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Diffstat (limited to 'lib/radix-tree.c')
| -rw-r--r-- | lib/radix-tree.c | 1239 |
1 files changed, 1239 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c new file mode 100644 index 0000000..be86b32 --- /dev/null +++ b/lib/radix-tree.c @@ -0,0 +1,1239 @@ +/* + * Copyright (C) 2001 Momchil Velikov + * Portions Copyright (C) 2001 Christoph Hellwig + * Copyright (C) 2005 SGI, Christoph Lameter + * Copyright (C) 2006 Nick Piggin + * + * 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> +#include <linux/rcupdate.h> + + +#ifdef __KERNEL__ +#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6) +#else +#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */ +#endif + +#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 height; /* Height from the bottom */ + unsigned int count; + struct rcu_head rcu_head; + void *slots[RADIX_TREE_MAP_SIZE]; + unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS]; +}; + +struct radix_tree_path { + struct radix_tree_node *node; + int offset; +}; + +#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long)) +#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \ + RADIX_TREE_MAP_SHIFT)) + +/* + * The height_to_maxindex array needs to be one deeper than the maximum + * path as height 0 holds only 1 entry. + */ +static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly; + +/* + * Radix tree node cache. + */ +static struct kmem_cache *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, }; + +static inline gfp_t root_gfp_mask(struct radix_tree_root *root) +{ + return root->gfp_mask & __GFP_BITS_MASK; +} + +static inline void tag_set(struct radix_tree_node *node, unsigned int tag, + int offset) +{ + __set_bit(offset, node->tags[tag]); +} + +static inline void tag_clear(struct radix_tree_node *node, unsigned int tag, + int offset) +{ + __clear_bit(offset, node->tags[tag]); +} + +static inline int tag_get(struct radix_tree_node *node, unsigned int tag, + int offset) +{ + return test_bit(offset, node->tags[tag]); +} + +static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag) +{ + root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT)); +} + +static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag) +{ + root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT)); +} + +static inline void root_tag_clear_all(struct radix_tree_root *root) +{ + root->gfp_mask &= __GFP_BITS_MASK; +} + +static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag) +{ + return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT)); +} + +/* + * Returns 1 if any slot in the node has this tag set. + * Otherwise returns 0. + */ +static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag) +{ + int idx; + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (node->tags[tag][idx]) + return 1; + } + return 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 = NULL; + gfp_t gfp_mask = root_gfp_mask(root); + + if (!(gfp_mask & __GFP_WAIT)) { + struct radix_tree_preload *rtp; + + /* + * Provided the caller has preloaded here, we will always + * succeed in getting a node here (and never reach + * kmem_cache_alloc) + */ + rtp = &__get_cpu_var(radix_tree_preloads); + if (rtp->nr) { + ret = rtp->nodes[rtp->nr - 1]; + rtp->nodes[rtp->nr - 1] = NULL; + rtp->nr--; + } + } + if (ret == NULL) + ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); + + BUG_ON(radix_tree_is_indirect_ptr(ret)); + return ret; +} + +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); + + /* + * 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); + node->slots[0] = NULL; + node->count = 0; + + kmem_cache_free(radix_tree_node_cachep, node); +} + +static inline void +radix_tree_node_free(struct radix_tree_node *node) +{ + call_rcu(&node->rcu_head, radix_tree_node_rcu_free); +} + +/* + * 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(gfp_t 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; +} +EXPORT_SYMBOL(radix_tree_preload); + +/* + * 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; + 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; + } + + do { + unsigned int newheight; + if (!(node = radix_tree_node_alloc(root))) + return -ENOMEM; + + /* Increase the height. */ + node->slots[0] = radix_tree_indirect_to_ptr(root->rnode); + + /* Propagate the aggregated tag info into the new root */ + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { + if (root_tag_get(root, tag)) + tag_set(node, tag, 0); + } + + newheight = root->height+1; + node->height = newheight; + node->count = 1; + node = radix_tree_ptr_to_indirect(node); + rcu_assign_pointer(root->rnode, node); + root->height = newheight; + } 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, *slot; + unsigned int height, shift; + int offset; + int error; + + BUG_ON(radix_tree_is_indirect_ptr(item)); + + /* Make sure the tree is high enough. */ + if (index > radix_tree_maxindex(root->height)) { + error = radix_tree_extend(root, index); + if (error) + return error; + } + + slot = radix_tree_indirect_to_ptr(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 (!