[PATCH v3 25/33] radix-tree: Add radix_tree_split_preload()

Matthew Wilcox
2016-11-28T19:59:10Z

From: Matthew Wilcox <willy@linux.intel.com>

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()).

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
---
include/linux/radix-tree.h | 1 +
lib/radix-tree.c | 24 +++++++++++++++++++-
tools/testing/radix-tree/multiorder.c | 42 +++++++++++++++++++++++++++++++++--
tools/testing/radix-tree/test.h | 5 +++++
4 files changed, 69 insertions(+), 3 deletions(-)

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 1f4b561..5dea8f6 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -345,6 +345,7 @@ static inline void radix_tree_preload_end(void)
preempt_enable();
}

+int radix_tree_split_preload(unsigned old_order, unsigned new_order, gfp_t);
int radix_tree_split(struct radix_tree_root *, unsigned long index,
unsigned new_order);
int radix_tree_join(struct radix_tree_root *, unsigned long index,
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 704201b..9d24bec 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -367,7 +367,7 @@ radix_tree_node_free(struct radix_tree_node *node)
* To make use of this facility, the radix tree must be initialised without
* __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
*/
-static int __radix_tree_preload(gfp_t gfp_mask, int nr)
+static int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
{
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
@@ -433,6 +433,28 @@ int radix_tree_maybe_preload(gfp_t gfp_mask)
}
EXPORT_SYMBOL(radix_tree_maybe_preload);

+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+/*
+ * Preload with enough objects to ensure that we can split a single entry
+ * of order @old_order into many entries of size @new_order
+ */
+int radix_tree_split_preload(unsigned int old_order, unsigned int new_order,
+ gfp_t gfp_mask)
+{
+ unsigned top = 1 << (old_order % RADIX_TREE_MAP_SHIFT);
+ unsigned layers = (old_order / RADIX_TREE_MAP_SHIFT) -
+ (new_order / RADIX_TREE_MAP_SHIFT);
+ unsigned nr = 0;
+
+ WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
+ BUG_ON(new_order >= old_order);
+
+ while (layers--)
+ nr = nr * RADIX_TREE_MAP_SIZE + 1;
+ return __radix_tree_preload(gfp_mask, top * nr);
+}
+#endif
+
/*
* The same as function above, but preload number of nodes required to insert
* (1 << order) continuous naturally-aligned elements.
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index fa6effe..5421f01 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 e11e4d2..7c2611c 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;
--
2.10.2