3.7.0-rc8 btrfs locking issue

Jim Schutt
2012-12-05T16:24:48Z

Hi,

I'm hitting a btrfs locking issue with 3.7.0-rc8.

The btrfs filesystem in question is backing a Ceph OSD
under a heavy write load from many cephfs clients.

I reported this issue a while ago:
http://www.spinics.net/lists/linux-btrfs/msg19370.html
when I was testing what I thought might be part of the
3.7 btrfs patch queue, using Josef Bacik's btrfs-next tree.

I spent some time attempting to bisect the btrfs patch queue
just before it was merged for 3.7, but got nowhere due to
false negatives.

I've just been able to get back to testing 3.7-rc, and found
that I can still trigger the issue.

First I get this lockdep splat:

[ 1184.201331] =============================================
[ 1184.206716] [ INFO: possible recursive locking detected ]
[ 1184.212111] 3.7.0-rc8-00013-gdf2fc24 #438 Not tainted
[ 1184.217156] ---------------------------------------------
[ 1184.222544] ceph-osd/42177 is trying to acquire lock:
[ 1184.227589] (&fs_info->chunk_mutex){+.+...}, at: [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.237270]
[ 1184.237270] but task is already holding lock:
[ 1184.243114] (&fs_info->chunk_mutex){+.+...}, at: [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.252786]
[ 1184.252786] other info that might help us debug this:
[ 1184.259303] Possible unsafe locking scenario:
[ 1184.259303]
[ 1184.265220] CPU0
[ 1184.267680] ----
[ 1184.270133] lock(&fs_info->chunk_mutex);
[ 1184.274276] lock(&fs_info->chunk_mutex);
[ 1184.278417]
[ 1184.278417] *** DEADLOCK ***
[ 1184.278417]
[ 1184.284325] May be due to missing lock nesting notation
[ 1184.284325]
[ 1184.291099] 4 locks held by ceph-osd/42177:
[ 1184.295277] #0: (sb_writers#7){.+.+.+}, at: [<ffffffffa0584664>] btrfs_file_aio_write+0x64/0x320 [btrfs]
[ 1184.305103] #1: (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffffa058466e>] btrfs_file_aio_write+0x6e/0x320 [btrfs]
[ 1184.316108] #2: (sb_internal){.+.+..}, at: [<ffffffffa05746f4>] start_transaction+0x1c4/0x450 [btrfs]
[ 1184.325632] #3: (&fs_info->chunk_mutex){+.+...}, at: [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.335761]
[ 1184.335761] stack backtrace:
[ 1184.340126] Pid: 42177, comm: ceph-osd Not tainted 3.7.0-rc8-00013-gdf2fc24 #438
[ 1184.347508] Call Trace:
[ 1184.349962] [<ffffffff81042eca>] ? vprintk_emit+0x42a/0x4c0
[ 1184.355619] [<ffffffff8109b579>] print_deadlock_bug+0xe9/0x100
[ 1184.361556] [<ffffffff8109d246>] validate_chain+0x596/0x750
[ 1184.367222] [<ffffffff8109d849>] __lock_acquire+0x449/0x510
