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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888142bebc38 of 8 bytes by task 3645 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_remap+0x161/0x170 kernel/trace/blktrace.c:1021
 trace_block_bio_remap include/trace/events/block.h:505 [inline]
 blk_partition_remap block/blk-core.c:550 [inline]
 submit_bio_noacct+0x89e/0x900 block/blk-core.c:746
 submit_bio+0xb7/0xc0 block/blk-core.c:838
 mpage_bio_submit_read fs/mpage.c:82 [inline]
 mpage_readahead+0x28f/0x2d0 fs/mpage.c:385
 blkdev_readahead+0x1c/0x20 block/fops.c:401
 read_pages+0xa6/0x560 mm/readahead.c:160
 page_cache_ra_unbounded+0x2a9/0x2e0 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+0x251/0x2a0 mm/readahead.c:704
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages+0x254/0xea0 mm/filemap.c:2563
 filemap_read+0x1fb/0x670 mm/filemap.c:2658
 blkdev_read_iter+0x217/0x2c0 block/fops.c:616
 call_read_iter include/linux/fs.h:1865 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3da/0x5c0 fs/read_write.c:470
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 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 0xffff888142bebc38 of 8 bytes by task 6455 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:381 [inline]
 submit_bio_noacct_nocheck+0x57d/0x5e0 block/blk-core.c:689
 submit_bio_noacct+0x75c/0x900 block/blk-core.c:805
 submit_bio+0xb7/0xc0 block/blk-core.c:838
 mpage_bio_submit_read fs/mpage.c:82 [inline]
 mpage_readahead+0x28f/0x2d0 fs/mpage.c:385
 blkdev_readahead+0x1c/0x20 block/fops.c:401
 read_pages+0xa6/0x560 mm/readahead.c:160
 page_cache_ra_unbounded+0x2a9/0x2e0 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+0x251/0x2a0 mm/readahead.c:704
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages+0x254/0xea0 mm/filemap.c:2563
 filemap_read+0x1fb/0x670 mm/filemap.c:2658
 blkdev_read_iter+0x217/0x2c0 block/fops.c:616
 call_read_iter include/linux/fs.h:1865 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3da/0x5c0 fs/read_write.c:470
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 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: 6455 Comm: udevd Tainted: G        W          6.5.0-rc2-syzkaller-00345-gc2782531397f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
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