Hi guys,

Just got a reproducible error in btrfs/058.
The backtrace is completely in VFS territory, not btrfs related lock at all:

BTRFS info (device dm-5): checking UUID tree
sysrq: Show Blocked State
  task                        PC stack   pid father
rm              D    0 560678 560445 0x00000000
Call Trace:
 __schedule+0x5c7/0xea0
 ? __sched_text_start+0x8/0x8
 ? lock_downgrade+0x380/0x380
 ? lock_contended+0x730/0x730
 ? debug_check_no_locks_held+0x60/0x60
 schedule+0x7b/0x170
 schedule_preempt_disabled+0x18/0x30
 __mutex_lock+0x481/0xc70
 ? __fdget_pos+0x7e/0x80
 ? mutex_trylock+0x190/0x190
 ? debug_lockdep_rcu_enabled+0x26/0x40
 ? kmem_cache_free+0x157/0x3b0
 ? putname+0x73/0x80
 ? __ia32_sys_rmdir+0x30/0x30
 ? __check_object_size+0x134/0x1e6
 mutex_lock_nested+0x1b/0x20
 ? mutex_lock_nested+0x1b/0x20
 __fdget_pos+0x7e/0x80
 ksys_lseek+0x1d/0xf0
 __x64_sys_lseek+0x43/0x50
 do_syscall_64+0x79/0xe0
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f7518e5652b
Code: Bad RIP value.
RSP: 002b:00007ffead7508e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000008
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7518e5652b
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f7518f267e0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000002 R14: 00007f7518f2be68 R15: 00007f7518f287e0

Is this a known bug in VFS layer?

Thanks,
Qu