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BUG: KCSAN: data-race in blk_mq_free_request / blk_mq_free_request

write to 0xffffe8ffffd12748 of 8 bytes by task 703 on cpu 1:
 blk_mq_free_request+0x17d/0x330 block/blk-mq.c:522
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:557
 blk_mq_end_request block/blk-mq.c:566 [inline]
 blk_mq_dispatch_rq_list+0x634/0xfa0 block/blk-mq.c:1388
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:186 [inline]
 blk_mq_do_dispatch_sched+0x370/0x610 block/blk-mq-sched.c:199
 __blk_mq_sched_dispatch_requests+0x21e/0x2c0 block/blk-mq-sched.c:310
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1488
 blk_mq_run_work_fn+0x3d/0x50 block/blk-mq.c:1820
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2275
 worker_thread+0x636/0xae0 kernel/workqueue.c:2421
 kthread+0x1d0/0x1f0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffffe8ffffd12748 of 8 bytes by task 11791 on cpu 0:
 blk_mq_free_request+0x16a/0x330 block/blk-mq.c:522
 __blk_mq_end_request+0x214/0x230 block/blk-mq.c:557
 blk_mq_end_request block/blk-mq.c:566 [inline]
 blk_mq_dispatch_rq_list+0x634/0xfa0 block/blk-mq.c:1388
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:186 [inline]
 blk_mq_do_dispatch_sched+0x370/0x610 block/blk-mq-sched.c:199
 __blk_mq_sched_dispatch_requests+0x21e/0x2c0 block/blk-mq-sched.c:310
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue+0xbc/0x140 block/blk-mq.c:1488
 __blk_mq_delay_run_hw_queue+0x163/0x2d0 block/blk-mq.c:1565
 blk_mq_run_hw_queue+0x22c/0x250 block/blk-mq.c:1618
 blk_mq_sched_insert_requests+0x13f/0x200 block/blk-mq-sched.c:491
 blk_mq_flush_plug_list+0x2f5/0x3c0 block/blk-mq.c:1942
 blk_flush_plug_list+0x235/0x260 block/blk-core.c:1749
 blk_finish_plug+0x44/0x60 block/blk-core.c:1766
 read_pages+0x2d9/0x530 mm/readahead.c:150
 page_cache_ra_unbounded+0x3a8/0x400 mm/readahead.c:238
 do_page_cache_ra mm/readahead.c:267 [inline]
 force_page_cache_ra+0x236/0x270 mm/readahead.c:298
 page_cache_sync_ra+0xb5/0xd0 mm/readahead.c:572
 page_cache_sync_readahead include/linux/pagemap.h:840 [inline]
 filemap_get_pages mm/filemap.c:2375 [inline]
 filemap_read+0x380/0x1210 mm/filemap.c:2458
 generic_file_read_iter+0x84/0x3e0 mm/filemap.c:2609
 blkdev_read_iter+0xb3/0xc0 fs/block_dev.c:1727
 call_read_iter include/linux/fs.h:1971 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x565/0x5d0 fs/read_write.c:496
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11791 Comm: systemd-udevd Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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