Btrfs: fix missing release of the space/qgroup reservation in start_transaction()

When we fail to start a transaction, we need to release the reserved free space
and qgroup space, fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/transaction.c

@@ -333,12 +333,14 @@ start_transaction(struct btrfs_root *root, u64 num_items, int type,
 					  &root->fs_info->trans_block_rsv,
 					  num_bytes, flush);
 		if (ret)
-			return ERR_PTR(ret);
+			goto reserve_fail;
 	}
 again:
 	h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
-	if (!h)
-		return ERR_PTR(-ENOMEM);
+	if (!h) {
+		ret = -ENOMEM;
+		goto alloc_fail;
+	}
 
 	/*
 	 * If we are JOIN_NOLOCK we're already committing a transaction and
@@ -365,11 +367,7 @@ start_transaction(struct btrfs_root *root, u64 num_items, int type,
 	if (ret < 0) {
 		/* We must get the transaction if we are JOIN_NOLOCK. */
 		BUG_ON(type == TRANS_JOIN_NOLOCK);
-
-		if (type < TRANS_JOIN_NOLOCK)
-			sb_end_intwrite(root->fs_info->sb);
-		kmem_cache_free(btrfs_trans_handle_cachep, h);
-		return ERR_PTR(ret);
+		goto join_fail;
 	}
 
 	cur_trans = root->fs_info->running_transaction;
@@ -410,6 +408,19 @@ start_transaction(struct btrfs_root *root, u64 num_items, int type,
 	if (!current->journal_info && type != TRANS_USERSPACE)
 		current->journal_info = h;
 	return h;
+
+join_fail:
+	if (type < TRANS_JOIN_NOLOCK)
+		sb_end_intwrite(root->fs_info->sb);
+	kmem_cache_free(btrfs_trans_handle_cachep, h);
+alloc_fail:
+	if (num_bytes)
+		btrfs_block_rsv_release(root, &root->fs_info->trans_block_rsv,
+					num_bytes);
+reserve_fail:
+	if (qgroup_reserved)
+		btrfs_qgroup_free(root, qgroup_reserved);
+	return ERR_PTR(ret);
 }
 
 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,