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  3. 07 Apr, 2009 1 commit
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  13. 18 Feb, 2009 1 commit
    • Peter Zijlstra's avatar
      fs/super.c: add lockdep annotation to s_umount · ada723dc
      Peter Zijlstra authored 
      Li Zefan said:

Thread 1:
  for ((; ;))
  {
      mount -t cpuset xxx /mnt > /dev/null 2>&1
      cat /mnt/cpus > /dev/null 2>&1
      umount /mnt > /dev/null 2>&1
  }

Thread 2:
  for ((; ;))
  {
      mount -t cpuset xxx /mnt > /dev/null 2>&1
      umount /mnt > /dev/null 2>&1
  }

(Note: It is irrelevant which cgroup subsys is used.)

After a while a lockdep warning showed up:

=============================================
[ INFO: possible recursive locking detected ]
2.6.28 #479
---------------------------------------------
mount/13554 is trying to acquire lock:
 (&type->s_umount_key#19){--..}, at: [<c049d888>] sget+0x5e/0x321

but task is already holding lock:
 (&type->s_umount_key#19){--..}, at: [<c049da0c>] sget+0x1e2/0x321

other info that might help us debug this:
1 lock held by mount/13554:
 #0:  (&type->s_umount_key#19){--..}, at: [<c049da0c>] sget+0x1e2/0x321

stack backtrace:
Pid: 13554, comm: mount Not tainted 2.6.28-mc #479
Call Trace:
 [<c044ad2e>] validate_chain+0x4c6/0xbbd
 [<c044ba9b>] __lock_acquire+0x676/0x700
 [<c044bb82>] lock_acquire+0x5d/0x7a
 [<c049d888>] ? sget+0x5e/0x321
 [<c061b9b8>] down_write+0x34/0x50
 [<c049d888>] ? sget+0x5e/0x321
 [<c049d888>] sget+0x5e/0x321
 [<c045a2e7>] ? cgroup_set_super+0x0/0x3e
 [<c045959f>] ? cgroup_test_super+0x0/0x2f
 [<c045bcea>] cgroup_get_sb+0x98/0x2e7
 [<c045cfb6>] cpuset_get_sb+0x4a/0x5f
 [<c049dfa4>] vfs_kern_mount+0x40/0x7b
 [<c049e02d>] do_kern_mount+0x37/0xbf
 [<c04af4a0>] do_mount+0x5c3/0x61a
 [<c04addd2>] ? copy_mount_options+0x2c/0x111
 [<c04af560>] sys_mount+0x69/0xa0
 [<c0403251>] sysenter_do_call+0x12/0x31

The cause is after alloc_super() and then retry, an old entry in list
fs_supers is found, so grab_super(old) is called, but both functions hold
s_umount lock:

struct super_block *sget(...)
{
	...
retry:
	spin_lock(&sb_lock);
	if (test) {
		list_for_each_entry(old, &type->fs_supers, s_instances) {
			if (!test(old, data))
				continue;
			if (!grab_super(old))  <--- 2nd: down_write(&old->s_umount);
				goto retry;
			if (s)
				destroy_super(s);
			return old;
		}
	}
	if (!s) {
		spin_unlock(&sb_lock);
		s = alloc_super(type);   <--- 1th: down_write(&s->s_umount)
		if (!s)
			return ERR_PTR(-ENOMEM);
		goto retry;
	}
	...
}

It seems like a false positive, and seems like VFS but not cgroup needs to
be fixed.

Peter said:

We can simply put the new s_umount instance in a but lockdep doesn't
particularly cares about subclass order.

If there's any issue with the callers of sget() assuming the s_umount lock
being of sublcass 0, then there is another annotation we can use to fix
that, but lets not bother with that if this is sufficient.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=12673

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Reported-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Paul Menage <menage@google.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      ada723dc
  15. 08 Feb, 2009 1 commit
  17. 14 Jan, 2009 1 commit
  19. 08 Jan, 2009 1 commit
  21. 07 Jan, 2009 1 commit
  23. 03 Jan, 2009 1 commit
  25. 19 Dec, 2008 1 commit
  27. 23 Oct, 2008 2 commits
  29. 21 Oct, 2008 1 commit
  31. 24 Jul, 2008 1 commit
    • Kentaro Makita's avatar
      fix soft lock up at NFS mount via per-SB LRU-list of unused dentries · da3bbdd4
      Kentaro Makita authored 
      [Summary]

 Split LRU-list of unused dentries to one per superblock to avoid soft
 lock up during NFS mounts and remounting of any filesystem.

 Previously I posted here:
 http://lkml.org/lkml/2008/3/5/590

[Descriptions]

- background

  dentry_unused is a list of dentries which are not referenced.
  dentry_unused grows up when references on directories or files are
  released.  This list can be very long if there is huge free memory.

- the problem

  When shrink_dcache_sb() is called, it scans all dentry_unused linearly
  under spin_lock(), and if dentry->d_sb is differnt from given
  superblock, scan next dentry.  This scan costs very much if there are
  many entries, and very ineffective if there are many superblocks.

