BUG: Dentry ffff8881e6671110{i=0,n=.index}  still in use (1) [unmount of ext4 loop0]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 304 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 1 PID: 304 Comm: syz-executor964 Not tainted 5.4.147-syzkaller-00039-gcbb80ec0faf2 #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 60 13 c9 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 b7 0e b3 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:ffff8881dded7980 EFLAGS: 00010292
RAX: 0000000000000054 RBX: ffffffff85daa5c0 RCX: 3def14c06669ad00
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881ddd6a420 R08: ffffffff814b2a4c R09: ffffed103ede9608
R10: ffffed103ede9608 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881e6671110
FS:  00007f0e92c24700(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0e92c23f98 CR3: 00000001ed7e3000 CR4: 00000000003406e0
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
 deactivate_locked_super+0xaf/0x100 fs/super.c:335
 deactivate_super+0x168/0x210 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+0xc0a/0x2aa0 kernel/exit.c:812
 do_group_exit+0x15c/0x2c0 kernel/exit.c:910
 get_signal+0x150f/0x1e00 kernel/signal.c:2745
 do_signal+0x3b/0x580 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop arch/x86/entry/common.c:159 [inline]
 prepare_exit_to_usermode+0x207/0x310 arch/x86/entry/common.c:194
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f0e92c98219
Code: Bad RIP value.
RSP: 002b:00007f0e92c242f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f0e92d1d3f0 RCX: 00007f0e92c98219
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f0e92d1d3f8
RBP: 00007f0e92d1d3fc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: e5d26e84aa4cf3c6 R14: 6e656d6572636e69 R15: 00007f0e92d1d3f8
---[ end trace 355e5f8400416a8e ]---
VFS: Busy inodes after unmount of loop0. Self-destruct in 5 seconds.  Have a nice day...