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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888139eaac38 of 8 bytes by interrupt 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_rq kernel/trace/blktrace.c:848 [inline]
 blk_add_trace_rq_complete+0x1af/0x1c0 kernel/trace/blktrace.c:880
 trace_block_rq_complete include/trace/events/block.h:147 [inline]
 blk_update_request+0x807/0x850 block/blk-mq.c:859
 scsi_end_request+0x52/0x470 drivers/scsi/scsi_lib.c:541
 scsi_io_completion+0x95/0x1f0 drivers/scsi/scsi_lib.c:979
 scsi_finish_command+0x1b7/0x1c0 drivers/scsi/scsi.c:198
 scsi_complete+0x19e/0x1d0 drivers/scsi/scsi_lib.c:1446
 blk_complete_reqs block/blk-mq.c:1094 [inline]
 blk_done_softirq+0x92/0xc0 block/blk-mq.c:1099
 __do_softirq+0xf2/0x2c7 kernel/softirq.c:571
 __irq_exit_rcu kernel/softirq.c:650 [inline]
 irq_exit_rcu+0x41/0x70 kernel/softirq.c:662
 common_interrupt+0x9f/0xc0 arch/x86/kernel/irq.c:240
 asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:640
 decode_watchpoint kernel/kcsan/encoding.h:74 [inline]
 find_watchpoint kernel/kcsan/core.c:130 [inline]
 check_access kernel/kcsan/core.c:726 [inline]
 __tsan_read4+0x58/0x180 kernel/kcsan/core.c:1013
 jbd2__journal_start+0xb1/0x3b0 fs/jbd2/transaction.c:501
 __ext4_journal_start_sb+0x159/0x300 fs/ext4/ext4_jbd2.c:105
 __ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline]
 ext4_dirty_inode+0x58/0xa0 fs/ext4/inode.c:6007
 __mark_inode_dirty+0x15b/0x730 fs/fs-writeback.c:2400
 mark_inode_dirty include/linux/fs.h:2467 [inline]
 generic_write_end+0x175/0x350 fs/buffer.c:2184
 ext4_da_write_end+0x26c/0x620 fs/ext4/inode.c:3096
 generic_perform_write+0x264/0x3f0 mm/filemap.c:3764
 ext4_buffered_write_iter+0x235/0x3e0 fs/ext4/file.c:285
 ext4_file_write_iter+0x2c7/0x1170
 call_write_iter include/linux/fs.h:2191 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x468/0x760 fs/read_write.c:584
 ksys_write+0xe8/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:646
 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 0xffff888139eaac38 of 8 bytes by task 3859 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_bio kernel/trace/blktrace.c:907 [inline]
 blk_add_trace_bio_queue+0x12e/0x140 kernel/trace/blktrace.c:939
 trace_block_bio_queue include/trace/events/block.h:355 [inline]
 submit_bio_noacct+0x7cf/0x810 block/blk-core.c:785
 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: 0x0000000000000040 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3859 Comm: syz-executor.4 Tainted: G        W          6.1.0-rc2-syzkaller-00338-g576e61cea1e4-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
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