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BUG: KCSAN: data-race in blk_mq_run_hw_queue / blk_mq_sched_insert_request

write to 0xffff88812ab14810 of 8 bytes by task 2521 on cpu 0:
 __list_add include/linux/list.h:70 [inline]
 list_add include/linux/list.h:86 [inline]
 blk_mq_sched_bypass_insert block/blk-mq-sched.c:367 [inline]
 blk_mq_sched_insert_request+0x2fd/0x3f0 block/blk-mq-sched.c:394
 blk_mq_requeue_work+0x370/0x460 block/blk-mq.c:746
 process_one_work+0x413/0x8f0 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88812ab14810 of 8 bytes by task 11303 on cpu 1:
 list_empty_careful include/linux/list.h:301 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:69 [inline]
 blk_mq_run_hw_queue+0x10e/0x1c0 block/blk-mq.c:1508
 blk_mq_sched_insert_requests+0x198/0x260 block/blk-mq-sched.c:444
 blk_mq_flush_plug_list+0x2dc/0x490 block/blk-mq.c:1758
 blk_flush_plug_list+0x271/0x2a0 block/blk-core.c:1772
 blk_finish_plug block/blk-core.c:1789 [inline]
 blk_finish_plug+0x60/0x84 block/blk-core.c:1785
 read_pages+0xbc/0x2d0 mm/readahead.c:142
 __do_page_cache_readahead+0x353/0x390 mm/readahead.c:212
 ra_submit mm/internal.h:62 [inline]
 ondemand_readahead+0x35d/0x710 mm/readahead.c:492
 page_cache_sync_readahead+0x1ad/0x1e0 mm/readahead.c:527
 generic_file_buffered_read mm/filemap.c:2029 [inline]
 generic_file_read_iter+0xeb6/0x1440 mm/filemap.c:2302
 ext4_file_read_iter fs/ext4/file.c:131 [inline]
 ext4_file_read_iter+0x10f/0x370 fs/ext4/file.c:114
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x35c/0x500 fs/splice.c:313
 do_splice_to+0xf2/0x130 fs/splice.c:892
 splice_direct_to_actor+0x1b6/0x540 fs/splice.c:971
 do_splice_direct+0x161/0x1e0 fs/splice.c:1080
 do_sendfile+0x384/0x7f0 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x12a/0x140 fs/read_write.c:1567
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 11303 Comm: syz-executor.3 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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