diff options
| -rw-r--r-- | include/linux/radix-tree.h | 2 | ||||
| -rw-r--r-- | lib/radix-tree.c | 37 |
2 files changed, 39 insertions, 0 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index 355f6e80db0..c5da7491809 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -167,6 +167,8 @@ radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results, unsigned long first_index, unsigned int max_items); unsigned long radix_tree_next_hole(struct radix_tree_root *root, unsigned long index, unsigned long max_scan); +unsigned long radix_tree_prev_hole(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan); int radix_tree_preload(gfp_t gfp_mask); void radix_tree_init(void); void *radix_tree_tag_set(struct radix_tree_root *root, diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 4bb42a0344e..5301a52cdb4 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -666,6 +666,43 @@ unsigned long radix_tree_next_hole(struct radix_tree_root *root, } EXPORT_SYMBOL(radix_tree_next_hole); +/** + * radix_tree_prev_hole - find the prev hole (not-present entry) + * @root: tree root + * @index: index key + * @max_scan: maximum range to search + * + * Search backwards in the range [max(index-max_scan+1, 0), index] + * for the first hole. + * + * Returns: the index of the hole if found, otherwise returns an index + * outside of the set specified (in which case 'index - return >= max_scan' + * will be true). In rare cases of wrap-around, LONG_MAX will be returned. + * + * radix_tree_next_hole may be called under rcu_read_lock. However, like + * radix_tree_gang_lookup, this will not atomically search a snapshot of + * the tree at a single point in time. For example, if a hole is created + * at index 10, then subsequently a hole is created at index 5, + * radix_tree_prev_hole covering both indexes may return 5 if called under + * rcu_read_lock. + */ +unsigned long radix_tree_prev_hole(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan) +{ + unsigned long i; + + for (i = 0; i < max_scan; i++) { + if (!radix_tree_lookup(root, index)) + break; + index--; + if (index == LONG_MAX) + break; + } + + return index; +} +EXPORT_SYMBOL(radix_tree_prev_hole); + static unsigned int __lookup(struct radix_tree_node *slot, void ***results, unsigned long index, unsigned int max_items, unsigned long *next_index) |