When using btrfs and a kernel with lockdep enabled (4.9-rc7, but this easily
could have been there for a while) I got the following lockdep warning:
[ 37.796703] =============================================
[ 37.796773] [ INFO: possible recursive locking detected ]
[ 37.796854] 4.9.0-rc7 #351 Tainted: G L
[ 37.796917] ---------------------------------------------
[ 37.796986] systemd-journal/280 is trying to acquire lock:
[ 37.797051] (
[ 37.797077] &ei->log_mutex
[ 37.797119] ){+.+...}
[ 37.797135] , at:
[ 37.797176] [<ffffffff8182714d>] btrfs_log_inode+0x33d/0x20a0
[ 37.797254]
but task is already holding lock:
[ 37.797328] (
[ 37.797353] &ei->log_mutex
[ 37.797396] ){+.+...}
[ 37.797411] , at:
[ 37.797449] [<ffffffff8182714d>] btrfs_log_inode+0x33d/0x20a0
[ 37.797521]
other info that might help us debug this:
[ 37.797603] Possible unsafe locking scenario:
[ 37.797682] CPU0
[ 37.797717] ----
[ 37.797751] lock(
[ 37.797782] &ei->log_mutex
[ 37.797822] );
[ 37.797848] lock(
[ 37.797878] &ei->log_mutex
[ 37.797920] );
[ 37.797946]
*** DEADLOCK ***
[ 37.798020] May be due to missing lock nesting notation
[ 37.798120] 3 locks held by systemd-journal/280:
[ 37.798180] #0:
[ 37.798208] (
[ 37.798238] &sb->s_type->i_mutex_key
[ 37.798269] #9
[ 37.798299] ){+.+.+.}
[ 37.798315] , at:
[ 37.798354] [<ffffffff817a0511>] btrfs_sync_file+0x1b1/0x990
[ 37.798425] #1:
[ 37.798453] (
[ 37.798483] sb_internal
[ 37.798501] ){.+.+.+}
[ 37.798538] , at:
[ 37.798553] [<ffffffff8175ca9c>] start_transaction+0x7bc/0xe60
[ 37.798632] #2:
[ 37.798660] (
[ 37.798690] &ei->log_mutex
[ 37.798711] ){+.+...}
[ 37.798747] , at:
[ 37.798763] [<ffffffff8182714d>] btrfs_log_inode+0x33d/0x20a0
[ 37.798840]
stack backtrace:
[ 37.798902] CPU: 2 PID: 280 Comm: systemd-journal Tainted: G L
4.9.0-rc7 #351
[ 37.799017] Hardware name: Dell Inc. Inspiron 15-7568/0M5YMV, BIOS 01.00.00
08/07/2015
[ 37.799111] ffff880213ca72d0 ffffffff81a1fe82 ffffffff84056000
ffffffff83a98ae0
[ 37.799230] ffff880213ca7498 ffffffff811f43c1 dffffc0000000000
ffff88021470cf20
[ 37.799348] dffffc0000000000 ffffffff82fa15c0 ffff88021470cf00
1ffff10042794e72
[ 37.799465] Call Trace:
[ 37.799522] [<ffffffff81a1fe82>] dump_stack+0x68/0x96
[ 37.799591] [<ffffffff811f43c1>] __lock_acquire+0x1bd1/0x5290
[ 37.799670] [<ffffffff811f27f0>] ? debug_check_no_locks_freed+0x280/0x280
[ 37.799760] [<ffffffff811f27f0>] ? debug_check_no_locks_freed+0x280/0x280
[ 37.799849] [<ffffffff811f1c88>] ? mark_held_locks+0xc8/0x120
[ 37.799926] [<ffffffff811f1c88>] ? mark_held_locks+0xc8/0x120
[ 37.800001] [<ffffffff82764c41>] ? __mutex_unlock_slowpath+0x221/0x420
[ 37.800088] [<ffffffff811f84fd>] lock_acquire+0xdd/0x190
[ 37.800160] [<ffffffff8182714d>] ? btrfs_log_inode+0x33d/0x20a0
[ 37.800239] [<ffffffff82764a20>] ?
