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, 11 insertions, 2 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 6e674d76186d..4d7d9abef42f 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2841,7 +2841,7 @@ static noinline int check_parent_dirs_for_sync(struct btrfs_trans_handle *trans,
                 if (!parent || !parent->d_inode || sb != parent->d_inode->i_sb)
                         break;
 
-                if (parent == sb->s_root)
+                if (IS_ROOT(parent))
                         break;
 
                 parent = parent->d_parent;
@@ -2880,6 +2880,12 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
                 goto end_no_trans;
         }
 
+        if (root != BTRFS_I(inode)->root ||
+            btrfs_root_refs(&root->root_item) == 0) {
+                ret = 1;
+                goto end_no_trans;
+        }
+
         ret = check_parent_dirs_for_sync(trans, inode, parent,
                                          sb, last_committed);
         if (ret)
@@ -2907,12 +2913,15 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
                         break;
 
                 inode = parent->d_inode;
+                if (root != BTRFS_I(inode)->root)
+                        break;
+
                 if (BTRFS_I(inode)->generation >
                     root->fs_info->last_trans_committed) {
                         ret = btrfs_log_inode(trans, root, inode, inode_only);
                         BUG_ON(ret);
                 }
-                if (parent == sb->s_root)
+                if (IS_ROOT(parent))
                         break;
 
                 parent = parent->d_parent;