linux-kernel - Re: [PATCH v4] page_io: zswap: do not crash the kernel on decompression failure

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Message-ID: <CAKEwX=OtUGzTnP3RMz3hG2v3AKqG2LJ71_w5sQL+kxR1wnAGKg@mail.gmail.com>
Date: Thu, 6 Mar 2025 14:08:32 -0800
From: Nhat Pham <nphamcs@...il.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, chengming.zhou@...ux.dev, 
	linux-mm@...ck.org, kernel-team@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] page_io: zswap: do not crash the kernel on
 decompression failure

On Thu, Mar 6, 2025 at 1:32 PM Yosry Ahmed <yosry.ahmed@...ux.dev> wrote:
>
> On Thu, Mar 06, 2025 at 12:50:10PM -0800, Nhat Pham wrote:
>
> Couple of nits below, but otherwise LGTM:
>
> Acked-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
>
> (I did expect the swap zeromap change in the same series, so if you send
> it separately make sure to mention it's on top of this one because they
> will conflict otherwise)

Yeah of course. I actually have already finished that second patch,
but wanna spend a bit more time proofreading things :)

>
> [..]
> > @@ -1606,7 +1628,26 @@ bool zswap_store(struct folio *folio)
> >       return ret;
> >  }
> >
> > -bool zswap_load(struct folio *folio)
> > +/**
> > + * zswap_load() - load a page from zswap
>
> nit: folio
>
> > + * @folio: folio to load
> > + *
> > + * Return: 0 on success, or one of the following error codes:
>
> nit: Maybe worth mentioning that the folio is unlocked and marked
> uptodate on success for completeness.

Will do!

>
> > + *
> > + *  -EIO: if the swapped out content was in zswap, but could not be loaded
> > + *  into the page due to a decompression failure. The folio is unlocked, but
> > + *  NOT marked up-to-date, so that an IO error is emitted (e.g. do_swap_page()
> > + *  will SIGBUS).
> > + *
> > + *  -EINVAL: if the swapped out content was in zswap, but the page belongs
> > + *  to a large folio, which is not supported by zswap. The folio is unlocked,
> > + *  but NOT marked up-to-date, so that an IO error is emitted (e.g.
> > + *  do_swap_page() will SIGBUS).
> > + *
> > + *  -ENOENT: if the swapped out content was not in zswap. The folio remains
> > + *  locked on return.
> > + */
> > +int zswap_load(struct folio *folio)
> [..]