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BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / __blk_mq_sched_dispatch_requests

write to 0xffff8881090ae810 of 8 bytes by task 885 on cpu 1:
 INIT_LIST_HEAD include/linux/list.h:36 [inline]
 list_splice_init include/linux/list.h:483 [inline]
 __blk_mq_sched_dispatch_requests+0x137/0x290 block/blk-mq-sched.c:308
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:360
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1500
 blk_mq_run_work_fn+0x3d/0x50 block/blk-mq.c:1832
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2276
 worker_thread+0x636/0xae0 kernel/workqueue.c:2422
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff8881090ae810 of 8 bytes by task 30446 on cpu 0:
 list_empty_careful include/linux/list.h:319 [inline]
 __blk_mq_sched_dispatch_requests+0x80/0x290 block/blk-mq-sched.c:305
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:360
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1500
 __blk_mq_delay_run_hw_queue+0x163/0x2f0 block/blk-mq.c:1577
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1630
 blk_mq_get_tag+0x205/0x610 block/blk-mq-tag.c:127
 __blk_mq_alloc_request+0x22a/0x290 block/blk-mq.c:386
 blk_mq_submit_bio+0x26d/0xe80 block/blk-mq.c:2207
 __submit_bio_noacct_mq block/blk-core.c:1011 [inline]
 submit_bio_noacct+0x6f2/0x7e0 block/blk-core.c:1044
 submit_bio+0x10c/0x190 include/linux/vmstat.h:81
 submit_bh_wbc+0x2f3/0x330 fs/buffer.c:3050
 __block_write_full_page+0x648/0xa10 fs/buffer.c:1805
 block_write_full_page+0x240/0x260 fs/buffer.c:2976
 blkdev_writepage+0x20/0x30 fs/block_dev.c:639
 __writepage+0x32/0xc0 mm/page-writeback.c:2314
 write_cache_pages+0x4d7/0x810 mm/page-writeback.c:2249
 generic_writepages+0x64/0xa0 mm/page-writeback.c:2340
 blkdev_writepages+0x19/0x20 fs/block_dev.c:1677
 do_writepages+0x7b/0x150 mm/page-writeback.c:2355
 __filemap_fdatawrite_range mm/filemap.c:413 [inline]
 filemap_write_and_wait_range+0x20a/0x390 mm/filemap.c:686
 filemap_write_and_wait include/linux/fs.h:2897 [inline]
 __sync_blockdev fs/block_dev.c:526 [inline]
 sync_blockdev fs/block_dev.c:535 [inline]
 blkdev_put+0x8b/0x4e0 fs/block_dev.c:1530
 blkdev_close+0x47/0x50 fs/block_dev.c:1584
 __fput+0x25b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:164
 get_signal+0x156c/0x15e0 kernel/signal.c:2581
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:865
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888101be37c8 -> 0xffff888101be3948

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30446 Comm: syz-executor.2 Not tainted 5.14.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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