radix-tree: omplement function radix_tree_range_tag_if_tagged

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>

1 files changed, 94 insertions, 0 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 05da38bcc298..e907858498a6 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -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