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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88811fc9e238 of 8 bytes by task 2502 on cpu 1:
 relay_switch_subbuf+0x478/0x490 kernel/relay.c:790
 relay_reserve include/linux/relay.h:261 [inline]
 __blk_add_trace+0x820/0x860 kernel/trace/blktrace.c:271
 blk_add_trace_rq+0x15b/0x1a0 kernel/trace/blktrace.c:809
 blk_add_trace_rq_issue+0x58/0x70 kernel/trace/blktrace.c:823
 trace_block_rq_issue include/trace/events/block.h:207 [inline]
 blk_mq_start_request+0x21f/0x370 block/blk-mq.c:648
 scsi_mq_prep_fn drivers/scsi/scsi_lib.c:1601 [inline]
 scsi_queue_rq+0xb59/0x1800 drivers/scsi/scsi_lib.c:1671
 blk_mq_dispatch_rq_list+0xbe9/0xe40 block/blk-mq.c:1238
 blk_mq_sched_dispatch_requests+0x283/0x380 block/blk-mq-sched.c:209
 __blk_mq_run_hw_queue+0xb7/0x160 block/blk-mq.c:1368
 __blk_mq_delay_run_hw_queue+0x31b/0x3a0 block/blk-mq.c:1436
 blk_mq_run_hw_queue+0xfd/0x1c0 block/blk-mq.c:1473
 blk_mq_run_hw_queues+0xac/0xf0 block/blk-mq.c:1486
 blk_mq_requeue_work+0x3a9/0x460 block/blk-mq.c:741
 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

write to 0xffff88811fc9e238 of 8 bytes by task 10186 on cpu 0:
 relay_switch_subbuf+0x478/0x490 kernel/relay.c:790
 relay_reserve include/linux/relay.h:261 [inline]
 __blk_add_trace+0x820/0x860 kernel/trace/blktrace.c:271
 blk_add_trace_bio.isra.0+0xda/0xf0 kernel/trace/blktrace.c:861
 blk_add_trace_bio_queue+0x3d/0x50 kernel/trace/blktrace.c:898
 trace_block_bio_queue include/trace/events/block.h:357 [inline]
 generic_make_request_checks+0xea1/0x1040 block/blk-core.c:968
 generic_make_request+0x3e/0x700 block/blk-core.c:1020
 submit_bio+0x96/0x3c0 block/blk-core.c:1192
 ext4_io_submit+0xdf/0x110 fs/ext4/page-io.c:384
 ext4_writepages+0x98e/0x2500 fs/ext4/inode.c:2728
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1c5/0x230 mm/filemap.c:421
 file_write_and_wait_range+0xfd/0x160 mm/filemap.c:782
 ext4_sync_file+0x266/0xaf0 fs/ext4/fsync.c:153
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10186 Comm: syz-executor.1 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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