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BUG: KCSAN: data-race in deadline_remove_request / ll_back_merge_fn

write to 0xffff88812975ccb8 of 8 bytes by task 2500 on cpu 1:
 deadline_remove_request+0x1e5/0x260 block/mq-deadline.c:123
 deadline_move_request block/mq-deadline.c:176 [inline]
 __dd_dispatch_request block/mq-deadline.c:365 [inline]
 dd_dispatch_request+0x421/0x500 block/mq-deadline.c:387
 blk_mq_do_dispatch_sched+0x1e3/0x260 block/blk-mq-sched.c:103
 blk_mq_sched_dispatch_requests+0x2b4/0x380 block/blk-mq-sched.c:211
 __blk_mq_run_hw_queue+0xb7/0x160 block/blk-mq.c:1368
 blk_mq_run_work_fn+0x57/0x70 block/blk-mq.c:1597
 process_one_work+0x3d4/0x890 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 0xffff88812975ccb8 of 8 bytes by task 19161 on cpu 0:
 req_set_nomerge block/blk.h:259 [inline]
 ll_new_hw_segment block/blk-merge.c:583 [inline]
 ll_new_hw_segment block/blk-merge.c:566 [inline]
 ll_back_merge_fn+0xa63/0xd80 block/blk-merge.c:600
 bio_attempt_back_merge+0x55/0x290 block/blk-core.c:607
 blk_attempt_plug_merge+0x208/0x210 block/blk-core.c:725
 blk_mq_make_request+0x87c/0xf60 block/blk-mq.c:1926
 generic_make_request block/blk-core.c:1066 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1008
 submit_bio+0x96/0x3c0 block/blk-core.c:1192
 iomap_dio_submit_bio.isra.0+0xfc/0x120 fs/iomap/direct-io.c:70
 iomap_dio_bio_actor+0x40a/0x960 fs/iomap/direct-io.c:306
 iomap_dio_actor+0x87/0x3a0 fs/iomap/direct-io.c:382
 iomap_apply+0x20d/0x6a0 fs/iomap/apply.c:80
 iomap_dio_rw+0x67e/0x9a0 fs/iomap/direct-io.c:498
 ext4_dio_write_iter fs/ext4/file.c:438 [inline]
 ext4_file_write_iter+0xc38/0xd40 fs/ext4/file.c:545
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 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: 0 PID: 19161 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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