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Subject: Re: [PATCH] block: revert pushing the final release of request_queue
 to a workqueue.
To:     Ming Lei <ming.lei@redhat.com>
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From:   "yukuai (C)" <yukuai3@huawei.com>
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Date:   Sat, 8 Feb 2020 14:12:30 +0800
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On 2020/2/7 21:04, Ming Lei wrote:
> But blk_mq_debugfs_register() in your step 3 for adding loop still may
> fail, that is why I suggest to consider to move
> blk_mq_debugfs_register() into blk_unregister_queue().

I think therer might be a problem.

static void loop_remove(struct loop_device *lo)
{
         del_gendisk(lo->lo_disk);
         blk_cleanup_queue(lo->lo_queue);
         blk_mq_free_tag_set(&lo->tag_set);
         put_disk(lo->lo_disk);
         kfree(lo);
}

blk_unregister_queue() is called in del_gendisk(), while
blk_cleanup_queue() remove other files or dirs. And
blk_mq_debugfs_register() should be called at last since it
will remove everything.

Thanks
Yu Kuai