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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88814ff38238 of 8 bytes by task 17439 on cpu 0:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:711
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6ba/0x710 kernel/trace/blktrace.c:275
 blk_add_trace_bio_remap+0x218/0x230 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:611
 submit_bio_noacct+0x378/0x820 block/blk-core.c:797
 submit_bio+0x139/0x150
 ext4_io_submit+0x4f/0x60 fs/ext4/page-io.c:378
 ext4_writepages+0x94a/0x1970 fs/ext4/inode.c:2824
 do_writepages+0x1db/0x350 mm/page-writeback.c:2352
 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:779
 ext4_sync_file+0xad/0x560 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2732 [inline]
 ext4_buffered_write_iter+0x23f/0x280 fs/ext4/file.c:277
 ext4_file_write_iter+0x211/0xdf0
 do_iter_readv_writev+0x27b/0x300
 do_iter_write+0x16f/0x5c0 fs/read_write.c:852
 vfs_iter_write+0x4c/0x70 fs/read_write.c:893
 iter_file_splice_write+0x44a/0x7c0 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x660 fs/splice.c:891
 do_splice_direct+0xfb/0x180 fs/splice.c:979
 do_sendfile+0x3ad/0x900 fs/read_write.c:1246
 __do_sys_sendfile64 fs/read_write.c:1311 [inline]
 __se_sys_sendfile64 fs/read_write.c:1297 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1297
 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+0x44/0xae

write to 0xffff88814ff38238 of 8 bytes by task 1404 on cpu 1:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:711
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6ba/0x710 kernel/trace/blktrace.c:275
 blk_add_trace_bio kernel/trace/blktrace.c:906 [inline]
 blk_add_trace_bio_queue+0x15d/0x170 kernel/trace/blktrace.c:938
 trace_block_bio_queue include/trace/events/block.h:355 [inline]
 submit_bio_noacct+0x7e3/0x820 block/blk-core.c:857
 submit_bio+0x139/0x150
 submit_bh_wbc+0x2a8/0x2f0 fs/buffer.c:3045
 submit_bh+0x1e/0x30 fs/buffer.c:3051
 journal_submit_commit_record+0x307/0x3a0
 jbd2_journal_commit_transaction+0x1710/0x2490 fs/jbd2/commit.c:914
 kjournald2+0x1af/0x370 fs/jbd2/journal.c:213
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0x0000000000000040 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1404 Comm: jbd2/sda1-8 Tainted: G        W         5.18.0-rc7-syzkaller-00164-g6c3f5bec9b40-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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