BUG: Dentry still in use [unmount of msdos loop5]

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0cd79a87 Merge 5.4.98 into android12-5.4
git tree: android12-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=1318ee14d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4085e235e8045525
dashboard link: https://syzkaller.appspot.com/bug?extid=d2c0d6f879434971c4b3
compiler: Debian clang version 11.0.1-2

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+d2c0d6...@syzkaller.appspotmail.com

BUG: Dentry 00000000cb28573b{i=0,n=.index} still in use (1) [unmount of msdos loop5]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 358 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 358 Comm: syz-executor.5 Not tainted 5.4.98-syzkaller-00277-g0cd79a8750fa #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d8/0x24e lib/dump_stack.c:118
panic+0x285/0x740 kernel/panic.c:221
report_bug+0x380/0x4d0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap arch/x86/kernel/traps.c:272 [inline]
do_invalid_op+0x6e/0x110 arch/x86/kernel/traps.c:291
invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:1029
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 00 ca e8 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 87 43 b0 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:ffff8881bb627c58 EFLAGS: 00010282
RAX: 0000000000000055 RBX: ffffffff85fc4f20 RCX: 3f79e02a185f7400
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881e439f420 R08: ffffffff814e6147 R09: ffffed103ede5e08
R10: ffffed103ede5e08 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881e8957aa0
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
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: 0033:0x4671f7
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:00007ffde3e91bf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000004671f7
RDX: 00007ffde3e91cc9 RSI: 0000000000000002 RDI: 00007ffde3e91cc0
RBP: 00007ffde3e91cc0 R08: 00000000ffffffff R09: 00007ffde3e91a90
R10: 000000000299678b R11: 0000000000000246 R12: 00000000004bbd54
R13: 00007ffde3e92d90 R14: 00000000029966f0 R15: 00007ffde3e92dd0
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

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