Hi,
after scrub start, scrub cancel, umount, mount of a two disk raid1
(data + metadata):
[12999.229791] ======================================================
[12999.236029] WARNING: possible circular locking dependency detected
[12999.242261] 4.14.35 #36 Not tainted
[12999.245806] ------------------------------------------------------
[12999.252037] btrfs/4682 is trying to acquire lock:
[12999.256794] ("%s-%s""btrfs", name){+.+.}, at: [<ffffffff9b06f900>] flush_workqueue+0x70/0x480
[12999.265486]
but task is already holding lock:
[12999.271390] (&fs_info->scrub_lock){+.+.}, at: [<ffffffffc03e82f1>] btrfs_scrub_dev+0x311/0x650 [btrfs]
[12999.280887]
which lock already depends on the new lock.
[12999.289147]
the existing dependency chain (in reverse order) is:
[12999.296721]
-> #3 (&fs_info->scrub_lock){+.+.}:
[12999.302949] __mutex_lock+0x66/0x9a0
[12999.307287] btrfs_scrub_dev+0x105/0x650 [btrfs]
[12999.312615] btrfs_ioctl+0x19a0/0x2030 [btrfs]
[12999.317706] do_vfs_ioctl+0x8c/0x6a0
[12999.321951] SyS_ioctl+0x6f/0x80
[12999.325860] do_syscall_64+0x64/0x170
[12999.330202] entry_SYSCALL_64_after_hwframe+0x42/0xb7
[12999.335930]
-> #2 (&fs_devs->device_list_mutex){+.+.}:
[12999.342798] __mutex_lock+0x66/0x9a0
[12999.347049] reada_start_machine_worker+0xb0/0x3c0 [btrfs]
[12999.353324] btrfs_worker_helper+0x8b/0x630 [btrfs]
[12999.358926] process_one_work+0x242/0x6a0
[12999.363613] worker_thread+0x32/0x3f0
[12999.367894] kthread+0x11f/0x140
[12999.371792] ret_from_fork+0x3a/0x50
[12999.376038]
-> #1 ((&work->normal_work)){+.+.}:
[12999.382254] process_one_work+0x20c/0x6a0
[12999.386881] worker_thread+0x32/0x3f0
[12999.391216] kthread+0x11f/0x140
[12999.395107] ret_from_fork+0x3a/0x50
[12999.399290]
-> #0 ("%s-%s""btrfs", name){+.+.}:
[12999.405455] lock_acquire+0x93/0x220
[12999.409683] flush_workqueue+0x97/0x480
[12999.414129] drain_workqueue+0xa4/0x180
[12999.418620] destroy_workqueue+0xe/0x1e0
[12999.423202] btrfs_destroy_workqueue+0x57/0x280 [btrfs]
[12999.429137] scrub_workers_put+0x29/0x60 [btrfs]
[12999.434426] btrfs_scrub_dev+0x324/0x650 [btrfs]
[12999.439764] btrfs_ioctl+0x19a0/0x2030 [btrfs]
[12999.444870] do_vfs_ioctl+0x8c/0x6a0
[12999.449115] SyS_ioctl+0x6f/0x80
[12999.453017] do_syscall_64+0x64/0x170
[12999.457367] entry_SYSCALL_64_after_hwframe+0x42/0xb7
[12999.463103]
other info that might help us debug this:
[12999.471370] Chain exists of:
"%s-%s""btrfs", name --> &fs_devs->device_list_mutex --> &fs_info->scrub_lock
[12999.484396] Possible unsafe locking scenario:
[12999.490524] CPU0 CPU1
[12999.495161] ---- ----
[12999.499840] lock(&fs_info->scrub_lock);
[12999.504001] lock(&fs_devs->device_list_mutex);
[12999.511341] lock(&fs_info->scrub_lock);
[12999.518074] lock("%s-%s""btrfs", name);
[12999.522243]
*** DEADLOCK ***
[12999.528347] 2 locks held by btrfs/4682:
[12999.532330] #0: (sb_writers#15){.+.+}, at: [<ffffffff9b1fd163>] mnt_want_write_file+0x33/0xb0
[12999.541310] #1: (&fs_info->scrub_lock){+.+.}, at: [<ffffffffc03e82f1>] btrfs_scrub_dev+0x311/0x650 [btrfs]
[12999.551389]
stack backtrace:
[12999.555917] CPU: 3 PID: 4682 Comm: btrfs Not tainted 4.14.35 #36
[12999.562139] Hardware name: Supermicro X8SIL/X8SIL, BIOS 1.2a 06/27/2012
[12999.569487] Call Trace:
[12999.572049] dump_stack+0x67/0x95
[12999.575530] print_circular_bug.isra.42+0x1ce/0x1db
[12999.580580] __lock_acquire+0x121c/0x1300
[12999.584758] ? lock_acquire+0x93/0x220
[12999.588668] lock_acquire+0x93/0x220
[12999.592316] ? flush_workqueue+0x70/0x480
[12999.596485] flush_workqueue+0x97/0x480
[12999.600487] ? flush_workqueue+0x70/0x480
[12999.604596] ? find_held_lock+0x2d/0x90
[12999.608541] ? drain_workqueue+0xa4/0x180
[12999.612724] drain_workqueue+0xa4/0x180
[12999.616730] destroy_workqueue+0xe/0x1e0
[12999.620784] btrfs_destroy_workqueue+0x57/0x280 [btrfs]
[12999.626252] scrub_workers_put+0x29/0x60 [btrfs]
[12999.631087] btrfs_scrub_dev+0x324/0x650 [btrfs]
[12999.635814] ? __sb_start_write+0x137/0x1a0
[12999.640156] ? mnt_want_write_file+0x33/0xb0
[12999.644624] btrfs_ioctl+0x19a0/0x2030 [btrfs]
[12999.649194] ? find_held_lock+0x2d/0x90
[12999.653146] ? do_vfs_ioctl+0x8c/0x6a0
[12999.657095] ? btrfs_ioctl_get_supported_features+0x20/0x20 [btrfs]
[12999.663572] do_vfs_ioctl+0x8c/0x6a0
[12999.667203] ? __fget+0x100/0x1f0
[12999.670627] SyS_ioctl+0x6f/0x80
[12999.673954] do_syscall_64+0x64/0x170
[12999.677777] entry_SYSCALL_64_after_hwframe+0x42/0xb7
[12999.682993] RIP: 0033:0x7f409f638f07
[12999.686667] RSP: 002b:00007f409f549d38 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[12999.694458] RAX: ffffffffffffffda RBX: 000055a730ca04b0 RCX: 00007f409f638f07
[12999.701808] RDX: 000055a730ca04b0 RSI: 00000000c400941b RDI: 0000000000000003
[12999.709208] RBP: 0000000000000000 R08: 00007f409f54a700 R09: 0000000000000000
[12999.716550] R10: 00007f409f54a700 R11: 0000000000000246 R12: 00007ffdd7f5481e
[12999.723899] R13: 00007ffdd7f5481f R14: 00007ffdd7f54820 R15: 0000000000000000
Regards,
Petr
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