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

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Message-Id: <20240308192334.845b27504a663ec8af4f2aad@linux-foundation.org>
Date: Fri, 8 Mar 2024 19:23:34 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Barry Song <21cnbao@...il.com>
Cc: herbert@...dor.apana.org.au, 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>,
 davem@...emloft.net, hannes@...xchg.org, linux-crypto@...r.kernel.org,
 linux-mm@...ck.org, zhouchengming@...edance.com, nphamcs@...il.com,
 yosryahmed@...gle.com
Subject: Re: [PATCH v6 0/2] zswap: remove the memcpy if acomp is not
 sleepable

On Fri, 8 Mar 2024 19:57:38 +0800 Barry Song <21cnbao@...il.com> wrote:

> Hi Andrew,
> 
> On Thu, Feb 22, 2024 at 4:11 PM Barry Song <21cnbao@...il.com> 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
> 
> Can you please pull this into mm-tree? This used to have 3 patches.
> 
> 3/3 was separated according to Herbert's requirements and has
> been in a crypto tree.
> crypto: scomp - remove memcpy if sg_nents is 1 and pages are lowmem
> https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=77292bb8ca
> 
> Two drivers fixes(patch 1 needs) have also been in crypto tree:
> crypto: hisilicon/zip - fix the missing CRYPTO_ALG_ASYNC in cra_flags
> https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=db8ac88385
> 
> crypto: iaa - fix the missing CRYPTO_ALG_ASYNC in cra_flags
> https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=30dd94dba35
> 
> So it should be quite safe to pull this series into mm-tree now.

But this zswap chage requires the presence of the other patches, yes?

So the mm.git tree alone will be buggy?  And if mm.git merges ahead of
the other trees, there will be a window where mainline will be buggy?

If so, I think it wuold be better to merge the zswap patch in the next
merge window.