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Date:   Sat, 23 Apr 2022 18:29:37 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        Christoph Hellwig <hch@lst.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
        Dan Williams <dan.j.williams@intel.com>,
        yukuai <yukuai3@huawei.com>
Subject: Re: [PATCH V2 2/2] block: fix "Directory XXXXX with parent 'block'
 already present!"
Message-ID: <20220423162937.GA28340@lst.de>
References: <20220423143952.3162999-1-ming.lei@redhat.com> <20220423143952.3162999-3-ming.lei@redhat.com>
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On Sat, Apr 23, 2022 at 10:39:52PM +0800, Ming Lei wrote:
> q->debugfs_dir is used by blk-mq debugfs and blktrace. The dentry is
> created when adding disk, and removed when releasing request queue.
> 
> There is small window between releasing disk and releasing request
> queue, and during the period, one disk with same name may be created
> and added, so debugfs_create_dir() may complain with "Directory XXXXX
> with parent 'block' already present!"
> 
> Fixes the issue by moving debugfs_create_dir() into blk_alloc_queue(),
> and the dir name is named with q->id from beginning, and switched to
> disk name when adding disk, and finally changed to q->id in disk_release().

As said before I very much think this is going in the wrong direction.

As the debugfs directory use the name of the gendisk, the lifetime rules
should simply match those of the gendisk.  If anyone wants to trace
SCSI commands sent before probing the gendisk or after removing it
they can use blktrace on the /dev/sg node.