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BUG: KCSAN: data-race in bio_endio / blk_mq_submit_bio

write to 0xffff88813a5e6514 of 2 bytes by task 20989 on cpu 1:
 bio_set_flag include/linux/bio.h:264 [inline]
 rq_qos_throttle block/blk-rq-qos.h:180 [inline]
 blk_mq_submit_bio+0x228/0x1060 block/blk-mq.c:2185
 __submit_bio_noacct_mq block/blk-core.c:1014 [inline]
 submit_bio_noacct+0x7c2/0x9a0 block/blk-core.c:1047
 submit_bio+0x200/0x370 block/blk-core.c:1118
 blk_next_bio block/blk-lib.c:19 [inline]
 __blkdev_issue_zero_pages+0x135/0x2f0 block/blk-lib.c:318
 blkdev_issue_zeroout+0x173/0x2a0 block/blk-lib.c:412
 blk_ioctl_zeroout block/ioctl.c:174 [inline]
 blkdev_common_ioctl+0x1081/0x10a0 block/ioctl.c:469
 blkdev_ioctl+0x16e/0x3c0 block/ioctl.c:577
 block_ioctl+0x6d/0x80 fs/block_dev.c:1667
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813a5e6514 of 2 bytes by interrupt on cpu 0:
 bio_flagged include/linux/bio.h:259 [inline]
 bio_remaining_done block/bio.c:1391 [inline]
 bio_endio+0x3c/0x370 block/bio.c:1421
 req_bio_endio block/blk-core.c:265 [inline]
 blk_update_request+0x4f5/0xb40 block/blk-core.c:1456
 blk_mq_end_request+0x22/0x50 block/blk-mq.c:564
 end_cmd+0x80/0x140 drivers/block/null_blk/main.c:699
 null_complete_rq+0x18/0x20 drivers/block/null_blk/main.c:726
 blk_complete_reqs block/blk-mq.c:576 [inline]
 blk_done_softirq+0x69/0x90 block/blk-mq.c:581
 __do_softirq+0x13c/0x2c3 kernel/softirq.c:345
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:652
 smpboot_thread_fn+0x34f/0x520 kernel/smpboot.c:165
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12 Comm: ksoftirqd/0 Tainted: G        W         5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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