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Diffstat (limited to 'lib/radix-tree.c')
| -rw-r--r-- | lib/radix-tree.c | 807 |
1 files changed, 807 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c new file mode 100644 index 00000000000..04d664377f2 --- /dev/null +++ b/lib/radix-tree.c @@ -0,0 +1,807 @@ +/* + * Copyright (C) 2001 Momchil Velikov + * Portions Copyright (C) 2001 Christoph Hellwig + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2, or (at + * your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include <linux/errno.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/radix-tree.h> +#include <linux/percpu.h> +#include <linux/slab.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/gfp.h> +#include <linux/string.h> +#include <linux/bitops.h> + + +#ifdef __KERNEL__ +#define RADIX_TREE_MAP_SHIFT 6 +#else +#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */ +#endif +#define RADIX_TREE_TAGS 2 + +#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT) +#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1) + +#define RADIX_TREE_TAG_LONGS \ + ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG) + +struct radix_tree_node { + unsigned int count; + void *slots[RADIX_TREE_MAP_SIZE]; + unsigned long tags[RADIX_TREE_TAGS][RADIX_TREE_TAG_LONGS]; +}; + +struct radix_tree_path { + struct radix_tree_node *node, **slot; + int offset; +}; + +#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) +#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2) + +static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH]; + +/* + * Radix tree node cache. + */ +static kmem_cache_t *radix_tree_node_cachep; + +/* + * Per-cpu pool of preloaded nodes + */ +struct radix_tree_preload { + int nr; + struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH]; +}; +DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; + +/* + * This assumes that the caller has performed appropriate preallocation, and + * that the caller has pinned this thread of control to the current CPU. + */ +static struct radix_tree_node * +radix_tree_node_alloc(struct radix_tree_root *root) +{ + struct radix_tree_node *ret; + + ret = kmem_cache_alloc(radix_tree_node_cachep, root->gfp_mask); + if (ret == NULL && !(root->gfp_mask & __GFP_WAIT)) { + struct radix_tree_preload *rtp; + + rtp = &__get_cpu_var(radix_tree_preloads); + if (rtp->nr) { + ret = rtp->nodes[rtp->nr - 1]; + rtp->nodes[rtp->nr - 1] = NULL; + rtp->nr--; + } + } + return ret; +} + +static inline void +radix_tree_node_free(struct radix_tree_node *node) +{ + kmem_cache_free(radix_tree_node_cachep, node); +} + +/* + * Load up this CPU's radix_tree_node buffer with sufficient objects to + * ensure that the addition of a single element in the tree cannot fail. On + * success, return zero, with preemption disabled. On error, return -ENOMEM + * with preemption not disabled. + */ +int radix_tree_preload(int gfp_mask) +{ + struct radix_tree_preload *rtp; + struct radix_tree_node *node; + int ret = -ENOMEM; + + preempt_disable(); + rtp = &__get_cpu_var(radix_tree_preloads); + while (rtp->nr < ARRAY_SIZE(rtp->nodes)) { + preempt_enable(); + node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); + if (node == NULL) + goto out; + preempt_disable(); + rtp = &__get_cpu_var(radix_tree_preloads); + if (rtp->nr < ARRAY_SIZE(rtp->nodes)) + rtp->nodes[rtp->nr++] = node; + else + kmem_cache_free(radix_tree_node_cachep, node); + } + ret = 0; +out: + return ret; +} + +static inline void tag_set(struct radix_tree_node *node, int tag, int offset) +{ + if (!test_bit(offset, &node->tags[tag][0])) + __set_bit(offset, &node->tags[tag][0]); +} + +static inline void tag_clear(struct radix_tree_node *node, int tag, int offset) +{ + __clear_bit(offset, &node->tags[tag][0]); +} + +static inline int tag_get(struct radix_tree_node *node, int tag, int offset) +{ + return test_bit(offset, &node->tags[tag][0]); +} + +/* + * Return