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BUG: KCSAN: data-race in relay_switch_subbuf / relay_switch_subbuf

write to 0xffff888112c85e38 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:894
 scsi_end_request+0x56/0x4d0 drivers/scsi/scsi_lib.c:631
 scsi_io_completion+0xc7/0x200 drivers/scsi/scsi_lib.c:1068
 scsi_finish_command+0x1be/0x1d0 drivers/scsi/scsi.c:198
 scsi_complete+0x19a/0x1d0 drivers/scsi/scsi_lib.c:1530
 blk_complete_reqs block/blk-mq.c:1129 [inline]
 blk_done_softirq+0x74/0xb0 block/blk-mq.c:1134
 __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+0x81/0x90 arch/x86/kernel/irq.c:247
 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
 __rcu_read_lock+0x0/0x50
 rcu_read_lock include/linux/rcupdate.h:779 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0x92/0xac0 net/batman-adv/network-coding.c:719
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

write to 0xffff888112c85e38 of 8 bytes by task 6378 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:2767 [inline]
 blk_mq_flush_plug_list+0x647/0xde0 block/blk-mq.c:2817
 __blk_flush_plug+0x216/0x290 block/blk-core.c:1190
 blk_finish_plug+0x48/0x70 block/blk-core.c:1217
 ext4_do_writepages+0x1bd1/0x2110 fs/ext4/inode.c:2730
 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]
 file_write_and_wait_range+0xc8/0x170 mm/filemap.c:788
 ext4_sync_file+0x134/0x6c0 fs/ext4/fsync.c:158
 vfs_fsync_range+0x122/0x140 fs/sync.c:188
 generic_write_sync include/linux/fs.h:2795 [inline]
 ext4_buffered_write_iter+0x338/0x380 fs/ext4/file.c:305
 ext4_file_write_iter+0x29f/0xe30
 __kernel_write_iter+0x265/0x490 fs/read_write.c:523
 dump_emit_page fs/coredump.c:890 [inline]
 dump_user_range+0x3a7/0x550 fs/coredump.c:951
 elf_core_dump+0x1aa6/0x1bc0 fs/binfmt_elf.c:2077
 do_coredump+0x1033/0x1890 fs/coredump.c:764
 get_signal+0xdc1/0x1080 kernel/signal.c:2896
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 irqentry_exit_to_user_mode+0x94/0x130 kernel/entry/common.c:231
 irqentry_exit+0x12/0x50 kernel/entry/common.c:334
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

value changed: 0x0000000000000038 -> 0x0000000000000030

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6378 Comm: syz-executor.4 Tainted: G        W          6.9.0-rc4-syzkaller-00214-g13a2e429f644 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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