On Mon, Jul 1, 2024 at 11:52 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Sun, 30 Jun 2024 11:22:31 +1200 Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> > From: Barry Song <v-songbaohua@xxxxxxxx>
> >
> > If CONFIG_ZSWAP is set to N, it means zswap cannot be enabled.
> > zswap_never_enabled() should return true.
> >
> > ...
> >
> > --- a/include/linux/zswap.h
> > +++ b/include/linux/zswap.h
> > @@ -68,7 +68,7 @@ static inline bool zswap_is_enabled(void)
> >
> > static inline bool zswap_never_enabled(void)
> > {
> > - return false;
> > + return true;
> > }
>
> Well, that code was as wrong as it's possible to get.
>
> But what effect does this have? Seems "not much"? Perhaps we'll
> attempt a zswap_load() which later fails for other reasons?
Actually zswap_load() is a noop with !CONFIG_ZSWAP, so it doesn't have
an effect there. The only effect is that with Barry's latest large
folio swapin patches for zram, we will always fallback to order-0
swapin, even mistakenly when !CONFIG_ZSWAP.
Basically the bug just makes Barry's in progress patches not work at all.
