migrate_pages: try to split pages on queuing

We are not able to migrate THPs.  It means it's not enough to split only
PMD on migration -- we need to split compound page under it too.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.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
index 5f7f9da..973434e 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -489,14 +489,33 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr,
        struct page *page;
        struct queue_pages *qp = walk->private;
        unsigned long flags = qp->flags;
-       int nid;
+       int nid, ret;
        pte_t *pte;
        spinlock_t *ptl;
 
-       split_huge_pmd(vma, pmd, addr);
-       if (pmd_trans_unstable(pmd))
-               return 0;
+       if (pmd_trans_huge(*pmd)) {
+               ptl = pmd_lock(walk->mm, pmd);
+               if (pmd_trans_huge(*pmd)) {
+                       page = pmd_page(*pmd);
+                       if (is_huge_zero_page(page)) {
+                               spin_unlock(ptl);
+                               split_huge_pmd(vma, pmd, addr);
+                       } else {
+                               get_page(page);
+                               spin_unlock(ptl);
+                               lock_page(page);
+                               ret = split_huge_page(page);
+                               unlock_page(page);
+                               put_page(page);
+                               if (ret)
+                                       return 0;
+                       }
+               } else {
+                       spin_unlock(ptl);
+               }
+       }
 
+retry:
        pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
        for (; addr != end; pte++, addr += PAGE_SIZE) {
                if (!pte_present(*pte))
@@ -513,6 +532,21 @@ 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)) {
+                       get_page(page);
+                       pte_unmap_unlock(pte, ptl);
+                       lock_page(page);
+                       ret = split_huge_page(page);
+                       unlock_page(page);
+                       put_page(page);
+                       /* Failed to split -- skip. */
+                       if (ret) {
+                               pte = pte_offset_map_lock(walk->mm, pmd,
+                                               addr, &ptl);
+                               continue;
+                       }
+                       goto retry;
+               }
 
                if (flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL))
                        migrate_page_add(page, qp->pagelist, flags);