nolock() call, but then there was an error
later on add_delayed_ref_head(). In this case, since
add_delayed_ref_head() returned an error, the caller went to free the
record. Since add_delayed_ref_head() couldn't set this kfree'd pointer
to NULL, then kfree() would have acted on a non-NULL 'record' object
which was pointing to memory already freed by the callee.
The problem comes from the fact that the responsibility to kfree the
object is on both the caller and the callee at the same time. Hence, the
fix for this is to shift the ownership of the 'qrecord' object out of
the add_delayed_ref_head(). That is, we will never attempt to kfree()
the given object inside of this function, and will expect the caller to
act on the 'qrecord' object on its own. The only exception where the
'qrecord' object cannot be kfree'd is if it was inserted into the
tracing logic, for which we already have the 'qrecord_inserted_ret'
boolean to account for this. Hence, the caller has to kfree the object
only if add_delayed_ref_head() reports not to have inserted it on the
tracing logic.
As a side-effect of the above, we must guarantee that
'qrecord_inserted_ret' is properly initialized at the start of the
function, not at the end, and then set when an actual insert
happens. This way we avoid 'qrecord_inserted_ret' having an invalid
value on an early exit.
The documentation from the add_delayed_ref_head() has also been updated
to reflect on the exact ownership of the 'qrecord' object.
Fixes: 6ef8fbce01 ("btrfs: fix missing error handling when adding delayed ref with qgroups enabled")
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When compiling with -Wshadow there are warnings in the subpage helper
macros that are used in functions like btrfs_subpage_dump_bitmap() or
btrfs_subpage_clear_and_test_dirty() that also use 'bfs' (for struct
btrfs_folio_state) or blocks_per_folio.
Add '__' to the macro variables and unify naming in all subpage macros.
Signed-off-by: David Sterba <dsterba@suse.com>
Use struct_size() to replace the open-coded calculation, remove the
comment as use of the helper is self explanatory.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Mehdi Ben Hadj Khelifa <mehdi.benhadjkhelifa@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
When compiling with -Wshadow (also in 'make W=2' build) there are
several reports of shadowed variables that seem to be harmless:
- btrfs_do_encoded_write() - we can reuse 'ordered', there's no previous
value that would need to be preserved
- scrub_write_endio() - we need a standalone 'i' for bio iteration
- scrub_stripe() - duplicate ret2 for errors that must not overwrite 'ret'
- btrfs_subpage_set_writeback() - 'flags' is used for another irqsave lock
but is not overwritten when reused for xarray
due to scoping, but for clarity let's rename it
- process_dir_items_leaf() - duplicate 'ret', used only for immediate checks
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
There's a warning when -Wformat=2 is used:
fs/btrfs/print-tree.c: In function ‘key_type_string’:
fs/btrfs/print-tree.c:424:17: warning: format not a string literal and no format arguments [-Wformat-nonliteral]
424 | scnprintf(buf, buf_size, key_to_str[key->type]);
We're printing fixed strings from a table so there's no problem but
let's fix the warning so we could enable the warning in fs/btrfs/.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[STATIC CHECK REPORT]
Smatch is reporting that find_lock_delalloc_range() used to do a null
pointer check before accessing fs_info, but now we're accessing it for
sectorsize unconditionally.
[FALSE ALERT]
This is a false alert, the existing null pointer check is introduced in
commit f7b12a62f0 ("btrfs: replace BTRFS_MAX_EXTENT_SIZE with
fs_info->max_extent_size"), but way before that, commit 7c0260ee09
("btrfs: tests, require fs_info for root") is already forcing every
btrfs_root to have a correct fs_info pointer.
So there is no way that btrfs_root::fs_info is NULL.
[FIX]
Just remove the unnecessary NULL pointer checker.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: f7b12a62f0 ("btrfs: replace BTRFS_MAX_EXTENT_SIZE with fs_info->max_extent_size")
Closes: https://lore.kernel.org/r/202509250925.4L4JQTtn-lkp@intel.com/
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
We are using 'ret' and 'err' variables to track return values and errors,
which is pattern that is error prone and we had quite some bugs due to
this pattern in the past.