the maximum key which can be store into a + * radix tree with height HEIGHT. + */ +static inline unsigned long radix_tree_maxindex(unsigned int height) +{ + return height_to_maxindex[height]; +} + +/* + * Extend a radix tree so it can store key @index. + */ +static int radix_tree_extend(struct radix_tree_root *root, unsigned long index) +{ + struct radix_tree_node *node; + unsigned int height; + char tags[RADIX_TREE_TAGS]; + int tag; + + /* Figure out what the height should be. */ + height = root->height + 1; + while (index > radix_tree_maxindex(height)) + height++; + + if (root->rnode == NULL) { + root->height = height; + goto out; + } + + /* + * Prepare the tag status of the top-level node for propagation + * into the newly-pushed top-level node(s) + */ + for (tag = 0; tag < RADIX_TREE_TAGS; tag++) { + int idx; + + tags[tag] = 0; + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (root->rnode->tags[tag][idx]) { + tags[tag] = 1; + break; + } + } + } + + do { + if (!(node = radix_tree_node_alloc(root))) + return -ENOMEM; + + /* Increase the height. */ + node->slots[0] = root->rnode; + + /* Propagate the aggregated tag info into the new root */ + for (tag = 0; tag < RADIX_TREE_TAGS; tag++) { + if (tags[tag]) + tag_set(node, tag, 0); + } + + node->count = 1; + root->rnode = node; + root->height++; + } while (height > root->height); +out: + return 0; +} + +/** + * radix_tree_insert - insert into a radix tree + * @root: radix tree root + * @index: index key + * @item: item to insert + * + * Insert an item into the radix tree at position @index. + */ +int radix_tree_insert(struct radix_tree_root *root, + unsigned long index, void *item) +{ + struct radix_tree_node *node = NULL, *tmp, **slot; + unsigned int height, shift; + int offset; + int error; + + /* Make sure the tree is high enough. */ + if ((!index && !root->rnode) || + index > radix_tree_maxindex(root->height)) { + error = radix_tree_extend(root, index); + if (error) + return error; + } + + slot = &root->rnode; + height = root->height; + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + offset = 0; /* uninitialised var warning */ + while (height > 0) { + if (*slot == NULL) { + /* Have to add a child node. */ + if (!(tmp = radix_tree_node_alloc(root))) + return -ENOMEM; + *slot = tmp; + if (node) + node->count++; + } + + /* Go a level down */ + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + node = *slot; + slot = (struct radix_tree_node **)(node->slots + offset); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + if (*slot != NULL) + return -EEXIST; + if (node) { + node->count++; + BUG_ON(tag_get(node, 0, offset)); + BUG_ON(tag_get(node, 1, offset)); + } + + *slot = item; + return 0; +} +EXPORT_SYMBOL(radix_tree_insert); + +/** + * radix_tree_lookup - perform lookup operation on a radix tree + * @root: radix tree root + * @index: index key + * + * Lookup the item at the position @index in the radix tree @root. + */ +void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index) +{ + unsigned int height, shift; + struct radix_tree_node **slot; + + height = root->height; + if (index > radix_tree_maxindex(height)) + return NULL; + + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + slot = &root->rnode; + + while (height > 0) { + if (*slot == NULL) + return NULL; + + slot = (struct radix_tree_node **) + ((*slot)->slots + + ((index >> shift) & RADIX_TREE_MAP_MASK)); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + return *slot; +} +EXPORT_SYMBOL(radix_tree_lookup); + +/** + * radix_tree_tag_set - set a tag on a radix tree node + * @root: radix tree root + * @index: index key + * @tag: tag index + * + * Set the search tag corresponging to @index in the radix tree. From + * the root all the way down to the leaf node. + * + * Returns the address of the tagged item. Setting a tag on a not-present + * item is a bug. + */ +void *radix_tree_tag_set(struct