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>
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 55ca73c..a4b00e9 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -192,6 +192,10 @@
 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)