Re: [stable 5.10 PATCH] mm: hwpoison: remove the unnecessary THP check

[Yang Shi]

On Thu, Nov 4, 2021 at 9:53 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Nov 03, 2021 at 10:46:24AM +0100, Greg KH wrote:
> > On Mon, Nov 01, 2021 at 12:48:56PM -0700, Yang Shi wrote:
> > > commit c7cb42e94473aafe553c0f2a3d8ca904599399ed upstream.
> > >
> > > When handling THP hwpoison checked if the THP is in allocation or free
> > > stage since hwpoison may mistreat it as hugetlb page.  After commit
> > > 415c64c1453a ("mm/memory-failure: split thp earlier in memory error
> > > handling") the problem has been fixed, so this check is no longer
> > > needed.  Remove it.  The side effect of the removal is hwpoison may
> > > report unsplit THP instead of unknown error for shmem THP.  It seems not
> > > like a big deal.
> > >
> > > The following patch "mm: filemap: check if THP has hwpoisoned subpage
> > > for PMD page fault" depends on this, which fixes shmem THP with
> > > hwpoisoned subpage(s) are mapped PMD wrongly.  So this patch needs to be
> > > backported to -stable as well.
> > >
> > > Link: https://lkml.kernel.org/r/20211020210755.23964-2-shy828301@xxxxxxxxx
> > > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> > > Suggested-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > > Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > > Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> > > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > > Cc: Oscar Salvador <osalvador@xxxxxxx>
> > > Cc: Peter Xu <peterx@xxxxxxxxxx>
> > > Cc: <stable@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > ---
> > > mm-filemap-check-if-thp-has-hwpoisoned-subpage-for-pmd-page-fault.patch
> > > depends on this one.
> >
> > Both now queued up, thanks.
>
> This breaks the build, see:
>         https://lore.kernel.org/r/acabc414-164b-cd65-6a1a-cf912d8621d7@xxxxxxxxxxxx
>
> so I'm going to drop both of these now.  Please fix this up and resend a
> tested series.

Thanks for catching this. It is because I accidentally left the
PAGEFLAG_* macros into CONFIG_TRANSHUGE_PAGE section, so it is:

#ifdef CONFIG_TRANSHUGE_PAGE
...
#if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_TRANSHUGE_PAGE)
PAGEFLAG_xxx
#else
PAGEFLAG_FALSE_xxx
#endif
...
#endif

So when THP is disabled the PAGEFLAG_FALSE_xxx macro is actually absent.

The upstream has the same issue, will send a patch to fix it soon, and
send fixes (folded the new fix in) to -stable later. Sorry for the
inconvenience.

>
> thanks,
>
> greg k-h