__ww_mutex_lock_interruptible+0x1500/0x1500
[ 37.800333] [<ffffffff82760004>] mutex_lock_nested+0xa4/0x7e0
[ 37.803435] [<ffffffff8182714d>] ? btrfs_log_inode+0x33d/0x20a0
[ 37.806090] [<ffffffff8275ff60>] ? mutex_trylock+0x3f0/0x3f0
[ 37.808347] [<ffffffff8173b2af>] ? __btrfs_btree_balance_dirty+0xcf/0x1a0
[ 37.811207] [<ffffffff81873c3b>] ?
btrfs_commit_inode_delayed_inode+0x23b/0x360
[ 37.814263] [<ffffffff8182714d>] btrfs_log_inode+0x33d/0x20a0
[ 37.817343] [<ffffffff8148683f>] ? iget5_locked+0x8f/0x3a0
[ 37.820420] [<ffffffff82769a92>] ? _raw_spin_unlock+0x22/0x30
[ 37.823462] [<ffffffff8175f2d0>] ? btrfs_i_callback+0x20/0x20
[ 37.826466] [<ffffffff81826e10>] ? btrfs_log_changed_extents+0x15b0/0x15b0
[ 37.829300] [<ffffffff817b4922>] ? release_extent_buffer+0x102/0x150
[ 37.832101] [<ffffffff817b4922>] ? release_extent_buffer+0x102/0x150
[ 37.834628] [<ffffffff817c6052>] ? free_extent_buffer+0xe2/0x220
[ 37.837466] [<ffffffff816d1215>] ? btrfs_release_path+0x85/0x1b0
[ 37.840325] [<ffffffff81828533>] btrfs_log_inode+0x1723/0x20a0
[ 37.843265] [<ffffffff81826e10>] ? btrfs_log_changed_extents+0x15b0/0x15b0
[ 37.846248] [<ffffffff82760471>] ? mutex_lock_nested+0x511/0x7e0
[ 37.849177] [<ffffffff811f1c88>] ? mark_held_locks+0xc8/0x120
[ 37.852120] [<ffffffff82764c41>] ? __mutex_unlock_slowpath+0x221/0x420
[ 37.855053] [<ffffffff82764a20>] ?
__ww_mutex_lock_interruptible+0x1500/0x1500
[ 37.858013] [<ffffffff818295e9>] btrfs_log_inode_parent+0x689/0x2280
[ 37.860982] [<ffffffff81828f60>] ? btrfs_end_log_trans+0x70/0x70
[ 37.863918] [<ffffffff8147a191>] ? dget_parent+0x91/0x350
[ 37.866855] [<ffffffff8147a1a9>] ? dget_parent+0xa9/0x350
[ 37.869762] [<ffffffff8182e434>] btrfs_log_dentry_safe+0x74/0xa0
[ 37.872650] [<ffffffff817a08ae>] btrfs_sync_file+0x54e/0x990
[ 37.875570] [<ffffffff817a0360>] ? start_ordered_ops+0x20/0x20
[ 37.878502] [<ffffffff81003629>] ? syscall_trace_enter+0x289/0x7c0
[ 37.881140] [<ffffffff817a0360>] ? start_ordered_ops+0x20/0x20
[ 37.883550] [<ffffffff814c0158>] vfs_fsync_range+0xe8/0x280
[ 37.886026] [<ffffffff814c0348>] do_fsync+0x38/0x60
[ 37.888499] [<ffffffff814c0a10>] ? SyS_syncfs+0xc0/0xc0
[ 37.891003] [<ffffffff814c0a1b>] SyS_fsync+0xb/0x10
[ 37.893851] [<ffffffff81003f1c>] do_syscall_64+0x17c/0x420
[ 37.896879] [<ffffffff8276a224>] entry_SYSCALL64_slow_path+0x25/0x25
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