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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888136dece38 of 8 bytes by task 43 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+0x215/0x270 block/blk-mq.c:1249
 scsi_queue_rq+0x14cc/0x1a30 drivers/scsi/scsi_lib.c:1758
 blk_mq_dispatch_rq_list+0x7b1/0x11f0 block/blk-mq.c:2049
 __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+0x69a/0xdd0 block/blk-mq-sched.c:309
 blk_mq_sched_dispatch_requests+0x99/0x100 block/blk-mq-sched.c:333
 blk_mq_run_work_fn+0x65/0xe0 block/blk-mq.c:2434
 process_one_work kernel/workqueue.c:2630 [inline]
 process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2703
 worker_thread+0x525/0x730 kernel/workqueue.c:2784
 kthread+0x1d7/0x210 kernel/kthread.c:388
 ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

write to 0xffff888136dece38 of 8 bytes by task 14366 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+0x529/0x670 block/mq-deadline.c:878
 blk_mq_dispatch_plug_list block/blk-mq.c:2762 [inline]
 blk_mq_flush_plug_list+0x686/0xe00 block/blk-mq.c:2817
 __blk_flush_plug+0x210/0x260 block/blk-core.c:1142
 blk_finish_plug+0x47/0x60 block/blk-core.c:1166
 swap_cluster_readahead+0x438/0x4e0 mm/swap_state.c:664
 swapin_readahead+0x8d/0x710 mm/swap_state.c:858
 do_swap_page+0x306/0x1780 mm/memory.c:3822
 handle_pte_fault mm/memory.c:4981 [inline]
 __handle_mm_fault mm/memory.c:5119 [inline]
 handle_mm_fault+0xa2e/0x2cc0 mm/memory.c:5284
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x2f7/0x6c0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
 __get_user_8+0x11/0x20 arch/x86/lib/getuser.S:85
 fetch_robust_entry kernel/futex/core.c:758 [inline]
 exit_robust_list+0x31/0x270 kernel/futex/core.c:786
 futex_cleanup kernel/futex/core.c:1018 [inline]
 futex_exit_release+0xdf/0x130 kernel/futex/core.c:1119
 exit_mm_release+0x1a/0x30 kernel/fork.c:1651
 exit_mm+0x37/0x180 kernel/exit.c:539
 do_exit+0x580/0x1660 kernel/exit.c:861
 do_group_exit+0x101/0x150 kernel/exit.c:1024
 get_signal+0xf3c/0x1090 kernel/signal.c:2892
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14366 Comm: syz-executor.1 Not tainted 6.6.0-rc4-syzkaller-00229-g82714078aee4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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