(slot = radix_tree_node_alloc(root))) + return -ENOMEM; + slot->height = height; + if (node) { + rcu_assign_pointer(node->slots[offset], slot); + node->count++; + } else + rcu_assign_pointer(root->rnode, + radix_tree_ptr_to_indirect(slot)); + } + + /* Go a level down */ + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + node = slot; + slot = node->slots[offset]; + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + if (slot != NULL) + return -EEXIST; + + if (node) { + node->count++; + rcu_assign_pointer(node->slots[offset], item); + BUG_ON(tag_get(node, 0, offset)); + BUG_ON(tag_get(node, 1, offset)); + } else { + rcu_assign_pointer(root->rnode, item); + BUG_ON(root_tag_get(root, 0)); + BUG_ON(root_tag_get(root, 1)); + } + + return 0; +} +EXPORT_SYMBOL(radix_tree_insert); + +/** + * radix_tree_lookup_slot - lookup a slot in a radix tree + * @root: radix tree root + * @index: index key + * + * Returns: the slot corresponding to the position @index in the + * radix tree @root. This is useful for update-if-exists operations. + * + * This function can be called under rcu_read_lock iff the slot is not + * modified by radix_tree_replace_slot, otherwise it must be called + * exclusive from other writers. Any dereference of the slot must be done + * using radix_tree_deref_slot. + */ +void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index) +{ + unsigned int height, shift; + struct radix_tree_node *node, **slot; + + node = rcu_dereference(root->rnode); + if (node == NULL) + return NULL; + + if (!radix_tree_is_indirect_ptr(node)) { + if (index > 0) + return NULL; + return (void **)&root->rnode; + } + node = radix_tree_indirect_to_ptr(node); + + height = node->height; + if (index > radix_tree_maxindex(height)) + return NULL; + + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + do { + slot = (struct radix_tree_node **) + (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK)); + node = rcu_dereference(*slot); + if (node == NULL) + return NULL; + + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } while (height > 0); + + return (void **)slot; +} +EXPORT_SYMBOL(radix_tree_lookup_slot); + +/** + * 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. + * + * This function can be called under rcu_read_lock, however the caller + * must manage lifetimes of leaf nodes (eg. RCU may also be used to free + * them safely). No RCU barriers are required to access or modify the + * returned item, however. + */ +void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index) +{ + unsigned int height, shift; + struct radix_tree_node *node, **slot; + + node = rcu_dereference(root->rnode); + if (node == NULL) + return NULL; + + if (!radix_tree_is_indirect_ptr(node)) { + if (index > 0) + return NULL; + return node; + } + node = radix_tree_indirect_to_ptr(node); + + height = node->height; + if (index > radix_tree_maxindex(height)) + return NULL; + + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + do { + slot = (struct radix_tree_node **) + (node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK)); + node = rcu_dereference(*slot); + if (node == NULL) + return NULL; + + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } while (height > 0); + + return node; +} +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 (which must be < RADIX_TREE_MAX_TAGS) + * corresponding 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, unsigned int tag) +{ + unsigned int height, shift; + struct radix_tree_node *slot; + + height = root->height; + BUG_ON(index > radix_tree_maxindex(height)); + + slot = radix_tree_indirect_to_ptr(root->rnode); + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + + while (height > 0) { + int offset; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + if (!tag_get(slot, tag, offset)) + tag_set(slot, tag, offset); + slot = slot->slots[offset]; + BUG_ON(slot == NULL); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + /* set the root's tag bit */ + if (slot && !root_tag_get(root, tag)) + root_tag_set(root, tag); + + 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 (which must be < RADIX_TREE_MAX_TAGS) + * corresponding 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, unsigned int tag) +{ + /* + * The radix tree path needs to be one longer than the maximum path + * since the "list" is null terminated. + */ + struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path; + struct