Hi,
I hit the following lockdep trace on linux-4.2.8 and I could steadily
re-produce it on some of my machine. Although the trace shows up, the
file system works quite well without seeing any operations being stuck
on it. Does it mean that the trace is just a false alarm? Thanks.
BTW, I've saw some similar traces previously in the mailing list and
found that the patch, "ext4: add lockdep annotations for i_data_sem
(daf647d2dd58)", which is already included in my kernel.
======================================================
<4>[ 205.633705] [ INFO: possible circular locking dependency detected ]
<4>[ 205.639962] 4.2.8 #3 Tainted: G W O
<4>[ 205.644395] -------------------------------------------------------
<4>[ 205.650650] rm/19302 is trying to acquire lock:
<4>[ 205.655174] (&s->s_dquot.dqio_mutex){+.+...}, at:
[<ffffffff81250678>] dquot_commit+0x28/0xc0
<4>[ 205.663835]
<4>[ 205.663835] but task is already holding lock:
<4>[ 205.669659] (&ei->i_data_sem){++++..}, at: [<ffffffff812b2329>]
ext4_truncate+0x379/0x680
<4>[ 205.677960]
<4>[ 205.677960] which lock already depends on the new lock.
<4>[ 205.677960]
<4>[ 205.686119]
<4>[ 205.686119] the existing dependency chain (in reverse order) is:
<4>[ 205.693586]
<4>[ 205.693586] -> #1 (&ei->i_data_sem){++++..}:
<4>[ 205.698071] [<ffffffff810cde05>] lock_acquire+0xd5/0x280
<4>[ 205.703995] [<ffffffff81c82727>] down_read+0x47/0x60
<4>[ 205.709573] [<ffffffff812acefb>] ext4_map_blocks+0x48b/0x5f0
<4>[ 205.715845] [<ffffffff812ad653>] ext4_getblk+0x43/0x190
<4>[ 205.721682] [<ffffffff812ad7ae>] ext4_bread+0xe/0xa0
<4>[ 205.727260] [<ffffffff812c225d>] ext4_quota_read+0xcd/0x110
<4>[ 205.733442] [<ffffffff81254687>] read_blk+0x47/0x50
<4>[ 205.738933] [<ffffffff81255452>] find_tree_dqentry+0x42/0x230
<4>[ 205.745290] [<ffffffff812555b4>] find_tree_dqentry+0x1a4/0x230
<4>[ 205.751730] [<ffffffff812555b4>] find_tree_dqentry+0x1a4/0x230
<4>[ 205.758172] [<ffffffff812555b4>] find_tree_dqentry+0x1a4/0x230
<4>[ 205.764612] [<ffffffff81255773>] qtree_read_dquot+0x133/0x260
<4>[ 205.770968] [<ffffffff81253d89>] v2_read_dquot+0x29/0x30
<4>[ 205.776892] [<ffffffff8124f7f6>] dquot_acquire+0xe6/0x130
<4>[ 205.782902] [<ffffffff812c1c9a>] ext4_acquire_dquot+0x6a/0xb0
<4>[ 205.789258] [<ffffffff81251970>] dqget+0x3c0/0x420
<4>[ 205.794662] [<ffffffff81251afd>] __dquot_initialize+0x12d/0x230
<4>[ 205.801187] [<ffffffff81251c0e>] dquot_initialize+0xe/0x10
<4>[ 205.807283] [<ffffffff812d215b>] ext4_fill_super+0x2d9b/0x3150
<4>[ 205.813729] [<ffffffff811e0f00>] mount_bdev+0x180/0x1b0
