btrfs: rename and export read_node_slot

Preparatory work for code that will be moved out of ctree and uses this
function.
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -1792,8 +1792,8 @@ static void root_sub_used(struct btrfs_root *root, u32 size)
 /* given a node and slot number, this reads the blocks it points to.  The
  * extent buffer is returned with a reference taken (but unlocked).
  */
-static noinline struct extent_buffer *read_node_slot(
-				struct extent_buffer *parent, int slot)
+struct extent_buffer *btrfs_read_node_slot(struct extent_buffer *parent,
+					   int slot)
 {
 	int level = btrfs_header_level(parent);
 	struct extent_buffer *eb;
@@ -1862,7 +1862,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 			return 0;
 
 		/* promote the child to a root */
-		child = read_node_slot(mid, 0);
+		child = btrfs_read_node_slot(mid, 0);
 		if (IS_ERR(child)) {
 			ret = PTR_ERR(child);
 			btrfs_handle_fs_error(fs_info, ret, NULL);
@@ -1902,7 +1902,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 	    BTRFS_NODEPTRS_PER_BLOCK(fs_info) / 4)
 		return 0;
 
-	left = read_node_slot(parent, pslot - 1);
+	left = btrfs_read_node_slot(parent, pslot - 1);
 	if (IS_ERR(left))
 		left = NULL;
 
@@ -1917,7 +1917,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
 		}
 	}
 
-	right = read_node_slot(parent, pslot + 1);
+	right = btrfs_read_node_slot(parent, pslot + 1);
 	if (IS_ERR(right))
 		right = NULL;
 
@@ -2077,7 +2077,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
 	if (!parent)
 		return 1;
 
-	left = read_node_slot(parent, pslot - 1);
+	left = btrfs_read_node_slot(parent, pslot - 1);
 	if (IS_ERR(left))
 		left = NULL;
 
@@ -2129,7 +2129,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
 		btrfs_tree_unlock(left);
 		free_extent_buffer(left);
 	}
-	right = read_node_slot(parent, pslot + 1);
+	right = btrfs_read_node_slot(parent, pslot + 1);
 	if (IS_ERR(right))
 		right = NULL;
 
@@ -3783,7 +3783,7 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
 
 	btrfs_assert_tree_locked(path->nodes[1]);
 
-	right = read_node_slot(upper, slot + 1);
+	right = btrfs_read_node_slot(upper, slot + 1);
 	/*
 	 * slot + 1 is not valid or we fail to read the right node,
 	 * no big deal, just return.
@@ -4017,7 +4017,7 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
 
 	btrfs_assert_tree_locked(path->nodes[1]);
 
-	left = read_node_slot(path->nodes[1], slot - 1);
+	left = btrfs_read_node_slot(path->nodes[1], slot - 1);
 	/*
 	 * slot - 1 is not valid or we fail to read the left node,
 	 * no big deal, just return.
@@ -5224,7 +5224,7 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
 			goto out;
 		}
 		btrfs_set_path_blocking(path);
-		cur = read_node_slot(cur, slot);
+		cur = btrfs_read_node_slot(cur, slot);
 		if (IS_ERR(cur)) {
 			ret = PTR_ERR(cur);
 			goto out;
@@ -5251,7 +5251,7 @@ static int tree_move_down(struct btrfs_path *path, int *level)
 	struct extent_buffer *eb;
 
 	BUG_ON(*level == 0);
-	eb = read_node_slot(path->nodes[*level], path->slots[*level]);
+	eb = btrfs_read_node_slot(path->nodes[*level], path->slots[*level]);
 	if (IS_ERR(eb))
 		return PTR_ERR(eb);
 

fs/btrfs/ctree.h

@@ -2587,6 +2587,9 @@ int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
 			 struct btrfs_path *path,
 			 u64 min_trans);
+struct extent_buffer *btrfs_read_node_slot(struct extent_buffer *parent,
+					   int slot);
+
 enum btrfs_compare_tree_result {
 	BTRFS_COMPARE_TREE_NEW,
 	BTRFS_COMPARE_TREE_DELETED,