==================================================================
BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff8881419ae038 of 8 bytes by task 582 on cpu 1:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6a7/0x700 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:848 [inline]
 blk_add_trace_rq_insert+0x1b2/0x1c0 kernel/trace/blktrace.c:855
 trace_block_rq_insert include/trace/events/block.h:213 [inline]
 dd_insert_request+0x30b/0x570 block/mq-deadline.c:744
 dd_insert_requests+0xfc/0x140 block/mq-deadline.c:781
 blk_mq_sched_insert_requests+0xc0/0x2a0 block/blk-mq-sched.c:477
 blk_mq_dispatch_plug_list+0x1e9/0x2c0 block/blk-mq.c:2694
 blk_mq_flush_plug_list+0x2ea/0x340 block/blk-mq.c:2736
 __blk_flush_plug+0x25a/0x2b0 block/blk-core.c:1137
 blk_finish_plug+0x44/0x60 block/blk-core.c:1161
 read_pages+0x4e1/0x560 mm/readahead.c:184
 page_cache_ra_unbounded+0x2de/0x320 mm/readahead.c:270
 do_page_cache_ra mm/readahead.c:300 [inline]
 page_cache_ra_order mm/readahead.c:560 [inline]
 ondemand_readahead+0x541/0x6d0 mm/readahead.c:682
 page_cache_sync_ra+0xdc/0xf0 mm/readahead.c:709
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages mm/filemap.c:2581 [inline]
 filemap_read+0x3fd/0x1510 mm/filemap.c:2675
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2821
 ext4_file_read_iter+0x1c8/0x280
 call_read_iter include/linux/fs.h:2185 [inline]
 generic_file_splice_read+0xde/0x2b0 fs/splice.c:309
 do_splice_to fs/splice.c:793 [inline]
 splice_direct_to_actor+0x26c/0x620 fs/splice.c:865
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff8881419ae038 of 8 bytes by task 579 on cpu 0:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6a7/0x700 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:848 [inline]
 blk_add_trace_rq_issue+0x1b2/0x1c0 kernel/trace/blktrace.c:861
 trace_block_rq_issue include/trace/events/block.h:227 [inline]
 blk_mq_start_request+0x23b/0x280 block/blk-mq.c:1220
 scsi_queue_rq+0x13d8/0x1570 drivers/scsi/scsi_lib.c:1759
 blk_mq_dispatch_rq_list+0x977/0x1250 block/blk-mq.c:1992
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:173 [inline]
 blk_mq_do_dispatch_sched+0x49d/0x7f0 block/blk-mq-sched.c:187
 __blk_mq_sched_dispatch_requests+0x1cd/0x270
 blk_mq_sched_dispatch_requests+0x8f/0xf0 block/blk-mq-sched.c:339
 __blk_mq_run_hw_queue+0x7e/0x100 block/blk-mq.c:2110
 __blk_mq_delay_run_hw_queue+0x15b/0x2e0 block/blk-mq.c:2186
 blk_mq_run_hw_queue+0x180/0x320 block/blk-mq.c:2234
 blk_mq_sched_insert_requests+0x1cb/0x2a0 block/blk-mq-sched.c:493
 blk_mq_dispatch_plug_list+0x1e9/0x2c0 block/blk-mq.c:2694
 blk_mq_flush_plug_list+0x2ea/0x340 block/blk-mq.c:2736
 __blk_flush_plug+0x25a/0x2b0 block/blk-core.c:1137
 blk_finish_plug+0x44/0x60 block/blk-core.c:1161
 __iomap_dio_rw+0xd27/0x1000 fs/iomap/direct-io.c:610
 iomap_dio_rw+0x3c/0x80 fs/iomap/direct-io.c:690
 ext4_dio_write_iter fs/ext4/file.c:587 [inline]
 ext4_file_write_iter+0xa27/0x1170 fs/ext4/file.c:698
 do_iter_write+0x494/0x750 fs/read_write.c:861
 vfs_iter_write+0x4c/0x70 fs/read_write.c:902
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x305/0x620 fs/splice.c:886
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 579 Comm: syz-executor.0 Not tainted 6.1.0-rc6-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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syz-executor.0 (579) used greatest stack depth: 9200 bytes left