radix-tree: add radix_tree_split_preload()

Calculate how many nodes we need to allocate to split an old_order entry
into multiple entries, each of size new_order.  The test suite checks
that we allocated exactly the right number of nodes; neither too many
(checked by rtp->nr == 0), nor too few (checked by comparing
nr_allocated before and after the call to radix_tree_split()).

Link: http://lkml.kernel.org/r/1480369871-5271-60-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>

2 files changed, 45 insertions, 2 deletions

diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index fa6effe997a3..5421f015f46c 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -389,35 +389,67 @@ static void multiorder_join(void)
         }
 }
 
+static void check_mem(unsigned old_order, unsigned new_order, unsigned alloc)
+{
+        struct radix_tree_preload *rtp = &radix_tree_preloads;
+        if (rtp->nr != 0)
+                printf("split(%u %u) remaining %u\n", old_order, new_order,
+                                                        rtp->nr);
+        /*
+         * Can't check for equality here as some nodes may have been
+         * RCU-freed while we ran.  But we should never finish with more
+         * nodes allocated since they should have all been preloaded.
+         */
+        if (nr_allocated > alloc)
+                printf("split(%u %u) allocated %u %u\n", old_order, new_order,
+                                                        alloc, nr_allocated);
+}
+
 static void __multiorder_split(int old_order, int new_order)
 {
-        RADIX_TREE(tree, GFP_KERNEL);
+        RADIX_TREE(tree, GFP_ATOMIC);
         void **slot;
         struct radix_tree_iter iter;
         struct radix_tree_node *node;
         void *item;
+        unsigned alloc;
+
+        radix_tree_preload(GFP_KERNEL);
+        assert(item_insert_order(&tree, 0, old_order) == 0);
+        radix_tree_preload_end();
+
+        /* Wipe out the preloaded cache or it'll confuse check_mem() */
+        radix_tree_cpu_dead(0);
 
-        item_insert_order(&tree, 0, old_order);
         radix_tree_tag_set(&tree, 0, 2);
+
+        radix_tree_split_preload(old_order, new_order, GFP_KERNEL);
+        alloc = nr_allocated;
         radix_tree_split(&tree, 0, new_order);
+        check_mem(old_order, new_order, alloc);
         radix_tree_for_each_slot(slot, &tree, &iter, 0) {
                 radix_tree_iter_replace(&tree, &iter, slot,
                                         item_create(iter.index, new_order));
         }
+        radix_tree_preload_end();
 
         item_kill_tree(&tree);
 
+        radix_tree_preload(GFP_KERNEL);
         __radix_tree_insert(&tree, 0, old_order, (void *)0x12);
+        radix_tree_preload_end();
 
         item = __radix_tree_lookup(&tree, 0, &node, NULL);
         assert(item == (void *)0x12);
         assert(node->exceptional > 0);
 
+        radix_tree_split_preload(old_order, new_order, GFP_KERNEL);
         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));
         }
+        radix_tree_preload_end();
 
         item = __radix_tree_lookup(&tree, 0, &node, NULL);
         assert(item != (void *)0x12);
@@ -425,16 +457,20 @@ static void __multiorder_split(int old_order, int new_order)
 
         item_kill_tree(&tree);
 
+        radix_tree_preload(GFP_KERNEL);
         __radix_tree_insert(&tree, 0, old_order, (void *)0x12);
+        radix_tree_preload_end();
 
         item = __radix_tree_lookup(&tree, 0, &node, NULL);
         assert(item == (void *)0x12);
         assert(node->exceptional > 0);
 
+        radix_tree_split_preload(old_order, new_order, GFP_KERNEL);
         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);
         }
+        radix_tree_preload_end();
 
         item = __radix_tree_lookup(&tree, 0, &node, NULL);
         assert(item == (void *)0x16);
@@ -471,4 +507,6 @@ void multiorder_checks(void)
         multiorder_tagged_iteration();
         multiorder_join();
         multiorder_split();
+
+        radix_tree_cpu_dead(0);
 }
diff --git a/tools/testing/radix-tree/test.h b/tools/testing/radix-tree/test.h
index e11e4d260b4e..7c2611caa6d2 100644
--- a/tools/testing/radix-tree/test.h
+++ b/tools/testing/radix-tree/test.h
@@ -52,3 +52,8 @@ int root_tag_get(struct radix_tree_root *root, unsigned int tag);
 unsigned long node_maxindex(struct radix_tree_node *);
 unsigned long shift_maxindex(unsigned int shift);
 int radix_tree_cpu_dead(unsigned int cpu);
+struct radix_tree_preload {
+        unsigned nr;
+        struct radix_tree_node *nodes;
+};
+extern struct radix_tree_preload radix_tree_preloads;