mm, thp: fix migration of PTE-mapped transparent huge pages

kiryl · torvalds · commit 0a2e280b6d8e · 2016-03-09T15:43:42.000-08:00
We don't have native support of THP migration, so we have to split huge page into small pages in order to migrate it to different node. This includes PTE-mapped huge pages. I made mistake in refcounting patchset: we don't actually split PTE-mapped huge page in queue_pages_pte_range(), if we step on head page. The result is that the head page is queued for migration, but none of tail pages: putting head page on queue takes pin on the page and any subsequent attempts of split_huge_pages() would fail and we skip queuing tail pages. unmap_and_move_huge_page() will eventually split the huge pages, but only one of 512 pages would get migrated. Let's fix the situation. Fixes: 248db92 ("migrate_pages: try to split pages on queuing") Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
@@ -532,7 +532,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
 		nid = page_to_nid(page);
 		if (node_isset(nid, *qp->nmask) == !!(flags & MPOL_MF_INVERT))
 			continue;
-		if (PageTail(page) && PageAnon(page)) {
+		if (PageTransCompound(page) && PageAnon(page)) {
 			get_page(page);
 			pte_unmap_unlock(pte, ptl);
 			lock_page(page);
