1 files changed, 132 insertions, 2 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 05da38bcc298..efd16fa80b1c 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -174,14 +174,16 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
 {
         struct radix_tree_node *node =
                         container_of(head, struct radix_tree_node, rcu_head);
+        int i;
 
         /*
          * must only free zeroed nodes into the slab. radix_tree_shrink
          * can leave us with a non-NULL entry in the first slot, so clear
          * that here to make sure.
          */
-        tag_clear(node, 0, 0);
-        tag_clear(node, 1, 0);
+        for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
+                tag_clear(node, i, 0);
+
         node->slots[0] = NULL;
         node->count = 0;
 
@@ -609,6 +611,134 @@ 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 tags must be set from the leaf level only and propagated back up the
+ * path to the root. We must do this so that we resolve the full path before
+ * setting any tags on intermediate nodes. If we set tags as we descend, then
+ * we can get to the leaf node and find that the index that has the iftag
+ * set is outside the range we are scanning. This reults in dangling tags and
+ * can lead to problems with later tag operations (e.g. livelocks on lookups).
+ *
+ * The function returns number of leaves where the tag was set and sets
+ * *first_indexp to the first unscanned index.
+ * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
+ * be prepared to handle that.
+ */
+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;
+        struct radix_tree_path path[height];
+        struct radix_tree_path *pathp = path;
+        struct radix_tree_node *slot;
+        unsigned int shift;
+        unsigned long tagged = 0;
+        unsigned long index = *first_indexp;
+
+        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);
+
+        /*
+         * we fill the path from (root->height - 2) to 0, leaving the index at
+         * (root->height - 1) as a terminator. Zero the node in the terminator
+         * so that we can use this to end walk loops back up the path.
+         */
+        path[height - 1].node = NULL;
+
+        for (;;) {
+                int offset;
+
+                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+                if (!slot->slots[offset])
+                        goto next;
+                if (!tag_get(slot, iftag, offset))
+                        goto next;
+                if (height > 1) {
+                        /* Go down one level */
+                        height--;
+                        shift -= RADIX_TREE_MAP_SHIFT;
+                        path[height - 1].node = slot;
+                        path[height - 1].offset = offset;
+                        slot = slot->slots[offset];
+                        continue;
+                }
+
+                /* tag the leaf */
+                tagged++;
+                tag_set(slot, settag, offset);
+
+                /* walk back up the path tagging interior nodes */
+                pathp = &path[0];
+                while (pathp->node) {
+                        /* stop if we find a node with the tag already set */
+                        if (tag_get(pathp->node, settag, pathp->offset))
+                                break;
+                        tag_set(pathp->node, settag, pathp->offset);
+                        pathp++;
+                }
+
+next:
+                /* Go to next item at level determined by 'shift' */
+                index = ((index >> shift) + 1) << shift;
+                /* Overflow can happen when last_index is ~0UL... */
+                if (index > last_index || !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 = path[height - 1].node;
+                        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