linux-kernel - Re: [PATCH v15 03/12] block: add copy offload support

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Date:   Fri, 8 Sep 2023 07:55:57 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Nitesh Shetty <nj.shetty@...sung.com>
Cc:     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>,
        martin.petersen@...cle.com, mcgrof@...nel.org,
        gost.dev@...sung.com, Anuj Gupta <anuj20.g@...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 03/12] block: add copy offload support

On 9/7/23 09:16, Nitesh Shetty wrote:
> On 07/09/23 07:49AM, Hannes Reinecke wrote:
>> On 9/6/23 18:38, Nitesh Shetty wrote:
>>
>> Hmm. That looks a bit odd. Why do you have to use wait_for_completion?
> 
> wait_for_completion is waiting for all the copy IOs to complete,
> when caller does not pass endio handler.
> Copy IO submissions are still async, as in previous revisions.
> 
>> Can't you submit the 'src' bio, and then submit the 'dst' bio from the 
>> endio handler of the 'src' bio?
> We can't do this with the current bio merging approach.
> 'src' bio waits for the 'dst' bio to arrive in request layer.
> Note that both bio's should be present in request reaching the driver,
> to form the copy-cmd.
> 
Hmm. I guess it would be possible, but in the end we can always change
it later once the infrastructure is in.

So:

Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

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