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BUG: KCSAN: data-race in blk_mq_request_bypass_insert / blk_mq_run_hw_queue

write to 0xffff888129fc3010 of 8 bytes by task 3256 on cpu 0:
 __list_add include/linux/list.h:70 [inline]
 list_add include/linux/list.h:86 [inline]
 blk_mq_request_bypass_insert+0x6a/0x130 block/blk-mq.c:1859
 blk_mq_sched_insert_request+0x1b4/0x330 block/blk-mq-sched.c:559
 blk_mq_requeue_work+0x36b/0x490 block/blk-mq.c:813
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888129fc3010 of 8 bytes by task 21542 on cpu 1:
 list_empty_careful include/linux/list.h:319 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:72 [inline]
 blk_mq_run_hw_queue+0x12e/0x260 block/blk-mq.c:1660
 blk_mq_sched_insert_request+0x2ae/0x330 block/blk-mq-sched.c:576
 blk_mq_submit_bio+0x988/0x1130 block/blk-mq.c:2224
 __submit_bio_noacct_mq block/blk-core.c:1179 [inline]
 submit_bio_noacct+0x772/0x950 block/blk-core.c:1212
 submit_bio+0x200/0x370 block/blk-core.c:1282
 submit_bh_wbc+0x397/0x3d0 fs/buffer.c:3070
 submit_bh fs/buffer.c:3076 [inline]
 write_dirty_buffer+0xd4/0xe0 fs/buffer.c:3144
 fat_sync_bhs+0x52/0x160 fs/fat/misc.c:357
 fat_ent_write+0x85/0xd0 fs/fat/fatent.c:417
 fat_chain_add+0x149/0x400 fs/fat/misc.c:130
 fat_add_cluster fs/fat/inode.c:113 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x429/0x5a0 fs/fat/inode.c:190
 __block_write_begin_int+0x4bf/0xfd0 fs/buffer.c:2011
 __block_write_begin fs/buffer.c:2061 [inline]
 block_write_begin+0x4f/0x1c0 fs/buffer.c:2120
 cont_write_begin+0x42c/0x610 fs/buffer.c:2469
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x196/0x390 mm/filemap.c:3403
 __generic_file_write_iter+0x154/0x330 mm/filemap.c:3532
 generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3564
 call_write_iter include/linux/fs.h:1882 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x665/0x6f0 fs/read_write.c:578
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 21542 Comm: syz-executor.2 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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