syzbot

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BUG: KCSAN: data-race in blk_mq_sched_dispatch_requests / blk_mq_sched_insert_request

write to 0xffff88812a7ed410 of 8 bytes by task 2517 on cpu 0:
 __list_add include/linux/list.h:70 [inline]
 list_add include/linux/list.h:86 [inline]
 blk_mq_sched_bypass_insert block/blk-mq-sched.c:367 [inline]
 blk_mq_sched_insert_request+0x2f2/0x3e0 block/blk-mq-sched.c:394
 blk_mq_requeue_work+0x347/0x440 block/blk-mq.c:746
 process_one_work+0x424/0x930 kernel/workqueue.c:2264
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2410
 kthread+0x1cb/0x1f0 kernel/kthread.c:255
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88812a7ed410 of 8 bytes by task 14237 on cpu 1:
 list_empty_careful include/linux/list.h:301 [inline]
 blk_mq_sched_dispatch_requests+0x33d/0x380 block/blk-mq-sched.c:187
 __blk_mq_run_hw_queue+0xb1/0x150 block/blk-mq.c:1382
 __blk_mq_delay_run_hw_queue+0x315/0x390 block/blk-mq.c:1459
 blk_mq_run_hw_queue+0xfa/0x1b0 block/blk-mq.c:1512
 blk_mq_sched_insert_requests+0x19c/0x270 block/blk-mq-sched.c:444
 blk_mq_flush_plug_list+0x2f0/0x4c0 block/blk-mq.c:1758
 blk_flush_plug_list+0x281/0x2b0 block/blk-core.c:1772
 blk_finish_plug block/blk-core.c:1789 [inline]
 blk_finish_plug+0x59/0x7a block/blk-core.c:1785
 ext4_writepages+0xc5c/0x1d40 fs/ext4/inode.c:2833
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1bb/0x220 mm/filemap.c:421
 file_write_and_wait_range+0xfb/0x160 mm/filemap.c:760
 ext4_sync_file+0x26e/0x8b0 fs/ext4/fsync.c:153
 vfs_fsync_range+0x7c/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2867 [inline]
 ext4_buffered_write_iter+0x211/0x280 fs/ext4/file.c:277
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:693
 do_iter_write fs/read_write.c:998 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:979
 vfs_iter_write+0x56/0x80 fs/read_write.c:1039
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14237 Comm: syz-executor.2 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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