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Date:   Mon, 25 Apr 2022 09:49:18 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        linux-block@vger.kernel.org,
        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: <20220425074918.GA10320@lst.de>
References: <20220423143952.3162999-1-ming.lei@redhat.com> <20220423143952.3162999-3-ming.lei@redhat.com> <20220423162937.GA28340@lst.de> <YmUXPA4EE5jOo1yz@T590>
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On Sun, Apr 24, 2022 at 05:24:12PM +0800, Ming Lei wrote:
> > 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.
> 
> Not sure blktrace can trace on /dev/sg since blktrace works on
> block_device.

Unless someone broke it recently it does.  Take a look at all the mess
it causes in the blktrace code.