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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff88813cbd7a38 of 8 bytes by interrupt on cpu 1:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:844 [inline]
 blk_add_trace_rq_complete+0x1b7/0x1c0 kernel/trace/blktrace.c:876
 trace_block_rq_complete include/trace/events/block.h:149 [inline]
 blk_update_request+0x8f8/0x950 block/blk-mq.c:899
 scsi_end_request+0x52/0x4f0 drivers/scsi/scsi_lib.c:631
 scsi_io_completion+0x9f/0x200 drivers/scsi/scsi_lib.c:1069
 scsi_finish_command+0x1be/0x1d0 drivers/scsi/scsi.c:198
 scsi_complete+0x19a/0x1d0 drivers/scsi/scsi_lib.c:1531
 blk_complete_reqs block/blk-mq.c:1134 [inline]
 blk_done_softirq+0x74/0xb0 block/blk-mq.c:1139
 __do_softirq+0xc8/0x285 kernel/softirq.c:554
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu kernel/softirq.c:633 [inline]
 irq_exit_rcu+0x3c/0x90 kernel/softirq.c:645
 common_interrupt+0x43/0x90 arch/x86/kernel/irq.c:247
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693

write to 0xffff88813cbd7a38 of 8 bytes by task 24656 on cpu 0:
 relay_switch_subbuf+0x39e/0x3b0 kernel/relay.c:708
 relay_reserve include/linux/relay.h:248 [inline]
 __blk_add_trace+0x66a/0x730 kernel/trace/blktrace.c:276
 blk_add_trace_rq kernel/trace/blktrace.c:844 [inline]
 blk_add_trace_rq_insert+0x1ba/0x1d0 kernel/trace/blktrace.c:851
 trace_block_rq_insert include/trace/events/block.h:215 [inline]
 dd_insert_request block/mq-deadline.c:823 [inline]
 dd_insert_requests+0x52f/0x670 block/mq-deadline.c:877
 blk_mq_dispatch_plug_list block/blk-mq.c:2772 [inline]
 blk_mq_flush_plug_list+0x647/0xde0 block/blk-mq.c:2822
 blk_add_rq_to_plug+0x102/0x3e0 block/blk-mq.c:1299
 blk_mq_submit_bio+0xa22/0xd90 block/blk-mq.c:3014
 __submit_bio+0x11c/0x370 block/blk-core.c:619
 __submit_bio_noacct_mq block/blk-core.c:698 [inline]
 submit_bio_noacct_nocheck+0x597/0x6d0 block/blk-core.c:727
 submit_bio_noacct+0x681/0x830 block/blk-core.c:837
 submit_bio+0x218/0x230 block/blk-core.c:879
 ext4_io_submit fs/ext4/page-io.c:378 [inline]
 io_submit_add_bh fs/ext4/page-io.c:419 [inline]
 ext4_bio_write_folio+0x6c0/0x9a0 fs/ext4/page-io.c:563
 mpage_submit_folio fs/ext4/inode.c:1869 [inline]
 mpage_map_and_submit_buffers fs/ext4/inode.c:2115 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2254 [inline]
 ext4_do_writepages+0x13a7/0x2110 fs/ext4/inode.c:2679
 ext4_writepages+0x159/0x2e0 fs/ext4/inode.c:2768
 do_writepages+0x1d8/0x480 mm/page-writeback.c:2612
 filemap_fdatawrite_wbc+0xdb/0x100 mm/filemap.c:397
 __filemap_fdatawrite_range mm/filemap.c:430 [inline]
 filemap_write_and_wait_range+0xb6/0x1f0 mm/filemap.c:685
 filemap_write_and_wait include/linux/pagemap.h:64 [inline]
 ext4_bmap+0x14e/0x180 fs/ext4/inode.c:3109
 bmap+0x5d/0x90 fs/inode.c:1792
 ioctl_fibmap fs/ioctl.c:77 [inline]
 file_ioctl fs/ioctl.c:328 [inline]
 do_vfs_ioctl+0x1353/0x1560 fs/ioctl.c:883
 __do_sys_ioctl fs/ioctl.c:902 [inline]
 __se_sys_ioctl+0x81/0x150 fs/ioctl.c:890
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 24656 Comm: syz-executor.1 Tainted: G        W          6.9.0-rc1-syzkaller-00178-g317c7bc0ef03 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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