On 13.01.21 06:22, Muchun Song wrote: > All pages isolated for the migration have an elevated reference count > and therefore seeing a reference count equal to 1 means that the last > user of the page has dropped the reference and the page has became > unused and there doesn't make much sense to migrate it anymore. This has > been done for regular pages and this patch does the same for hugetlb > pages. Although the likelyhood of the race is rather small for hugetlb > pages it makes sense the two code paths in sync. > > Signed-off-by: Muchun Song <[email protected]> > Reviewed-by: Mike Kravetz <[email protected]> > Acked-by: Yang Shi <[email protected]> > Acked-by: Michal Hocko <[email protected]> > --- > mm/migrate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 4385f2fb5d18..a6631c4eb6a6 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1279,6 +1279,12 @@ static int unmap_and_move_huge_page(new_page_t > get_new_page, > return -ENOSYS; > } > > + if (page_count(hpage) == 1) { > + /* page was freed from under us. So we are done. */ > + putback_active_hugepage(hpage); > + return MIGRATEPAGE_SUCCESS; > + } > + > new_hpage = get_new_page(hpage, private); > if (!new_hpage) > return -ENOMEM; >
Happy to say that I now know understand what's going on here Reviewed-by: David Hildenbrand <[email protected]> -- Thanks, David / dhildenb
