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Merge branch 'radix-tree' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev

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* 'radix-tree' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/xfsdev:
  radix-tree: radix_tree_range_tag_if_tagged() can set incorrect tags
  radix-tree: clear all tags in radix_tree_node_rcu_free
This commit is contained in:
Linus Torvalds 2010-08-22 19:55:14 -07:00
commit 9ee47476d6
1 changed files with 49 additions and 16 deletions
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65
lib/radix-tree.c
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@ -174,14 +174,16 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
{
struct radix_tree_node *node =
container_of(head, struct radix_tree_node, rcu_head);
int i;
/*
* must only free zeroed nodes into the slab. radix_tree_shrink
* can leave us with a non-NULL entry in the first slot, so clear
* that here to make sure.
*/
tag_clear(node, 0, 0);
tag_clear(node, 1, 0);
for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
tag_clear(node, i, 0);
node->slots[0] = NULL;
node->count = 0;
@ -623,6 +625,13 @@ EXPORT_SYMBOL(radix_tree_tag_get);
* also settag. The function stops either after tagging nr_to_tag items or
* after reaching last_index.
*
* The tags must be set from the leaf level only and propagated back up the
* path to the root. We must do this so that we resolve the full path before
* setting any tags on intermediate nodes. If we set tags as we descend, then
* we can get to the leaf node and find that the index that has the iftag
* set is outside the range we are scanning. This reults in dangling tags and
* can lead to problems with later tag operations (e.g. livelocks on lookups).
*
* The function returns number of leaves where the tag was set and sets
* *first_indexp to the first unscanned index.
* WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
@ -633,9 +642,13 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
unsigned long nr_to_tag,
unsigned int iftag, unsigned int settag)
{
unsigned int height = root->height, shift;
unsigned long tagged = 0, index = *first_indexp;
struct radix_tree_node *open_slots[height], *slot;
unsigned int height = root->height;
struct radix_tree_path path[height];
struct radix_tree_path *pathp = path;
struct radix_tree_node *slot;
unsigned int shift;
unsigned long tagged = 0;
unsigned long index = *first_indexp;
last_index = min(last_index, radix_tree_maxindex(height));
if (index > last_index)
@ -655,6 +668,13 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = radix_tree_indirect_to_ptr(root->rnode);
/*
* we fill the path from (root->height - 2) to 0, leaving the index at
* (root->height - 1) as a terminator. Zero the node in the terminator
* so that we can use this to end walk loops back up the path.
*/
path[height - 1].node = NULL;
for (;;) {
int offset;
@ -663,17 +683,30 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
goto next;
if (!tag_get(slot, iftag, offset))
goto next;
tag_set(slot, settag, offset);
if (height == 1) {
tagged++;
goto next;
if (height > 1) {
/* Go down one level */
height--;
shift -= RADIX_TREE_MAP_SHIFT;
path[height - 1].node = slot;
path[height - 1].offset = offset;
slot = slot->slots[offset];
continue;
}
/* Go down one level */
height--;
shift -= RADIX_TREE_MAP_SHIFT;
open_slots[height] = slot;
slot = slot->slots[offset];
continue;
/* tag the leaf */
tagged++;
tag_set(slot, settag, offset);
/* walk back up the path tagging interior nodes */
pathp = &path[0];
while (pathp->node) {
/* stop if we find a node with the tag already set */
if (tag_get(pathp->node, settag, pathp->offset))
break;
tag_set(pathp->node, settag, pathp->offset);
pathp++;
}
next:
/* Go to next item at level determined by 'shift' */
index = ((index >> shift) + 1) << shift;
@ -688,7 +721,7 @@ next:
* last_index is guaranteed to be in the tree, what
* we do below cannot wander astray.
*/
slot = open_slots[height];
slot = path[height - 1].node;
height++;
shift += RADIX_TREE_MAP_SHIFT;
}