BUG: Dentry still in use [unmount of erofs loop2]

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4109c89bbb12 FROMGIT: f2fs: should use GFP_NOFS for direct..
git tree: android12-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=12db4af3300000
kernel config: https://syzkaller.appspot.com/x/.config?x=12fdca0186751701
dashboard link: https://syzkaller.appspot.com/bug?extid=945704666c3389b647d9
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+945704...@syzkaller.appspotmail.com

BUG: Dentry ffff888199c26550{i=0,n=.index} still in use (2) [unmount of erofs loop2]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 362 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 1 PID: 362 Comm: syz-executor.2 Not tainted 5.4.125-syzkaller-00007-g4109c89bbb12 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:umount_check+0x179/0x1c0 fs/dcache.c:1588
Code: ff 4c 8b 0b 48 81 c5 20 04 00 00 48 c7 c7 a0 0a e9 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 37 a2 af ff 48 83 c4 08 <0f> 0b e9 fd fe ff ff 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c d4 fe ff
RSP: 0018:ffff8881ae7f7c30 EFLAGS: 00010296
RAX: 0000000000000055 RBX: ffffffff86013440 RCX: 941ac59cbf9ec300
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881e8c9c420 R08: ffffffff814e90d7 R09: ffffed103ede9608
R10: ffffed103ede9608 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000002 R14: 0000000000000000 R15: ffff888199c26550
FS: 0000555556b35400(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fffe64dbf68 CR3: 00000001ae693000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
d_walk+0x2d9/0x540 fs/dcache.c:1307
do_one_tree fs/dcache.c:1604 [inline]
shrink_dcache_for_umount+0x8a/0x1a0 fs/dcache.c:1620
generic_shutdown_super+0x63/0x2a0 fs/super.c:447
kill_block_super+0x79/0xd0 fs/super.c:1444
erofs_kill_sb+0x5b/0xc0 fs/erofs/super.c:442
deactivate_locked_super+0xaf/0x100 fs/super.c:335
deactivate_super+0x1b3/0x270 fs/super.c:366
cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102
task_work_run+0x186/0x1b0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
prepare_exit_to_usermode+0x2b0/0x310 arch/x86/entry/common.c:194
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f3bfd74ab97
Code: ff d0 48 89 c7 b8 3c 00 00 00 0f 05 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffe64dc6a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f3bfd74ab97
RDX: 00007fffe64dc77c RSI: 0000000000000002 RDI: 00007fffe64dc770
RBP: 00007fffe64dc770 R08: 00000000ffffffff R09: 00007fffe64dc540
R10: 0000555556b36bd3 R11: 0000000000000246 R12: 00007f3bfd7a2e90
R13: 00007fffe64dd840 R14: 0000555556b36b00 R15: 00007fffe64dd880
---[ end trace ecbfee3ab4577fb0 ]---
VFS: Busy inodes after unmount of loop2. Self-destruct in 5 seconds. Have a nice day...


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.