WARNING in __blk_mq_delay_run_hw_queue

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    b145b0eb Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146c860d600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1ec3be9936e004f6
dashboard link: https://syzkaller.appspot.com/bug?extid=d44e1b26ce5c3e77458d
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=165fcefb600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162d03db600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d44e1b26ce5c3e77458d@xxxxxxxxxxxxxxxxxxxxxxxxx

blk_update_request: I/O error, dev nbd0, sector 4 op 0x0:(READ) flags 0x0  
phys_seg 2 prio class 0
Buffer I/O error on dev nbd0, logical block 2, async page read
Buffer I/O error on dev nbd0, logical block 3, async page read
------------[ cut here ]------------
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137 cpu_max_bits_warn  
include/linux/cpumask.h:137 [inline]
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137 cpumask_check  
include/linux/cpumask.h:144 [inline]
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137 cpumask_check  
include/linux/cpumask.h:142 [inline]
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137 cpumask_test_cpu  
include/linux/cpumask.h:360 [inline]
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137  
blk_mq_hctx_next_cpu block/blk-mq.c:1443 [inline]
WARNING: CPU: 0 PID: 2496 at include/linux/cpumask.h:137  
__blk_mq_delay_run_hw_queue+0x498/0x600 block/blk-mq.c:1479
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 2496 Comm: kworker/0:1H Not tainted 5.4.0-rc1+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: kblockd blk_mq_requeue_work
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:cpu_max_bits_warn include/linux/cpumask.h:137 [inline]
RIP: 0010:cpumask_check include/linux/cpumask.h:144 [inline]
RIP: 0010:cpumask_check include/linux/cpumask.h:142 [inline]
RIP: 0010:cpumask_test_cpu include/linux/cpumask.h:360 [inline]
RIP: 0010:blk_mq_hctx_next_cpu block/blk-mq.c:1443 [inline]
RIP: 0010:__blk_mq_delay_run_hw_queue+0x498/0x600 block/blk-mq.c:1479
Code: 01 00 00 41 c7 84 24 24 01 00 00 01 00 00 00 41 bd 40 00 00 00 e9 ab  
fe ff ff 41 bd 40 00 00 00 e9 a0 fe ff ff e8 48 68 41 fe <0f> 0b e9 50 fd  
ff ff e8 3c 68 41 fe 48 c7 c2 40 b9 c5 89 4c 89 fe
RSP: 0018:ffff8880a3287b18 EFLAGS: 00010293
RAX: ffff8880a32720c0 RBX: 0000000000000040 RCX: ffffffff8331a7e6
RDX: 0000000000000000 RSI: ffffffff8331aa98 RDI: 0000000000000005
RBP: ffff8880a3287b58 R08: ffff8880a32720c0 R09: ffffed101141a05a
R10: ffffed101141a059 R11: ffff88808a0d02cf R12: ffff88808a0d0280
R13: 0000000000000040 R14: ffff88808a0d03a4 R15: 0000000000000000
 blk_mq_run_hw_queue+0x19d/0x350 block/blk-mq.c:1508
 blk_mq_run_hw_queues+0x112/0x1a0 block/blk-mq.c:1525
 blk_mq_requeue_work+0x502/0x780 block/blk-mq.c:775
 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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