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

write to 0xffff88813b790038 of 8 bytes by task 2644 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_remap+0x169/0x180 kernel/trace/blktrace.c:1025
 trace_block_bio_remap include/trace/events/block.h:479 [inline]
 blk_partition_remap+0x170/0x1b0 block/blk-core.c:555
 submit_bio_noacct+0x394/0x810 block/blk-core.c:739
 submit_bio+0xfb/0x110 block/blk-core.c:841
 iomap_dio_submit_bio fs/iomap/direct-io.c:77 [inline]
 iomap_dio_bio_iter+0xa0d/0xbd0 fs/iomap/direct-io.c:360
 __iomap_dio_rw+0x981/0x1000 fs/iomap/direct-io.c:601
 iomap_dio_rw+0x3c/0x80 fs/iomap/direct-io.c:689
 ext4_dio_write_iter fs/ext4/file.c:587 [inline]
 ext4_file_write_iter+0xa36/0x11b0 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

write to 0xffff88813b790038 of 8 bytes by task 2649 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_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+0xe74/0xed0 block/blk-mq.c:2971
 __submit_bio block/blk-core.c:605 [inline]
 __submit_bio_noacct_mq block/blk-core.c:682 [inline]
 submit_bio_noacct_nocheck+0x83d/0xaa0 block/blk-core.c:699
 submit_bio_noacct+0x6a5/0x810 block/blk-core.c:805
 submit_bio+0xfb/0x110 block/blk-core.c:841
 iomap_dio_submit_bio fs/iomap/direct-io.c:77 [inline]
 iomap_dio_bio_iter+0xa0d/0xbd0 fs/iomap/direct-io.c:360
 __iomap_dio_rw+0x981/0x1000 fs/iomap/direct-io.c:601
 iomap_dio_rw+0x3c/0x80 fs/iomap/direct-io.c:689
 ext4_dio_write_iter fs/ext4/file.c:587 [inline]
 ext4_file_write_iter+0xa36/0x11b0 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: 0x0000000000000030 -> 0x0000000000000040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2649 Comm: syz-executor.4 Tainted: G        W          6.2.0-rc1-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
==================================================================
syz-executor.4 (2649) used greatest stack depth: 9944 bytes left