linux-kernel - Re: [dm-devel] [PATCH v14 00/11] Implement copy offload support

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Message-ID: <2cc56fb5-ddba-b6d0-f66b-aa8fffa42af0@acm.org>
Date:   Fri, 11 Aug 2023 14:50:51 -0700
From:   Bart Van Assche <bvanassche@....org>
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, linux-doc@...r.kernel.org,
        gost.dev@...sung.com, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-block@...r.kernel.org,
        mcgrof@...nel.org, dlemoal@...nel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [dm-devel] [PATCH v14 00/11] Implement copy offload support

On 8/11/23 03:52, Nitesh Shetty wrote:
> We achieve copy offload by sending 2 bio's with source and destination
> info and merge them to form a request. This request is sent to driver.
> So this design works only for request based storage drivers.

[ ... ]

> Overall series supports:
> ========================
> 	1. Driver
> 		- NVMe Copy command (single NS, TP 4065), including support
> 		in nvme-target (for block and file back end).
> 
> 	2. Block layer
> 		- Block-generic copy (REQ_OP_COPY_DST/SRC), operation with
>                    interface accommodating two block-devs
>                  - Merging copy requests in request layer
> 		- Emulation, for in-kernel user when offload is natively
>                  absent
> 		- dm-linear support (for cases not requiring split)
> 
> 	3. User-interface
> 		- copy_file_range

Is this sufficient? The combination of dm-crypt, dm-linear and the NVMe 
driver is very common. What is the plan for supporting dm-crypt? 
Shouldn't bio splitting be supported for dm-linear?

Thanks,

Bart.