tree 5f04af963600fd632de3eec68bc27c16e946b887
parent 30f471fd88e0304bee2c17ef1a4651e705870817
author Kirill A. Shutemov <kirill.shutemov@linux.intel.com> 1457561310 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1457567022 -0800

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: 248db92da13f2507 ("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>