radix-tree: omplement function radix_tree_range_tag_if_tagged
Jan Kara [Tue, 10 Aug 2010 00:19:11 +0000 (17:19 -0700)]
Implement function for setting one tag if another tag is set for each item
in given range.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/radix-tree.h
lib/radix-tree.c

index 55ca73c..a4b00e9 100644 (file)
@@ -192,6 +192,10 @@ unsigned int
 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
                unsigned long first_index, unsigned int max_items,
                unsigned int tag);
+unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
+               unsigned long *first_indexp, unsigned long last_index,
+               unsigned long nr_to_tag,
+               unsigned int fromtag, unsigned int totag);
 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
 
 static inline void radix_tree_preload_end(void)
index 05da38b..e907858 100644 (file)
@@ -609,6 +609,100 @@ int radix_tree_tag_get(struct radix_tree_root *root,
 EXPORT_SYMBOL(radix_tree_tag_get);
 
 /**
+ * radix_tree_range_tag_if_tagged - for each item in given range set given
+ *                                tag if item has another tag set
+ * @root:              radix tree root
+ * @first_indexp:      pointer to a starting index of a range to scan
+ * @last_index:                last index of a range to scan
+ * @nr_to_tag:         maximum number items to tag
+ * @iftag:             tag index to test
+ * @settag:            tag index to set if tested tag is set
+ *
+ * This function scans range of radix tree from first_index to last_index
+ * (inclusive).  For each item in the range if iftag is set, the function sets
+ * also settag. The function stops either after tagging nr_to_tag items or
+ * after reaching last_index.
+ *
+ * The function returns number of leaves where the tag was set and sets
+ * *first_indexp to the first unscanned index.
+ */
+unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
+               unsigned long *first_indexp, unsigned long last_index,
+               unsigned long nr_to_tag,
+               unsigned int iftag, unsigned int settag)
+{
+       unsigned int height = root->height, shift;
+       unsigned long tagged = 0, index = *first_indexp;
+       struct radix_tree_node *open_slots[height], *slot;
+
+       last_index = min(last_index, radix_tree_maxindex(height));
+       if (index > last_index)
+               return 0;
+       if (!nr_to_tag)
+               return 0;
+       if (!root_tag_get(root, iftag)) {
+               *first_indexp = last_index + 1;
+               return 0;
+       }
+       if (height == 0) {
+               *first_indexp = last_index + 1;
+               root_tag_set(root, settag);
+               return 1;
+       }
+
+       shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
+       slot = radix_tree_indirect_to_ptr(root->rnode);
+
+       for (;;) {
+               int offset;
+
+               offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+               if (!slot->slots[offset])
+                       goto next;
+               if (!tag_get(slot, iftag, offset))
+                       goto next;
+               tag_set(slot, settag, offset);
+               if (height == 1) {
+                       tagged++;
+                       goto next;
+               }
+               /* Go down one level */
+               height--;
+               shift -= RADIX_TREE_MAP_SHIFT;
+               open_slots[height] = slot;
+               slot = slot->slots[offset];
+               continue;
+next:
+               /* Go to next item at level determined by 'shift' */
+               index = ((index >> shift) + 1) << shift;
+               if (index > last_index)
+                       break;
+               if (tagged >= nr_to_tag)
+                       break;
+               while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
+                       /*
+                        * We've fully scanned this node. Go up. Because
+                        * last_index is guaranteed to be in the tree, what
+                        * we do below cannot wander astray.
+                        */
+                       slot = open_slots[height];
+                       height++;
+                       shift += RADIX_TREE_MAP_SHIFT;
+               }
+       }
+       /*
+        * The iftag must have been set somewhere because otherwise
+        * we would return immediated at the beginning of the function
+        */
+       root_tag_set(root, settag);
+       *first_indexp = index;
+
+       return tagged;
+}
+EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
+
+
+/**
  *     radix_tree_next_hole    -    find the next hole (not-present entry)
  *     @root:          tree root
  *     @index:         index key