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BUG: KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_do_dispatch_sched

write to 0xffff888101c17810 of 8 bytes by task 709 on cpu 0:
 __list_splice include/linux/list.h:444 [inline]
 list_splice_tail_init include/linux/list.h:499 [inline]
 blk_mq_dispatch_rq_list+0xdd7/0x1040 block/blk-mq.c:1428
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:201 [inline]
 blk_mq_do_dispatch_sched+0x3b5/0x640 block/blk-mq-sched.c:214
 __blk_mq_sched_dispatch_requests+0x1eb/0x290 block/blk-mq-sched.c:329
 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 0xffff888101c17810 of 8 bytes by task 29921 on cpu 1:
 list_empty_careful include/linux/list.h:319 [inline]
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:140 [inline]
 blk_mq_do_dispatch_sched+0x167/0x640 block/blk-mq-sched.c:214
 __blk_mq_sched_dispatch_requests+0x1eb/0x290 block/blk-mq-sched.c:329
 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
 fat_writepage+0x20/0x30 fs/fat/inode.c:199
 writeout mm/migrate.c:832 [inline]
 fallback_migrate_page mm/migrate.c:856 [inline]
 move_to_new_page+0x2ea/0x670 mm/migrate.c:907
 __unmap_and_move mm/migrate.c:1069 [inline]
 unmap_and_move mm/migrate.c:1136 [inline]
 migrate_pages+0xd4d/0x1530 mm/migrate.c:1411
 do_mbind+0xd43/0xf50 mm/mempolicy.c:1340
 kernel_mbind mm/mempolicy.c:1475 [inline]
 __do_sys_mbind mm/mempolicy.c:1482 [inline]
 __se_sys_mbind mm/mempolicy.c:1478 [inline]
 __x64_sys_mbind+0x10a/0x130 mm/mempolicy.c:1478
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888101c17808 -> 0xffff888101c61cc8

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 29921 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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