On Tue, Dec 01, 2015 at 12:53:25PM -0800, Dave Hansen wrote:
> On 11/18/2015 03:25 PM, Kirill A. Shutemov wrote:
> > --- a/mm/filemap.c
> > +++ b/mm/filemap.c
> > @@ -2068,11 +2068,6 @@ void filemap_map_pages(struct fault_env *fe,
> ...
> > if (file->f_ra.mmap_miss > 0)
> > file->f_ra.mmap_miss--;
> > - do_set_pte(fe, page);
> > +
> > + fe->address += (iter.index - last_pgoff) << PAGE_SHIFT;
> > + if (fe->pte)
> > + fe->pte += iter.index - last_pgoff;
> > + last_pgoff = iter.index;
> > + if (do_set_pte(fe, NULL, page)) {
> > + /* failed to setup page table: giving up */
> > + if (!fe->pte)
> > + break;
> > + goto unlock;
> > + }
> > unlock_page(page);
> > goto next;
>
> Hey Kirill,
>
> Is there a case here where do_set_pte() returns an error and _still_
> manages to populate fe->pte?
Yes. If the page is already mapped, we will get VM_FAULT_NOPAGE:
do_set_pte()
pte_alloc_one_map()
!pmd_none(*fe->pmd) => goto map_pte;
fe->pte = pte_offset_map_lock()
!pte_none(*fe->pte) => return VM_FAULT_NOPAGE;
--
Kirill A. Shutemov
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