radix_tree_root *root, + unsigned long index, int tag) +{ + unsigned int height, shift; + struct radix_tree_node **slot; + + height = root->height; + if (index > radix_tree_maxindex(height)) + return NULL; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + slot = &root->rnode; + + while (height > 0) { + int offset; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + tag_set(*slot, tag, offset); + slot = (struct radix_tree_node **)((*slot)->slots + offset); + BUG_ON(*slot == NULL); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + return *slot; +} +EXPORT_SYMBOL(radix_tree_tag_set); + +/** + * radix_tree_tag_clear - clear a tag on a radix tree node + * @root: radix tree root + * @index: index key + * @tag: tag index + * + * Clear the search tag corresponging to @index in the radix tree. If + * this causes the leaf node to have no tags set then clear the tag in the + * next-to-leaf node, etc. + * + * Returns the address of the tagged item on success, else NULL. ie: + * has the same return value and semantics as radix_tree_lookup(). + */ +void *radix_tree_tag_clear(struct radix_tree_root *root, + unsigned long index, int tag) +{ + struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path; + unsigned int height, shift; + void *ret = NULL; + + height = root->height; + if (index > radix_tree_maxindex(height)) + goto out; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + pathp->node = NULL; + pathp->slot = &root->rnode; + + while (height > 0) { + int offset; + + if (*pathp->slot == NULL) + goto out; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + pathp[1].offset = offset; + pathp[1].node = *pathp[0].slot; + pathp[1].slot = (struct radix_tree_node **) + (pathp[1].node->slots + offset); + pathp++; + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + ret = *pathp[0].slot; + if (ret == NULL) + goto out; + + do { + int idx; + + tag_clear(pathp[0].node, tag, pathp[0].offset); + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (pathp[0].node->tags[tag][idx]) + goto out; + } + pathp--; + } while (pathp[0].node); +out: + return ret; +} +EXPORT_SYMBOL(radix_tree_tag_clear); + +#ifndef __KERNEL__ /* Only the test harness uses this at present */ +/** + * radix_tree_tag_get - get a tag on a radix tree node + * @root: radix tree root + * @index: index key + * @tag: tag index + * + * Return the search tag corresponging to @index in the radix tree. + * + * Returns zero if the tag is unset, or if there is no corresponding item + * in the tree. + */ +int radix_tree_tag_get(struct radix_tree_root *root, + unsigned long index, int tag) +{ + unsigned int height, shift; + struct radix_tree_node **slot; + int saw_unset_tag = 0; + + height = root->height; + if (index > radix_tree_maxindex(height)) + return 0; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + slot = &root->rnode; + + for ( ; ; ) { + int offset; + + if (*slot == NULL) + return 0; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + + /* + * This is just a debug check. Later, we can bale as soon as + * we see an unset tag. + */ + if (!tag_get(*slot, tag, offset)) + saw_unset_tag = 1; + if (height == 1) { + int ret = tag_get(*slot, tag, offset); + + BUG_ON(ret && saw_unset_tag); + return ret; + } + slot = (struct radix_tree_node **)((*slot)->slots + offset); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } +} +EXPORT_SYMBOL(radix_tree_tag_get); +#endif + +static unsigned int +__lookup(struct radix_tree_root *root, void **results, unsigned long index, + unsigned int max_items, unsigned long *next_index) +{ + unsigned int nr_found = 0; + unsigned int shift; + unsigned int height = root->height; + struct radix_tree_node *slot; + + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + slot = root->rnode; + + while (height > 0) { + unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK; + + for ( ; i < RADIX_TREE_MAP_SIZE; i++) { + if (slot->slots[i] != NULL) + break; + index &= ~((1UL << shift) - 1); + index += 1UL << shift; + if (index == 0) + goto out; /* 32-bit wraparound */ + } + if (i == RADIX_TREE_MAP_SIZE) + goto out; + height--; + if (height == 0) { /* Bottom level: grab some items */ + unsigned long j = index & RADIX_TREE_MAP_MASK; + + for ( ; j < RADIX_TREE_MAP_SIZE; j++) { + index++; + if (slot->slots[j]) { + results[nr_found++] = slot->slots[j]; + if (nr_found == max_items) + goto out; + } + } + } + shift -= RADIX_TREE_MAP_SHIFT; + slot = slot->slots[i]; + } +out: + *next_index = index; + return nr_found; +} + +/** + * radix_tree_gang_lookup - perform multiple lookup on a radix tree + * @root: radix tree root + * @results: where the results of the lookup are placed + * @first_index: start the lookup from this key + * @max_items: place up to this many items at *results + * + * Performs an index-ascending scan of the tree for present items. Places + * them at *@results and returns the number of items which were placed at + * *@results. + * + * The implementation is naive. + */ +unsigned int +radix_tree_gang_lookup(struct radix_tree_root *root, void **results, + unsigned long first_index, unsigned int max_items) +{ + const unsigned long max_index = radix_tree_maxindex(root->height); + unsigned long cur_index = first_index; + unsigned int ret = 0; + + while (ret < max_items) { + unsigned int nr_found; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + nr_found = __lookup(root, results + ret, cur_index, + max_items - ret, &next_index); + ret += nr_found; + if (next_index == 0) + break; + cur_index = next_index; + } + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup); + +/* + * FIXME: the two tag_get()s here should use find_next_bit() instead of + * open-coding the search. + */ +static unsigned int +__lookup_tag(struct radix_tree_root *root, void **results, unsigned long index, + unsigned int max_items, unsigned long *next_index, int tag) +{ + unsigned int nr_found = 0; + unsigned int shift; + unsigned int height = root->height; + struct radix_tree_node *slot; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + slot = root->rnode; + + while (height > 0) { + unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK; + + for ( ; i < RADIX_TREE_MAP_SIZE; i++) { + if (tag_get(slot, tag, i)) { + BUG_ON(slot->slots[i] == NULL); + break; + } + index &= ~((1UL << shift) - 1); + index += 1UL << shift; + if (index == 0) + goto out; /* 32-bit wraparound */ + } + if (i == RADIX_TREE_MAP_SIZE) + goto out; + height--; + if (height == 0) { /* Bottom level: grab some items */ + unsigned long j = index & RADIX_TREE_MAP_MASK; + + for ( ; j < RADIX_TREE_MAP_SIZE; j++) { + index++; + if (tag_get(slot, tag, j)) { + BUG_ON(slot->slots[j] == NULL); + results[nr_found++] = slot->slots[j]; + if (nr_found == max_items) + goto out; + } + } + } + shift -= RADIX_TREE_MAP_SHIFT; + slot = slot->slots[i]; + } +out: + *next_index = index; + return nr_found; +} + +/** + * radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree + * based on a tag + * @root: radix tree root + * @results: where the results of the lookup are placed + * @first_index: start the lookup from this key + * @max_items: place up to this many items at *results + * @tag: the tag index + * + * Performs an index-ascending scan of the tree for present items which + * have the tag indexed by @tag set. Places the items at *@results and + * returns the number of items which were placed at *@results. + */ +unsigned int +radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results, + unsigned long first_index, unsigned int max_items, int tag) +{ + const unsigned long max_index = radix_tree_maxindex(root->height); + unsigned long cur_index = first_index; + unsigned int ret = 0; + + while (ret < max_items) { + unsigned int nr_found; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + nr_found = __lookup_tag(root, results + ret, cur_index, + max_items - ret, &next_index, tag); + ret += nr_found; + if (next_index == 0) + break; + cur_index = next_index; + } + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup_tag); + +/** + * radix_tree_delete - delete an item from a radix tree + * @root: radix tree root + * @index: index key + * + * Remove the item at @index from the radix tree rooted at @root. + * + * Returns the address of the deleted item, or NULL if it was not present. + */ +void *radix_tree_delete(struct radix_tree_root *root, unsigned long index) +{ + struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path; + struct radix_tree_path *orig_pathp; + unsigned int height, shift; + void *ret = NULL; + char tags[RADIX_TREE_TAGS]; + int nr_cleared_tags; + + height = root->height; + if (index > radix_tree_maxindex(height)) + goto out; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + pathp->node = NULL; + pathp->slot = &root->rnode; + + while (height > 0) { + int offset; + + if (*pathp->slot == NULL) + goto out; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + pathp[1].offset = offset; + pathp[1].node = *pathp[0].slot; + pathp[1].slot = (struct radix_tree_node **) + (pathp[1].node->slots + offset); + pathp++; + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + ret = *pathp[0].slot; + if (ret == NULL) + goto out; + + orig_pathp = pathp; + + /* + * Clear all tags associated with the just-deleted item + */ + memset(tags, 0, sizeof(tags)); + do { + int tag; + + nr_cleared_tags = RADIX_TREE_TAGS; + for (tag = 0; tag < RADIX_TREE_TAGS; tag++) { + int idx; + + if (tags[tag]) + continue; + + tag_clear(pathp[0].node, tag, pathp[0].offset); + + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (pathp[0].node->tags[tag][idx]) { + tags[tag] = 1; + nr_cleared_tags--; + break; + } + } + } + pathp--; + } while (pathp[0].node && nr_cleared_tags); + + pathp = orig_pathp; + *pathp[0].slot = NULL; + while (pathp[0].node && --pathp[0].node->count == 0) { + pathp--; + BUG_ON(*pathp[0].slot == NULL); + *pathp[0].slot = NULL; + radix_tree_node_free(pathp[1].node); + } + if (root->rnode == NULL) + root->height = 0; +out: + return ret; +} +EXPORT_SYMBOL(radix_tree_delete); + +/** + * radix_tree_tagged - test whether any items in the tree are tagged + * @root: radix tree root + * @tag: tag to test + */ +int radix_tree_tagged(struct radix_tree_root *root, int tag) +{ + int idx; + + if (!root->rnode) + return 0; + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (root->rnode->tags[tag][idx]) + return 1; + } + return 0; +} +EXPORT_SYMBOL(radix_tree_tagged); + +static void +radix_tree_node_ctor(void *node, kmem_cache_t *cachep, unsigned long flags) +{ + memset(node, 0, sizeof(struct radix_tree_node)); +} + +static __init unsigned long __maxindex(unsigned int height) +{ + unsigned int tmp = height * RADIX_TREE_MAP_SHIFT; + unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1; + + if (tmp >= RADIX_TREE_INDEX_BITS) + index = ~0UL; + return index; +} + +static __init void radix_tree_init_maxindex(void) +{ + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++) + height_to_maxindex[i] = __maxindex(i); +} + +#ifdef CONFIG_HOTPLUG_CPU +static int radix_tree_callback(struct notifier_block *nfb, + unsigned long action, + void *hcpu) +{ + int cpu = (long)hcpu; + struct radix_tree_preload *rtp; + + /* Free per-cpu pool of perloaded nodes */ + if (action == CPU_DEAD) { + rtp = &per_cpu(radix_tree_preloads, cpu); + while (rtp->nr) { + kmem_cache_free(radix_tree_node_cachep, + rtp->nodes[rtp->nr-1]); + rtp->nodes[rtp->nr-1] = NULL; + rtp->nr--; + } + } + return NOTIFY_OK; +} +#endif /* CONFIG_HOTPLUG_CPU */ + +void __init radix_tree_init(void) +{ + radix_tree_node_cachep = kmem_cache_create("radix_tree_node", + sizeof(struct radix_tree_node), 0, + SLAB_PANIC, radix_tree_node_ctor, NULL); + radix_tree_init_maxindex(); + hotcpu_notifier(radix_tree_callback, 0); +} |