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BUG: KCSAN: data-race in blk_mq_free_request / blk_mq_free_request

write to 0xffffe8ffffd12d80 of 8 bytes by interrupt on cpu 0:
 blk_mq_free_request+0x17d/0x330 block/blk-mq.c:523
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:558
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:567
 lo_complete_rq+0xca/0x170 drivers/block/loop.c:497
 blk_complete_reqs block/blk-mq.c:577 [inline]
 blk_done_softirq+0x69/0x90 block/blk-mq.c:582
 __do_softirq+0x12c/0x275 kernel/softirq.c:559
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:921
 smpboot_thread_fn+0x2a1/0x3f0 kernel/smpboot.c:165
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffffe8ffffd12d80 of 8 bytes by interrupt on cpu 1:
 blk_mq_free_request+0x16a/0x330 block/blk-mq.c:523
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:558
 blk_mq_end_request+0x37/0x50 block/blk-mq.c:567
 lo_complete_rq+0xca/0x170 drivers/block/loop.c:497
 blk_complete_reqs block/blk-mq.c:577 [inline]
 blk_done_softirq+0x69/0x90 block/blk-mq.c:582
 __do_softirq+0x12c/0x275 kernel/softirq.c:559
 run_ksoftirqd+0x13/0x20 kernel/softirq.c:921
 smpboot_thread_fn+0x2a1/0x3f0 kernel/smpboot.c:165
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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