<4>[ 205.819566] [<ffffffff812c18c0>] ext4_mount+0x10/0x20
<4>[ 205.825230] [<ffffffff811e17a4>] mount_fs+0x14/0xa0
<4>[ 205.830719] [<ffffffff81203736>] vfs_kern_mount+0x66/0x150
<4>[ 205.836815] [<ffffffff812066a5>] do_mount+0x1e5/0xd00
<4>[ 205.842476] [<ffffffff812074b6>] SyS_mount+0x86/0xc0
<4>[ 205.848048] [<ffffffff81c84bd7>]
entry_SYSCALL_64_fastpath+0x12/0x6f
<4>[ 205.855010]
<4>[ 205.855010] -> #0 (&s->s_dquot.dqio_mutex){+.+...}:
<4>[ 205.860103] [<ffffffff810ccccc>] __lock_acquire+0x1fdc/0x23a0
<4>[ 205.866464] [<ffffffff810cde05>] lock_acquire+0xd5/0x280
<4>[ 205.872393] [<ffffffff81c80990>] mutex_lock_nested+0x60/0x370
<4>[ 205.878753] [<ffffffff81250678>] dquot_commit+0x28/0xc0
<4>[ 205.884594] [<ffffffff812c1d4e>] ext4_write_dquot+0x6e/0xa0
<4>[ 205.890783] [<ffffffff812c1dbe>] ext4_mark_dquot_dirty+0x3e/0x60
<4>[ 205.897408] [<ffffffff81250857>] __dquot_free_space+0x147/0x310
<4>[ 205.903943] [<ffffffff812ebe0d>] ext4_free_blocks+0x77d/0x1010
<4>[ 205.910390] [<ffffffff812dbb66>] ext4_ext_remove_space+0x8f6/0x16a0
<4>[ 205.917271] [<ffffffff812de49f>] ext4_ext_truncate+0xaf/0xe0
<4>[ 205.923547] [<ffffffff812b23f0>] ext4_truncate+0x440/0x680
<4>[ 205.929651] [<ffffffff812b2a9f>] ext4_evict_inode+0x46f/0x730
<4>[ 205.936017] [<ffffffff811fe473>] evict+0xb3/0x180
<4>[ 205.941337] [<ffffffff811fecc7>] iput+0x187/0x350
<4>[ 205.946662] [<ffffffff811f0243>] do_unlinkat+0x163/0x340
<4>[ 205.952588] [<ffffffff811f0481>] SyS_unlink+0x11/0x20
<4>[ 205.958258] [<ffffffff81c84bd7>]
entry_SYSCALL_64_fastpath+0x12/0x6f
<4>[ 205.965226]
<4>[ 205.965226] other info that might help us debug this:
<4>[ 205.965226]
<4>[ 205.973217] Possible unsafe locking scenario:
<4>[ 205.973217]
<4>[ 205.979127] CPU0 CPU1
<4>[ 205.983652] ---- ----
<4>[ 205.988174] lock(&ei->i_data_sem);
<4>[ 205.991772] lock(&s->s_dquot.dqio_mutex);
<4>[ 205.998487] lock(&ei->i_data_sem);
<4>[ 206.004596] lock(&s->s_dquot.dqio_mutex);
<4>[ 206.008795]
<4>[ 206.008795] *** DEADLOCK ***
<4>[ 206.008795]
<4>[ 206.014708] 5 locks held by rm/19302:
<4>[ 206.018364] #0: (sb_writers#10){.+.+.+}, at:
[<ffffffff81204bbf>] mnt_want_write+0x1f/0x50
<4>[ 206.026870] #1: (sb_internal){.+.+..}, at:
[<ffffffff812b27a9>] ext4_evict_inode+0x179/0x730
<4>[ 206.035538] #2: (jbd2_handle){+.+...}, at:
[<ffffffff81306cc1>] start_this_handle+0x191/0x630
<4>[ 206.044298] #3: (&ei->i_data_sem){++++..}, at:
[<ffffffff812b2329>] ext4_truncate+0x379/0x680
<4>[ 206.053052] #4: (dquot_srcu){......}, at: [<ffffffff8125076a>]
__dquot_free_space+0x5a/0x310
<4>[ 206.061719]
