syzbot

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BUG: KCSAN: data-race in rq_qos_wait / rq_qos_wake_function

write to 0xffff88810259dc90 of 8 bytes by interrupt on cpu 0:
 __list_del include/linux/list.h:112 [inline]
 __list_del_entry include/linux/list.h:135 [inline]
 list_del_init include/linux/list.h:204 [inline]
 rq_qos_wake_function+0x85/0xe0 block/blk-rq-qos.c:228
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:93
 __wake_up_common_lock kernel/sched/wait.c:123 [inline]
 __wake_up+0x80/0xc0 kernel/sched/wait.c:142
 wbt_rqw_done+0x17d/0x260 block/blk-wbt.c:165
 __wbt_done block/blk-wbt.c:178 [inline]
 wbt_done+0xcf/0x1c0 block/blk-wbt.c:199
 __rq_qos_done+0x3b/0x70 block/blk-rq-qos.c:45
 rq_qos_done block/blk-rq-qos.h:153 [inline]
 blk_mq_free_request+0x270/0x330 block/blk-mq.c:527
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:555
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:564
 lo_complete_rq+0xca/0x180 drivers/block/loop.c:500
 blk_done_softirq+0x1a5/0x200 block/blk-mq.c:586
 __do_softirq+0x198/0x331 kernel/softirq.c:298
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:653
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x1ff/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff88810259dc90 of 8 bytes by task 26 on cpu 1:
 list_is_singular include/linux/list.h:360 [inline]
 wq_has_single_sleeper include/linux/wait.h:141 [inline]
 rq_qos_wait+0x122/0x210 block/blk-rq-qos.c:270
 __wbt_wait block/blk-wbt.c:518 [inline]
 wbt_wait+0x1bb/0x2b0 block/blk-wbt.c:583
 __rq_qos_throttle+0x39/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:182 [inline]
 blk_mq_submit_bio+0x233/0x1020 block/blk-mq.c:2174
 __submit_bio_noacct_mq block/blk-core.c:1022 [inline]
 submit_bio_noacct+0x77d/0x930 block/blk-core.c:1055
 submit_bio+0x1f3/0x360 block/blk-core.c:1125
 submit_bh_wbc+0x38c/0x3d0 fs/buffer.c:3054
 __block_write_full_page+0x618/0x9e0 fs/buffer.c:1810
 block_write_full_page+0x162/0x1a0 fs/buffer.c:2980
 blkdev_writepage+0x20/0x30 fs/block_dev.c:627
 __writepage+0x32/0xc0 mm/page-writeback.c:2311
 write_cache_pages+0x4bc/0x7f0 mm/page-writeback.c:2246
 generic_writepages+0x64/0xa0 mm/page-writeback.c:2337
 blkdev_writepages+0x19/0x20 fs/block_dev.c:1946
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __writeback_single_inode+0x84/0x560 fs/fs-writeback.c:1461
 writeback_sb_inodes+0x6a0/0x1020 fs/fs-writeback.c:1721
 __writeback_inodes_wb+0xb0/0x2a0 fs/fs-writeback.c:1790
 wb_writeback+0x290/0x660 fs/fs-writeback.c:1896
 wb_check_background_flush fs/fs-writeback.c:1964 [inline]
 wb_do_writeback+0x583/0x5d0 fs/fs-writeback.c:2052
 wb_workfn+0xb8/0x410 fs/fs-writeback.c:2080
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1ff/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26 Comm: kworker/u4:2 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-7:3)
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