  IOW, When we need to shrink unused dentries on one dentry, but scans
  unused dentries on all superblocks in the system.  For example, we scan
  500 dentries to unmount a filesystem, but scans 1,000,000 or more unused
  dentries on other superblocks.

  In our case , At mounting NFS*, shrink_dcache_sb() is called to shrink
  unused dentries on NFS, but scans 100,000,000 unused dentries on
  superblocks in the system such as local ext3 filesystems.  I hear NFS
  mounting took 1 min on some system in use.

* : NFS uses virtual filesystem in rpc layer, so NFS is affected by
  this problem.

  100,000,000 is possible number on large systems.

  Per-superblock LRU of unused dentried can reduce the cost in
  reasonable manner.

- How to fix

  I found this problem is solved by David Chinner's "Per-superblock
  unused dentry LRU lists V3"(1), so I rebase it and add some fix to
  reclaim with fairness, which is in Andrew Morton's comments(2).

  1) http://lkml.org/lkml/2006/5/25/318
  2) http://lkml.org/lkml/2006/5/25/320



  Split LRU-list of unused dentries to each superblocks.  Then, NFS
  mounting will check dentries under a superblock instead of all.  But
  this spliting will break LRU of dentry-unused.  So, I've attempted to
  make reclaim unused dentrins with fairness by calculate number of
  dentries to scan on this sb based on following way

  number of dentries to scan on this sb =
  count * (number of dentries on this sb / number of dentries in the machine)

- ToDo
 - I have to measuring performance number and do stress tests.

 - When unmount occurs during prune_dcache(), scanning on same
  superblock, It is unable to reach next superblock because it is gone
  away.  We restart scannig superblock from first one, it causes
  unfairness of reclaim unused dentries on first superblock.  But I think
  this happens very rarely.

- Test Results

  Result on 6GB boxes with excessive unused dentries.

Without patch:

$ cat /proc/sys/fs/dentry-state
10181835        10180203        45      0       0       0
# mount -t nfs 10.124.60.70:/work/kernel-src nfs
real    0m1.830s
user    0m0.001s
sys     0m1.653s

 With this patch:
$ cat /proc/sys/fs/dentry-state
10236610        10234751        45      0       0       0
# mount -t nfs 10.124.60.70:/work/kernel-src nfs
real    0m0.106s
user    0m0.002s
sys     0m0.032s

[akpm@linux-foundation.org: fix comments]
Signed-off-by: default avatarKentaro Makita <k-makita@np.css.fujitsu.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: David Chinner <dgc@sgi.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      da3bbdd4
  33. 29 Apr, 2008 1 commit
  35. 28 Apr, 2008 1 commit
  37. 22 Apr, 2008 1 commit
  39. 19 Apr, 2008 2 commits
  41. 20 Mar, 2008 1 commit
    • Randy Dunlap's avatar
      fs: fix kernel-doc notation warnings · a6b91919
      Randy Dunlap authored 
      
Fix kernel-doc notation warnings in fs/.

Warning(mmotm-2008-0314-1449//fs/super.c:560): missing initial short description on line:
 *	mark_files_ro
Warning(mmotm-2008-0314-1449//fs/locks.c:1277): missing initial short description on line:
 *	lease_get_mtime
Warning(mmotm-2008-0314-1449//fs/locks.c:1277): missing initial short description on line:
 *	lease_get_mtime
Warning(mmotm-2008-0314-1449//fs/namei.c:1368): missing initial short description on line:
 * lookup_one_len:  filesystem helper to lookup single pathname component
Warning(mmotm-2008-0314-1449//fs/buffer.c:3221): missing initial short description on line:
 * bh_uptodate_or_lock: Test whether the buffer is uptodate
Warning(mmotm-2008-0314-1449//fs/buffer.c:3240): missing initial short description on line:
 * bh_submit_read: Submit a locked buffer for reading
Warning(mmotm-2008-0314-1449//fs/fs-writeback.c:30): missing initial short description on line:
 * writeback_acquire: attempt to get exclusive writeback access to a device
Warning(mmotm-2008-0314-1449//fs/fs-writeback.c:47): missing initial short description on line:
 * writeback_in_progress: determine whether there is writeback in progress
Warning(mmotm-2008-0314-1449//fs/fs-writeback.c:58): missing initial short description on line:
 * writeback_release: relinquish exclusive writeback access against a device.
Warning(mmotm-2008-0314-1449//include/linux/jbd.h:351): contents before sections
Warning(mmotm-2008-0314-1449//include/linux/jbd.h:561): contents before sections
Warning(mmotm-2008-0314-1449//fs/jbd/transaction.c:1935): missing initial short description on line:
 * void journal_invalidatepage()
Signed-off-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a6b91919
  43. 18 Mar, 2008 1 commit
  45. 05 Mar, 2008 1 commit
    • Eric Paris's avatar
      LSM/SELinux: Interfaces to allow FS to control mount options · e0007529
      Eric Paris authored 
      
