diff options
| -rw-r--r-- | lib/radix-tree.c | 57 |
1 files changed, 44 insertions, 13 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 1014171dd1c5..e0ee8cb37e41 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -625,6 +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. */ @@ -633,9 +640,13 @@ 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 +666,13 @@ 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 +681,30 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, goto next; if (!tag_get(slot, iftag, offset)) 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; + } + + /* tag the leaf */ + tagged++; tag_set(slot, settag, offset); - if (height == 1) { - tagged++; - goto next; + + /* 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++; } - /* Go down one level */ - height--; - shift -= RADIX_TREE_MAP_SHIFT; - open_slots[height] = slot; - slot = slot->slots[offset]; - continue; + next: /* Go to next item at level determined by 'shift' */ index = ((index >> shift) + 1) << shift; @@ -687,7 +718,7 @@ 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; } |