On Mon, Jan 11, 2021 at 02:37:42PM +0000, Will Deacon wrote:
> On Mon, Jan 11, 2021 at 05:25:33PM +0300, Kirill A. Shutemov wrote:
> > On Fri, Jan 08, 2021 at 05:15:16PM +0000, Will Deacon wrote:
> > > diff --git a/mm/filemap.c b/mm/filemap.c
> > > index c1f2dc89b8a7..0fb9d1714797 100644
> > > --- a/mm/filemap.c
> > > +++ b/mm/filemap.c
> > > @@ -3051,14 +3051,18 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
> > > if (!pte_none(*vmf->pte))
> > > goto unlock;
> > >
> > > + /* We're about to handle the fault */
> > > + if (vmf->address == address) {
> > > + vmf->flags &= ~FAULT_FLAG_PREFAULT;
> > > + ret = VM_FAULT_NOPAGE;
> > > + } else {
> > > + vmf->flags |= FAULT_FLAG_PREFAULT;
> > > + }
> > > +
> >
> > Do we need to restore the oririnal status of the bit once we are done?
>
> I can certainly add that, although it doesn't look like we do that for
> vmf->pte, so it's hard to tell what the rules are here. It certainly feels
> odd to restore some fields but not others, as it looks like vmf->address
> will be out-of-whack with vmf->pte when filemap_map_pages() returns. Am I
> missing something?
Unlike vmf->flags or vmf->address, vmf->pte is not going to be reused.
finish_fault() will overwrite it.
Yeah, it's messy.
--
Kirill A. Shutemov
