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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88811e369438 of 8 bytes by task 9443 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:1253
 loop_queue_rq+0x44/0x650 drivers/block/loop.c:1845
 __blk_mq_issue_directly block/blk-mq.c:2611 [inline]
 blk_mq_request_issue_directly+0x1d0/0x330 block/blk-mq.c:2696
 blk_mq_plug_issue_direct+0x156/0x520 block/blk-mq.c:2717
 blk_mq_flush_plug_list+0x2a7/0xdc0 block/blk-mq.c:2826
 __blk_flush_plug+0x210/0x260 block/blk-core.c:1176
 blk_finish_plug+0x47/0x60 block/blk-core.c:1200
 read_pages+0x4bf/0x540 mm/readahead.c:183
 page_cache_ra_unbounded+0x2aa/0x2e0 mm/readahead.c:269
 do_page_cache_ra mm/readahead.c:299 [inline]
 force_page_cache_ra mm/readahead.c:330 [inline]
 page_cache_sync_ra+0x24b/0x2a0 mm/readahead.c:689
 page_cache_sync_readahead include/linux/pagemap.h:1300 [inline]
 filemap_get_pages+0x251/0xf90 mm/filemap.c:2498
 filemap_read+0x214/0x680 mm/filemap.c:2594
 blkdev_read_iter+0x217/0x2c0 block/fops.c:757
 call_read_iter include/linux/fs.h:2079 [inline]
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x5ab/0x6a0 fs/read_write.c:476
 ksys_read+0xeb/0x1a0 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:627
 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 0xffff88811e369438 of 8 bytes by task 3513 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_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:699
 submit_bio_noacct+0x67d/0x830 block/blk-core.c:826
 submit_bio+0x212/0x220 block/blk-core.c:868
 mpage_bio_submit_read fs/mpage.c:82 [inline]
 mpage_readahead+0x28a/0x2d0 fs/mpage.c:384
 blkdev_readahead+0x1c/0x20 block/fops.c:440
 read_pages+0x9f/0x540 mm/readahead.c:160
 page_cache_ra_unbounded+0x2aa/0x2e0 mm/readahead.c:269
 do_page_cache_ra mm/readahead.c:299 [inline]
 force_page_cache_ra mm/readahead.c:330 [inline]
 page_cache_sync_ra+0x24b/0x2a0 mm/readahead.c:689
 page_cache_sync_readahead include/linux/pagemap.h:1300 [inline]
 filemap_get_pages+0x251/0xf90 mm/filemap.c:2498
 filemap_read+0x214/0x680 mm/filemap.c:2594
 blkdev_read_iter+0x217/0x2c0 block/fops.c:757
 call_read_iter include/linux/fs.h:2079 [inline]
 new_sync_read fs/read_write.c:395 [inline]
 vfs_read+0x5ab/0x6a0 fs/read_write.c:476
 ksys_read+0xeb/0x1a0 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:627
 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

value changed: 0x0000000000000040 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 3513 Comm: udevd Tainted: G        W          6.8.0-rc3-syzkaller-00047-g047371968ffc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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