Re: [syzbot] WARNING in reiserfs_put_super

[syzbot <syzbot+fcdd69a8426baab36109@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    90d856e71443 Add linux-next specific files for 20210723
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=140c92b6300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=298516715f6ad5cd
dashboard link: https://syzkaller.appspot.com/bug?extid=fcdd69a8426baab36109
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=146b2066300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fcdd69a8426baab36109@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 8499 at kernel/workqueue.c:4413 destroy_workqueue.cold+0x5/0x71 kernel/workqueue.c:4413
Modules linked in:
CPU: 1 PID: 8499 Comm: syz-executor.5 Not tainted 5.14.0-rc2-next-20210723-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:destroy_workqueue.cold+0x5/0x71 kernel/workqueue.c:4413
Code: c5 3d 7a f8 b9 e8 03 00 00 31 d2 48 c7 c7 e0 ff 8a 89 f7 f1 89 c6 e8 fc 87 00 00 c6 44 24 2f 01 e9 e7 56 62 f8 e8 6f c4 8b f8 <0f> 0b 48 c7 c6 e0 04 8b 89 48 c7 c7 20 00 8b 89 49 8d 96 60 01 00
RSP: 0018:ffffc90001b3fcd0 EFLAGS: 00010093
RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
RDX: ffff88801bedd580 RSI: ffffffff88e9fd31 RDI: 0000000000000003
RBP: 000000000000000f R08: 0000000000000001 R09: 0000000000000003
R10: ffffffff814c5ab3 R11: 0000000000000000 R12: dffffc0000000000
R13: ffffe8ffffd91a00 R14: ffff88802a9d2400 R15: 0000000000000000
FS:  000000000290e400(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffef18ce720 CR3: 00000000370a3000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 reiserfs_put_super+0x234/0x5c0 fs/reiserfs/super.c:631
 generic_shutdown_super+0x14c/0x370 fs/super.c:465
 kill_block_super+0x97/0xf0 fs/super.c:1395
 deactivate_locked_super+0x94/0x160 fs/super.c:335
 deactivate_super+0xad/0xd0 fs/super.c:366
 cleanup_mnt+0x3a2/0x540 fs/namespace.c:1136
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x467a47
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:00007ffca786e4d8 EFLAGS: 00000246
 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000467a47
RDX: 00007ffca786e5a9 RSI: 0000000000000002 RDI: 00007ffca786e5a0
RBP: 00007ffca786e5a0 R08: 00000000ffffffff R09: 00007ffca786e370
R10: 000000000290f8e3 R11: 0000000000000246 R12: 00000000004bee90
R13: 00007ffca786f670 R14: 000000000290f810 R15: 00007ffca786f6b0