mmotm 2009-07-16-14-32 - lockdep whinge in ext3/quota code

[Valdis . Kletnieks]

Saw this while bisecting to find another issue.

quilt top:
memcg-add-comments-explaining-memory-barriers-checkpatch-fixes.patch

Some checking doesn't look like any of the 58 patches after that are
relevant (only the reiser4 patch references quotas, no grep hits for lockdep
or ext3).

About 30 seconds after boot:

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.31-rc3 #2
-------------------------------------------------------
rm/1562 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#11/4){+.+...}, at: [<ffffffff81139fd9>] ext3_quota_write+0xb5/0x274

but task is already holding lock:
 (&s->s_dquot.dqio_mutex){+.+...}, at: [<ffffffff811153d5>] dquot_commit+0x26/0xee

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&s->s_dquot.dqio_mutex){+.+...}:
       [<ffffffff81067010>] __lock_acquire+0xa1b/0xb97
       [<ffffffff81067278>] lock_acquire+0xec/0x110
       [<ffffffff814a04af>] __mutex_lock_common+0x5a/0x54e
       [<ffffffff814a0a43>] mutex_lock_nested+0x32/0x37
       [<ffffffff81115b54>] vfs_load_quota_inode+0x264/0x496
       [<ffffffff81116094>] vfs_quota_on_path+0x4c/0x55
       [<ffffffff81138e9d>] ext3_quota_on+0x14c/0x167
       [<ffffffff81119e4f>] do_quotactl+0xf4/0x44c
       [<ffffffff8111a491>] sys_quotactl+0x2ea/0x30e
       [<ffffffff8100b2ab>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

-> #0 (&sb->s_type->i_mutex_key#11/4){+.+...}:
       [<ffffffff81066eed>] __lock_acquire+0x8f8/0xb97
       [<ffffffff81067278>] lock_acquire+0xec/0x110
       [<ffffffff814a04af>] __mutex_lock_common+0x5a/0x54e
       [<ffffffff814a0a43>] mutex_lock_nested+0x32/0x37
       [<ffffffff81139fd9>] ext3_quota_write+0xb5/0x274
       [<ffffffff81119bd3>] qtree_write_dquot+0xce/0x127
       [<ffffffff81118924>] v2_write_dquot+0x27/0x29
       [<ffffffff8111544c>] dquot_commit+0x9d/0xee
       [<ffffffff8113a8ae>] ext3_write_dquot+0x69/0x8a
       [<ffffffff8111713f>] dqput+0x138/0x25c
       [<ffffffff81117993>] dquot_drop+0x6a/0x74
       [<ffffffff8111509f>] vfs_dq_drop+0x41/0x43
       [<ffffffff81130cba>] ext3_free_inode+0x96/0x28c
       [<ffffffff81134cce>] ext3_delete_inode+0xbf/0xdd
       [<ffffffff810e357d>] generic_delete_inode+0x135/0x1db
       [<ffffffff810e363a>] generic_drop_inode+0x17/0x56
       [<ffffffff810e252d>] iput+0x7a/0x7f
       [<ffffffff810db906>] do_unlinkat+0x123/0x176
       [<ffffffff810dbab8>] sys_unlinkat+0x24/0x26
       [<ffffffff8100b2ab>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

other info that might help us debug this:

2 locks held by rm/1562:
 #0:  (jbd_handle){+.+...}, at: [<ffffffff811433c9>] journal_start+0x10a/0x137
 #1:  (&s->s_dquot.dqio_mutex){+.+...}, at: [<ffffffff811153d5>] dquot_commit+0x26/0xee

stack backtrace:
Pid: 1562, comm: rm Not tainted 2.6.31-rc3 #2
Call Trace:
 [<ffffffff81066290>] print_circular_bug_tail+0x71/0x7c
 [<ffffffff81066eed>] __lock_acquire+0x8f8/0xb97
 [<ffffffff81139fd9>] ? ext3_quota_write+0xb5/0x274
 [<ffffffff81067278>] lock_acquire+0xec/0x110
 [<ffffffff81139fd9>] ? ext3_quota_write+0xb5/0x274
 [<ffffffff814a04af>] __mutex_lock_common+0x5a/0x54e
 [<ffffffff81139fd9>] ? ext3_quota_write+0xb5/0x274
 [<ffffffff810665e4>] ? check_irq_usage+0xad/0xbe
 [<ffffffff81139fd9>] ? ext3_quota_write+0xb5/0x274
 [<ffffffff810670e2>] ? __lock_acquire+0xaed/0xb97
 [<ffffffff814a0a43>] mutex_lock_nested+0x32/0x37
 [<ffffffff81139fd9>] ext3_quota_write+0xb5/0x274
 [<ffffffff81119bd3>] qtree_write_dquot+0xce/0x127
 [<ffffffff81034c90>] ? get_parent_ip+0x11/0x42
 [<ffffffff81118924>] v2_write_dquot+0x27/0x29
 [<ffffffff8111544c>] dquot_commit+0x9d/0xee
 [<ffffffff8113a8ae>] ext3_write_dquot+0x69/0x8a
 [<ffffffff8111713f>] dqput+0x138/0x25c
 [<ffffffff81117993>] dquot_drop+0x6a/0x74
 [<ffffffff8111509f>] vfs_dq_drop+0x41/0x43
 [<ffffffff81130cba>] ext3_free_inode+0x96/0x28c
 [<ffffffff81131d63>] ? ext3_mark_inode_dirty+0x48/0x53
 [<ffffffff81134cce>] ext3_delete_inode+0xbf/0xdd
 [<ffffffff81134c0f>] ? ext3_delete_inode+0x0/0xdd
 [<ffffffff810e357d>] generic_delete_inode+0x135/0x1db
 [<ffffffff810e363a>] generic_drop_inode+0x17/0x56
 [<ffffffff810e252d>] iput+0x7a/0x7f
 [<ffffffff810db906>] do_unlinkat+0x123/0x176
 [<ffffffff8107d440>] ? audit_syscall_entry+0x170/0x19c
 [<ffffffff810dbab8>] sys_unlinkat+0x24/0x26
 [<ffffffff8100b2ab>] system_call_fastpath+0x16/0x1b

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