======================================================
WARNING: possible circular locking dependency detected
5.10.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
kworker/0:1H/2971 is trying to acquire lock:
ffff888021a820e0 (&type->s_umount_key#85){+.+.}-{3:3}, at: freeze_super+0x44/0x3c0 fs/super.c:1716

but task is already holding lock:
ffffc9000150fd80 ((work_completion)(&(&gl->gl_work)->work)){+.+.}-{0:0}, at: process_one_work+0x733/0xfc0 kernel/workqueue.c:2247

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 ((work_completion)(&(&gl->gl_work)->work)){+.+.}-{0:0}:
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5435
       process_one_work+0x75d/0xfc0 kernel/workqueue.c:2248
       worker_thread+0xaa4/0x1460 kernel/workqueue.c:2418
       kthread+0x36b/0x390 kernel/kthread.c:292
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

-> #1 ((wq_completion)glock_workqueue){+.+.}-{0:0}:
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5435
       flush_workqueue+0x120/0x1620 kernel/workqueue.c:2783
       gfs2_gl_hash_clear+0x54/0x380 fs/gfs2/glock.c:1987
       gfs2_put_super+0x7d3/0x840 fs/gfs2/super.c:740
       generic_shutdown_super+0x120/0x2a0 fs/super.c:464
       kill_block_super+0x79/0xd0 fs/super.c:1446
       deactivate_locked_super+0xa7/0xf0 fs/super.c:335
       cleanup_mnt+0x462/0x510 fs/namespace.c:1118
       task_work_run+0x137/0x1c0 kernel/task_work.c:151
       tracehook_notify_resume include/linux/tracehook.h:188 [inline]
       exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
       exit_to_user_mode_prepare+0xe4/0x170 kernel/entry/common.c:191
       syscall_exit_to_user_mode+0x4a/0x170 kernel/entry/common.c:266
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #0 (&type->s_umount_key#85){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:2866 [inline]
       check_prevs_add+0x341/0x52b0 kernel/locking/lockdep.c:2991
       validate_chain kernel/locking/lockdep.c:3606 [inline]
       __lock_acquire+0x43cb/0x6210 kernel/locking/lockdep.c:4830
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5435
       down_write+0x55/0x130 kernel/locking/rwsem.c:1531
       freeze_super+0x44/0x3c0 fs/super.c:1716
       freeze_go_sync+0x14b/0x380 fs/gfs2/glops.c:587
       do_xmote+0x6b6/0x14c0 fs/gfs2/glock.c:616
       glock_work_func+0x2c3/0x450 fs/gfs2/glock.c:926
       process_one_work+0x789/0xfc0 kernel/workqueue.c:2272
       worker_thread+0xaa4/0x1460 kernel/workqueue.c:2418
       kthread+0x36b/0x390 kernel/kthread.c:292
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

other info that might help us debug this:

Chain exists of:
  &type->s_umount_key#85 --> (wq_completion)glock_workqueue --> (work_completion)(&(&gl->gl_work)->work)

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock((work_completion)(&(&gl->gl_work)->work));
                               lock((wq_completion)glock_workqueue);
                               lock((work_completion)(&(&gl->gl_work)->work));
  lock(&type->s_umount_key#85);

 *** DEADLOCK ***

2 locks held by kworker/0:1H/2971:
 #0: ffff88801735d938 ((wq_completion)glock_workqueue){+.+.}-{0:0}, at: process_one_work+0x6f4/0xfc0 kernel/workqueue.c:2245
 #1: ffffc9000150fd80 ((work_completion)(&(&gl->gl_work)->work)){+.+.}-{0:0}, at: process_one_work+0x733/0xfc0 kernel/workqueue.c:2247

stack backtrace:
CPU: 0 PID: 2971 Comm: kworker/0:1H Not tainted 5.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: glock_workqueue glock_work_func
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x137/0x1be lib/dump_stack.c:118
 print_circular_bug+0xb10/0xdb0 kernel/locking/lockdep.c:1994
 check_noncircular+0x221/0x2d0 kernel/locking/lockdep.c:2115
 check_prev_add kernel/locking/lockdep.c:2866 [inline]
 check_prevs_add+0x341/0x52b0 kernel/locking/lockdep.c:2991
 validate_chain kernel/locking/lockdep.c:3606 [inline]
 __lock_acquire+0x43cb/0x6210 kernel/locking/lockdep.c:4830
 lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5435
 down_write+0x55/0x130 kernel/locking/rwsem.c:1531
 freeze_super+0x44/0x3c0 fs/super.c:1716
 freeze_go_sync+0x14b/0x380 fs/gfs2/glops.c:587
 do_xmote+0x6b6/0x14c0 fs/gfs2/glock.c:616
 glock_work_func+0x2c3/0x450 fs/gfs2/glock.c:926
 process_one_work+0x789/0xfc0 kernel/workqueue.c:2272
 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2418
 kthread+0x36b/0x390 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296