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BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_run_hw_queue

write to 0xffff888102ac1410 of 8 bytes by task 3017 on cpu 0:
 INIT_LIST_HEAD include/linux/list.h:36 [inline]
 list_splice_init include/linux/list.h:483 [inline]
 __blk_mq_sched_dispatch_requests+0x16a/0x2a0 block/blk-mq-sched.c:289
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue+0xc1/0x140 block/blk-mq.c:1488
 __blk_mq_delay_run_hw_queue+0x188/0x330 block/blk-mq.c:1565
 blk_mq_run_hw_queue+0x231/0x260 block/blk-mq.c:1618
 blk_mq_run_hw_queues+0x1d1/0x230 block/blk-mq.c:1681
 blk_mq_requeue_work+0x3bd/0x3f0 block/blk-mq.c:797
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888102ac1410 of 8 bytes by task 3807 on cpu 1:
 list_empty_careful include/linux/list.h:319 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:72 [inline]
 blk_mq_run_hw_queue+0x12e/0x260 block/blk-mq.c:1614
 blk_mq_sched_insert_request+0x11f/0x240 block/blk-mq-sched.c:457
 blk_mq_submit_bio+0x8b1/0x1060 block/blk-mq.c:2243
 __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
 submit_bh_wbc+0x36b/0x3b0 fs/buffer.c:3055
 submit_bh fs/buffer.c:3061 [inline]
 __sync_dirty_buffer+0x136/0x1e0 fs/buffer.c:3156
 sync_dirty_buffer+0x16/0x20 fs/buffer.c:3169
 ext4_write_inode+0x285/0x390 fs/ext4/inode.c:5238
 write_inode+0x8c/0x1f0 fs/fs-writeback.c:1320
 __writeback_single_inode+0x286/0x4d0 fs/fs-writeback.c:1525
 writeback_single_inode+0x122/0x580 fs/fs-writeback.c:1580
 sync_inode fs/fs-writeback.c:2624 [inline]
 sync_inode_metadata+0x52/0x70 fs/fs-writeback.c:2644
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x359/0x6e0 fs/ext4/fsync.c:170
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2843 [inline]
 ext4_buffered_write_iter+0x38f/0x3e0 fs/ext4/file.c:277
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3807 Comm: syz-executor.4 Not tainted 5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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