Re: [PATCH -rc7] mm/huge_memory: mark huge_zero_page reserved

[Yang Shi <shy828301@gmail.com>]

On Tue, May 14, 2024 at 3:42 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue, 14 May 2024 15:28:12 -0600 Yang Shi <shy828301@gmail.com> wrote:
>
> > On Tue, May 14, 2024 at 3:14 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> > >
> > > On Sat, 11 May 2024 11:54:35 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> > >
> > > > When I did memory failure tests recently, below panic occurs:
> > > >
> > > >  kernel BUG at include/linux/mm.h:1135!
> > > >  invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
> > > >  CPU: 9 PID: 137 Comm: kswapd1 Not tainted 6.9.0-rc4-00491-gd5ce28f156fe-dirty #14
> > > >
> > > > ...
> > > >
> > > > --- a/mm/huge_memory.c
> > > > +++ b/mm/huge_memory.c
> > > > @@ -208,6 +208,7 @@ static bool get_huge_zero_page(void)
> > > >               __free_pages(zero_page, compound_order(zero_page));
> > > >               goto retry;
> > > >       }
> > > > +     __SetPageReserved(zero_page);
> > > >       WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
> > > >
> > > >       /* We take additional reference here. It will be put back by shrinker */
> > > > @@ -260,6 +261,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
> > > >               struct page *zero_page = xchg(&huge_zero_page, NULL);
> > > >               BUG_ON(zero_page == NULL);
> > > >               WRITE_ONCE(huge_zero_pfn, ~0UL);
> > > > +             __ClearPageReserved(zero_page);
> > > >               __free_pages(zero_page, compound_order(zero_page));
> > > >               return HPAGE_PMD_NR;
> > > >       }
> > >
> > > This causes a bit of a mess when staged ahead of mm-stable.  So to
> > > avoid disruption I staged it behind mm-stable.  This means that when
> > > the -stable maintainers try to merge it, they will ask for a fixed up
> > > version for older kernels so you can please just send them this
> > > version.
> >
> > Can you please drop this from mm-unstable since both I and David
> > nack'ed a similar patch in another thread.
> > https://lore.kernel.org/linux-mm/20240511032801.1295023-1-linmiaohe@huawei.com/
>
> That appears to link to the incorrect email thread?

I meant that patch is actually same with this one. Just used folio
interface instead of page. I'm not sure why Miaohe posted two. Maybe
target to different version.