Commit 0a2e280b authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

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



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: 248db92d ("migrate_pages: try to split pages on queuing")
Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 30f471fd

mm/mempolicy.c

+1 −1
Original line number Diff line number Diff line
@@ -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);