1 files changed, 22 insertions, 0 deletions
diff --git a/mm/memory.c b/mm/memory.c
index b8f97b8..15e1f19 100644
--- 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: