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BUG: KCSAN: data-race in __blk_queue_split / bio_endio

read to 0xffff8880a532be14 of 2 bytes by interrupt on cpu 1:
 bio_remaining_done block/bio.c:1757 [inline]
 bio_endio+0x3e/0x4f0 block/bio.c:1787
 req_bio_endio block/blk-core.c:242 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1462
 blk_mq_end_request+0x3f/0x2b0 block/blk-mq.c:568
 end_cmd drivers/block/null_blk_main.c:622 [inline]
 end_cmd+0xa9/0x1a0 drivers/block/null_blk_main.c:616
 null_complete_rq+0x22/0x30 drivers/block/null_blk_main.c:649
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 run_ksoftirqd+0x46/0x60 kernel/softirq.c:603
 smpboot_thread_fn+0x37d/0x4a0 kernel/smpboot.c:165
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

write to 0xffff8880a532be14 of 2 bytes by task 29726 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 __blk_queue_split+0x726/0xb40 block/blk-merge.c:328
 blk_mq_make_request+0x104/0xf60 block/blk-mq.c:1959
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 blk_next_bio+0x53/0x70 block/blk-lib.c:19
 __blkdev_issue_zero_pages+0x104/0x300 block/blk-lib.c:284
 blkdev_issue_zeroout+0x337/0x370 block/blk-lib.c:378
 blkdev_fallocate+0x26d/0x2f0 fs/block_dev.c:2089
 vfs_fallocate+0x3be/0x650 fs/open.c:309
 ksys_fallocate+0x61/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x5e/0x80 fs/open.c:338
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29726 Comm: syz-executor.1 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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