Introduce new LSM interfaces to allow an FS to deal with their own mount
options.  This includes a new string parsing function exported from the
LSM that an FS can use to get a security data blob and a new security
data blob.  This is particularly useful for an FS which uses binary
mount data, like NFS, which does not pass strings into the vfs to be
handled by the loaded LSM.  Also fix a BUG() in both SELinux and SMACK
when dealing with binary mount data.  If the binary mount data is less
than one page the copy_page() in security_sb_copy_data() can cause an
illegal page fault and boom.  Remove all NFSisms from the SELinux code
since they were broken by past NFS changes.
Signed-off-by: default avatarEric Paris <eparis@redhat.com>
Acked-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
Acked-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      e0007529
  47. 08 Feb, 2008 2 commits
  49. 19 Oct, 2007 5 commits
  51. 17 Oct, 2007 1 commit
    • Ken Chen's avatar
      writeback: fix periodic superblock dirty inode flushing · 0e0f4fc2
      Ken Chen authored 
      
Current -mm tree has bucketful of bug fixes in periodic writeback path.
However, we still hit a glitch where dirty pages on a given inode aren't
completely flushed to the disk, and system will accumulate large amount of
dirty pages beyond what dirty_expire_interval is designed for.

The problem is __sync_single_inode() will move an inode to sb->s_dirty list
even when there are more pending dirty pages on that inode.  If there is
another inode with a small number of dirty pages, we hit a case where the loop
iteration in wb_kupdate() terminates prematurely because wbc.nr_to_write > 0.
Thus leaving the inode that has large amount of dirty pages behind and it has
to wait for another dirty_writeback_interval before we flush it again.  We
effectively only write out MAX_WRITEBACK_PAGES every dirty_writeback_interval.
If the rate of dirtying is sufficiently high, the system will start
accumulate a large number of dirty pages.

So fix it by having another sb->s_more_io list on which to park the inode
while we iterate through sb->s_io and to allow each dirty inode which resides
on that sb to have an equal chance of flushing some amount of dirty pages.
Signed-off-by: default avatarKen Chen <kenchen@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0e0f4fc2
  53. 16 Jul, 2007 1 commit
    • Lee Schermerhorn's avatar
      hugetlbfs: handle empty options string · b4c07bce
      Lee Schermerhorn authored 
      
I was seeing a null pointer deref in fs/super.c:vfs_kern_mount().
Some file system get_sb() handler was returning NULL mnt_sb with
a non-negative return value.  I also noticed a "hugetlbfs: Bad
mount option:" message in the log.

Turns out that hugetlbfs_parse_options() was not checking for an
empty option string after call to strsep().  On failure,
hugetlbfs_parse_options() returns 1.  hugetlbfs_fill_super() just
passed this return code back up the call stack where
vfs_kern_mount() missed the error and proceeded with a NULL mnt_sb.

Apparently introduced by patch:
	hugetlbfs-use-lib-parser-fix-docs.patch

The problem was exposed by this line in my fstab:

none        /huge       hugetlbfs   defaults    0 0

It can also be demonstrated by invoking mount of hugetlbfs
directly with no options or a bogus option.

This patch:

1) adds the check for empty option to hugetlbfs_parse_options(),
2) enhances the error message to bracket any unrecognized
   option with quotes ,
3) modifies hugetlbfs_parse_options() to return -EINVAL on any
   unrecognized option,
4) adds a BUG_ON() to vfs_kern_mount() to catch any get_sb()
   handler that returns a NULL mnt->mnt_sb with a return value
   >= 0.
Signed-off-by: default avatarLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b4c07bce
  55. 08 May, 2007 1 commit
    • Miklos Szeredi's avatar
      add filesystem subtype support · 79c0b2df
      Miklos Szeredi authored 
      
There's a slight problem with filesystem type representation in fuse
based filesystems.

From the kernel's view, there are just two filesystem types: fuse and
fuseblk.  From the user's view there are lots of different filesystem
types.  The user is not even much concerned if the filesystem is fuse based
or not.  So there's a conflict of interest in how this should be
represented in fstab, mtab and /proc/mounts.

The current scheme is to encode the real filesystem type in the mount
source.  So an sshfs mount looks like this:

  sshfs#user@server:/   /mnt/server    fuse   rw,nosuid,nodev,...

This url-ish syntax works OK for sshfs and similar filesystems.  However
for block device based filesystems (ntfs-3g, zfs) it doesn't work, since
the kernel expects the mount source to be a real device name.

A possibly better scheme would be to encode the real type in the type
field as "type.subtype".  So fuse mounts would look like this:

  /dev/hda1       /mnt/windows   fuseblk.ntfs-3g   rw,...
  user@server:/   /mnt/server    fuse.sshfs        rw,nosuid,nodev,...

This patch adds the necessary code to the kernel so that this can be
correctly displayed in /proc/mounts.
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      79c0b2df
  57. 27 Apr, 2007 1 commit
  59. 12 Feb, 2007 1 commit
  61. 12 Jan, 2007 1 commit