From 53c59f262d747ea82e7414774c59a489501186a0 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 3 Apr 2014 14:47:39 -0700 Subject: [PATCH] lib: radix-tree: add radix_tree_delete_item() Provide a function that does not just delete an entry at a given index, but also allows passing in an expected item. Delete only if that item is still located at the specified index. This is handy when lockless tree traversals want to delete entries as well because they don't have to do an second, locked lookup to verify the slot has not changed under them before deleting the entry. Signed-off-by: Johannes Weiner Reviewed-by: Minchan Kim Reviewed-by: Rik van Riel Acked-by: Mel Gorman Cc: Andrea Arcangeli Cc: Bob Liu Cc: Christoph Hellwig Cc: Dave Chinner Cc: Greg Thelen Cc: Hugh Dickins Cc: Jan Kara Cc: KOSAKI Motohiro Cc: Luigi Semenzato Cc: Metin Doslu Cc: Michel Lespinasse Cc: Ozgun Erdogan Cc: Peter Zijlstra Cc: Roman Gushchin Cc: Ryan Mallon Cc: Tejun Heo Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/radix-tree.h | 1 + lib/radix-tree.c | 31 +++++++++++++++++++++++++++---- 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 403940787be1..1bf0a9c388d9 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -219,6 +219,7 @@ static inline void radix_tree_replace_slot(void **pslot, void *item) int radix_tree_insert(struct radix_tree_root *, unsigned long, void *); void *radix_tree_lookup(struct radix_tree_root *, unsigned long); void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long); +void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *); void *radix_tree_delete(struct radix_tree_root *, unsigned long); unsigned int radix_tree_gang_lookup(struct radix_tree_root *root, void **results, diff --git a/lib/radix-tree.c b/lib/radix-tree.c index bd4a8dfdf0b8..d832117e7d94 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1337,15 +1337,18 @@ static inline void radix_tree_shrink(struct radix_tree_root *root) } /** - * radix_tree_delete - delete an item from a radix tree + * radix_tree_delete_item - delete an item from a radix tree * @root: radix tree root * @index: index key + * @item: expected item * - * Remove the item at @index from the radix tree rooted at @root. + * Remove @item at @index from the radix tree rooted at @root. * - * Returns the address of the deleted item, or NULL if it was not present. + * Returns the address of the deleted item, or NULL if it was not present + * or the entry at the given @index was not @item. */ -void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) +void *radix_tree_delete_item(struct radix_tree_root *root, + unsigned long index, void *item) { struct radix_tree_node *node = NULL; struct radix_tree_node *slot = NULL; @@ -1380,6 +1383,11 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) if (slot == NULL) goto out; + if (item && slot != item) { + slot = NULL; + goto out; + } + /* * Clear all tags associated with the item to be deleted. * This way of doing it would be inefficient, but seldom is any set. @@ -1424,6 +1432,21 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) out: return slot; } +EXPORT_SYMBOL(radix_tree_delete_item); + +/** + * radix_tree_delete - delete an item from a radix tree + * @root: radix tree root + * @index: index key + * + * Remove the item at @index from the radix tree rooted at @root. + * + * Returns the address of the deleted item, or NULL if it was not present. + */ +void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) +{ + return radix_tree_delete_item(root, index, NULL); +} EXPORT_SYMBOL(radix_tree_delete); /**