[PATCH] remove radix_tree_reserve()

From Hugh Dickins.

radix_tree_reserve() exists solely for the tmpfs move_to_swap_cache()
and move_from_swap_cache() functions, and yet they don't need it: there
is no problem in the one page being simultaneously listed in two radix
trees (while both locks are held).  Use radix_tree_insert(), and remove
radix_tree_reserve(); also removed a few blank lines.

include/linux/radix-tree.h

@@ -21,8 +21,6 @@
 
 struct radix_tree_node;
 
-#define RADIX_TREE_SLOT_RESERVED ((void *)~0UL)
-
 struct radix_tree_root {
 	unsigned int		height;
 	int			gfp_mask;
@@ -41,7 +39,6 @@ do {					\
 	(root)->rnode = NULL;		\
 } while (0)
 
-extern int radix_tree_reserve(struct radix_tree_root *, unsigned long, void ***);
 extern int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
 extern void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
 extern int radix_tree_delete(struct radix_tree_root *, unsigned long);

lib/radix-tree.c

@@ -77,7 +77,6 @@ static inline unsigned long radix_tree_maxindex(unsigned int height)
 	return index;
 }
 
-
 /*
  *	Extend a radix tree so it can store key @index.
  */
@@ -109,16 +108,15 @@ static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
 	return 0;
 }
 
-
 /**
- *	radix_tree_reserve    -    reserve space in a radix tree
+ *	radix_tree_insert    -    insert into a radix tree
  *	@root:		radix tree root
  *	@index:		index key
- *	@pslot:		pointer to reserved slot
+ *	@item:		item to insert
  *
- *	Reserve a slot in a radix tree for the key @index.
+ *	Insert an item into the radix tree at position @index.
  */
-int radix_tree_reserve(struct radix_tree_root *root, unsigned long index, void ***pslot)
+int radix_tree_insert(struct radix_tree_root *root, unsigned long index, void *item)
 {
 	struct radix_tree_node *node = NULL, *tmp, **slot;
 	unsigned int height, shift;
@@ -158,36 +156,11 @@ int radix_tree_reserve(struct radix_tree_root *root, unsigned long index, void *
 	if (node)
 		node->count++;
 
-	*pslot = (void **)slot;
-	**pslot = RADIX_TREE_SLOT_RESERVED;
-	return 0;
-}
-
-EXPORT_SYMBOL(radix_tree_reserve);
-
-
-/**
- *	radix_tree_insert    -    insert into a radix tree
- *	@root:		radix tree root
- *	@index:		index key
- *	@item:		item to insert
- *
- *	Insert an item into the radix tree at position @index.
- */
-int radix_tree_insert(struct radix_tree_root *root, unsigned long index, void *item)
-{
-	void **slot;
-	int error;
-
-	error = radix_tree_reserve(root, index, &slot);
-	if (!error)
 	*slot = item;
-	return error;
+	return 0;
 }
-
 EXPORT_SYMBOL(radix_tree_insert);
 
-
 /**
  *	radix_tree_lookup    -    perform lookup operation on a radix tree
  *	@root:		radix tree root
@@ -267,8 +240,8 @@ __lookup(struct radix_tree_root *root, void **results, unsigned long index,
 out:
 	*next_index = index;
 	return nr_found;
-	
 }
+
 /**
  *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
  *	@root:		radix tree root
@@ -371,7 +344,6 @@ int radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 
 	return 0;
 }
-
 EXPORT_SYMBOL(radix_tree_delete);
 
 static void radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags)

mm/swap_state.c

@@ -199,16 +199,14 @@ void delete_from_swap_cache(struct page *page)
 int move_to_swap_cache(struct page *page, swp_entry_t entry)
 {
 	struct address_space *mapping = page->mapping;
-	void **pslot;
 	int err;
 
 	write_lock(&swapper_space.page_lock);
 	write_lock(&mapping->page_lock);
 
-	err = radix_tree_reserve(&swapper_space.page_tree, entry.val, &pslot);
+	err = radix_tree_insert(&swapper_space.page_tree, entry.val, page);
 	if (!err) {
 		__remove_from_page_cache(page);
-		*pslot = page;
 		___add_to_page_cache(page, &swapper_space, entry.val);
 	}
 
@@ -231,7 +229,6 @@ int move_from_swap_cache(struct page *page, unsigned long index,
 		struct address_space *mapping)
 {
 	swp_entry_t entry;
-	void **pslot;
 	int err;
 
 	BUG_ON(!PageLocked(page));
@@ -243,10 +240,9 @@ int move_from_swap_cache(struct page *page, unsigned long index,
 	write_lock(&swapper_space.page_lock);
 	write_lock(&mapping->page_lock);
 
-	err = radix_tree_reserve(&mapping->page_tree, index, &pslot);
+	err = radix_tree_insert(&mapping->page_tree, index, page);
 	if (!err) {
 		__delete_from_swap_cache(page);
-		*pslot = page;
 		___add_to_page_cache(page, mapping, index);
 	}