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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888118a7a838 of 8 bytes by task 23075 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_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_hw_queue+0x2a4/0x4c0 block/blk-mq.c:2264
 blk_mq_flush_plug_list+0x7f9/0xe00 block/blk-mq.c:2817
 blk_add_rq_to_plug+0x108/0x3e0 block/blk-mq.c:1293
 blk_mq_submit_bio+0x692/0xd70 block/blk-mq.c:3012
 __submit_bio+0x11c/0x350 block/blk-core.c:599
 __submit_bio_noacct_mq block/blk-core.c:678 [inline]
 submit_bio_noacct_nocheck+0x449/0x5e0 block/blk-core.c:707
 submit_bio_noacct+0x700/0x8a0 block/blk-core.c:801
 submit_bio+0xb7/0xc0 block/blk-core.c:834
 swap_writepage_bdev_async mm/page_io.c:368 [inline]
 __swap_writepage+0x625/0xc90 mm/page_io.c:386
 swap_writepage+0x6e/0x120 mm/page_io.c:204
 pageout mm/vmscan.c:1355 [inline]
 shrink_folio_list+0x1952/0x2540 mm/vmscan.c:2015
 reclaim_folio_list+0x7b/0x1d0 mm/vmscan.c:2801
 reclaim_pages+0x220/0x280 mm/vmscan.c:2837
 madvise_cold_or_pageout_pte_range+0x98c/0x9f0 mm/madvise.c:533
 walk_pmd_range mm/pagewalk.c:143 [inline]
 walk_pud_range mm/pagewalk.c:221 [inline]
 walk_p4d_range mm/pagewalk.c:256 [inline]
 walk_pgd_range+0x80a/0xec0 mm/pagewalk.c:293
 __walk_page_range+0xc2/0x320 mm/pagewalk.c:395
 walk_page_range+0x2c7/0x3f0 mm/pagewalk.c:521
 madvise_pageout_page_range mm/madvise.c:592 [inline]
 madvise_pageout mm/madvise.c:619 [inline]
 madvise_vma_behavior mm/madvise.c:1041 [inline]
 madvise_walk_vmas mm/madvise.c:1270 [inline]
 do_madvise+0x1f20/0x2970 mm/madvise.c:1450
 __do_sys_madvise mm/madvise.c:1463 [inline]
 __se_sys_madvise mm/madvise.c:1461 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1461
 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 0xffff888118a7a838 of 8 bytes by task 23078 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_bio kernel/trace/blktrace.c:903 [inline]
 blk_add_trace_bio_queue+0x12c/0x140 kernel/trace/blktrace.c:935
 trace_block_bio_queue include/trace/events/block.h:383 [inline]
 submit_bio_noacct_nocheck+0x57d/0x5e0 block/blk-core.c:690
 submit_bio_noacct+0x700/0x8a0 block/blk-core.c:801
 submit_bio+0xb7/0xc0 block/blk-core.c:834
 swap_writepage_bdev_async mm/page_io.c:368 [inline]
 __swap_writepage+0x625/0xc90 mm/page_io.c:386
 swap_writepage+0x6e/0x120 mm/page_io.c:204
 pageout mm/vmscan.c:1355 [inline]
 shrink_folio_list+0x1952/0x2540 mm/vmscan.c:2015
 reclaim_folio_list+0x7b/0x1d0 mm/vmscan.c:2801
 reclaim_pages+0x220/0x280 mm/vmscan.c:2837
 madvise_cold_or_pageout_pte_range+0x98c/0x9f0 mm/madvise.c:533
 walk_pmd_range mm/pagewalk.c:143 [inline]
 walk_pud_range mm/pagewalk.c:221 [inline]
 walk_p4d_range mm/pagewalk.c:256 [inline]
 walk_pgd_range+0x80a/0xec0 mm/pagewalk.c:293
 __walk_page_range+0xc2/0x320 mm/pagewalk.c:395
 walk_page_range+0x2c7/0x3f0 mm/pagewalk.c:521
 madvise_pageout_page_range mm/madvise.c:592 [inline]
 madvise_pageout mm/madvise.c:619 [inline]
 madvise_vma_behavior mm/madvise.c:1041 [inline]
 madvise_walk_vmas mm/madvise.c:1270 [inline]
 do_madvise+0x1f20/0x2970 mm/madvise.c:1450
 __do_sys_madvise mm/madvise.c:1463 [inline]
 __se_sys_madvise mm/madvise.c:1461 [inline]
 __x64_sys_madvise+0x60/0x70 mm/madvise.c:1461
 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

value changed: 0x0000000000000040 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23078 Comm: syz-executor.4 Not tainted 6.6.0-rc6-syzkaller-00182-gce55c22ec8b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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