linux-kernel - Re: [PATCH v4] mm/zswap: store <PAGE_SIZE compression failed page as-is

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Message-Id: <20250821213630.1771-1-sj@kernel.org>
Date: Thu, 21 Aug 2025 14:36:30 -0700
From: SeongJae Park <sj@...nel.org>
To: Chris Li <chrisl@...nel.org>
Cc: SeongJae Park <sj@...nel.org>,
	Barry Song <21cnbao@...il.com>,
	Nhat Pham <nphamcs@...il.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chengming Zhou <chengming.zhou@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Yosry Ahmed <yosry.ahmed@...ux.dev>,
	kernel-team@...a.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Takero Funaki <flintglass@...il.com>,
	David Hildenbrand <david@...hat.com>,
	Baoquan He <bhe@...hat.com>,
	Kairui Song <kasong@...cent.com>
Subject: Re: [PATCH v4] mm/zswap: store <PAGE_SIZE compression failed page as-is

On Thu, 21 Aug 2025 13:49:31 -0700 Chris Li <chrisl@...nel.org> wrote:

> On Thu, Aug 21, 2025 at 9:43 AM SeongJae Park <sj@...nel.org> wrote:
> >
> > On Thu, 21 Aug 2025 18:27:52 +0800 Barry Song <21cnbao@...il.com> wrote:
> >
> > > On Thu, Aug 21, 2025 at 1:33 AM Nhat Pham <nphamcs@...il.com> wrote:
> > > >
> > > > On Tue, Aug 19, 2025 at 6:37 PM Herbert Xu <herbert@...dor.apana.org.au> wrote:
> > > > >
> > > > > On Wed, Aug 20, 2025 at 01:34:01PM +1200, Barry Song wrote:
> > > > > >
> > > > > > We might want to revisit the old thread to check whether it is now safe for us
> > > > > > to move to PAGE_SIZE in zswap now.
> > > > >
> > > > > It's perfectly safe as LZO was fixed months ago.
> > > >
> > > > Perfect. Then I'll revive Chengming's patch (see [1]) to reduce the
> > > > compression buffer :)
> > >
> > > Nice!
> > >
> > > But perhaps we should wait until SeongJae sends a new version that
> > > addresses the counter issue?
> >
> > Is there a reason to wait?  I was thinking those are orthogonal problems?
> >
> > Anyway, for the counter (crypto_compress_fail), I don't have a strong opinion.
> > To my understanding, the options for path forward are...
> >
> > 1. remove it,
> > 2. keep it as is, or
> > 3. keep it, but account only -EINPROGRESS[1]
> >
> > If I'm not missing other options, I'm tempted to the first option (remove it)
> > since it doesn't change any existing things, and we can revisit later.
> 
> I am fine with 1) removing it. Maybe add a log once print error on the
> error code if -EINPROGRESS, just to know such extreme error has been
> triggered.
> >
> > Please let me know if I'm missing other options or if you have other preferences.
> 
> I just don't want to hide the extreme error case but I am also fine
> with just removing it. It is your call.

Thank you for your opinion, Chris!  Unless others have different opinions, I
will only remove the counter (option 1), since it is simplest and we can
consider adding another counter or error logs on top of it.


Thanks,
SJ

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