radix-tree: tidy up __radix_tree_create()

1. Rename the existing variable 'slot' to 'child'.
2. Introduce a new variable called 'slot' which is the address of the
   slot we're dealing with.  This lets us simplify the tree insertion,
   and removes the recalculation of 'slot' at the end of the function.
3. Using 'slot' in the sibling pointer insertion part makes the code
   more readable.

Signed-off-by: Matthew Wilcox <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Kirill Shutemov <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Neil Brown <[email protected]>
Cc: Ross Zwisler <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 23 insertions, 25 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 1a82066165db..9d9b4b9af4b6 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -499,12 +499,13 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 			unsigned order, struct radix_tree_node **nodep,
 			void ***slotp)
 {
-	struct radix_tree_node *node = NULL, *slot;
+	struct radix_tree_node *node = NULL, *child;
+	void **slot = (void **)&root->rnode;
 	unsigned long maxindex;
-	unsigned int shift, offset;
+	unsigned int shift, offset = 0;
 	unsigned long max = index | ((1UL << order) - 1);
 
-	shift = radix_tree_load_root(root, &slot, &maxindex);
+	shift = radix_tree_load_root(root, &child, &maxindex);
 
 	/* Make sure the tree is high enough.  */
 	if (max > maxindex) {
@@ -512,51 +513,48 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 		if (error < 0)
 			return error;
 		shift = error;
-		slot = root->rnode;
+		child = root->rnode;
 		if (order == shift)
 			shift += RADIX_TREE_MAP_SHIFT;
 	}
 
-	offset = 0;			/* uninitialised var warning */
 	while (shift > order) {
 		shift -= RADIX_TREE_MAP_SHIFT;
-		if (slot == NULL) {
+		if (child == NULL) {
 			/* Have to add a child node.  */
-			slot = radix_tree_node_alloc(root);
-			if (!slot)
+			child = radix_tree_node_alloc(root);
+			if (!child)
 				return -ENOMEM;
-			slot->shift = shift;
-			slot->offset = offset;
-			slot->parent = node;
-			if (node) {
-				rcu_assign_pointer(node->slots[offset],
-							node_to_entry(slot));
+			child->shift = shift;
+			child->offset = offset;
+			child->parent = node;
+			rcu_assign_pointer(*slot, node_to_entry(child));
+			if (node)
 				node->count++;
-			} else
-				rcu_assign_pointer(root->rnode,
-							node_to_entry(slot));
-		} else if (!radix_tree_is_internal_node(slot))
+		} else if (!radix_tree_is_internal_node(child))
 			break;
 
 		/* Go a level down */
-		node = entry_to_node(slot);
+		node = entry_to_node(child);
 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-		offset = radix_tree_descend(node, &slot, offset);
+		offset = radix_tree_descend(node, &child, offset);
+		slot = &node->slots[offset];
 	}
 
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
 	/* Insert pointers to the canonical entry */
 	if (order > shift) {
-		int i, n = 1 << (order - shift);
+		unsigned i, n = 1 << (order - shift);
 		offset = offset & ~(n - 1);
-		slot = node_to_entry(&node->slots[offset]);
+		slot = &node->slots[offset];
+		child = node_to_entry(slot);
 		for (i = 0; i < n; i++) {
-			if (node->slots[offset + i])
+			if (slot[i])
 				return -EEXIST;
 		}
 
 		for (i = 1; i < n; i++) {
-			rcu_assign_pointer(node->slots[offset + i], slot);
+			rcu_assign_pointer(slot[i], child);
 			node->count++;
 		}
 	}
@@ -565,7 +563,7 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 	if (nodep)
 		*nodep = node;
 	if (slotp)
-		*slotp = node ? node->slots + offset : (void **)&root->rnode;
+		*slotp = slot;
 	return 0;
 }