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

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Message-ID: <aSaUUez5J1w5WyE-@gondor.apana.org.au>
Date: Wed, 26 Nov 2025 13:46:57 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
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>,
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	"Gopal, Vinodh" <vinodh.gopal@...el.com>
Subject: Re: [PATCH v13 22/22] mm: zswap: Batched zswap_compress() with
 compress batching of large folios.

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.

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