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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888144819838 of 8 bytes by task 4043 on cpu 0:
 relay_switch_subbuf+0x399/0x3a0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x665/0x720 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:844 [inline]
 blk_add_trace_rq_issue+0x1b6/0x1c0 kernel/trace/blktrace.c:857
 trace_block_rq_issue include/trace/events/block.h:229 [inline]
 blk_mq_start_request+0x2a7/0x300 block/blk-mq.c:1254
 scsi_queue_rq+0x14a3/0x1a00 drivers/scsi/scsi_lib.c:1757
 blk_mq_dispatch_rq_list+0x2d9/0x10a0 block/blk-mq.c:2071
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:170 [inline]
 blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
 __blk_mq_sched_dispatch_requests+0x5ec/0xd20 block/blk-mq-sched.c:309
 blk_mq_sched_dispatch_requests+0x78/0xe0 block/blk-mq-sched.c:331
 blk_mq_run_hw_queue+0x298/0x4c0 block/blk-mq.c:2286
 blk_mq_flush_plug_list+0x7a7/0xdc0 block/blk-mq.c:2834
 blk_add_rq_to_plug+0x102/0x3d0 block/blk-mq.c:1300
 blk_mq_submit_bio+0x760/0x1020 block/blk-mq.c:3037
 __submit_bio+0x11c/0x350 block/blk-core.c:607
 __submit_bio_noacct_mq block/blk-core.c:686 [inline]
 submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:715
 submit_bio_noacct+0x67d/0x830 block/blk-core.c:825
 submit_bio+0xb7/0xc0 block/blk-core.c:858
 iomap_dio_submit_bio fs/iomap/direct-io.c:80 [inline]
 iomap_dio_bio_iter+0xa4a/0xbe0 fs/iomap/direct-io.c:417
 __iomap_dio_rw+0x8dd/0x1090 fs/iomap/direct-io.c:659
 iomap_dio_rw+0x40/0x90 fs/iomap/direct-io.c:748
 ext4_dio_write_iter fs/ext4/file.c:577 [inline]
 ext4_file_write_iter+0xa8a/0xe10 fs/ext4/file.c:696
 do_iter_readv_writev+0x2b0/0x330
 vfs_writev+0x2e9/0x860 fs/read_write.c:971
 do_pwritev fs/read_write.c:1072 [inline]
 __do_sys_pwritev2 fs/read_write.c:1131 [inline]
 __se_sys_pwritev2+0x10c/0x1d0 fs/read_write.c:1122
 __x64_sys_pwritev2+0x78/0x90 fs/read_write.c:1122
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

write to 0xffff888144819838 of 8 bytes by task 4025 on cpu 1:
 relay_switch_subbuf+0x399/0x3a0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x665/0x720 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:844 [inline]
 blk_add_trace_rq_insert+0x1b6/0x1c0 kernel/trace/blktrace.c:851
 trace_block_rq_insert include/trace/events/block.h:215 [inline]
 dd_insert_request block/mq-deadline.c:824 [inline]
 dd_insert_requests+0x52e/0x670 block/mq-deadline.c:878
 blk_mq_dispatch_plug_list block/blk-mq.c:2784 [inline]
 blk_mq_flush_plug_list+0x634/0xdc0 block/blk-mq.c:2834
 blk_add_rq_to_plug+0x102/0x3d0 block/blk-mq.c:1300
 blk_mq_submit_bio+0x760/0x1020 block/blk-mq.c:3037
 __submit_bio+0x11c/0x350 block/blk-core.c:607
 __submit_bio_noacct_mq block/blk-core.c:686 [inline]
 submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:715
 submit_bio_noacct+0x67d/0x830 block/blk-core.c:825
 submit_bio+0xb7/0xc0 block/blk-core.c:858
 ext4_io_submit+0x8a/0xa0 fs/ext4/page-io.c:378
 ext4_do_writepages+0xb3a/0x2100 fs/ext4/inode.c:2705
 ext4_writepages+0x15e/0x2e0 fs/ext4/inode.c:2774
 do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
 filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:388
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 __filemap_fdatawrite mm/filemap.c:427 [inline]
 filemap_flush+0x95/0xc0 mm/filemap.c:454
 ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3078
 ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:169
 __fput+0x299/0x630 fs/file_table.c:376
 ____fput+0x15/0x20 fs/file_table.c:404
 task_work_run+0x135/0x1a0 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x604/0x16d0 kernel/exit.c:871
 do_group_exit+0x101/0x150 kernel/exit.c:1020
 get_signal+0xf4e/0x10a0 kernel/signal.c:2893
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:105 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:201 [inline]
 syscall_exit_to_user_mode+0x58/0x130 kernel/entry/common.c:212
 do_syscall_64+0xda/0x1d0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4025 Comm: syz-executor.0 Not tainted 6.8.0-rc2-syzkaller-00055-g6764c317b6bb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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