linux-kernel - Re: [PATCH v13 22/22] mm: zswap: Batched zswap_compress() with compress batching of large folios.

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Message-ID: <j7vaexpi3lmheowozkymesvekasccdgnxijjip66ryngj66llf@kolcsjasxxdy>
Date: Wed, 26 Nov 2025 06:34:45 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: "Sridhar, Kanchana P" <kanchana.p.sridhar@...el.com>, 
	SeongJae Park <sj@...nel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "hannes@...xchg.org" <hannes@...xchg.org>, 
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	"kasong@...cent.com" <kasong@...cent.com>, "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, 
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	"Gomes, Vinicius" <vinicius.gomes@...el.com>, "Feghali, Wajdi K" <wajdi.k.feghali@...el.com>, 
	"Gopal, Vinodh" <vinodh.gopal@...el.com>
Subject: Re: [PATCH v13 22/22] mm: zswap: Batched zswap_compress() with
 compress batching of large folios.

On Wed, Nov 26, 2025 at 01:46:57PM +0800, Herbert Xu wrote:
> On Fri, Nov 14, 2025 at 03:37:53PM +0000, Yosry Ahmed wrote:
> >
> > Thanks for the clarification. I understand that the error code has
> > different sources for SW and HW compressors, but I do not like using
> > errp as an indirection. It makes the code unclear. I would rather we
> > explicitly check err for SW compressors and dlen for HW compressors.
> > 
> > That being said, I thought what Herbert suggested was that the same API
> > is used for both SW and HW compressors. IOW, either way we submit a
> > batch of pages (8 pages for SW compressors), and then the crypto API
> > would either give the entire batch to the compressor if it supports
> > batching, or loop over them internally and hand them page-by-page to
> > the compressor.
> > 
> > This would simplify usage as we do not have to handle the differences in
> > zswap.
> > 
> > If that is not doable, at the very least the API should be consistent.
> > Right now the error code and length are propagated differently to the
> > caller based on whether or not the compressor support batching.
> 
> Yes we should only have one code path in zswap, regardless of whether
> batching is used or not.
> 
> The degenerate case of a batch with a single page should be handled
> by the Crypto API.
> 
> So I will change crypto_acomp to take care of this case.

Nice :)

> 
> Cheers,
> -- 
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt