On Fri, Aug 09, 2024 at 07:27:27PM +0200, David Hildenbrand wrote:
> On 09.08.24 19:13, Vincent Donnefort wrote:
> > Hi,
> >
> > Sorry, reviving this thread as I have ran into something weird:
> >
> > On Wed, Dec 20, 2023 at 11:44:32PM +0100, David Hildenbrand wrote:
> > > Let's convert insert_page_into_pte_locked() and do_set_pmd(). While at it,
> > > perform some folio conversion.
> > >
> > > Reviewed-by: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> > > Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
> > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> > > ---
> > > mm/memory.c | 14 ++++++++------
> > > 1 file changed, 8 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/mm/memory.c b/mm/memory.c
> > > index 7f957e5a84311..c77d3952d261f 100644
> > > --- a/mm/memory.c
> > > +++ b/mm/memory.c
> >
> > [...]
> >
> > > vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
> > > {
> > > + struct folio *folio = page_folio(page);
> > > struct vm_area_struct *vma = vmf->vma;
> > > bool write = vmf->flags & FAULT_FLAG_WRITE;
> > > unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
> > > @@ -4418,8 +4421,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
> > > if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
> > > return ret;
> > > - page = compound_head(page);
> > > - if (compound_order(page) != HPAGE_PMD_ORDER)
> > > + if (page != &folio->page || folio_order(folio) != HPAGE_PMD_ORDER)
> > > return ret;
> >
> > Is this `page != &folio->page` expected? I believe this check wasn't there
> > before as we had `page = compound_head()`.
> >
> > It breaks the installation of a PMD level mapping for shmem when the fault
> > address is in the middle of this block. In its fault path, shmem sets
> >
> > vmf->page = folio_file_page(folio, vmf->pgoff)
> >
> > which fails this test above.
>
> Already fixed? :)
>
> commit ab1ffc86cb5bec1c92387b9811d9036512f8f4eb (tag:
> mm-hotfixes-stable-2024-06-26-17-28)
> Author: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
> Date: Tue Jun 11 08:32:16 2024 -0700
>
> mm/memory: don't require head page for do_set_pmd()
>
Duh of course I haven't looked anything recent enough, my bad!
Thanks for your quick answer!
>
> --
> Cheers,
>
> David / dhildenb
>