radix_tree_node *slot = NULL; + unsigned int height, shift; + + height = root->height; + if (index > radix_tree_maxindex(height)) + goto out; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + pathp->node = NULL; + slot = radix_tree_indirect_to_ptr(root->rnode); + + while (height > 0) { + int offset; + + if (slot == NULL) + goto out; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + pathp[1].offset = offset; + pathp[1].node = slot; + slot = slot->slots[offset]; + pathp++; + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } + + if (slot == NULL) + goto out; + + while (pathp->node) { + if (!tag_get(pathp->node, tag, pathp->offset)) + goto out; + tag_clear(pathp->node, tag, pathp->offset); + if (any_tag_set(pathp->node, tag)) + goto out; + pathp--; + } + + /* clear the root's tag bit */ + if (root_tag_get(root, tag)) + root_tag_clear(root, tag); + +out: + return slot; +} +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 (< RADIX_TREE_MAX_TAGS) + * + * Return values: + * + * 0: tag not present or not set + * 1: tag set + */ +int radix_tree_tag_get(struct radix_tree_root *root, + unsigned long index, unsigned int tag) +{ + unsigned int height, shift; + struct radix_tree_node *node; + int saw_unset_tag = 0; + + /* check the root's tag bit */ + if (!root_tag_get(root, tag)) + return 0; + + node = rcu_dereference(root->rnode); + if (node == NULL) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) + return (index == 0); + node = radix_tree_indirect_to_ptr(node); + + height = node->height; + if (index > radix_tree_maxindex(height)) + return 0; + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + + for ( ; ; ) { + int offset; + + if (node == 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(node, tag, offset)) + saw_unset_tag = 1; + if (height == 1) { + int ret = tag_get(node, tag, offset); + + BUG_ON(ret && saw_unset_tag); + return !!ret; + } + node = rcu_dereference(node->slots[offset]); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } +} +EXPORT_SYMBOL(radix_tree_tag_get); +#endif + +/** + * radix_tree_next_hole - find the next hole (not-present entry) + * @root: tree root + * @index: index key + * @max_scan: maximum range to search + * + * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest + * indexed hole. + * + * Returns: the index of the hole if found, otherwise returns an index + * outside of the set specified (in which case 'return - index >= max_scan' + * will be true). + * + * 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 + * 5, then subsequently a hole is created at index 10, radix_tree_next_hole + * covering both indexes may return 10 if called under rcu_read_lock. + */ +unsigned long radix_tree_next_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 == 0) + break; + } + + return index; +} +EXPORT_SYMBOL(radix_tree_next_hole); + +static unsigned int +__lookup(struct radix_tree_node *slot, void ***results, unsigned long index, + unsigned int max_items, unsigned long *next_index) +{ + unsigned int nr_found = 0; + unsigned int shift, height; + unsigned long i; + + height = slot->height; + if (height == 0) + goto out; + 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(slot->slots[i]); + if (slot == NULL) + goto out; + } + + /* Bottom level: grab some items */ + for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) { + index++; + if (slot->slots[i]) { + results[nr_found++] = &(slot->slots[i]); + if (nr_found == max_items) + goto out; + } + } +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. + * + * Like radix_tree_lookup, radix_tree_gang_lookup may be called under + * rcu_read_lock. In this case, rather than the returned results being + * an atomic snapshot of the tree at a single point in time, the semantics + * of an RCU protected gang lookup are as though multiple radix_tree_lookups + * have been issued in individual locks, and results stored in 'results'. + */ +unsigned int +radix_tree_gang_lookup(struct radix_tree_root *root, void **results, + unsigned long first_index, unsigned int max_items) +{ + unsigned long max_index; + struct radix_tree_node *node; + unsigned long cur_index = first_index; + unsigned int ret; + + node = rcu_dereference(root->rnode); + if (!node) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) { + if (first_index > 0) + return 0; + results[0] = node; + return 1; + } + node = radix_tree_indirect_to_ptr(node); + + max_index = radix_tree_maxindex(node->height); + + ret = 0; + while (ret < max_items) { + unsigned int nr_found, slots_found, i; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + slots_found = __lookup(node, (void ***)results + ret, cur_index, + max_items - ret, &next_index); + nr_found = 0; + for (i = 0; i < slots_found; i++) { + struct