[PATCH] radix_tag_get(): differentiate between no present node and tag unset cases

Simple patch to radix_tree_tag_get() to return different values for non
present node and tag unset.

The function is not used by any in-kernel callers (yet), but this
information is definitely useful.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 2e9bd54beba4..b972dd29289d 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -418,15 +418,16 @@ EXPORT_SYMBOL(radix_tree_tag_clear);
 
 #ifndef __KERNEL__      /* Only the test harness uses this at present */
 /**
- *      radix_tree_tag_get - get a tag on a radix tree node
- *      @root:          radix tree root
- *      @index:         index key
- *      @tag:           tag index
+ * radix_tree_tag_get - get a tag on a radix tree node
+ * @root:               radix tree root
+ * @index:              index key
+ * @tag:                tag index
  *
- *      Return the search tag corresponging to @index in the radix tree.
+ * Return values:
  *
- *      Returns zero if the tag is unset, or if there is no corresponding item
- *      in the tree.
+ *  0: tag not present
+ *  1: tag present, set
+ * -1: tag present, unset
  */
 int radix_tree_tag_get(struct radix_tree_root *root,
                         unsigned long index, int tag)
@@ -460,7 +461,7 @@ int radix_tree_tag_get(struct radix_tree_root *root,
                         int ret = tag_get(slot, tag, offset);
 
                         BUG_ON(ret && saw_unset_tag);
-                        return ret;
+                        return ret ? 1 : -1;
                 }
                 slot = slot->slots[offset];
                 shift -= RADIX_TREE_MAP_SHIFT;