On Fri, Mar 27, 2020 at 01:34:20PM -0400, Zi Yan wrote:
> On 27 Mar 2020, at 13:05, Kirill A. Shutemov wrote:
>
> > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add
> > pagevec. It's petty common for swapin case: we swap in pages just to
> > fail due to the extra pin.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > ---
> > mm/khugepaged.c | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 14d7afc90786..39e0994abeb8 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -585,11 +585,19 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > * The page must only be referenced by the scanned process
> > * and page swap cache.
> > */
> > + if (page_count(page) != 1 + PageSwapCache(page)) {
> > + /*
> > + * Drain pagevec and retry just in case we can get rid
> > + * of the extra pin, like in swapin case.
> > + */
> > + lru_add_drain();
> > + }
> > if (page_count(page) != 1 + PageSwapCache(page)) {
> > unlock_page(page);
> > result = SCAN_PAGE_COUNT;
> > goto out;
> > }
> > +
> > if (pte_write(pteval)) {
> > writable = true;
> > } else {
> > --
> > 2.26.0
>
> Looks good to me. Is the added empty line intentional?
Yes. It groups try and retry together.
--
Kirill A. Shutemov