[ 1184.372894] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.379417] [<ffffffff8109d9d9>] lock_acquire+0xc9/0x120
[ 1184.384855] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.391377] [<ffffffff8109d849>] ? __lock_acquire+0x449/0x510
[ 1184.397204] [<ffffffff814ab17d>] __mutex_lock_common+0x5d/0x3a0
[ 1184.403221] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.409762] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.416323] [<ffffffffa055a5c9>] ? do_chunk_alloc+0x179/0x340 [btrfs]
[ 1184.422849] [<ffffffff814ab62a>] mutex_lock_nested+0x4a/0x60
[ 1184.428640] [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1184.435018] [<ffffffffa05635bc>] find_free_extent+0xa3c/0xb70 [btrfs]
[ 1184.441555] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1184.449051] [<ffffffffa0563772>] btrfs_reserve_extent+0x82/0x190 [btrfs]
[ 1184.455843] [<ffffffffa0563905>] btrfs_alloc_free_block+0x85/0x230 [btrfs]
[ 1184.462828] [<ffffffffa054fb6a>] __btrfs_cow_block+0x14a/0x4b0 [btrfs]
[ 1184.469471] [<ffffffffa05a50d3>] ? btrfs_set_lock_blocking_rw+0xe3/0x160 [btrfs]
[ 1184.476962] [<ffffffffa055056d>] btrfs_cow_block+0x18d/0x230 [btrfs]
[ 1184.483426] [<ffffffffa0553460>] btrfs_search_slot+0x360/0x730 [btrfs]
[ 1184.490067] [<ffffffffa055426d>] btrfs_insert_empty_items+0x8d/0x100 [btrfs]
[ 1184.497199] [<ffffffff81159be3>] ? kmem_cache_alloc+0xd3/0x170
[ 1184.503151] [<ffffffffa0596f25>] btrfs_alloc_dev_extent+0xb5/0x190 [btrfs]
[ 1184.510125] [<ffffffffa059b0d7>] __btrfs_alloc_chunk+0x6a7/0x750 [btrfs]
[ 1184.516928] [<ffffffffa059b1de>] btrfs_alloc_chunk+0x5e/0x90 [btrfs]
[ 1184.523374] [<ffffffffa055a391>] ? check_system_chunk+0x71/0x130 [btrfs]
[ 1184.530179] [<ffffffffa055a71e>] do_chunk_alloc+0x2ce/0x340 [btrfs]
[ 1184.536555] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1184.544070] [<ffffffffa055e35c>] btrfs_check_data_free_space+0x13c/0x2b0 [btrfs]
[ 1184.551574] [<ffffffffa055ff00>] btrfs_delalloc_reserve_space+0x20/0x60 [btrfs]
[ 1184.558987] [<ffffffffa05842de>] __btrfs_buffered_write+0x15e/0x350 [btrfs]
[ 1184.566042] [<ffffffffa0584809>] btrfs_file_aio_write+0x209/0x320 [btrfs]
[ 1184.572944] [<ffffffffa0584600>] ? __btrfs_direct_write+0x130/0x130 [btrfs]
[ 1184.579984] [<ffffffff81165014>] do_sync_readv_writev+0x94/0xe0
[ 1184.585985] [<ffffffff81166023>] do_readv_writev+0xe3/0x1e0
[ 1184.591645] [<ffffffff81183112>] ? fget_light+0x122/0x170
[ 1184.597131] [<ffffffff81166166>] vfs_writev+0x46/0x60
[ 1184.602266] [<ffffffff8116629f>] sys_writev+0x5f/0xc0
[ 1184.607398] [<ffffffff81264b6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 1184.613832] [<ffffffff814b7042>] system_call_fastpath+0x16/0x1b

