radix-tree: add radix_tree_split

This new function splits a larger multiorder entry into smaller entries
(potentially multi-order entries).  These entries are initialised to
RADIX_TREE_RETRY to ensure that RCU walkers who see this state aren't
confused.  The caller should then call radix_tree_for_each_slot() and
radix_tree_replace_slot() in order to turn these retry entries into the
intended new entries.  Tags are replicated from the original multiorder
entry into each new entry.

Link: http://lkml.kernel.org/r/1480369871-5271-59-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index c9f656cf5f52..fa6effe997a3 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -389,6 +389,69 @@ static void multiorder_join(void)
         }
 }
 
+static void __multiorder_split(int old_order, int new_order)
+{
+        RADIX_TREE(tree, GFP_KERNEL);
+        void **slot;
+        struct radix_tree_iter iter;
+        struct radix_tree_node *node;
+        void *item;
+
+        item_insert_order(&tree, 0, old_order);
+        radix_tree_tag_set(&tree, 0, 2);
+        radix_tree_split(&tree, 0, new_order);
+        radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+                radix_tree_iter_replace(&tree, &iter, slot,
+                                        item_create(iter.index, new_order));
+        }
+
+        item_kill_tree(&tree);
+
+        __radix_tree_insert(&tree, 0, old_order, (void *)0x12);
+
+        item = __radix_tree_lookup(&tree, 0, &node, NULL);
+        assert(item == (void *)0x12);
+        assert(node->exceptional > 0);
+
+        radix_tree_split(&tree, 0, new_order);
+        radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+                radix_tree_iter_replace(&tree, &iter, slot,
+                                        item_create(iter.index, new_order));
+        }
+
+        item = __radix_tree_lookup(&tree, 0, &node, NULL);
+        assert(item != (void *)0x12);
+        assert(node->exceptional == 0);
+
+        item_kill_tree(&tree);
+
+        __radix_tree_insert(&tree, 0, old_order, (void *)0x12);
+
+        item = __radix_tree_lookup(&tree, 0, &node, NULL);
+        assert(item == (void *)0x12);
+        assert(node->exceptional > 0);
+
+        radix_tree_split(&tree, 0, new_order);
+        radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+                radix_tree_iter_replace(&tree, &iter, slot, (void *)0x16);
+        }
+
+        item = __radix_tree_lookup(&tree, 0, &node, NULL);
+        assert(item == (void *)0x16);
+        assert(node->exceptional > 0);
+
+        item_kill_tree(&tree);
+}
+
+static void multiorder_split(void)
+{
+        int i, j;
+
+        for (i = 9; i < 19; i++)
+                for (j = 0; j < i; j++)
+                        __multiorder_split(i, j);
+}
+
 void multiorder_checks(void)
 {
         int i;
@@ -407,4 +470,5 @@ void multiorder_checks(void)
         multiorder_iteration();
         multiorder_tagged_iteration();
         multiorder_join();
+        multiorder_split();
 }