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

write to 0xffff88814ae6e438 of 8 bytes by task 13412 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_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:1991
 __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:2109
 __blk_mq_delay_run_hw_queue+0x15b/0x2e0 block/blk-mq.c:2185
 blk_mq_run_hw_queue+0x180/0x320 block/blk-mq.c:2233
 blk_mq_sched_insert_requests+0x1cb/0x2a0 block/blk-mq-sched.c:493
 blk_mq_dispatch_plug_list+0x1e9/0x2c0 block/blk-mq.c:2693
 blk_mq_flush_plug_list+0x2ea/0x340 block/blk-mq.c:2735
 __blk_flush_plug+0x25a/0x2b0 block/blk-core.c:1138
 blk_finish_plug+0x44/0x60 block/blk-core.c:1162
 ext4_writepages+0x171d/0x1cf0 fs/ext4/inode.c:2885
 do_writepages+0x1db/0x350 mm/page-writeback.c:2469
 filemap_fdatawrite_wbc+0xd6/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0xd6/0x170 mm/filemap.c:774
 ext4_sync_file+0x105/0x6d0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2883 [inline]
 ext4_buffered_write_iter+0x398/0x3e0 fs/ext4/file.c:292
 ext4_file_write_iter+0x2c7/0x1170
 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

write to 0xffff88814ae6e438 of 8 bytes by task 13413 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_bio kernel/trace/blktrace.c:907 [inline]
 blk_add_trace_getrq+0x12e/0x140 kernel/trace/blktrace.c:944
 trace_block_getrq include/trace/events/block.h:366 [inline]
 blk_mq_submit_bio+0xe2d/0xe90 block/blk-mq.c:2906
 __submit_bio block/blk-core.c:591 [inline]
 __submit_bio_noacct_mq block/blk-core.c:668 [inline]
 submit_bio_noacct_nocheck+0x83d/0xaa0 block/blk-core.c:685
 submit_bio_noacct+0x6a5/0x810 block/blk-core.c:791
 submit_bio+0xfb/0x110 block/blk-core.c:827
 iomap_dio_submit_bio fs/iomap/direct-io.c:77 [inline]
 iomap_dio_bio_iter+0xa4d/0xc00 fs/iomap/direct-io.c:361
 __iomap_dio_rw+0x981/0x1000 fs/iomap/direct-io.c:602
 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_writev fs/read_write.c:934 [inline]
 do_pwritev+0x235/0x430 fs/read_write.c:1031
 __do_sys_pwritev2 fs/read_write.c:1090 [inline]
 __se_sys_pwritev2 fs/read_write.c:1081 [inline]
 __x64_sys_pwritev2+0x7e/0xa0 fs/read_write.c:1081
 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: 13413 Comm: syz-executor.1 Tainted: G        W          6.1.0-rc2-syzkaller-00487-gb72018ab8236-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
==================================================================