BUG: Dentry still in use [unmount of ext2 loop0]

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 11abbf48 Merge 5.4.105 into android12-5.4
git tree: android12-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=161135e6d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7fbcefc6ecb04c53
dashboard link: https://syzkaller.appspot.com/bug?extid=fcc20ecb13ebb5c01c2c
compiler: Debian clang version 11.0.1-2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110a2b2ad00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17b02e8ad00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fcc20e...@syzkaller.appspotmail.com

EXT4-fs (loop0): mounting ext2 file system using the ext4 subsystem
EXT4-fs (loop0): mounted filesystem without journal. Opts: ,errors=continue
incfs: Can't find or create .index dir in ./file0
BUG: Dentry ffff8881efe71dd0{i=0,n=.index} still in use (1) [unmount of ext2 loop0]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 339 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 339 Comm: syz-executor067 Not tainted 5.4.105-syzkaller-00495-g11abbf486c2e #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
__warn+0x1f1/0x200 kernel/panic.c:582
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 60 e9 e8 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 b7 e9 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:ffff8881e9777a58 EFLAGS: 00010282
RAX: 0000000000000054 RBX: ffffffff85fa92e0 RCX: eb03027bcf35db00
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881e9b76420 R08: ffffffff814e8047 R09: ffffed103ede5e08
R10: ffffed103ede5e08 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881efe71dd0
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
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xcb9/0x2bf0 kernel/exit.c:812
do_group_exit+0x15c/0x2c0 kernel/exit.c:910
__do_sys_exit_group+0x13/0x20 kernel/exit.c:921
__se_sys_exit_group+0x10/0x10 kernel/exit.c:919
__x64_sys_exit_group+0x37/0x40 kernel/exit.c:919
do_syscall_64+0xcb/0x1e0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x442fa9
Code: Bad RIP value.
RSP: 002b:00007ffc866426f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004b42f0 RCX: 0000000000442fa9
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffffffffffc0 R09: 00000000004af000
R10: 0000000001004005 R11: 0000000000000246 R12: 00000000004b42f0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.