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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff8881666b5238 of 8 bytes by task 4500 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_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_sched_dispatch_requests+0x1d4/0xdd0 block/blk-mq-sched.c:301
 blk_mq_sched_dispatch_requests+0x99/0x100 block/blk-mq-sched.c:333
 blk_mq_run_hw_queue+0x2a4/0x4c0 block/blk-mq.c:2264
 blk_execute_rq+0x13a/0x3d0 block/blk-mq.c:1404
 sg_scsi_ioctl drivers/scsi/scsi_ioctl.c:593 [inline]
 scsi_ioctl+0x13eb/0x1520 drivers/scsi/scsi_ioctl.c:901
 sg_ioctl_common drivers/scsi/sg.c:1106 [inline]
 sg_ioctl+0xda6/0x1870 drivers/scsi/sg.c:1160
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff8881666b5238 of 8 bytes by task 4459 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_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:1364 [inline]
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x3ff/0x6c0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 4459 Comm: syz-executor.1 Tainted: G        W          6.6.0-rc2-syzkaller-00244-g27bbf45eae9c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
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