blktests nvme/012 triggering LOCKDEP warning

["Theodore Y. Ts'o" <tytso@mit.edu>]

Is this a known issue?  nvme/012 is triggering the following lockdep warning:

Thanks,

					- Ted

[ 1964.751910] run blktests nvme/012 at 2019-02-11 20:58:31
[ 1964.977624] nvmet: adding nsid 1 to subsystem blktests-subsystem-1
[ 1965.006395] nvmet: creating controller 1 for subsystem blktests-subsystem-1 for NQN nqn.2014-08.org.nvmexpress:uuid:8a58b187-6d09-4c5d-bc03-593896d2d80d.
[ 1965.011811] nvme nvme0: ANA group 1: optimized.
[ 1965.011899] nvme nvme0: creating 2 I/O queues.
[ 1965.013966] nvme nvme0: new ctrl: "blktests-subsystem-1"

[ 1965.282478] ============================================
[ 1965.287922] WARNING: possible recursive locking detected
[ 1965.293364] 5.0.0-rc3-xfstests-00015-g1236f7d60242 #841 Not tainted
[ 1965.299762] --------------------------------------------
[ 1965.305207] ksoftirqd/1/16 is trying to acquire lock:
[ 1965.310389] 000000000282032e (&(&fq->mq_flush_lock)->rlock){..-.}, at: flush_end_io+0x4e/0x1d0
[ 1965.319146] 
               but task is already holding lock:
[ 1965.325106] 00000000cbadcbc2 (&(&fq->mq_flush_lock)->rlock){..-.}, at: flush_end_io+0x4e/0x1d0
[ 1965.333957] 
               other info that might help us debug this:
[ 1965.340615]  Possible unsafe locking scenario:

[ 1965.346664]        CPU0
[ 1965.349248]        ----
[ 1965.351820]   lock(&(&fq->mq_flush_lock)->rlock);
[ 1965.356654]   lock(&(&fq->mq_flush_lock)->rlock);
[ 1965.361490] 
                *** DEADLOCK ***

[ 1965.367541]  May be due to missing lock nesting notation

[ 1965.374636] 1 lock held by ksoftirqd/1/16:
[ 1965.378890]  #0: 00000000cbadcbc2 (&(&fq->mq_flush_lock)->rlock){..-.}, at: flush_end_io+0x4e/0x1d0
[ 1965.388080] 
               stack backtrace:
[ 1965.392570] CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.0.0-rc3-xfstests-00015-g1236f7d60242 #841
[ 1965.402002] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
[ 1965.411411] Call Trace:
[ 1965.413996]  dump_stack+0x67/0x90
[ 1965.417433]  __lock_acquire.cold.45+0x2b4/0x313
[ 1965.422194]  lock_acquire+0x98/0x160
[ 1965.425894]  ? flush_end_io+0x4e/0x1d0
[ 1965.429817]  _raw_spin_lock_irqsave+0x3b/0x80
[ 1965.434299]  ? flush_end_io+0x4e/0x1d0
[ 1965.438162]  flush_end_io+0x4e/0x1d0
[ 1965.441909]  blk_mq_complete_request+0x76/0x110
[ 1965.446580]  nvmet_req_complete+0x15/0x110 [nvmet]
[ 1965.452098]  nvmet_bio_done+0x27/0x50 [nvmet]
[ 1965.456634]  blk_update_request+0xd7/0x2d0
[ 1965.460869]  blk_mq_end_request+0x1a/0x100
[ 1965.465091]  blk_flush_complete_seq+0xe5/0x350
[ 1965.469660]  flush_end_io+0x12f/0x1d0
[ 1965.473436]  blk_done_softirq+0x9f/0xd0
[ 1965.477398]  __do_softirq+0xca/0x440
[ 1965.481092]  ? smpboot_thread_fn+0x2f/0x1e0
[ 1965.485512]  ? smpboot_thread_fn+0x74/0x1e0
[ 1965.489813]  ? smpboot_thread_fn+0x118/0x1e0
[ 1965.494379]  run_ksoftirqd+0x24/0x50
[ 1965.498081]  smpboot_thread_fn+0x113/0x1e0
[ 1965.502399]  ? sort_range+0x20/0x20
[ 1965.506008]  kthread+0x121/0x140
[ 1965.509395]  ? kthread_park+0x80/0x80
[ 1965.513290]  ret_from_fork+0x3a/0x50
[ 1965.527032] XFS (nvme0n1): Mounting V5 Filesystem
[ 1965.541778] XFS (nvme0n1): Ending clean mount
[ 2064.142830] XFS (nvme0n1): Unmounting Filesystem
[ 2064.171432] nvme nvme0: Removing ctrl: NQN "blktests-subsystem-1"