diff options
| -rw-r--r-- | fs/btrfs/ctree.c | 116 |
1 files changed, 70 insertions, 46 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 51dc8e0bc9c1..3abddd2cdfd3 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -862,6 +862,75 @@ struct extent_buffer *btrfs_read_node_slot(struct extent_buffer *parent, } /* + * Promote a child node to become the new tree root. + * + * @trans: Transaction handle + * @root: Tree root structure to update + * @path: Path holding nodes and locks + * @level: Level of the parent (old root) + * @parent: The parent (old root) with exactly one item + * + * This helper is called during rebalancing when the root node contains only + * a single item (nritems == 1). We can reduce the tree height by promoting + * that child to become the new root and freeing the old root node. The path + * locks and references are updated accordingly. + * + * Return: 0 on success, negative errno on failure. The transaction is aborted + * on critical errors. + */ +static int promote_child_to_root(struct btrfs_trans_handle *trans, + struct btrfs_root *root, struct btrfs_path *path, + int level, struct extent_buffer *parent) +{ + struct extent_buffer *child; + int ret; + + ASSERT(btrfs_header_nritems(parent) == 1); + + child = btrfs_read_node_slot(parent, 0); + if (IS_ERR(child)) + return PTR_ERR(child); + + btrfs_tree_lock(child); + ret = btrfs_cow_block(trans, root, child, parent, 0, &child, BTRFS_NESTING_COW); + if (ret) { + btrfs_tree_unlock(child); + free_extent_buffer(child); + return ret; + } + + ret = btrfs_tree_mod_log_insert_root(root->node, child, true); + if (unlikely(ret < 0)) { + btrfs_tree_unlock(child); + free_extent_buffer(child); + btrfs_abort_transaction(trans, ret); + return ret; + } + rcu_assign_pointer(root->node, child); + + add_root_to_dirty_list(root); + btrfs_tree_unlock(child); + + path->locks[level] = 0; + path->nodes[level] = NULL; + btrfs_clear_buffer_dirty(trans, parent); + btrfs_tree_unlock(parent); + /* Once for the path. */ + free_extent_buffer(parent); + + root_sub_used_bytes(root); + ret = btrfs_free_tree_block(trans, btrfs_root_id(root), parent, 0, 1); + /* Once for the root ptr. */ + free_extent_buffer_stale(parent); + if (unlikely(ret < 0)) { + btrfs_abort_transaction(trans, ret); + return ret; + } + + return 0; +} + +/* * node level balancing, used to make sure nodes are in proper order for * item deletion. We balance from the top down, so we have to make sure * that a deletion won't leave an node completely empty later on. @@ -900,55 +969,10 @@ static noinline int balance_level(struct btrfs_trans_handle *trans, * by promoting the node below to a root */ if (!parent) { - struct extent_buffer *child; - if (btrfs_header_nritems(mid) != 1) return 0; - /* promote the child to a root */ - child = btrfs_read_node_slot(mid, 0); - if (IS_ERR(child)) { - ret = PTR_ERR(child); - goto out; - } - - btrfs_tree_lock(child); - ret = btrfs_cow_block(trans, root, child, mid, 0, &child, - BTRFS_NESTING_COW); - if (ret) { - btrfs_tree_unlock(child); - free_extent_buffer(child); - goto out; - } - - ret = btrfs_tree_mod_log_insert_root(root->node, child, true); - if (unlikely(ret < 0)) { - btrfs_tree_unlock(child); - free_extent_buffer(child); - btrfs_abort_transaction(trans, ret); - goto out; - } - rcu_assign_pointer(root->node, child); - - add_root_to_dirty_list(root); - btrfs_tree_unlock(child); - - path->locks[level] = 0; - path->nodes[level] = NULL; - btrfs_clear_buffer_dirty(trans, mid); - btrfs_tree_unlock(mid); - /* once for the path */ - free_extent_buffer(mid); - - root_sub_used_bytes(root); - ret = btrfs_free_tree_block(trans, btrfs_root_id(root), mid, 0, 1); - /* once for the root ptr */ - free_extent_buffer_stale(mid); - if (unlikely(ret < 0)) { - btrfs_abort_transaction(trans, ret); - goto out; - } - return 0; + return promote_child_to_root(trans, root, path, level, mid); } if (btrfs_header_nritems(mid) > BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4) |