1 files changed, 31 insertions, 32 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 182b21825255..20f3b1f33f0e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -114,14 +114,11 @@ static void page_cache_tree_delete(struct address_space *mapping,
 				   struct page *page, void *shadow)
 {
 	struct radix_tree_node *node;
-	unsigned long index;
-	unsigned int offset;
-	unsigned int tag;
-	void **slot;
 
 	VM_BUG_ON(!PageLocked(page));
 
-	__radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
+	node = radix_tree_replace_clear_tags(&mapping->page_tree, page->index,
+								shadow);
 
 	if (shadow) {
 		mapping->nrexceptional++;
@@ -135,23 +132,9 @@ static void page_cache_tree_delete(struct address_space *mapping,
 	}
 	mapping->nrpages--;
 
-	if (!node) {
-		/* Clear direct pointer tags in root node */
-		mapping->page_tree.gfp_mask &= __GFP_BITS_MASK;
-		radix_tree_replace_slot(slot, shadow);
+	if (!node)
 		return;
-	}
-
-	/* Clear tree tags for the removed page */
-	index = page->index;
-	offset = index & RADIX_TREE_MAP_MASK;
-	for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
-		if (test_bit(offset, node->tags[tag]))
-			radix_tree_tag_clear(&mapping->page_tree, index, tag);
-	}
 
-	/* Delete page, swap shadow entry */
-	radix_tree_replace_slot(slot, shadow);
 	workingset_node_pages_dec(node);
 	if (shadow)
 		workingset_node_shadows_inc(node);
@@ -160,13 +143,15 @@ static void page_cache_tree_delete(struct address_space *mapping,
 			return;
 
 	/*
-	 * Track node that only contains shadow entries.
+	 * Track node that only contains shadow entries. DAX mappings contain
+	 * no shadow entries and may contain other exceptional entries so skip
+	 * those.
 	 *
 	 * Avoid acquiring the list_lru lock if already tracked.  The
 	 * list_empty() test is safe as node->private_list is
 	 * protected by mapping->tree_lock.
 	 */
-	if (!workingset_node_pages(node) &&
+	if (!dax_mapping(mapping) && !workingset_node_pages(node) &&
 	    list_empty(&node->private_list)) {
 		node->private_data = mapping;
 		list_lru_add(&workingset_shadow_nodes, &node->private_list);
@@ -213,7 +198,7 @@ void __delete_from_page_cache(struct page *page, void *shadow)
 			 * some other bad page check should catch it later.
 			 */
 			page_mapcount_reset(page);
-			atomic_sub(mapcount, &page->_count);
+			page_ref_sub(page, mapcount);
 		}
 	}
 
@@ -597,14 +582,24 @@ static int page_cache_tree_insert(struct address_space *mapping,
 		if (!radix_tree_exceptional_entry(p))
 			return -EEXIST;
 
-		if (WARN_ON(dax_mapping(mapping)))
-			return -EINVAL;
-
-		if (shadowp)
-			*shadowp = p;
 		mapping->nrexceptional--;
-		if (node)
-			workingset_node_shadows_dec(node);
+		if (!dax_mapping(mapping)) {
+			if (shadowp)
+				*shadowp = p;
+			if (node)
+				workingset_node_shadows_dec(node);
+		} else {
+			/* DAX can replace empty locked entry with a hole */
+			WARN_ON_ONCE(p !=
+				(void *)(RADIX_TREE_EXCEPTIONAL_ENTRY |
+					 RADIX_DAX_ENTRY_LOCK));
+			/* DAX accounts exceptional entries as normal pages */
+			if (node)
+				workingset_node_pages_dec(node);
+			/* Wakeup waiters for exceptional entry lock */
+			dax_wake_mapping_entry_waiter(mapping, page->index,
+						      false);
+		}
 	}
 	radix_tree_replace_slot(slot, page);
 	mapping->nrpages++;
@@ -713,8 +708,12 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 		 * The page might have been evicted from cache only
 		 * recently, in which case it should be activated like
 		 * any other repeatedly accessed page.
+		 * The exception is pages getting rewritten; evicting other
+		 * data from the working set, only to cache data that will
+		 * get overwritten with something else, is a waste of memory.
 		 */
-		if (shadow && workingset_refault(shadow)) {
+		if (!(gfp_mask & __GFP_WRITE) &&
+		    shadow && workingset_refault(shadow)) {
 			SetPageActive(page);
 			workingset_activation(page);
 		} else
@@ -2574,7 +2573,7 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 					pgoff_t index, unsigned flags)
 {
 	struct page *page;
-	int fgp_flags = FGP_LOCK|FGP_ACCESSED|FGP_WRITE|FGP_CREAT;
+	int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
 
 	if (flags & AOP_FLAG_NOFS)
 		fgp_flags |= FGP_NOFS;