btrfs: use label to deduplicate error path at btrfs_force_cow_block()

At btrfs_force_cow_block() we have several error paths that need to
unlock the "cow" extent buffer, drop the reference on it and then return
an error. This is a bit verbose so add a label where we perform these
tasks and make the error paths jump to that label.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -588,19 +588,15 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 
 	ret = update_ref_for_cow(trans, root, buf, cow, &last_ref);
 	if (ret) {
-		btrfs_tree_unlock(cow);
-		free_extent_buffer(cow);
 		btrfs_abort_transaction(trans, ret);
-		return ret;
+		goto error_unlock_cow;
 	}
 
 	if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) {
 		ret = btrfs_reloc_cow_block(trans, root, buf, cow);
 		if (ret) {
-			btrfs_tree_unlock(cow);
-			free_extent_buffer(cow);
 			btrfs_abort_transaction(trans, ret);
-			return ret;
+			goto error_unlock_cow;
 		}
 	}
 
@@ -612,10 +608,8 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 
 		ret = btrfs_tree_mod_log_insert_root(root->node, cow, true);
 		if (ret < 0) {
-			btrfs_tree_unlock(cow);
-			free_extent_buffer(cow);
 			btrfs_abort_transaction(trans, ret);
-			return ret;
+			goto error_unlock_cow;
 		}
 		atomic_inc(&cow->refs);
 		rcu_assign_pointer(root->node, cow);
@@ -625,20 +619,16 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 		free_extent_buffer(buf);
 		add_root_to_dirty_list(root);
 		if (ret < 0) {
-			btrfs_tree_unlock(cow);
-			free_extent_buffer(cow);
 			btrfs_abort_transaction(trans, ret);
-			return ret;
+			goto error_unlock_cow;
 		}
 	} else {
 		WARN_ON(trans->transid != btrfs_header_generation(parent));
 		ret = btrfs_tree_mod_log_insert_key(parent, parent_slot,
 						    BTRFS_MOD_LOG_KEY_REPLACE);
 		if (ret) {
-			btrfs_tree_unlock(cow);
-			free_extent_buffer(cow);
 			btrfs_abort_transaction(trans, ret);
-			return ret;
+			goto error_unlock_cow;
 		}
 		btrfs_set_node_blockptr(parent, parent_slot,
 					cow->start);
@@ -648,19 +638,15 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 		if (last_ref) {
 			ret = btrfs_tree_mod_log_free_eb(buf);
 			if (ret) {
-				btrfs_tree_unlock(cow);
-				free_extent_buffer(cow);
 				btrfs_abort_transaction(trans, ret);
-				return ret;
+				goto error_unlock_cow;
 			}
 		}
 		ret = btrfs_free_tree_block(trans, btrfs_root_id(root), buf,
 					    parent_start, last_ref);
 		if (ret < 0) {
-			btrfs_tree_unlock(cow);
-			free_extent_buffer(cow);
 			btrfs_abort_transaction(trans, ret);
-			return ret;
+			goto error_unlock_cow;
 		}
 	}
 	if (unlock_orig)
@@ -669,6 +655,11 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans,
 	btrfs_mark_buffer_dirty(trans, cow);
 	*cow_ret = cow;
 	return 0;
+
+error_unlock_cow:
+	btrfs_tree_unlock(cow);
+	free_extent_buffer(cow);
+	return ret;
 }
 
 static inline int should_cow_block(struct btrfs_trans_handle *trans,