============================================
WARNING: possible recursive locking detected
5.17.0-rc5-next-20220222-syzkaller #0 Not tainted
--------------------------------------------
f2fs_ckpt-7:1/7458 is trying to acquire lock:
ffff88801e8fc390 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2160 [inline]
ffff88801e8fc390 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: f2fs_write_checkpoint+0x535/0x5ea0 fs/f2fs/checkpoint.c:1620

but task is already holding lock:
ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2160 [inline]
ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: __write_checkpoint_sync fs/f2fs/checkpoint.c:1749 [inline]
ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: __checkpoint_and_complete_reqs+0xdd/0x360 fs/f2fs/checkpoint.c:1769

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sem->internal_rwsem#2);
  lock(&sem->internal_rwsem#2);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by f2fs_ckpt-7:1/7458:
 #0: ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: f2fs_down_write fs/f2fs/f2fs.h:2160 [inline]
 #0: ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: __write_checkpoint_sync fs/f2fs/checkpoint.c:1749 [inline]
 #0: ffff88801e8fd398 (&sem->internal_rwsem#2){+.+.}-{3:3}, at: __checkpoint_and_complete_reqs+0xdd/0x360 fs/f2fs/checkpoint.c:1769

stack backtrace:
CPU: 1 PID: 7458 Comm: f2fs_ckpt-7:1 Not tainted 5.17.0-rc5-next-20220222-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_deadlock_bug kernel/locking/lockdep.c:2989 [inline]
 check_deadlock kernel/locking/lockdep.c:3032 [inline]
 validate_chain kernel/locking/lockdep.c:3821 [inline]
 __lock_acquire.cold+0x12c/0x3a7 kernel/locking/lockdep.c:5060
 lock_acquire kernel/locking/lockdep.c:5672 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5637
 down_write+0x90/0x150 kernel/locking/rwsem.c:1514
 f2fs_down_write fs/f2fs/f2fs.h:2160 [inline]
 f2fs_write_checkpoint+0x535/0x5ea0 fs/f2fs/checkpoint.c:1620
 __write_checkpoint_sync fs/f2fs/checkpoint.c:1750 [inline]
 __checkpoint_and_complete_reqs+0xea/0x360 fs/f2fs/checkpoint.c:1769
 issue_checkpoint_thread+0xdf/0x250 fs/f2fs/checkpoint.c:1800
 kthread+0x2e9/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>