fs/ext4: use rbtree postorder iteration helper instead of opencoding

Use rbtree_postorder_for_each_entry_safe() to destroy the rbtree instead
of opencoding an alternate postorder iteration that modifies the tree

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Michel Lespinasse <walken@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 29 deletions

diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c
index 3f11656bd72e..41eb9dcfac7e 100644
--- a/fs/ext4/block_validity.c
+++ b/fs/ext4/block_validity.c
@@ -180,37 +180,12 @@ int ext4_setup_system_zone(struct super_block *sb)
 /* Called when the filesystem is unmounted */
 void ext4_release_system_zone(struct super_block *sb)
 {
-        struct rb_node  *n = EXT4_SB(sb)->system_blks.rb_node;
-        struct rb_node  *parent;
-        struct ext4_system_zone *entry;
+        struct ext4_system_zone *entry, *n;
 
-        while (n) {
-                /* Do the node's children first */
-                if (n->rb_left) {
-                        n = n->rb_left;
-                        continue;
-                }
-                if (n->rb_right) {
-                        n = n->rb_right;
-                        continue;
-                }
-                /*
-                 * The node has no children; free it, and then zero
-                 * out parent's link to it.  Finally go to the
-                 * beginning of the loop and try to free the parent
-                 * node.
-                 */
-                parent = rb_parent(n);
-                entry = rb_entry(n, struct ext4_system_zone, node);
+        rbtree_postorder_for_each_entry_safe(entry, n,
+                        &EXT4_SB(sb)->system_blks, node)
                 kmem_cache_free(ext4_system_zone_cachep, entry);
-                if (!parent)
-                        EXT4_SB(sb)->system_blks = RB_ROOT;
-                else if (parent->rb_left == n)
-                        parent->rb_left = NULL;
-                else if (parent->rb_right == n)
-                        parent->rb_right = NULL;
-                n = parent;
-        }
+
         EXT4_SB(sb)->system_blks = RB_ROOT;
 }