KCSAN: data-race in wbt_issue / wbt_issue (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 245a4300 Merge branch 'rcu/kcsan' into tip/locking/kcsan
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=16c20aaee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a4b9db179318d21f
dashboard link: https://syzkaller.appspot.com/bug?extid=af579360e06c53f6bae1
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [ax...@kernel.dk linux...@vger.kernel.org
linux-...@vger.kernel.org el...@google.com]

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+af5793...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in wbt_issue / wbt_issue

read to 0xffff88812a12ae28 of 8 bytes by task 2498 on cpu 1:
wbt_issue block/blk-wbt.c:617 [inline]
wbt_issue+0x8e/0xf0 block/blk-wbt.c:603
__rq_qos_issue+0x4a/0x80 block/blk-rq-qos.c:54
rq_qos_issue block/blk-rq-qos.h:159 [inline]
blk_mq_start_request+0x32a/0x370 block/blk-mq.c:654
loop_queue_rq+0x64/0x280 drivers/block/loop.c:1911
blk_mq_dispatch_rq_list+0xbe9/0xe40 block/blk-mq.c:1238
blk_mq_do_dispatch_sched+0x11d/0x260 block/blk-mq-sched.c:115
blk_mq_sched_dispatch_requests+0x2b4/0x380 block/blk-mq-sched.c:211
__blk_mq_run_hw_queue+0xb7/0x160 block/blk-mq.c:1368
blk_mq_run_work_fn+0x57/0x70 block/blk-mq.c:1597
process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
worker_thread+0xa0/0x800 kernel/workqueue.c:2410
kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff88812a12ae28 of 8 bytes by task 1480 on cpu 0:
wbt_issue block/blk-wbt.c:619 [inline]
wbt_issue+0xd0/0xf0 block/blk-wbt.c:603
__rq_qos_issue+0x4a/0x80 block/blk-rq-qos.c:54
rq_qos_issue block/blk-rq-qos.h:159 [inline]
blk_mq_start_request+0x32a/0x370 block/blk-mq.c:654
loop_queue_rq+0x64/0x280 drivers/block/loop.c:1911
blk_mq_dispatch_rq_list+0xbe9/0xe40 block/blk-mq.c:1238
blk_mq_do_dispatch_sched+0x11d/0x260 block/blk-mq-sched.c:115
blk_mq_sched_dispatch_requests+0x2b4/0x380 block/blk-mq-sched.c:211
__blk_mq_run_hw_queue+0xb7/0x160 block/blk-mq.c:1368
__blk_mq_delay_run_hw_queue+0x31b/0x3a0 block/blk-mq.c:1436
blk_mq_run_hw_queue+0xfd/0x1c0 block/blk-mq.c:1473
blk_mq_sched_insert_requests+0x198/0x260 block/blk-mq-sched.c:444
blk_mq_flush_plug_list+0x572/0x6c0 block/blk-mq.c:1733
blk_flush_plug_list+0x271/0x2a0 block/blk-core.c:1768
blk_finish_plug block/blk-core.c:1785 [inline]
blk_finish_plug+0x60/0x84 block/blk-core.c:1781
read_pages+0xbc/0x2d0 mm/readahead.c:142
__do_page_cache_readahead+0x353/0x390 mm/readahead.c:212
force_page_cache_readahead+0x13a/0x1f0 mm/readahead.c:243
page_cache_sync_readahead+0x1cf/0x1e0 mm/readahead.c:522
generic_file_buffered_read mm/filemap.c:2051 [inline]
generic_file_read_iter+0xeb6/0x1440 mm/filemap.c:2324
blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2039
call_read_iter include/linux/fs.h:1896 [inline]
new_sync_read+0x389/0x4f0 fs/read_write.c:414
__vfs_read+0xb1/0xc0 fs/read_write.c:427
vfs_read fs/read_write.c:461 [inline]
vfs_read+0x143/0x2c0 fs/read_write.c:446
ksys_read+0xd5/0x1b0 fs/read_write.c:587
__do_sys_read fs/read_write.c:597 [inline]
__se_sys_read fs/read_write.c:595 [inline]
__x64_sys_read+0x4c/0x60 fs/read_write.c:595
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1480 Comm: blkid Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
==================================================================


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[syzbot]

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