radix_tree_node *slot; + slot = *(((void ***)results)[ret + i]); + if (!slot) + continue; + results[ret + nr_found] = rcu_dereference(slot); + nr_found++; + } + ret += nr_found; + if (next_index == 0) + break; + cur_index = next_index; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup); + +/** + * radix_tree_gang_lookup_slot - perform multiple slot lookup on 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 + * their slots at *@results and returns the number of items which were + * placed at *@results. + * + * The implementation is naive. + * + * Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must + * be dereferenced with radix_tree_deref_slot, and if using only RCU + * protection, radix_tree_deref_slot may fail requiring a retry. + */ +unsigned int +radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results, + unsigned long first_index, unsigned int max_items) +{ + unsigned long max_index; + struct radix_tree_node *node; + unsigned long cur_index = first_index; + unsigned int ret; + + node = rcu_dereference(root->rnode); + if (!node) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) { + if (first_index > 0) + return 0; + results[0] = (void **)&root->rnode; + return 1; + } + node = radix_tree_indirect_to_ptr(node); + + max_index = radix_tree_maxindex(node->height); + + ret = 0; + while (ret < max_items) { + unsigned int slots_found; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + slots_found = __lookup(node, results + ret, cur_index, + max_items - ret, &next_index); + ret += slots_found; + if (next_index == 0) + break; + cur_index = next_index; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup_slot); + +/* + * 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_node *slot, void ***results, unsigned long index, + unsigned int max_items, unsigned long *next_index, unsigned int tag) +{ + unsigned int nr_found = 0; + unsigned int shift, height; + + height = slot->height; + if (height == 0) + goto out; + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + while (height > 0) { + unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ; + + for (;;) { + if (tag_get(slot, tag, i)) + 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; + } + 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)) + continue; + /* + * Even though the tag was found set, we need to + * recheck that we have a non-NULL node, because + * if this lookup is lockless, it may have been + * subsequently deleted. + * + * Similar care must be taken in any place that + * lookup ->slots[x] without a lock (ie. can't + * rely on its value remaining the same). + */ + if (slot->slots[j]) { + results[nr_found++] = &(slot->slots[j]); + if (nr_found == max_items) + goto out; + } + } + } + shift -= RADIX_TREE_MAP_SHIFT; + slot = rcu_dereference(slot->slots[i]); + if (slot == NULL) + break; + } +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 (< RADIX_TREE_MAX_TAGS) + * + * 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, + unsigned int tag) +{ + struct radix_tree_node *node; + unsigned long max_index; + unsigned long cur_index = first_index; + unsigned int ret; + + /* check the root's tag bit */ + if (!root_tag_get(root, tag)) + return 0; + + node = rcu_dereference(root->rnode); + if (!node) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) { + if (first_index > 0) + return 0; + results[0] = node; + return 1; + } + node = radix_tree_indirect_to_ptr(node); + + max_index = radix_tree_maxindex(node->height); + + ret = 0; + while (ret < max_items) { + unsigned int nr_found, slots_found, i; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + slots_found = __lookup_tag(node, (void ***)results + ret, + cur_index, max_items - ret, &next_index, tag); + nr_found = 0; + for (i = 0; i < slots_found; i++) { + struct radix_tree_node *slot; + slot = *(((void ***)results)[ret + i]); + if (!slot) + continue; + results[ret + nr_found] = rcu_dereference(slot); + nr_found++; + } + ret += nr_found; + if (next_index == 0) + break; + cur_index = next_index; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup_tag); + +/** + * radix_tree_gang_lookup_tag_slot - perform multiple slot 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 (< RADIX_TREE_MAX_TAGS) + * + * Performs an index-ascending scan of the tree for present items which + * have the tag indexed by @tag set. Places the slots at *@results and + * returns the number of slots which were placed at *@results. + */ +unsigned int +radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results, + unsigned long first_index, unsigned int max_items, + unsigned int tag) +{ + struct radix_tree_node *node; + unsigned long max_index; + unsigned long cur_index = first_index; + unsigned int ret; + + /* check