and then a little later:

[ 1319.463719] INFO: task ceph-osd:42177 blocked for more than 120 seconds.
[ 1319.470409] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1319.478227] ceph-osd D 0000000000000246 0 42177 1 0x00000000
[ 1319.485330] ffff880402c4d358 0000000000000046 00007fffeccc49d0 ffff880402c4dfd8
[ 1319.492852] ffff880402c4c010 ffff880402c4c000 ffff880402c4c000 ffff880402c4c000
[ 1319.500449] ffff880402c4dfd8 ffff880402c4c000 ffff880c2151bec0 ffff8804e9403ec0
[ 1319.508012] Call Trace:
[ 1319.510495] [<ffffffff814acc5d>] schedule+0x5d/0x60
[ 1319.515478] [<ffffffff814acf67>] schedule_preempt_disabled+0x27/0x40
[ 1319.521967] [<ffffffff814ab375>] __mutex_lock_common+0x255/0x3a0
[ 1319.528090] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1319.534659] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1319.541264] [<ffffffff814ab62a>] mutex_lock_nested+0x4a/0x60
[ 1319.547118] [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1319.553532] [<ffffffffa05635bc>] find_free_extent+0xa3c/0xb70 [btrfs]
[ 1319.560122] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1319.567620] [<ffffffffa0563772>] btrfs_reserve_extent+0x82/0x190 [btrfs]
[ 1319.574460] [<ffffffffa0563905>] btrfs_alloc_free_block+0x85/0x230 [btrfs]
[ 1319.581464] [<ffffffffa054fb6a>] __btrfs_cow_block+0x14a/0x4b0 [btrfs]
[ 1319.588117] [<ffffffffa05a50d3>] ? btrfs_set_lock_blocking_rw+0xe3/0x160 [btrfs]
[ 1319.595644] [<ffffffffa055056d>] btrfs_cow_block+0x18d/0x230 [btrfs]
[ 1319.602110] [<ffffffffa0553460>] btrfs_search_slot+0x360/0x730 [btrfs]
[ 1319.608767] [<ffffffffa055426d>] btrfs_insert_empty_items+0x8d/0x100 [btrfs]
[ 1319.615897] [<ffffffff81159be3>] ? kmem_cache_alloc+0xd3/0x170
[ 1319.621910] [<ffffffffa0596f25>] btrfs_alloc_dev_extent+0xb5/0x190 [btrfs]
[ 1319.628893] [<ffffffffa059b0d7>] __btrfs_alloc_chunk+0x6a7/0x750 [btrfs]
[ 1319.635736] [<ffffffffa059b1de>] btrfs_alloc_chunk+0x5e/0x90 [btrfs]
[ 1319.642184] [<ffffffffa055a391>] ? check_system_chunk+0x71/0x130 [btrfs]
[ 1319.649009] [<ffffffffa055a71e>] do_chunk_alloc+0x2ce/0x340 [btrfs]
[ 1319.655366] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1319.662935] [<ffffffffa055e35c>] btrfs_check_data_free_space+0x13c/0x2b0 [btrfs]
[ 1319.670465] [<ffffffffa055ff00>] btrfs_delalloc_reserve_space+0x20/0x60 [btrfs]
[ 1319.677891] [<ffffffffa05842de>] __btrfs_buffered_write+0x15e/0x350 [btrfs]
[ 1319.685000] [<ffffffffa0584809>] btrfs_file_aio_write+0x209/0x320 [btrfs]
[ 1319.691952] [<ffffffffa0584600>] ? __btrfs_direct_write+0x130/0x130 [btrfs]
[ 1319.699054] [<ffffffff81165014>] do_sync_readv_writev+0x94/0xe0
[ 1319.705118] [<ffffffff81166023>] do_readv_writev+0xe3/0x1e0
[ 1319.710828] [<ffffffff81183112>] ? fget_light+0x122/0x170
[ 1319.716324] [<ffffffff81166166>] vfs_writev+0x46/0x60
[ 1319.721466] [<ffffffff8116629f>] sys_writev+0x5f/0xc0
[ 1319.726674] [<ffffffff81264b6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 1319.733198] [<ffffffff814b7042>] system_call_fastpath+0x16/0x1b
[ 1319.739274] INFO: lockdep is turned off.
[ 1319.743261] INFO: task ceph-osd:42236 blocked for more than 120 seconds.
[ 1319.749953] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1319.757812] ceph-osd D 0000000000000246 0 42236 1 0x00000000
[ 1319.765056] ffff88052e7bdcc8 0000000000000046 ffff880624666120 ffff88052e7bdfd8
[ 1319.772785] ffff88052e7bc010 ffff88052e7bc000 ffff88052e7bc000 ffff88052e7bc000
[ 1319.780332] ffff88052e7bdfd8 ffff88052e7bc000 ffff88062453bec0 ffff88052e7b5e20
[ 1319.787905] Call Trace:
[ 1319.790368] [<ffffffff814acc5d>] schedule+0x5d/0x60
[ 1319.795335] [<ffffffff814acf67>] schedule_preempt_disabled+0x27/0x40
[ 1319.801762] [<ffffffff814ab375>] __mutex_lock_common+0x255/0x3a0
[ 1319.807861] [<ffffffffa0548b4f>] ? btrfs_statfs+0x5f/0x240 [btrfs]
[ 1319.814143] [<ffffffff811703cf>] ? final_putname+0x3f/0x50
[ 1319.819724] [<ffffffffa0548b4f>] ? btrfs_statfs+0x5f/0x240 [btrfs]
[ 1319.825982] [<ffffffff814ab62a>] mutex_lock_nested+0x4a/0x60
[ 1319.831731] [<ffffffffa0548b4f>] btrfs_statfs+0x5f/0x240 [btrfs]
[ 1319.837846] [<ffffffff811968c0>] statfs_by_dentry+0x60/0x90
[ 1319.843508] [<ffffffff81196a0b>] vfs_statfs+0x1b/0xb0
[ 1319.848659] [<ffffffff81196c00>] user_statfs+0x40/0x60
[ 1319.853887] [<ffffffff81196caa>] sys_statfs+0x2a/0x50
[ 1319.859036] [<ffffffff814b7042>] system_call_fastpath+0x16/0x1b
[ 1319.865035] INFO: lockdep is turned off.

and then later still:

