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Message-Id: <1481667692-14500-3-git-send-email-mawilcox@linuxonhyperv.com>
Date: Tue, 13 Dec 2016 14:21:29 -0800
From: Matthew Wilcox <mawilcox@...uxonhyperv.com>
To: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <mawilcox@...rosoft.com>, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org,
Konstantin Khlebnikov <koct9i@...il.com>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/5] radix-tree: Ensure counts are initialised
From: Matthew Wilcox <mawilcox@...rosoft.com>
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.
Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
---
lib/radix-tree.c | 41 ++++++++++++++++---------------
tools/testing/radix-tree/multiorder.c | 45 +++++++++++++++++++++++++++++++----
2 files changed, 61 insertions(+), 25 deletions(-)
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index a227727..6f382e0 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -287,7 +287,10 @@ static void radix_tree_dump(struct radix_tree_root *root)
* that the caller has pinned this thread of control to the current CPU.
*/
static struct radix_tree_node *
-radix_tree_node_alloc(struct radix_tree_root *root)
+radix_tree_node_alloc(struct radix_tree_root *root,
+ struct radix_tree_node *parent,
+ unsigned int shift, unsigned int offset,
+ unsigned int count, unsigned int exceptional)
{
struct radix_tree_node *ret = NULL;
gfp_t gfp_mask = root_gfp_mask(root);
@@ -332,6 +335,13 @@ radix_tree_node_alloc(struct radix_tree_root *root)
ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
out:
BUG_ON(radix_tree_is_internal_node(ret));
+ if (ret) {
+ ret->parent = parent;
+ ret->shift = shift;
+ ret->offset = offset;
+ ret->count = count;
+ ret->exceptional = exceptional;
+ }
return ret;
}
@@ -537,8 +547,8 @@ static int radix_tree_extend(struct radix_tree_root *root,
goto out;
do {
- struct radix_tree_node *node = radix_tree_node_alloc(root);
-
+ struct radix_tree_node *node = radix_tree_node_alloc(root,
+ NULL, shift, 0, 1, 0);
if (!node)
return -ENOMEM;
@@ -549,16 +559,11 @@ static int radix_tree_extend(struct radix_tree_root *root,
}
BUG_ON(shift > BITS_PER_LONG);
- node->shift = shift;
- node->offset = 0;
- node->count = 1;
- node->parent = NULL;
if (radix_tree_is_internal_node(slot)) {
entry_to_node(slot)->parent = node;
- } else {
+ } else if (radix_tree_exceptional_entry(slot)) {
/* Moving an exceptional root->rnode to a node */
- if (radix_tree_exceptional_entry(slot))
- node->exceptional = 1;
+ node->exceptional = 1;
}
node->slots[0] = slot;
slot = node_to_entry(node);
@@ -711,14 +716,10 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
shift -= RADIX_TREE_MAP_SHIFT;
if (child == NULL) {
/* Have to add a child node. */
- child = radix_tree_node_alloc(root);
+ child = radix_tree_node_alloc(root, node, shift,
+ offset, 0, 0);
if (!child)
return -ENOMEM;
- child->shift = shift;
- child->offset = offset;
- child->count = 0;
- child->exceptional = 0;
- child->parent = node;
rcu_assign_pointer(*slot, node_to_entry(child));
if (node)
node->count++;
@@ -1208,13 +1209,11 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,
for (;;) {
if (node->shift > order) {
- child = radix_tree_node_alloc(root);
+ child = radix_tree_node_alloc(root, node,
+ node->shift - RADIX_TREE_MAP_SHIFT,
+ offset, 0, 0);
if (!child)
goto nomem;
- child->shift = node->shift - RADIX_TREE_MAP_SHIFT;
- child->offset = offset;
- child->count = 0;
- child->parent = node;
if (node != parent) {
node->count++;
node->slots[offset] = node_to_entry(child);
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index 08b4e16..f79812a 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)
--
2.10.2
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