the root's tag bit */ + if (!root_tag_get(root, tag)) + return 0; + + node = rcu_dereference(root->rnode); + if (!node) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) { + if (first_index > 0) + return 0; + results[0] = (void **)&root->rnode; + return 1; + } + node = radix_tree_indirect_to_ptr(node); + + max_index = radix_tree_maxindex(node->height); + + ret = 0; + while (ret < max_items) { + unsigned int slots_found; + unsigned long next_index; /* Index of next search */ + + if (cur_index > max_index) + break; + slots_found = __lookup_tag(node, results + ret, + cur_index, max_items - ret, &next_index, tag); + ret += slots_found; + if (next_index == 0) + break; + cur_index = next_index; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot); + + +/** + * radix_tree_shrink - shrink height of a radix tree to minimal + * @root radix tree root + */ +static inline void radix_tree_shrink(struct radix_tree_root *root) +{ + /* try to shrink tree height */ + while (root->height > 0) { + struct radix_tree_node *to_free = root->rnode; + void *newptr; + + BUG_ON(!radix_tree_is_indirect_ptr(to_free)); + to_free = radix_tree_indirect_to_ptr(to_free); + + /* + * The candidate node has more than one child, or its child + * is not at the leftmost slot, we cannot shrink. + */ + if (to_free->count != 1) + break; + if (!to_free->slots[0]) + break; + + /* + * We don't need rcu_assign_pointer(), since we are simply + * moving the node from one part of the tree to another. If + * it was safe to dereference the old pointer to it + * (to_free->slots[0]), it will be safe to dereference the new + * one (root->rnode). + */ + newptr = to_free->slots[0]; + if (root->height > 1) + newptr = radix_tree_ptr_to_indirect(newptr); + root->rnode = newptr; + root->height--; + radix_tree_node_free(to_free); + } +} + +/** + * 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) +{ + /* + * The radix tree path needs to be one longer than the maximum path + * since the "list" is null terminated. + */ + struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path; + struct radix_tree_node *slot = NULL; + struct radix_tree_node *to_free; + unsigned int height, shift; + int tag; + int offset; + + height = root->height; + if (index > radix_tree_maxindex(height)) + goto out; + + slot = root->rnode; + if (height == 0) { + root_tag_clear_all(root); + root->rnode = NULL; + goto out; + } + slot = radix_tree_indirect_to_ptr(slot); + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + pathp->node = NULL; + + do { + if (slot == NULL) + goto out; + + pathp++; + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + pathp->offset = offset; + pathp->node = slot; + slot = slot->slots[offset]; + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } while (height > 0); + + if (slot == NULL) + goto out; + + /* + * Clear all tags associated with the just-deleted item + */ + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { + if (tag_get(pathp->node, tag, pathp->offset)) + radix_tree_tag_clear(root, index, tag); + } + + to_free = NULL; + /* Now free the nodes we do not need anymore */ + while (pathp->node) { + pathp->node->slots[pathp->offset] = NULL; + pathp->node->count--; + /* + * Queue the node for deferred freeing after the + * last reference to it disappears (set NULL, above). + */ + if (to_free) + radix_tree_node_free(to_free); + + if (pathp->node->count) { + if (pathp->node == + radix_tree_indirect_to_ptr(root->rnode)) + radix_tree_shrink(root); + goto out; + } + + /* Node with zero slots in use so free it */ + to_free = pathp->node; + pathp--; + + } + root_tag_clear_all(root); + root->height = 0; + root->rnode = NULL; + if (to_free) + radix_tree_node_free(to_free); + +out: + return slot; +} +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, unsigned int tag) +{ + return root_tag_get(root, tag); +} +EXPORT_SYMBOL(radix_tree_tagged); + +static void +radix_tree_node_ctor(void *node) +{ + memset(node, 0, sizeof(struct radix_tree_node)); +} + +static __init unsigned long __maxindex(unsigned int height) +{ + unsigned int width = height * RADIX_TREE_MAP_SHIFT; + int shift = RADIX_TREE_INDEX_BITS - width; + + if (shift < 0) + return ~0UL; + if (shift >= BITS_PER_LONG) + return 0UL; + return ~0UL >> shift; +} + +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); +} + +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 || action == CPU_DEAD_FROZEN) { + 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; +} + +void __init radix_tree_init(void) +{ + radix_tree_node_cachep = kmem_cache_create("radix_tree_node", + sizeof(struct radix_tree_node), 0, + SLAB_PANIC | SLAB_RECLAIM_ACCOUNT, + radix_tree_node_ctor); + radix_tree_init_maxindex(); + hotcpu_notifier(radix_tree_callback, 0); +} |