[ 1439.546768] INFO: task btrfs-transacti:27591 blocked for more than 120 seconds.
[ 1439.554139] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1439.561949] btrfs-transacti D ffff880993231810 0 27591 2 0x00000000
[ 1439.569205] ffff8808e79d3c58 0000000000000046 0000000000000000 ffff8808e79d3fd8
[ 1439.576820] ffff8808e79d2010 ffff8808e79d2000 ffff8808e79d2000 ffff8808e79d2000
[ 1439.584384] ffff8808e79d3fd8 ffff8808e79d2000 ffff880b3f165e20 ffff8808d8cdbec0
[ 1439.592040] Call Trace:
[ 1439.594573] [<ffffffff814acc5d>] schedule+0x5d/0x60
[ 1439.599646] [<ffffffff814aac3d>] schedule_timeout+0x3d/0x260
[ 1439.605402] [<ffffffff8109c410>] ? trace_hardirqs_on_caller+0x20/0x1d0
[ 1439.612023] [<ffffffff8109c5cd>] ? trace_hardirqs_on+0xd/0x10
[ 1439.617939] [<ffffffff8106781a>] ? prepare_to_wait+0x7a/0x90
[ 1439.623788] [<ffffffffa0573a46>] btrfs_commit_transaction+0x336/0xa10 [btrfs]
[ 1439.631128] [<ffffffffa05748fb>] ? start_transaction+0x3cb/0x450 [btrfs]
[ 1439.637943] [<ffffffff810674e0>] ? wake_up_bit+0x40/0x40
[ 1439.643380] [<ffffffffa056c223>] transaction_kthread+0x123/0x210 [btrfs]
[ 1439.650259] [<ffffffffa056c100>] ? btrfs_bio_wq_end_io+0x90/0x90 [btrfs]
[ 1439.657134] [<ffffffff81066dd1>] kthread+0xe1/0xf0
[ 1439.662109] [<ffffffff81066cf0>] ? __init_kthread_worker+0x70/0x70
[ 1439.668398] [<ffffffff814b6f9c>] ret_from_fork+0x7c/0xb0
[ 1439.673858] [<ffffffff81066cf0>] ? __init_kthread_worker+0x70/0x70
[ 1439.680181] INFO: lockdep is turned off.
[ 1439.685095] INFO: task ceph-osd:42177 blocked for more than 120 seconds.
[ 1439.691847] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1439.699743] ceph-osd D 0000000000000246 0 42177 1 0x00000000
[ 1439.706941] ffff880402c4d358 0000000000000046 00007fffeccc49d0 ffff880402c4dfd8
[ 1439.714494] ffff880402c4c010 ffff880402c4c000 ffff880402c4c000 ffff880402c4c000
[ 1439.722039] ffff880402c4dfd8 ffff880402c4c000 ffff880c2151bec0 ffff8804e9403ec0
[ 1439.729688] Call Trace:
[ 1439.732217] [<ffffffff814acc5d>] schedule+0x5d/0x60
[ 1439.737179] [<ffffffff814acf67>] schedule_preempt_disabled+0x27/0x40
[ 1439.743705] [<ffffffff814ab375>] __mutex_lock_common+0x255/0x3a0
[ 1439.749843] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1439.756481] [<ffffffffa055a5d3>] ? do_chunk_alloc+0x183/0x340 [btrfs]
[ 1439.763037] [<ffffffff814ab62a>] mutex_lock_nested+0x4a/0x60
[ 1439.768854] [<ffffffffa055a5d3>] do_chunk_alloc+0x183/0x340 [btrfs]
[ 1439.775290] [<ffffffffa05635bc>] find_free_extent+0xa3c/0xb70 [btrfs]
[ 1439.781932] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1439.789534] [<ffffffffa0563772>] btrfs_reserve_extent+0x82/0x190 [btrfs]
[ 1439.796474] [<ffffffffa0563905>] btrfs_alloc_free_block+0x85/0x230 [btrfs]
[ 1439.803499] [<ffffffffa054fb6a>] __btrfs_cow_block+0x14a/0x4b0 [btrfs]
[ 1439.810253] [<ffffffffa05a50d3>] ? btrfs_set_lock_blocking_rw+0xe3/0x160 [btrfs]
[ 1439.817877] [<ffffffffa055056d>] btrfs_cow_block+0x18d/0x230 [btrfs]
