mm/zswap: use postorder iteration when destroying rbtree

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Reviewed-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 14 deletions

diff --git a/mm/zswap.c b/mm/zswap.c
index efed4c8b7f5b..841e35f1db22 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -790,26 +790,14 @@ static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
 static void zswap_frontswap_invalidate_area(unsigned type)
 {
         struct zswap_tree *tree = zswap_trees[type];
-        struct rb_node *node;
-        struct zswap_entry *entry;
+        struct zswap_entry *entry, *n;
 
         if (!tree)
                 return;
 
         /* walk the tree and free everything */
         spin_lock(&tree->lock);
-        /*
-         * TODO: Even though this code should not be executed because
-         * the try_to_unuse() in swapoff should have emptied the tree,
-         * it is very wasteful to rebalance the tree after every
-         * removal when we are freeing the whole tree.
-         *
-         * If post-order traversal code is ever added to the rbtree
-         * implementation, it should be used here.
-         */
-        while ((node = rb_first(&tree->rbroot))) {
-                entry = rb_entry(node, struct zswap_entry, rbnode);
-                rb_erase(&entry->rbnode, &tree->rbroot);
+        rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode) {
                 zbud_free(tree->pool, entry->handle);
                 zswap_entry_cache_free(entry);
                 atomic_dec(&zswap_stored_pages);