==================================================================
BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88813b1cd238 of 8 bytes by task 23291 on cpu 0:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6a7/0x700 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:848 [inline]
 blk_add_trace_rq_insert+0x1b2/0x1c0 kernel/trace/blktrace.c:855
 trace_block_rq_insert include/trace/events/block.h:213 [inline]
 dd_insert_request+0x30b/0x570 block/mq-deadline.c:744
 dd_insert_requests+0xfc/0x140 block/mq-deadline.c:781
 blk_mq_sched_insert_requests+0xc0/0x2a0 block/blk-mq-sched.c:477
 blk_mq_dispatch_plug_list+0x1e9/0x2c0 block/blk-mq.c:2693
 blk_mq_flush_plug_list+0x2ea/0x340 block/blk-mq.c:2735
 __blk_flush_plug+0x25a/0x2b0 block/blk-core.c:1138
 blk_finish_plug+0x44/0x60 block/blk-core.c:1162
 read_pages+0x4e1/0x560 mm/readahead.c:184
 page_cache_ra_unbounded+0x2de/0x320 mm/readahead.c:270
 do_page_cache_ra mm/readahead.c:300 [inline]
 page_cache_ra_order mm/readahead.c:560 [inline]
 ondemand_readahead+0x541/0x6d0 mm/readahead.c:682
 page_cache_sync_ra+0xdc/0xf0 mm/readahead.c:709
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages mm/filemap.c:2581 [inline]
 filemap_read+0x3fd/0x1510 mm/filemap.c:2675
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2821
 ext4_file_read_iter+0x1c8/0x280
 call_read_iter include/linux/fs.h:2185 [inline]
 generic_file_splice_read+0xde/0x2b0 fs/splice.c:309
 do_splice_to fs/splice.c:793 [inline]
 splice_direct_to_actor+0x26c/0x620 fs/splice.c:865
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffff88813b1cd238 of 8 bytes by task 23296 on cpu 1:
 relay_switch_subbuf+0x39d/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x6a7/0x700 kernel/trace/blktrace.c:276
 blk_add_trace_bio kernel/trace/blktrace.c:907 [inline]
 blk_add_trace_getrq+0x12e/0x140 kernel/trace/blktrace.c:944
 trace_block_getrq include/trace/events/block.h:366 [inline]
 blk_mq_submit_bio+0xe2d/0xe90 block/blk-mq.c:2906
 __submit_bio block/blk-core.c:591 [inline]
 __submit_bio_noacct_mq block/blk-core.c:668 [inline]
 submit_bio_noacct_nocheck+0x83d/0xaa0 block/blk-core.c:685
 submit_bio_noacct+0x6a5/0x810 block/blk-core.c:791
 submit_bio+0xfb/0x110 block/blk-core.c:827
 ext4_mpage_readpages+0x115b/0x11a0 fs/ext4/readpage.c:407
 ext4_readahead+0x99/0xa0 fs/ext4/inode.c:3243
 read_pages+0xa6/0x560 mm/readahead.c:161
 page_cache_ra_unbounded+0x2de/0x320 mm/readahead.c:270
 do_page_cache_ra mm/readahead.c:300 [inline]
 page_cache_ra_order mm/readahead.c:560 [inline]
 ondemand_readahead+0x541/0x6d0 mm/readahead.c:682
 page_cache_sync_ra+0xdc/0xf0 mm/readahead.c:709
 page_cache_sync_readahead include/linux/pagemap.h:1213 [inline]
 filemap_get_pages mm/filemap.c:2581 [inline]
 filemap_read+0x3fd/0x1510 mm/filemap.c:2675
 generic_file_read_iter+0x72/0x320 mm/filemap.c:2821
 ext4_file_read_iter+0x1c8/0x280
 call_read_iter include/linux/fs.h:2185 [inline]
 generic_file_splice_read+0xde/0x2b0 fs/splice.c:309
 do_splice_to fs/splice.c:793 [inline]
 splice_direct_to_actor+0x26c/0x620 fs/splice.c:865
 do_splice_direct+0xfb/0x180 fs/splice.c:974
 do_sendfile+0x3bf/0x910 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x10c/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23296 Comm: syz-executor.2 Tainted: G        W          6.1.0-rc3-syzkaller-00011-g5aaef24b5c6d-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
==================================================================
syz-executor.2 (23296) used greatest stack depth: 9744 bytes left