radix-tree: ensure counts are initialised

radix_tree_join() was freeing nodes with a non-zero ->exceptional count,
and radix_tree_split() wasn't zeroing ->exceptional when it allocated
the new node.  Fix this by making all callers of radix_tree_node_alloc()
pass in the new counts (and some other always-initialised fields), which
will prevent the problem recurring if in future we decide to do
something similar.

Link: http://lkml.kernel.org/r/1481667692-14500-3-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>

1 files changed, 41 insertions, 4 deletions

diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index 08b4e16dc86f..f79812a5e070 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -355,7 +355,7 @@ void multiorder_tagged_iteration(void)
         item_kill_tree(&tree);
 }
 
-static void __multiorder_join(unsigned long index,
+static void multiorder_join1(unsigned long index,
                                 unsigned order1, unsigned order2)
 {
         unsigned long loc;
@@ -373,7 +373,7 @@ static void __multiorder_join(unsigned long index,
         item_kill_tree(&tree);
 }
 
-static void __multiorder_join2(unsigned order1, unsigned order2)
+static void multiorder_join2(unsigned order1, unsigned order2)
 {
         RADIX_TREE(tree, GFP_KERNEL);
         struct radix_tree_node *node;
@@ -393,6 +393,39 @@ static void __multiorder_join2(unsigned order1, unsigned order2)
         item_kill_tree(&tree);
 }
 
+/*
+ * This test revealed an accounting bug for exceptional entries at one point.
+ * Nodes were being freed back into the pool with an elevated exception count
+ * by radix_tree_join() and then radix_tree_split() was failing to zero the
+ * count of exceptional entries.
+ */
+static void multiorder_join3(unsigned int order)
+{
+        RADIX_TREE(tree, GFP_KERNEL);
+        struct radix_tree_node *node;
+        void **slot;
+        struct radix_tree_iter iter;
+        unsigned long i;
+
+        for (i = 0; i < (1 << order); i++) {
+                radix_tree_insert(&tree, i, (void *)0x12UL);
+        }
+
+        radix_tree_join(&tree, 0, order, (void *)0x16UL);
+        rcu_barrier();
+
+        radix_tree_split(&tree, 0, 0);
+
+        radix_tree_for_each_slot(slot, &tree, &iter, 0) {
+                radix_tree_iter_replace(&tree, &iter, slot, (void *)0x12UL);
+        }
+
+        __radix_tree_lookup(&tree, 0, &node, NULL);
+        assert(node->exceptional == node->count);
+
+        item_kill_tree(&tree);
+}
+
 static void multiorder_join(void)
 {
         int i, j, idx;
@@ -400,16 +433,20 @@ static void multiorder_join(void)
         for (idx = 0; idx < 1024; idx = idx * 2 + 3) {
                 for (i = 1; i < 15; i++) {
                         for (j = 0; j < i; j++) {
-                                __multiorder_join(idx, i, j);
+                                multiorder_join1(idx, i, j);
                         }
                 }
         }
 
         for (i = 1; i < 15; i++) {
                 for (j = 0; j < i; j++) {
-                        __multiorder_join2(i, j);
+                        multiorder_join2(i, j);
                 }
         }
+
+        for (i = 3; i < 10; i++) {
+                multiorder_join3(i);
+        }
 }
 
 static void check_mem(unsigned old_order, unsigned new_order, unsigned alloc)