syzbot

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BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / __blk_mq_sched_dispatch_requests

write to 0xffff888101a1f010 of 8 bytes by task 969 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+0x16a/0x2c0 block/blk-mq-sched.c:299
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:351
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1499
 __blk_mq_delay_run_hw_queue+0x163/0x2f0 block/blk-mq.c:1576
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1629
 blk_mq_run_hw_queues+0x1d1/0x230 block/blk-mq.c:1692
 blk_mq_requeue_work+0x3e6/0x420 block/blk-mq.c:798
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 worker_thread+0x636/0xae0 kernel/workqueue.c:2421
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888101a1f010 of 8 bytes by task 8083 on cpu 0:
 list_empty_careful include/linux/list.h:319 [inline]
 __blk_mq_sched_dispatch_requests+0xb1/0x2c0 block/blk-mq-sched.c:296
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:351
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1499
 __blk_mq_delay_run_hw_queue+0x163/0x2f0 block/blk-mq.c:1576
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1629
 blk_mq_sched_insert_requests+0x13f/0x200 block/blk-mq-sched.c:501
 blk_mq_flush_plug_list+0x2f5/0x3c0 block/blk-mq.c:1954
 blk_flush_plug_list+0x235/0x260 block/blk-core.c:1747
 blk_finish_plug+0x44/0x60 block/blk-core.c:1764
 ext4_writepages+0x18a1/0x1d10 fs/ext4/inode.c:2851
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range mm/filemap.c:413 [inline]
 file_write_and_wait_range+0x180/0x210 mm/filemap.c:792
 ext4_sync_file+0x105/0x670 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2982 [inline]
 ext4_buffered_write_iter+0x39c/0x3f0 fs/ext4/file.c:277
 ext4_file_write_iter+0x2e7/0x11d0 fs/ext4/file.c:519
 call_write_iter include/linux/fs.h:2114 [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+0x773/0xda0 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+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8083 Comm: syz-executor.4 Tainted: G        W         5.13.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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