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authorMatthew Wilcox <willy@linux.intel.com>2016-05-20 17:02:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-20 17:58:30 -0700
commitafe0e395b6d1817fa5393f1ad6fcbf71406b016d (patch)
tree9b455efe13df6db7997f8a56602c4d93bf7dc4d2
parent4f3755d1ae3cd856a5c7da3dea12cced8dc51fbf (diff)
downloadlinux-sh-afe0e395b6d1817fa5393f1ad6fcbf71406b016d.tar.gz
radix-tree: fix several shrinking bugs with multiorder entries
Setting the indirect bit on the user data entry used to be unambiguous because the tree walking code knew not to expect internal nodes in the last level of the tree. Multiorder entries can appear at any level of the tree, and a leaf with the indirect bit set is indistinguishable from a pointer to a node. Introduce a special entry (RADIX_TREE_RETRY) which is neither a valid user entry, nor a valid pointer to a node. The radix_tree_deref_retry() function continues to work the same way, but tree walking code can distinguish it from a pointer to a node. Also fix the condition for setting slot->parent to NULL; it does not matter what height the tree is, it only matters whether slot is an indirect pointer. Move this code above the comment which is referring to the assignment to root->rnode. Also fix the condition for preventing the tree from shrinking to a single entry if it's a multiorder entry. Add a test-case to the test suite that checks that the tree goes back down to its original height after an item is inserted & deleted from a higher index in the tree. Signed-off-by: Matthew Wilcox <willy@linux.intel.com> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com> Cc: Jan Kara <jack@suse.com> Cc: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/radix-tree.c23
-rw-r--r--tools/testing/radix-tree/multiorder.c39
2 files changed, 51 insertions, 11 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index f13ddbba8ace..a1ba41730071 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -80,6 +80,8 @@ static inline void *indirect_to_ptr(void *ptr)
return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
}
+#define RADIX_TREE_RETRY ptr_to_indirect(NULL)
+
#ifdef CONFIG_RADIX_TREE_MULTIORDER
/* Sibling slots point directly to another slot in the same node */
static inline bool is_sibling_entry(struct radix_tree_node *parent, void *node)
@@ -1443,6 +1445,14 @@ static inline void radix_tree_shrink(struct radix_tree_root *root)
slot = to_free->slots[0];
if (!slot)
break;
+ if (!radix_tree_is_indirect_ptr(slot) && (root->height > 1))
+ break;
+
+ if (radix_tree_is_indirect_ptr(slot)) {
+ slot = indirect_to_ptr(slot);
+ slot->parent = NULL;
+ slot = ptr_to_indirect(slot);
+ }
/*
* We don't need rcu_assign_pointer(), since we are simply
@@ -1451,14 +1461,6 @@ static inline void radix_tree_shrink(struct radix_tree_root *root)
* (to_free->slots[0]), it will be safe to dereference the new
* one (root->rnode) as far as dependent read barriers go.
*/
- if (root->height > 1) {
- if (!radix_tree_is_indirect_ptr(slot))
- break;
-
- slot = indirect_to_ptr(slot);
- slot->parent = NULL;
- slot = ptr_to_indirect(slot);
- }
root->rnode = slot;
root->height--;
@@ -1480,9 +1482,8 @@ static inline void radix_tree_shrink(struct radix_tree_root *root)
* also results in a stale slot). So tag the slot as indirect
* to force callers to retry.
*/
- if (root->height == 0)
- *((unsigned long *)&to_free->slots[0]) |=
- RADIX_TREE_INDIRECT_PTR;
+ if (!radix_tree_is_indirect_ptr(slot))
+ to_free->slots[0] = RADIX_TREE_RETRY;
radix_tree_node_free(to_free);
}
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index cfe718c78eb6..71f34a047002 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -46,6 +46,41 @@ static void multiorder_check(unsigned long index, int order)
item_check_absent(&tree, i);
}
+static void multiorder_shrink(unsigned long index, int order)
+{
+ unsigned long i;
+ unsigned long max = 1 << order;
+ RADIX_TREE(tree, GFP_KERNEL);
+ struct radix_tree_node *node;
+
+ printf("Multiorder shrink index %ld, order %d\n", index, order);
+
+ assert(item_insert_order(&tree, 0, order) == 0);
+
+ node = tree.rnode;
+
+ assert(item_insert(&tree, index) == 0);
+ assert(node != tree.rnode);
+
+ assert(item_delete(&tree, index) != 0);
+ assert(node == tree.rnode);
+
+ for (i = 0; i < max; i++) {
+ struct item *item = item_lookup(&tree, i);
+ assert(item != 0);
+ assert(item->index == 0);
+ }
+ for (i = max; i < 2*max; i++)
+ item_check_absent(&tree, i);
+
+ if (!item_delete(&tree, 0)) {
+ printf("failed to delete index %ld (order %d)\n", index, order); abort();
+ }
+
+ for (i = 0; i < 2*max; i++)
+ item_check_absent(&tree, i);
+}
+
void multiorder_checks(void)
{
int i;
@@ -55,4 +90,8 @@ void multiorder_checks(void)
multiorder_check(0, i);
multiorder_check((1UL << i) + 1, i);
}
+
+ for (i = 0; i < 15; i++)
+ multiorder_shrink((1UL << (i + RADIX_TREE_MAP_SHIFT)), i);
+
}