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Subject: Re: [PATCH 0/3] block: blk_interposer - Block Layer Interposer
To:     Hannes Reinecke <hare@suse.de>, Mike Snitzer <snitzer@redhat.com>,
        Sergei Shtepa <sergei.shtepa@veeam.com>, hch@lst.de
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        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Pavel Tide <Pavel.TIde@veeam.com>, dm-devel@redhat.com
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From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <6bc5ff77-4977-a9bd-3fb8-ce35e1179b94@kernel.dk>
Date:   Sat, 12 Dec 2020 11:14:31 -0700
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On 12/11/20 11:03 AM, Hannes Reinecke wrote:
> On 12/11/20 6:04 PM, Jens Axboe wrote:
>> On 12/11/20 9:56 AM, Hannes Reinecke wrote:
>>> On 12/11/20 5:33 PM, Jens Axboe wrote:
>>>> On 12/11/20 9:30 AM, Mike Snitzer wrote:
>>>>> While I still think there needs to be a proper _upstream_ consumer of
>>>>> blk_interposer as a condition of it going in.. I'll let others make the
>>>>> call.
>>>>
>>>> That's an unequivocal rule.
>>>>
>>>>> As such, I'll defer to Jens, Christoph and others on whether your
>>>>> minimalist blk_interposer hook is acceptable in the near-term.
>>>>
>>>> I don't think so, we don't do short term bandaids just to plan on
>>>> ripping that out when the real functionality is there. IMHO, the dm
>>>> approach is the way to go - it provides exactly the functionality that
>>>> is needed in an appropriate way, instead of hacking some "interposer"
>>>> into the core block layer.
>>>>
>>> Which is my plan, too.
>>>
>>> I'll be working with the Veeam folks to present a joint patchset
>>> (including the DM bits) for the next round.
>>
>> Just to be clear, core block additions for something that dm will
>> consume is obviously fine. Adding this as block layer functionality than
>> then exposes an application API for setting it up, tearing down, etc -
>> that is definitely NOT
>>
> That was never my intention.
> Any consumers of this thing would need to be in-kernel.
> If that was your concern.

Yep, that is/was indeed my concern!

-- 
Jens Axboe