<4>[ 206.061719] stack backtrace:
<4>[ 206.066072] CPU: 0 PID: 19302 Comm: rm Tainted: G W O 4.2.8 #3
<4>[ 206.072848] Hardware name: To be filled by O.E.M. To be filled
by O.E.M./MAHOBAY, BIOS QC30AR23 08/14/2014
<4>[ 206.082486] ffffffff82effc40 ffff88004cebf7d8 ffffffff81c767eb
0000000000000007
<4>[ 206.089919] ffffffff82effc40 ffff88004cebf828 ffffffff81c739cd
ffff880044724e08
<4>[ 206.097364] ffff88004cebf898 ffff88004cebf828 0000000000000005
ffff880044724640
<4>[ 206.104807] Call Trace:
<4>[ 206.107257] [<ffffffff81c767eb>] dump_stack+0x4c/0x65
<4>[ 206.112393] [<ffffffff81c739cd>] print_circular_bug+0x202/0x213
<4>[ 206.118394] [<ffffffff810ccccc>] __lock_acquire+0x1fdc/0x23a0
<4>[ 206.124222] [<ffffffff810cde05>] lock_acquire+0xd5/0x280
<4>[ 206.129616] [<ffffffff81250678>] ? dquot_commit+0x28/0xc0
<4>[ 206.135099] [<ffffffff81c80990>] mutex_lock_nested+0x60/0x370
<4>[ 206.140931] [<ffffffff81250678>] ? dquot_commit+0x28/0xc0
<4>[ 206.146414] [<ffffffff812c1d3a>] ? ext4_write_dquot+0x5a/0xa0
<4>[ 206.152245] [<ffffffff8130784a>] ? jbd2__journal_start+0x1a/0x20
<4>[ 206.158766] [<ffffffff81250678>] dquot_commit+0x28/0xc0
<4>[ 206.164074] [<ffffffff812c1d4e>] ext4_write_dquot+0x6e/0xa0
<4>[ 206.169731] [<ffffffff812c1dbe>] ext4_mark_dquot_dirty+0x3e/0x60
<4>[ 206.175821] [<ffffffff81250857>] __dquot_free_space+0x147/0x310
<4>[ 206.181825] [<ffffffff8125076a>] ? __dquot_free_space+0x5a/0x310
<4>[ 206.187917] [<ffffffff812ebc62>] ? ext4_free_blocks+0x5d2/0x1010
<4>[ 206.194005] [<ffffffff812ebe0d>] ext4_free_blocks+0x77d/0x1010
<4>[ 206.199920] [<ffffffff810ca7e1>] ? mark_held_locks+0x71/0x90
<4>[ 206.205662] [<ffffffff811cadc6>] ? __kmalloc+0xa6/0x5d0
<4>[ 206.210972] [<ffffffff810c8f4d>] ? __lock_is_held+0x4d/0x70
<4>[ 206.216627] [<ffffffff812db2ca>] ? ext4_ext_remove_space+0x5a/0x16a0
<4>[ 206.223061] [<ffffffff812dbb66>] ext4_ext_remove_space+0x8f6/0x16a0
<4>[ 206.229412] [<ffffffff812de49f>] ext4_ext_truncate+0xaf/0xe0
<4>[ 206.235157] [<ffffffff812b23f0>] ext4_truncate+0x440/0x680
<4>[ 206.240723] [<ffffffff812b2a9f>] ext4_evict_inode+0x46f/0x730
<4>[ 206.246551] [<ffffffff811fe473>] evict+0xb3/0x180
<4>[ 206.251339] [<ffffffff811fecc7>] iput+0x187/0x350
<4>[ 206.256129] [<ffffffff811f0243>] do_unlinkat+0x163/0x340
<4>[ 206.261525] [<ffffffff812041c0>] ? mnt_get_count+0x60/0x60
<4>[ 206.267092] [<ffffffff81002044>] ? lockdep_sys_exit_thunk+0x12/0x14
<4>[ 206.273441] [<ffffffff811f0481>] SyS_unlink+0x11/0x20
<4>[ 206.278578] [<ffffffff81c84bd7>] entry_SYSCALL_64_fastpath+0x12/0x6f
