Btrfs: recursion free-first pass

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 96 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index dd11532cb2f6..6fbaece43ff6 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -50,7 +50,7 @@ static int inc_block_ref(struct ctree_root *root, u64 blocknr)
         return 0;
 }
 
-static int lookup_block_ref(struct ctree_root *root, u64 blocknr, int *refs)
+static int lookup_block_ref(struct ctree_root *root, u64 blocknr, u32 *refs)
 {
         struct ctree_path path;
         int ret;
@@ -415,6 +415,100 @@ struct tree_buffer *alloc_free_block(struct ctree_root *root)
         return buf;
 }
 
+int walk_down_tree(struct ctree_root *root, struct ctree_path *path, int *level)
+{
+        struct tree_buffer *next;
+        struct tree_buffer *cur;
+        u64 blocknr;
+        int ret;
+        u32 refs;
+
+        ret = lookup_block_ref(root, path->nodes[*level]->blocknr, &refs);
+        BUG_ON(ret);
+        if (refs > 1)
+                goto out;
+        while(*level > 0) {
+                cur = path->nodes[*level];
+                if (path->slots[*level] >= cur->node.header.nritems)
+                        break;
+                blocknr = cur->node.blockptrs[path->slots[*level]];
+                ret = lookup_block_ref(root, blocknr, &refs);
+                if (refs != 1 || *level == 1) {
+                        path->slots[*level]++;
+                        ret = free_extent(root, blocknr, 1);
+                        BUG_ON(ret);
+                        continue;
+                }
+                BUG_ON(ret);
+                next = read_tree_block(root, blocknr);
+                if (path->nodes[*level-1]) {
+                        tree_block_release(root, path->nodes[*level-1]);
+                }
+                path->nodes[*level-1] = next;
+                *level = node_level(next->node.header.flags);
+                path->slots[*level] = 0;
+        }
+out:
+        ret = free_extent(root, path->nodes[*level]->blocknr, 1);
+        path->nodes[*level] = NULL;
+        *level += 1;
+        BUG_ON(ret);
+        return 0;
+}
+
+int walk_up_tree(struct ctree_root *root, struct ctree_path *path, int *level)
+{
+        int i;
+        int slot;
+        int ret;
+        for(i = *level; i < MAX_LEVEL - 1 && path->nodes[i]; i++) {
+                slot = path->slots[i];
+                if (slot < path->nodes[i]->node.header.nritems - 1) {
+                        path->slots[i]++;
+                        *level = i;
+                        return 0;
+                } else {
+                        ret = free_extent(root,
+                                          path->nodes[*level]->blocknr, 1);
+                        *level = i + 1;
+                        BUG_ON(ret);
+                }
+        }
+        return 1;
+}
+
+int btrfs_drop_snapshot(struct ctree_root *root, struct tree_buffer *snap)
+{
+        int ret;
+        int level;
+        struct ctree_path path;
+        int i;
+        int orig_level;
+
+        init_path(&path);
+
+        level = node_level(snap->node.header.flags);
+        orig_level = level;
+        path.nodes[level] = snap;
+        path.slots[level] = 0;
+        while(1) {
+                ret = walk_down_tree(root, &path, &level);
+                if (ret > 0)
+                        break;
+                ret = walk_up_tree(root, &path, &level);
+                if (ret > 0)
+                        break;
+        }
+        for (i = 0; i < orig_level; i++) {
+                if (path.nodes[i])
+                        tree_block_release(root, path.nodes[i]);
+        }
+
+        return 0;
+}
+
+
+#if 0
 int btrfs_drop_snapshot(struct ctree_root *root, struct tree_buffer *snap)
 {
         int ret;
@@ -441,4 +535,4 @@ int btrfs_drop_snapshot(struct ctree_root *root, struct tree_buffer *snap)
         BUG_ON(ret);
         return 0;
 }
-
+#endif