Btrfs: add snapshot/subvolume destroy ioctl

This patch adds snapshot/subvolume destroy ioctl.  A subvolume that isn't being
used and doesn't contains links to other subvolumes can be destroyed.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 8fc922982183..4bd04f3fa8bb 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5463,9 +5463,24 @@ int btrfs_drop_snapshot(struct btrfs_root *root, int update_ref)
         ret = btrfs_del_root(trans, tree_root, &root->root_key);
         BUG_ON(ret);
 
-        free_extent_buffer(root->node);
-        free_extent_buffer(root->commit_root);
-        kfree(root);
+        if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
+                ret = btrfs_find_last_root(tree_root, root->root_key.objectid,
+                                           NULL, NULL);
+                BUG_ON(ret < 0);
+                if (ret > 0) {
+                        ret = btrfs_del_orphan_item(trans, tree_root,
+                                                    root->root_key.objectid);
+                        BUG_ON(ret);
+                }
+        }
+
+        if (root->in_radix) {
+                btrfs_free_fs_root(tree_root->fs_info, root);
+        } else {
+                free_extent_buffer(root->node);
+                free_extent_buffer(root->commit_root);
+                kfree(root);
+        }
 out:
         btrfs_end_transaction(trans, tree_root);
         kfree(wc);