diff options
| -rw-r--r-- | include/linux/radix-tree.h | 1 | ||||
| -rw-r--r-- | lib/radix-tree.c | 92 | ||||
| -rw-r--r-- | mm/shmem.c | 38 |
3 files changed, 94 insertions, 37 deletions
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index b7edf82..9d4539c 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -252,6 +252,7 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, unsigned long nr_to_tag, unsigned int fromtag, unsigned int totag); int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag); +unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item); static inline void radix_tree_preload_end(void) { diff --git a/lib/radix-tree.c b/lib/radix-tree.c index 348eaef..a2f9da5 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -1203,6 +1203,98 @@ radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, } EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot); +#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP) +#include <linux/sched.h> /* for cond_resched() */ + +/* + * This linear search is at present only useful to shmem_unuse_inode(). + */ +static unsigned long __locate(struct radix_tree_node *slot, void *item, + unsigned long index, unsigned long *found_index) +{ + unsigned int shift, height; + unsigned long i; + + height = slot->height; + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + for ( ; height > 1; height--) { + i = (index >> shift) & RADIX_TREE_MAP_MASK; + for (;;) { + if (slot->slots[i] != NULL) + break; + index &= ~((1UL << shift) - 1); + index += 1UL << shift; + if (index == 0) + goto out; /* 32-bit wraparound */ + i++; + if (i == RADIX_TREE_MAP_SIZE) + goto out; + } + + shift -= RADIX_TREE_MAP_SHIFT; + slot = rcu_dereference_raw(slot->slots[i]); + if (slot == NULL) + goto out; + } + + /* Bottom level: check items */ + for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) { + if (slot->slots[i] == item) { + *found_index = index + i; + index = 0; + goto out; + } + } + index += RADIX_TREE_MAP_SIZE; +out: + return index; +} + +/** + * radix_tree_locate_item - search through radix tree for item + * @root: radix tree root + * @item: item to be found + * + * Returns index where item was found, or -1 if not found. + * Caller must hold no lock (since this time-consuming function needs + * to be preemptible), and must check afterwards if item is still there. + */ +unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) +{ + struct radix_tree_node *node; + unsigned long max_index; + unsigned long cur_index = 0; + unsigned long found_index = -1; + + do { + rcu_read_lock(); + node = rcu_dereference_raw(root->rnode); + if (!radix_tree_is_indirect_ptr(node)) { + rcu_read_unlock(); + if (node == item) + found_index = 0; + break; + } + + node = indirect_to_ptr(node); + max_index = radix_tree_maxindex(node->height); + if (cur_index > max_index) + break; + + cur_index = __locate(node, item, cur_index, &found_index); + rcu_read_unlock(); + cond_resched(); + } while (cur_index != 0 && cur_index <= max_index); + + return found_index; +} +#else +unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) +{ + return -1; +} +#endif /* CONFIG_SHMEM && CONFIG_SWAP */ /** * radix_tree_shrink - shrink height of a radix tree to minimal @@ -357,42 +357,6 @@ export: } /* - * Lockless lookup of swap entry in radix tree, avoiding refcount on pages. - */ -static pgoff_t shmem_find_swap(struct address_space *mapping, void *radswap) -{ - void **slots[PAGEVEC_SIZE]; - pgoff_t indices[PAGEVEC_SIZE]; - unsigned int nr_found; - -restart: - nr_found = 1; - indices[0] = -1; - while (nr_found) { - pgoff_t index = indices[nr_found - 1] + 1; - unsigned int i; - - rcu_read_lock(); - nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, - slots, indices, index, PAGEVEC_SIZE); - for (i = 0; i < nr_found; i++) { - void *item = radix_tree_deref_slot(slots[i]); - if (radix_tree_deref_retry(item)) { - rcu_read_unlock(); - goto restart; - } - if (item == radswap) { - rcu_read_unlock(); - return indices[i]; - } - } - rcu_read_unlock(); - cond_resched(); - } - return -1; -} - -/* * Remove swap entry from radix tree, free the swap and its page cache. */ static int shmem_free_swap(struct address_space *mapping, @@ -612,7 +576,7 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, int error; radswap = swp_to_radix_entry(swap); - index = shmem_find_swap(mapping, radswap); + index = radix_tree_locate_item(&mapping->page_tree, radswap); if (index == -1) return 0; |
