linux/fs/block_dev.c

1305 lines
31 KiB

[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 02:02:57 -07:00
[PATCH] VFS: Permit filesystem to override root dentry on mount Extend the get_sb() filesystem operation to take an extra argument that permits the VFS to pass in the target vfsmount that defines the mountpoint. The filesystem is then required to manually set the superblock and root dentry pointers. For most filesystems, this should be done with simple_set_mnt() which will set the superblock pointer and then set the root dentry to the superblock's s_root (as per the old default behaviour). The get_sb() op now returns an integer as there's now no need to return the superblock pointer. This patch permits a superblock to be implicitly shared amongst several mount points, such as can be done with NFS to avoid potential inode aliasing. In such a case, simple_set_mnt() would not be called, and instead the mnt_root and mnt_sb would be set directly. The patch also makes the following changes: (*) the get_sb_*() convenience functions in the core kernel now take a vfsmount pointer argument and return an integer, so most filesystems have to change very little. (*) If one of the convenience function is not used, then get_sb() should normally call simple_set_mnt() to instantiate the vfsmount. This will always return 0, and so can be tail-called from get_sb(). (*) generic_shutdown_super() now calls shrink_dcache_sb() to clean up the dcache upon superblock destruction rather than shrink_dcache_anon(). This is required because the superblock may now have multiple trees that aren't actually bound to s_root, but that still need to be cleaned up. The currently called functions assume that the whole tree is rooted at s_root, and that anonymous dentries are not the roots of trees which results in dentries being left unculled. However, with the way NFS superblock sharing are currently set to be implemented, these assumptions are violated: the root of the filesystem is simply a dummy dentry and inode (the real inode for '/' may well be inaccessible), and all the vfsmounts are rooted on anonymous[*] dentries with child trees. [*] Anonymous until discovered from another tree. (*) The documentation has been adjusted, including the additional bit of changing ext2_* into foo_* in the documentation. [akpm@osdl.org: convert ipath_fs, do other stuff] Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Cc: Nathan Scott <nathans@sgi.com> Cc: Roland Dreier <rolandd@cisco.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 02:02:57 -07:00
[PATCH] lockdep: fix blkdev_open() warning On Wed, 2006-08-09 at 07:57 +0200, Rolf Eike Beer wrote: > ============================================= > [ INFO: possible recursive locking detected ] > --------------------------------------------- > parted/7929 is trying to acquire lock: > (&bdev->bd_mutex){--..}, at: [<c105eb8d>] __blkdev_put+0x1e/0x13c > > but task is already holding lock: > (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > > other info that might help us debug this: > 1 lock held by parted/7929: > #0: (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > stack backtrace: > [<c1003aad>] show_trace_log_lvl+0x58/0x15b > [<c100495f>] show_trace+0xd/0x10 > [<c1004979>] dump_stack+0x17/0x1a > [<c102dee5>] __lock_acquire+0x753/0x99c > [<c102e3b0>] lock_acquire+0x4a/0x6a > [<c1204501>] mutex_lock_nested+0xc8/0x20c > [<c105eb8d>] __blkdev_put+0x1e/0x13c > [<c105ecc4>] blkdev_put+0xa/0xc > [<c105f18a>] do_open+0x336/0x3a8 > [<c105f21b>] blkdev_open+0x1f/0x4c > [<c1057b40>] __dentry_open+0xc7/0x1aa > [<c1057c91>] nameidata_to_filp+0x1c/0x2e > [<c1057cd1>] do_filp_open+0x2e/0x35 > [<c1057dd7>] do_sys_open+0x38/0x68 > [<c1057e33>] sys_open+0x16/0x18 > [<c1002845>] sysenter_past_esp+0x56/0x8d OK, I'm having a look here; its all new to me so bear with me. blkdev_open() calls do_open(bdev, ...,BD_MUTEX_NORMAL) and takes mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_NORMAL) then something fails, and we're thrown to: out_first: where if (bdev != bdev->bd_contains) blkdev_put(bdev->bd_contains) which is __blkdev_put(bdev->bd_contains, BD_MUTEX_NORMAL) which does mutex_lock_nested(&bdev->bd_contains->bd_mutex, BD_MUTEX_NORMAL) <--- lockdep trigger When going to out_first, dbev->bd_contains is either bdev or whole, and since we take the branch it must be whole. So it seems to me the following patch would be the right one: [akpm@osdl.org: compile fix] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arjan van de Ven <arjan@linux.intel.com> Acked-by: NeilBrown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-08-27 01:23:31 -07:00
[PATCH] lockdep: fix blkdev_open() warning On Wed, 2006-08-09 at 07:57 +0200, Rolf Eike Beer wrote: > ============================================= > [ INFO: possible recursive locking detected ] > --------------------------------------------- > parted/7929 is trying to acquire lock: > (&bdev->bd_mutex){--..}, at: [<c105eb8d>] __blkdev_put+0x1e/0x13c > > but task is already holding lock: > (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > > other info that might help us debug this: > 1 lock held by parted/7929: > #0: (&bdev->bd_mutex){--..}, at: [<c105eec6>] do_open+0x72/0x3a8 > stack backtrace: > [<c1003aad>] show_trace_log_lvl+0x58/0x15b > [<c100495f>] show_trace+0xd/0x10 > [<c1004979>] dump_stack+0x17/0x1a > [<c102dee5>] __lock_acquire+0x753/0x99c > [<c102e3b0>] lock_acquire+0x4a/0x6a > [<c1204501>] mutex_lock_nested+0xc8/0x20c > [<c105eb8d>] __blkdev_put+0x1e/0x13c > [<c105ecc4>] blkdev_put+0xa/0xc > [<c105f18a>] do_open+0x336/0x3a8 > [<c105f21b>] blkdev_open+0x1f/0x4c > [<c1057b40>] __dentry_open+0xc7/0x1aa > [<c1057c91>] nameidata_to_filp+0x1c/0x2e > [<c1057cd1>] do_filp_open+0x2e/0x35 > [<c1057dd7>] do_sys_open+0x38/0x68 > [<c1057e33>] sys_open+0x16/0x18 > [<c1002845>] sysenter_past_esp+0x56/0x8d OK, I'm having a look here; its all new to me so bear with me. blkdev_open() calls do_open(bdev, ...,BD_MUTEX_NORMAL) and takes mutex_lock_nested(&bdev->bd_mutex, BD_MUTEX_NORMAL) then something fails, and we're thrown to: out_first: where if (bdev != bdev->bd_contains) blkdev_put(bdev->bd_contains) which is __blkdev_put(bdev->bd_contains, BD_MUTEX_NORMAL) which does mutex_lock_nested(&bdev->bd_contains->bd_mutex, BD_MUTEX_NORMAL) <--- lockdep trigger When going to out_first, dbev->bd_contains is either bdev or whole, and since we take the branch it must be whole. So it seems to me the following patch would be the right one: [akpm@osdl.org: compile fix] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arjan van de Ven <arjan@linux.intel.com> Acked-by: NeilBrown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-08-27 01:23:31 -07:00