linux-kernel - Re: [PATCH v6 0/2] zswap: remove the memcpy if acomp is not sleepable

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Message-ID: <20240308121139.GA116548@cmpxchg.org>
Date: Fri, 8 Mar 2024 07:11:39 -0500
From: Johannes Weiner <hannes@...xchg.org>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, davem@...emloft.net,
	herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org,
	linux-mm@...ck.org, nphamcs@...il.com, yosryahmed@...gle.com,
	zhouchengming@...edance.com, chriscli@...gle.com, chrisl@...nel.org,
	ddstreet@...e.org, linux-kernel@...r.kernel.org,
	sjenning@...hat.com, vitaly.wool@...sulko.com,
	Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH v6 0/2] zswap: remove the memcpy if acomp is not sleepable

On Thu, Feb 22, 2024 at 09:11:33PM +1300, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.com>
> 
> In zswap, if we use zsmalloc, we cannot sleep while we map the
> compressed memory, so we copy it to a temporary buffer. By
> knowing the alg won't sleep can help zswap to avoid the
> memcpy.
> Thus we introduce an API in crypto to expose if acomp is async,
> and zswap can use it to decide if it can remove copying to the
> tmp buffer.
> 
> -v6:
>  * add acked-by of Herbert, Thanks!
>  * remove patch 3/3 from the series, as that one will go
>    through crypto
> 
> Barry Song (2):
>   crypto: introduce: acomp_is_async to expose if comp drivers might
>     sleep
>   mm/zswap: remove the memcpy if acomp is not sleepable
> 
>  include/crypto/acompress.h | 6 ++++++
>  mm/zswap.c                 | 6 ++++--
>  2 files changed, 10 insertions(+), 2 deletions(-)

Acked-by: Johannes Weiner <hannes@...xchg.org>

Looks good to me.

One small question: why cache is_sleepable in zswap instead of
checking acomp_is_async() directly? It doesn't look expensive.