BUG: Dentry ffff8881f11b1330{i=0,n=.index}  still in use (1) [unmount of ext4 loop5]
------------[ cut here ]------------
WARNING: CPU: 0 PID: 13172 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 0 PID: 13172 Comm: syz-executor.5 Not tainted 5.4.123-syzkaller-00835-g3e256ddba1ff #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 20 02 e9 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 67 a6 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:ffff8881e38f7918 EFLAGS: 00010286
RAX: 0000000000000054 RBX: ffffffff85fa9d60 RCX: 0aac5ff9fd189000
RDX: ffffc90001c91000 RSI: 000000000003ed45 RDI: 000000000003ed46
RBP: ffff8881dd1a6420 R08: ffffffff814e8437 R09: ffffed103edc5e08
R10: ffffed103edc5e08 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881f11b1330
FS:  00007ff1a1972700(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7a3ca76020 CR3: 00000001e7380000 CR4: 00000000001406f0
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+0x1b3/0x270 fs/super.c:366
 cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102
 task_work_run+0x186/0x1b0 kernel/task_work.c:113
 get_signal+0x1f34/0x1fc0 kernel/signal.c:2539
 do_signal+0x8d/0x610 arch/x86/kernel/signal.c:793
 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: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff1a1972188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00000000200001c0
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffe13a7c8df R14: 00007ff1a1972300 R15: 0000000000022000
---[ end trace 03e4c46bb8b8f40f ]---
BUG: Dentry ffff8881f11b1330{i=0,n=.index}  still in use (1) [unmount of ext4 loop5]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 13172 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 1 PID: 13172 Comm: syz-executor.5 Tainted: G        W         5.4.123-syzkaller-00835-g3e256ddba1ff #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 20 02 e9 84 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 67 a6 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:ffff8881e38f7918 EFLAGS: 00010286
RAX: 0000000000000054 RBX: ffffffff85fa9d60 RCX: 0aac5ff9fd189000
RDX: ffffc90001c91000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: ffff8881dd1a6420 R08: ffffffff814e8437 R09: ffffed103ede5e08
R10: ffffed103ede5e08 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881f11b1330
FS:  00007ff1a1972700(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31721000 CR3: 00000001e7380000 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
 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
 get_signal+0x1f34/0x1fc0 kernel/signal.c:2539
 do_signal+0x8d/0x610 arch/x86/kernel/signal.c:793
 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: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff1a1972188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00000000200001c0
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffe13a7c8df R14: 00007ff1a1972300 R15: 0000000000022000
---[ end trace 03e4c46bb8b8f410 ]---
VFS: Busy inodes after unmount of loop5. Self-destruct in 5 seconds.  Have a nice day...