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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88813c1d3e38 of 8 bytes by task 6240 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:2907
 __submit_bio block/blk-core.c:590 [inline]
 __submit_bio_noacct_mq block/blk-core.c:667 [inline]
 submit_bio_noacct_nocheck+0x83d/0xaa0 block/blk-core.c:684
 submit_bio_noacct+0x6a5/0x810 block/blk-core.c:790
 submit_bio+0xfb/0x110 block/blk-core.c:826
 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_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 0xffff88813c1d3e38 of 8 bytes by task 6250 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_plug+0x48/0x60 kernel/trace/blktrace.c:954
 trace_block_plug include/trace/events/block.h:379 [inline]
 blk_add_rq_to_plug+0x30f/0x390 block/blk-mq.c:1260
 blk_mq_submit_bio+0x90b/0xe90 block/blk-mq.c:2927
 __submit_bio block/blk-core.c:590 [inline]
 __submit_bio_noacct_mq block/blk-core.c:667 [inline]
 submit_bio_noacct_nocheck+0x83d/0xaa0 block/blk-core.c:684
 submit_bio_noacct+0x6a5/0x810 block/blk-core.c:790
 submit_bio+0xfb/0x110 block/blk-core.c:826
 ext4_mpage_readpages+0x115b/0x11a0 fs/ext4/readpage.c:407
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3243
 read_pages+0xa6/0x560 mm/readahead.c:161
 page_cache_ra_unbounded+0x12a/0x320 mm/readahead.c:242
 do_page_cache_ra+0xa7/0xc0 mm/readahead.c:300
 ondemand_readahead+0x6c3/0x6d0 mm/readahead.c:655
 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

value changed: 0x0000000000000030 -> 0x0000000000000038

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6250 Comm: syz-executor.1 Not tainted 6.1.0-rc5-syzkaller-00326-g77c51ba552a1-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
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