[ 1439.824427] [<ffffffffa0553460>] btrfs_search_slot+0x360/0x730 [btrfs]
[ 1439.831162] [<ffffffffa055426d>] btrfs_insert_empty_items+0x8d/0x100 [btrfs]
[ 1439.838423] [<ffffffff81159be3>] ? kmem_cache_alloc+0xd3/0x170
[ 1439.844514] [<ffffffffa0596f25>] btrfs_alloc_dev_extent+0xb5/0x190 [btrfs]
[ 1439.851619] [<ffffffffa059b0d7>] __btrfs_alloc_chunk+0x6a7/0x750 [btrfs]
[ 1439.858535] [<ffffffffa059b1de>] btrfs_alloc_chunk+0x5e/0x90 [btrfs]
[ 1439.865079] [<ffffffffa055a391>] ? check_system_chunk+0x71/0x130 [btrfs]
[ 1439.871939] [<ffffffffa055a71e>] do_chunk_alloc+0x2ce/0x340 [btrfs]
[ 1439.878375] [<ffffffffa05569e9>] ? btrfs_reduce_alloc_profile+0xa9/0x120 [btrfs]
[ 1439.885933] [<ffffffffa055e35c>] btrfs_check_data_free_space+0x13c/0x2b0 [btrfs]
[ 1439.893514] [<ffffffffa055ff00>] btrfs_delalloc_reserve_space+0x20/0x60 [btrfs]
[ 1439.901018] [<ffffffffa05842de>] __btrfs_buffered_write+0x15e/0x350 [btrfs]
[ 1439.908226] [<ffffffffa0584809>] btrfs_file_aio_write+0x209/0x320 [btrfs]
[ 1439.915235] [<ffffffffa0584600>] ? __btrfs_direct_write+0x130/0x130 [btrfs]
[ 1439.922375] [<ffffffff81165014>] do_sync_readv_writev+0x94/0xe0
[ 1439.928475] [<ffffffff81166023>] do_readv_writev+0xe3/0x1e0
[ 1439.934197] [<ffffffff81183112>] ? fget_light+0x122/0x170
[ 1439.939738] [<ffffffff81166166>] vfs_writev+0x46/0x60
[ 1439.944948] [<ffffffff8116629f>] sys_writev+0x5f/0xc0
[ 1439.950139] [<ffffffff81264b6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 1439.956621] [<ffffffff814b7042>] system_call_fastpath+0x16/0x1b
[ 1439.962742] INFO: lockdep is turned off.
[ 1439.966769] INFO: task ceph-osd:42236 blocked for more than 120 seconds.
[ 1439.973558] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 1439.981513] ceph-osd D 0000000000000246 0 42236 1 0x00000000
[ 1439.988788] ffff88052e7bdcc8 0000000000000046 ffff880624666120 ffff88052e7bdfd8
[ 1439.996611] ffff88052e7bc010 ffff88052e7bc000 ffff88052e7bc000 ffff88052e7bc000
[ 1440.004237] ffff88052e7bdfd8 ffff88052e7bc000 ffff88062453bec0 ffff88052e7b5e20
[ 1440.011956] Call Trace:
[ 1440.014516] [<ffffffff814acc5d>] schedule+0x5d/0x60
[ 1440.019578] [<ffffffff814acf67>] schedule_preempt_disabled+0x27/0x40
[ 1440.026054] [<ffffffff814ab375>] __mutex_lock_common+0x255/0x3a0
[ 1440.032245] [<ffffffffa0548b4f>] ? btrfs_statfs+0x5f/0x240 [btrfs]
[ 1440.038624] [<ffffffff811703cf>] ? final_putname+0x3f/0x50
[ 1440.044323] [<ffffffffa0548b4f>] ? btrfs_statfs+0x5f/0x240 [btrfs]
[ 1440.050952] [<ffffffff814ab62a>] mutex_lock_nested+0x4a/0x60
[ 1440.056805] [<ffffffffa0548b4f>] btrfs_statfs+0x5f/0x240 [btrfs]
[ 1440.063029] [<ffffffff811968c0>] statfs_by_dentry+0x60/0x90
[ 1440.068739] [<ffffffff81196a0b>] vfs_statfs+0x1b/0xb0
[ 1440.073962] [<ffffffff81196c00>] user_statfs+0x40/0x60
[ 1440.079203] [<ffffffff81196caa>] sys_statfs+0x2a/0x50
[ 1440.084401] [<ffffffff814b7042>] system_call_fastpath+0x16/0x1b
[ 1440.090816] INFO: lockdep is turned off.

Please let me know what I can do to help resolve this issue.

Thanks -- Jim