radix tree test suite: add new tag check

We have a check that setting a tag on a single entry at root succeeds,
but we were missing a check that clearing a tag on that same entry also
succeeds.

Link: http://lkml.kernel.org/r/1481667692-14500-4-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/radix-tree/tag_check.c

@@ -324,6 +324,9 @@ static void single_check(void)
 	assert(ret == 1);
 	ret = radix_tree_gang_lookup_tag(&tree, (void **)items, 0, BATCH, 1);
 	assert(ret == 1);
+	item_tag_clear(&tree, 0, 0);
+	ret = radix_tree_gang_lookup_tag(&tree, (void **)items, 0, BATCH, 0);
+	assert(ret == 0);
 	item_kill_tree(&tree);
 }