WARNING: locking bug in finish_writeback_work

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 0e141f75 erspan: remove the incorrect mtu limit for erspan
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1348becd600000
kernel config: https://syzkaller.appspot.com/x/.config?x=6ffbfa7e4a36190f
dashboard link: https://syzkaller.appspot.com/bug?extid=ee0a325ad70da2857a7e
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk net...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ee0a32...@syzkaller.appspotmail.com

DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use))
WARNING: CPU: 0 PID: 8687 at kernel/locking/lockdep.c:3925
__lock_acquire+0x15de/0x4a00 kernel/locking/lockdep.c:3925
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 8687 Comm: kworker/u4:6 Not tainted 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2dc/0x755 kernel/panic.c:220
__warn.cold+0x2f/0x3c kernel/panic.c:581
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:179 [inline]
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:__lock_acquire+0x15de/0x4a00 kernel/locking/lockdep.c:3925
Code: d2 0f 85 bf 28 00 00 44 8b 3d ae f4 6c 08 45 85 ff 0f 85 34 fc ff ff
48 c7 c6 c0 39 ac 87 48 c7 c7 20 15 ac 87 e8 ba 57 eb ff <0f> 0b e9 1d fc
ff ff 4c 8b 95 28 ff ff ff 4c 8b 9d 20 ff ff ff 4c
RSP: 0018:ffff888065257930 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815ca866 RDI: ffffed100ca4af18
RBP: ffff888065257a48 R08: ffff88806524a680 R09: fffffbfff11f4051
R10: fffffbfff11f4050 R11: ffffffff88fa0283 R12: a2e8b980bb644513
R13: ffffffffbb644513 R14: 0000000000000000 R15: 0000000000000000
lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4487
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159
__wake_up_common_lock+0xc8/0x150 kernel/sched/wait.c:122
__wake_up+0xe/0x10 kernel/sched/wait.c:142
finish_writeback_work.isra.0+0xf6/0x120 fs/fs-writeback.c:168
wb_do_writeback fs/fs-writeback.c:2030 [inline]
wb_workfn+0x34f/0x1220 fs/fs-writeback.c:2070
process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.