On Wed, Mar 19, 2014 at 01:33:05PM -0700, Andrew Morton wrote: > On Tue, 18 Mar 2014 22:29:39 -0400 Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> wrote: > > > We have a race where we try to migrate an invalid page, resulting in > > hitting VM_BUG_ON_PAGE in isolate_huge_page(). > > queue_pages_hugetlb() is OK to fail, so let's check !PageHeadHuge to keep > > invalid hugepage from queuing. > > > > .. > > > > --- v3.14-rc7-mmotm-2014-03-18-16-37.orig/mm/mempolicy.c > > +++ v3.14-rc7-mmotm-2014-03-18-16-37/mm/mempolicy.c > > @@ -530,6 +530,17 @@ static int queue_pages_hugetlb(pte_t *pte, unsigned long addr, > > if (!pte_present(entry)) > > return 0; > > page = pte_page(entry); > > + > > + /* > > + * Trinity found that page could be a non-hugepage. This is an > > + * unexpected behavior, but it's not clear how this problem happens. > > + * So let's simply skip such corner case. Page migration can often > > + * fail for various reasons, so it's ok to just skip the address > > + * unsuitable to hugepage migration. > > + */ > > + if (!PageHeadHuge(page)) > > + return 0; > > + > > Whoa, we won't be doing this thanks. The day we resort to this sort of > thing is the day we revert to the 2.2.26 VM. > > I suppose I'd be OK with putting > > if (WARN_ON(!PageHeadHuge(page))) > return 0; > > in there as a temporary be-kind-to-testers thing, but we must get a > full understanding of what's happening in there. I agree. > Was this problem caused by or exposed by the pagetable walker patches? I'm not sure, but at least I'm the last person who touched around error point, so I feel responsible for this. Naoya -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>