Re: [PATCH v2 5/5] mm/khugepaged: Convert collapse_pte_mapped_thp() to use folios

[Kefeng Wang]

On 2023/10/19 7:01, Vishal Moola wrote:
> On Wed, Oct 18, 2023 at 01:32:13PM -0700, Vishal Moola (Oracle) wrote:
> > This removes 2 calls to compound_head() and helps convert khugepaged to
> > use folios throughout.
> >
> > Previously, if the address passed to collapse_pte_mapped_thp()
> > corresponded to a tail page, the scan would fail immediately. Using
> > filemap_lock_folio() we can get the corresponding folio back and try to
> > operate on the folio instead.
> >
> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
>
> Hi Andrew, I've attached a fix patch addressing the syzbot issue.
> It can be squashed into this patch, syzbot tested it on v2 already as
> well.

Hi Vishal, only IS_ERR(folio) is enough since filemap_lock_folio won't 
return NULL.