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, 64 insertions, 5 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 5ef72599a581..9351428f30e2 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -94,17 +94,23 @@ int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
                 goto out;
 
         BUG_ON(ret == 0);
+        if (path->slots[0] == 0) {
+                ret = 1;
+                goto out;
+        }
         l = path->nodes[0];
-        BUG_ON(path->slots[0] == 0);
         slot = path->slots[0] - 1;
         btrfs_item_key_to_cpu(l, &found_key, slot);
-        if (found_key.objectid != objectid) {
+        if (found_key.objectid != objectid ||
+            found_key.type != BTRFS_ROOT_ITEM_KEY) {
                 ret = 1;
                 goto out;
         }
-        read_extent_buffer(l, item, btrfs_item_ptr_offset(l, slot),
-                           sizeof(*item));
-        memcpy(key, &found_key, sizeof(found_key));
+        if (item)
+                read_extent_buffer(l, item, btrfs_item_ptr_offset(l, slot),
+                                   sizeof(*item));
+        if (key)
+                memcpy(key, &found_key, sizeof(found_key));
         ret = 0;
 out:
         btrfs_free_path(path);
@@ -249,6 +255,59 @@ err:
         return ret;
 }
 
+int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        int err = 0;
+        int ret;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = BTRFS_ORPHAN_OBJECTID;
+        key.type = BTRFS_ORPHAN_ITEM_KEY;
+        key.offset = 0;
+
+        while (1) {
+                ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
+                if (ret < 0) {
+                        err = ret;
+                        break;
+                }
+
+                leaf = path->nodes[0];
+                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+                        ret = btrfs_next_leaf(tree_root, path);
+                        if (ret < 0)
+                                err = ret;
+                        if (ret != 0)
+                                break;
+                        leaf = path->nodes[0];
+                }
+
+                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+                btrfs_release_path(tree_root, path);
+
+                if (key.objectid != BTRFS_ORPHAN_OBJECTID ||
+                    key.type != BTRFS_ORPHAN_ITEM_KEY)
+                        break;
+
+                ret = btrfs_find_dead_roots(tree_root, key.offset);
+                if (ret) {
+                        err = ret;
+                        break;
+                }
+
+                key.offset++;
+        }
+
+        btrfs_free_path(path);
+        return err;
+}
+
 /* drop the root item for 'key' from 'root' */
 int btrfs_del_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                    struct btrfs_key *key)