syzbot

============================================
WARNING: possible recursive locking detected
4.19.211-syzkaller #0 Not tainted
--------------------------------------------
syz-executor410/8111 is trying to acquire lock:
00000000889d2034 (&type->i_mutex_dir_key#7){++++}, at: inode_lock include/linux/fs.h:748 [inline]
00000000889d2034 (&type->i_mutex_dir_key#7){++++}, at: fuse_reverse_inval_entry+0x2e1/0x660 fs/fuse/dir.c:1006

but task is already holding lock:
000000002dcc6122 (&type->i_mutex_dir_key#7){++++}, at: inode_lock include/linux/fs.h:748 [inline]
000000002dcc6122 (&type->i_mutex_dir_key#7){++++}, at: fuse_reverse_inval_entry+0xaa/0x660 fs/fuse/dir.c:987

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

       CPU0
       ----
  lock(&type->i_mutex_dir_key#7);
  lock(&type->i_mutex_dir_key#7);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz-executor410/8111:
 #0: 00000000c09bad4f (&fc->killsb){.+.+}, at: fuse_notify_delete fs/fuse/dev.c:1582 [inline]
 #0: 00000000c09bad4f (&fc->killsb){.+.+}, at: fuse_notify fs/fuse/dev.c:1819 [inline]
 #0: 00000000c09bad4f (&fc->killsb){.+.+}, at: fuse_dev_do_write+0x2343/0x2bc0 fs/fuse/dev.c:1894
 #1: 000000002dcc6122 (&type->i_mutex_dir_key#7){++++}, at: inode_lock include/linux/fs.h:748 [inline]
 #1: 000000002dcc6122 (&type->i_mutex_dir_key#7){++++}, at: fuse_reverse_inval_entry+0xaa/0x660 fs/fuse/dir.c:987

stack backtrace:
CPU: 1 PID: 8111 Comm: syz-executor410 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline]
 check_deadlock kernel/locking/lockdep.c:1808 [inline]
 validate_chain kernel/locking/lockdep.c:2404 [inline]
 __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 down_write+0x34/0x90 kernel/locking/rwsem.c:70
 inode_lock include/linux/fs.h:748 [inline]
 fuse_reverse_inval_entry+0x2e1/0x660 fs/fuse/dir.c:1006
 fuse_notify_delete fs/fuse/dev.c:1585 [inline]
 fuse_notify fs/fuse/dev.c:1819 [inline]
 fuse_dev_do_write+0x239e/0x2bc0 fs/fuse/dev.c:1894
 fuse_dev_write+0x153/0x1e0 fs/fuse/dev.c:1978
 call_write_iter include/linux/fs.h:1821 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x51b/0x770 fs/read_write.c:487
 vfs_write+0x1f3/0x540 fs/read_write.c:549
 ksys_write+0x12b/0x2a0 fs/read_write.c:599
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f1afebf6769
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1afeba82f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: fffff