linux-kernel - Re: [PATCH v2 04/10] crypto/compress: add asynchronous compression support

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Date:	Wed, 27 Jan 2016 15:59:05 +0800
From:	"Li, Weigang" <weigang.li@...el.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>,
	Joonsoo Kim <js1304@...il.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Minchan Kim <minchan@...nel.org>,
	"Dan Streetman" <ddstreet@...e.org>,
	<linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 04/10] crypto/compress: add asynchronous compression
 support

On 1/27/2016 3:41 PM, Herbert Xu wrote:
> On Tue, Jan 26, 2016 at 05:15:06PM +0900, Joonsoo Kim wrote:
>> From: Weigang Li <weigang.li@...el.com>
>>
>> Now, asynchronous compression APIs are supported. There is no asynchronous
>> compression driver now but this APIs can be used as front-end to
>> synchronous compression algorithm. In this case, scatterlist would be
>> linearlized when needed so it would cause some overhead.
>>
>> Signed-off-by: Weigang Li <weigang.li@...el.com>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> I think we should be able to use this for the synchronous case
> too, like we do with skcipher and ahash.
>
> The main difference that I can see right now is that acomp always
> allocates a context through the request object while scomp does not.
>
> This difference is entirely artificial as we could also make the
> context conditional for acomp.
>
> The reason we had the shash/ahash division is because the shash
> interface offers a direct pointer interface while ahash is SG-based.
> Otherwise ahash is just as able as shash to handle synchronous
> requests.
>
> At this point in time I don't see such a fundamental distinction
> between acomp and scomp.
>
> Cheers,
>
The acomp is also SG-based, while scomp only accepts flat buffer.