Simplify this and use a single variable, named 'ret', to track errors and
the return value.
Also rename the variable 'rw' to 'bg_is_ro' which is more meaningful name,
and change its type from int to bool.
Reviewed-by: Boris Burkov <boris@bur.io>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
In this code:
used_buses = max_t(unsigned int, available_buses,
pci_hotplug_bus_size - 1);
max_t() casts the 'unsigned long' pci_hotplug_bus_size (either 32 or 64
bits) to 'unsigned int' (32 bits) result type, so there's a potential of
discarding significant bits.
Instead, use max(a, b), which casts 'unsigned int' to 'unsigned long' and
cannot discard significant bits.
In this case, pci_hotplug_bus_size is constrained to <= 0xff by pci_setup()
so this doesn't fix a bug, but it makes static analysis easier.
Signed-off-by: David Laight <david.laight.linux@gmail.com>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251119224140.8616-26-david.laight.linux@gmail.com
FEAT_SPE_EFT and FEAT_SPE_FDS etc have new user facing format attributes
so document them. Also document existing 'event_filter' bits that were
missing from the doc and the fact that latency values are stored in the
weight field.
Reviewed-by: Leo Yan <leo.yan@arm.com>
Tested-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
perf_event_attr has gained a new field, config4, so add support for it
extending the existing configN support.
Reviewed-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Tested-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
To pickup config4 changes.
Tested-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
The macro FAN_FROM_REG evaluates its arguments multiple times. When used
with shared driver data, this leads to Time-of-Check to Time-of-Use
(TOCTOU) race conditions, potentially causing divide-by-zero errors.
Convert the macro to a static function to ensure arguments are evaluated
only once.
Additionally, in fan_div_store, move the reading of the old register
value and the calculation of the minimum limit inside the update lock.
This ensures that the read-modify-write sequence operates on consistent
data, preventing race conditions during fan divider updates.
Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251124165900.4713-1-hanguidong02@gmail.com
[groeck: Dropped unnecessary line split]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'.
Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long'
and so cannot discard significant bits.
In this case the 'unsigned long' value is small enough that the result
is ok.
Detected by an extra check added to min_t().
Signed-off-by: David Laight <david.laight.linux@gmail.com>
[ rjw: Subject adjustment ]
Link: https://patch.msgid.link/20251119224140.8616-14-david.laight.linux@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
The functions fan1_input_show and fan1_target_show check shared data for
zero before using it as a divisor. These accesses are currently
lockless. If the data changes to zero between the check and the
division, it causes a divide-by-zero error.
Explicitly acquire the update lock around these checks and calculations
to ensure the data remains stable, preventing Time-of-Check to
Time-of-Use (TOCTOU) race conditions.
Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z8B-g@mail.gmail.com/
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://lore.kernel.org/r/20251124165508.4667-1-hanguidong02@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Continue recent cleanups of comments in the swap handling code.
Unify the use of white space in the comments, drop some unuseful
comments outside function bodies, and move some other comments into
function bodies.
No functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/5943864.DvuYhMxLoT@rafael.j.wysocki
When disassembling alternatives replace trailing NOPs with a single
indication of the number of bytes covered with NOPs.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-31-alexandre.chartre@oracle.com
Add the --wide option to provide a wide output when disassembling.
With this option, the disassembly of alternatives is displayed
side-by-side instead of one above the other.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-30-alexandre.chartre@oracle.com
When disassembling, if an instruction has alternatives which are all
made of a single instruction then print each alternative on a single
line (instruction + description) so that the output is more compact.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-29-alexandre.chartre@oracle.com
Improve the naming of group alternatives by showing the feature name and
flags used by the alternative.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-28-alexandre.chartre@oracle.com
Add a function to get the name of a CPU feature. The function is
architecture dependent and currently only implemented for x86. The
feature names are automatically generated from the cpufeatures.h
include file.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@oracle.com
