mm/zswap: use postorder iteration when destroying rbtree

Change-Id: I83b93b7eaadb7c66981f1119eda1119c978d1b9c
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>

diff --git a/mm/zswap.c b/mm/zswap.c
index efed4c8..841e35f 100644 (file)
--- 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);