1 files changed, 52 insertions, 43 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1638814c7848..6fbf707c0ce2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -536,7 +536,9 @@ static inline int is_page_cache_freeable(struct page *page)
 	 * that isolated the page, the page cache radix tree and
 	 * optional buffer heads at page->private.
 	 */
-	return page_count(page) - page_has_private(page) == 2;
+	int radix_pins = PageTransHuge(page) && PageSwapCache(page) ?
+		HPAGE_PMD_NR : 1;
+	return page_count(page) - page_has_private(page) == 1 + radix_pins;
 }
 
 static int may_write_to_inode(struct inode *inode, struct scan_control *sc)
@@ -666,6 +668,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 			    bool reclaimed)
 {
 	unsigned long flags;
+	int refcount;
 
 	BUG_ON(!PageLocked(page));
 	BUG_ON(mapping != page_mapping(page));
@@ -696,11 +699,15 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 	 * Note that if SetPageDirty is always performed via set_page_dirty,
 	 * and thus under tree_lock, then this ordering is not required.
 	 */
-	if (!page_ref_freeze(page, 2))
+	if (unlikely(PageTransHuge(page)) && PageSwapCache(page))
+		refcount = 1 + HPAGE_PMD_NR;
+	else
+		refcount = 2;
+	if (!page_ref_freeze(page, refcount))
 		goto cannot_free;
 	/* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
 	if (unlikely(PageDirty(page))) {
-		page_ref_unfreeze(page, 2);
+		page_ref_unfreeze(page, refcount);
 		goto cannot_free;
 	}
 
@@ -1122,58 +1129,56 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 * Try to allocate it some swap space here.
 		 * Lazyfree page could be freed directly
 		 */
-		if (PageAnon(page) && PageSwapBacked(page) &&
-		    !PageSwapCache(page)) {
-			if (!(sc->gfp_mask & __GFP_IO))
-				goto keep_locked;
-			if (PageTransHuge(page)) {
-				/* cannot split THP, skip it */
-				if (!can_split_huge_page(page, NULL))
-					goto activate_locked;
-				/*
-				 * Split pages without a PMD map right
-				 * away. Chances are some or all of the
-				 * tail pages can be freed without IO.
-				 */
-				if (!compound_mapcount(page) &&
-				    split_huge_page_to_list(page, page_list))
-					goto activate_locked;
-			}
-			if (!add_to_swap(page)) {
-				if (!PageTransHuge(page))
-					goto activate_locked;
-				/* Split THP and swap individual base pages */
-				if (split_huge_page_to_list(page, page_list))
-					goto activate_locked;
-				if (!add_to_swap(page))
-					goto activate_locked;
-			}
-
-			/* XXX: We don't support THP writes */
-			if (PageTransHuge(page) &&
-				  split_huge_page_to_list(page, page_list)) {
-				delete_from_swap_cache(page);
-				goto activate_locked;
-			}
+		if (PageAnon(page) && PageSwapBacked(page)) {
+			if (!PageSwapCache(page)) {
+				if (!(sc->gfp_mask & __GFP_IO))
+					goto keep_locked;
+				if (PageTransHuge(page)) {
+					/* cannot split THP, skip it */
+					if (!can_split_huge_page(page, NULL))
+						goto activate_locked;
+					/*
+					 * Split pages without a PMD map right
+					 * away. Chances are some or all of the
+					 * tail pages can be freed without IO.
+					 */
+					if (!compound_mapcount(page) &&
+					    split_huge_page_to_list(page,
+								    page_list))
+						goto activate_locked;
+				}
+				if (!add_to_swap(page)) {
+					if (!PageTransHuge(page))
+						goto activate_locked;
+					/* Fallback to swap normal pages */
+					if (split_huge_page_to_list(page,
+								    page_list))
+						goto activate_locked;
+					if (!add_to_swap(page))
+						goto activate_locked;
+				}
 
-			may_enter_fs = 1;
+				may_enter_fs = 1;
 
-			/* Adding to swap updated mapping */
-			mapping = page_mapping(page);
+				/* Adding to swap updated mapping */
+				mapping = page_mapping(page);
+			}
 		} else if (unlikely(PageTransHuge(page))) {
 			/* Split file THP */
 			if (split_huge_page_to_list(page, page_list))
 				goto keep_locked;
 		}
 
-		VM_BUG_ON_PAGE(PageTransHuge(page), page);
-
 		/*
 		 * The page is mapped into the page tables of one or more
 		 * processes. Try to unmap it here.
 		 */
 		if (page_mapped(page)) {
-			if (!try_to_unmap(page, ttu_flags | TTU_BATCH_FLUSH)) {
+			enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH;
+
+			if (unlikely(PageTransHuge(page)))
+				flags |= TTU_SPLIT_HUGE_PMD;
+			if (!try_to_unmap(page, flags)) {
 				nr_unmap_fail++;
 				goto activate_locked;
 			}
@@ -1313,7 +1318,11 @@ free_it:
 		 * Is there need to periodically free_page_list? It would
 		 * appear not as the counts should be low
 		 */
-		list_add(&page->lru, &free_pages);
+		if (unlikely(PageTransHuge(page))) {
+			mem_cgroup_uncharge(page);
+			(*get_compound_page_dtor(page))(page);
+		} else
+			list_add(&page->lru, &free_pages);
 		continue;
 
 activate_locked: