BUG: Dentry ffff8881ecbbfaa0{i=0,n=.index}  still in use (1) [unmount of ext4 loop0]
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WARNING: CPU: 0 PID: 342 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 0 PID: 342 Comm: syz-executor448 Not tainted 5.4.125-syzkaller-00009-g546305780d82 #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 08 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:ffff8881e6eb7738 EFLAGS: 00010282
RAX: 0000000000000054 RBX: ffffffff85faa1c0 RCX: e40e0e78559c7800
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881f35f6420 R08: ffffffff814e90d7 R09: ffffed103edc9608
R10: ffffed103edc9608 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881ecbbfaa0
FS:  00007f2d95f74700(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2d96039178 CR3: 0000000005e0e000 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
 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
 get_signal+0x164f/0x1fc0 kernel/signal.c:2745
 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: 0033:0x7f2d95fe8259
Code: Bad RIP value.
RSP: 002b:00007f2d95f742f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f2d9606d3f0 RCX: 00007f2d95fe8259
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2d9606d3f8
RBP: 00007f2d9606d3fc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 6e656d6572636e69 R14: e5d26e84aa4cf3c6 R15: 00007f2d9606d3f8
---[ end trace 808564a9ece349c9 ]---
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WARNING: CPU: 0 PID: 342 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Modules linked in:
CPU: 0 PID: 342 Comm: syz-executor448 Tainted: G        W         5.4.125-syzkaller-00009-g546305780d82 #0
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 08 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:ffff8881e6eb7738 EFLAGS: 00010282
RAX: 0000000000000054 RBX: ffffffff85faa1c0 RCX: e40e0e78559c7800
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000000
R10: ffffed103edc9608 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881ecbbfaa0
FS:  00007f2d95f74700(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2d95fe822f CR3: 0000000005e0e000 CR4: 00000000001406f0
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
 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
 get_signal+0x164f/0x1fc0 kernel/signal.c:2745
 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: 0033:0x7f2d95fe8259
Code: Bad RIP value.
RSP: 002b:00007f2d95f742f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f2d9606d3f0 RCX: 00007f2d95fe8259
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f2d9606d3f8
RBP: 00007f2d9606d3fc R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 6e656d6572636e69 R14: e5d26e84aa4cf3c6 R15: 00007f2d9606d3f8
---[ end trace 808564a9ece349ca ]---
VFS: Busy inodes after unmount of loop0. Self-destruct in 5 seconds.  Have a nice day...