mm: move VM_LOCKED check to __mlock_vma_pages_range()

[deliverable/linux.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index b8f97b8575b7fa5b765ac2fa044b24538feb1844..15e1f19a3b1003a5aa5e0b618766cfe648b3b81d 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1310,6 +1310,28 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
                 */
                mark_page_accessed(page);
        }
+       if (flags & FOLL_MLOCK) {
+               /*
+                * The preliminary mapping check is mainly to avoid the
+                * pointless overhead of lock_page on the ZERO_PAGE
+                * which might bounce very badly if there is contention.
+                *
+                * If the page is already locked, we don't need to
+                * handle it now - vmscan will handle it later if and
+                * when it attempts to reclaim the page.
+                */
+               if (page->mapping && trylock_page(page)) {
+                       lru_add_drain();  /* push cached pages to LRU */
+                       /*
+                        * Because we lock page here and migration is
+                        * blocked by the pte's page reference, we need
+                        * only check for file-cache page truncation.
+                        */
+                       if (page->mapping)
+                               mlock_vma_page(page);
+                       unlock_page(page);
+               }
+       }
 unlock:
        pte_unmap_unlock(ptep, ptl);
 out: