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BUG: KCSAN: data-race in blk_mq_run_hw_queue / blk_mq_sched_insert_request

read to 0xffff888129def810 of 8 bytes by task 9643 on cpu 1:
 list_empty_careful include/linux/list.h:287 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:69 [inline]
 blk_mq_run_hw_queue+0x10e/0x1c0 block/blk-mq.c:1469
 blk_mq_sched_insert_request+0x27c/0x3f0 block/blk-mq-sched.c:410
 blk_mq_make_request+0x78b/0xf60 block/blk-mq.c:2009
 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
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3135
 submit_bh fs/buffer.c:3141 [inline]
 __sync_dirty_buffer+0xd3/0x210 fs/buffer.c:3227
 sync_dirty_buffer+0x24/0x40 fs/buffer.c:3240
 ext4_write_inode+0x312/0x330 fs/ext4/inode.c:5091
 write_inode fs/fs-writeback.c:1312 [inline]
 __writeback_single_inode+0x6f7/0x8e0 fs/fs-writeback.c:1511
 writeback_single_inode+0x232/0x310 fs/fs-writeback.c:1565
 sync_inode fs/fs-writeback.c:2602 [inline]
 sync_inode_metadata+0x74/0xa0 fs/fs-writeback.c:2622
 ext4_fsync_nojournal fs/ext4/fsync.c:94 [inline]
 ext4_sync_file+0x4b5/0xaf0 fs/ext4/fsync.c:172
 vfs_fsync_range+0x82/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2856 [inline]
 ext4_buffered_write_iter+0x222/0x290 fs/ext4/file.c:259
 ext4_file_write_iter+0xf4/0xd40 fs/ext4/file.c:547
 call_write_iter include/linux/fs.h:1902 [inline]
 do_iter_readv_writev+0x487/0x5b0 fs/read_write.c:693
 do_iter_write fs/read_write.c:970 [inline]
 do_iter_write+0x13b/0x3c0 fs/read_write.c:951
 vfs_iter_write+0x5c/0x80 fs/read_write.c:983
 iter_file_splice_write+0x530/0x840 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0xa0/0xc0 fs/splice.c:1037
 splice_direct_to_actor+0x22b/0x540 fs/splice.c:992
 do_splice_direct+0x161/0x1e0 fs/splice.c:1080
 do_sendfile+0x384/0x7f0 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1519 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0xbe/0x140 fs/read_write.c:1511
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888129def810 of 8 bytes by task 2499 on cpu 0:
 __list_add include/linux/list.h:63 [inline]
 list_add include/linux/list.h:79 [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:738
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2499 Comm: kworker/0:1H Not tainted 5.5.0-rc1-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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