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BUG: KCSAN: data-race in dd_has_work / dd_insert_requests

write to 0xffff88810388a2a8 of 8 bytes by task 28303 on cpu 0:
 __list_add syzkaller/managers/upstream-kcsan-gce/kernel/./include/linux/list.h:70 [inline]
 list_add_tail syzkaller/managers/upstream-kcsan-gce/kernel/./include/linux/list.h:100 [inline]
 dd_insert_request syzkaller/managers/upstream-kcsan-gce/kernel/block/mq-deadline.c:521 [inline]
 dd_insert_requests+0x38e/0x4f0 syzkaller/managers/upstream-kcsan-gce/kernel/block/mq-deadline.c:537
 blk_mq_sched_insert_requests+0xc3/0x210 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq-sched.c:486
 blk_mq_flush_plug_list+0x2f5/0x400 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:1915
 blk_flush_plug_list+0x235/0x260 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-core.c:1755
 blk_mq_submit_bio+0x81c/0x1040 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:2211
 __submit_bio_noacct_mq syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-core.c:1028 [inline]
 submit_bio_noacct+0x78d/0x960 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-core.c:1061
 submit_bio+0x200/0x360 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-core.c:1131
 iomap_dio_submit_bio syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/direct-io.c:76 [inline]
 iomap_dio_bio_actor+0x88d/0xac0 syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/direct-io.c:312
 iomap_dio_actor+0x26e/0x3b0 syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/direct-io.c:387
 iomap_apply+0x1e1/0x4a0 syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/apply.c:84
 __iomap_dio_rw+0x448/0x9b0 syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/direct-io.c:517
 iomap_dio_rw+0x30/0x70 syzkaller/managers/upstream-kcsan-gce/kernel/fs/iomap/direct-io.c:605
 ext4_dio_write_iter syzkaller/managers/upstream-kcsan-gce/kernel/fs/ext4/file.c:552 [inline]
 ext4_file_write_iter+0xe6a/0x1060 syzkaller/managers/upstream-kcsan-gce/kernel/fs/ext4/file.c:662
 call_write_iter syzkaller/managers/upstream-kcsan-gce/kernel/./include/linux/fs.h:1901 [inline]
 aio_write+0x2b4/0x390 syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1581
 __io_submit_one syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1840 [inline]
 io_submit_one+0x67c/0x1270 syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1883
 __do_sys_io_submit syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1942 [inline]
 __se_sys_io_submit+0xf5/0x270 syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1912
 __x64_sys_io_submit+0x3f/0x50 syzkaller/managers/upstream-kcsan-gce/kernel/fs/aio.c:1912
 do_syscall_64+0x39/0x80 syzkaller/managers/upstream-kcsan-gce/kernel/arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810388a2a8 of 8 bytes by task 2048 on cpu 1:
 list_empty_careful syzkaller/managers/upstream-kcsan-gce/kernel/./include/linux/list.h:319 [inline]
 dd_has_work+0xfe/0x110 syzkaller/managers/upstream-kcsan-gce/kernel/block/mq-deadline.c:590
 __blk_mq_do_dispatch_sched syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq-sched.c:135 [inline]
 blk_mq_do_dispatch_sched+0x138/0x610 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq-sched.c:199
 __blk_mq_sched_dispatch_requests+0x1fd/0x2a0 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq-sched.c:310
 blk_mq_sched_dispatch_requests+0x9f/0x110 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:1515 [inline]
 __blk_mq_delay_run_hw_queue+0x207/0x420 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:1592
 blk_mq_run_hw_queue+0x231/0x260 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:1645
 blk_mq_run_hw_queues syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:1663 [inline]
 blk_mq_requeue_work+0x423/0x490 syzkaller/managers/upstream-kcsan-gce/kernel/block/blk-mq.c:824
 process_one_work+0x3e1/0x950 syzkaller/managers/upstream-kcsan-gce/kernel/kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 syzkaller/managers/upstream-kcsan-gce/kernel/kernel/workqueue.c:2421
 kthread+0x20b/0x230 syzkaller/managers/upstream-kcsan-gce/kernel/kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 syzkaller/managers/upstream-kcsan-gce/kernel/arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2048 Comm: kworker/1:1H Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_requeue_work
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