linux-kernel - Re: [PATCH v15 09/12] dm: Add support for copy offload

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Message-ID: <cb767dc9-1732-4e31-bcc6-51c187750d66@suse.de>
Date:   Fri, 8 Sep 2023 08:13:37 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Nitesh Shetty <nj.shetty@...sung.com>,
        Jens Axboe <axboe@...nel.dk>, Jonathan Corbet <corbet@....net>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com,
        Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>
Cc:     martin.petersen@...cle.com, mcgrof@...nel.org,
        gost.dev@...sung.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v15 09/12] dm: Add support for copy offload

On 9/6/23 18:38, Nitesh Shetty wrote:
> Before enabling copy for dm target, check if underlying devices and
> dm target support copy. Avoid split happening inside dm target.
> Fail early if the request needs split, currently splitting copy
> request is not supported.
> 
And here is where I would have expected the emulation to take place;
didn't you have it in one of the earlier iterations?
After all, device-mapper already has the infrastructure for copying
data between devices, so adding a copy-offload emulation for 
device-mapper should be trivial.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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