diff options
Diffstat (limited to 'kernel/lib/radix-tree.c')
| -rw-r--r-- | kernel/lib/radix-tree.c | 1491 |
1 files changed, 1491 insertions, 0 deletions
diff --git a/kernel/lib/radix-tree.c b/kernel/lib/radix-tree.c new file mode 100644 index 000000000..77015b1cc --- /dev/null +++ b/kernel/lib/radix-tree.c @@ -0,0 +1,1491 @@ +/* + * Copyright (C) 2001 Momchil Velikov + * Portions Copyright (C) 2001 Christoph Hellwig + * Copyright (C) 2005 SGI, Christoph Lameter + * Copyright (C) 2006 Nick Piggin + * Copyright (C) 2012 Konstantin Khlebnikov + * + * 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/export.h> +#include <linux/radix-tree.h> +#include <linux/percpu.h> +#include <linux/slab.h> +#include <linux/kmemleak.h> +#include <linux/notifier.h> +#include <linux/cpu.h> +#include <linux/string.h> +#include <linux/bitops.h> +#include <linux/rcupdate.h> +#include <linux/preempt_mask.h> /* in_interrupt() */ + + +/* + * 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; + +/* + * The radix tree is variable-height, so an insert operation not only has + * to build the branch to its corresponding item, it also has to build the + * branch to existing items if the size has to be increased (by + * radix_tree_extend). + * + * The worst case is a zero height tree with just a single item at index 0, + * and then inserting an item at index ULONG_MAX. This requires 2 new branches + * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared. + * Hence: + */ +#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1) + +/* + * Per-cpu pool of preloaded nodes + */ +struct radix_tree_preload { + int nr; + struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE]; +}; +static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, }; + +static inline void *ptr_to_indirect(void *ptr) +{ + return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR); +} + +static inline void *indirect_to_ptr(void *ptr) +{ + return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR); +} + +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; +} + +/** + * radix_tree_find_next_bit - find the next set bit in a memory region + * + * @addr: The address to base the search on + * @size: The bitmap size in bits + * @offset: The bitnumber to start searching at + * + * Unrollable variant of find_next_bit() for constant size arrays. + * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero. + * Returns next bit offset, or size if nothing found. + */ +static __always_inline unsigned long +radix_tree_find_next_bit(const unsigned long *addr, + unsigned long size, unsigned long offset) +{ + if (!__builtin_constant_p(size)) + return find_next_bit(addr, size, offset); + + if (offset < size) { + unsigned long tmp; + + addr += offset / BITS_PER_LONG; + tmp = *addr >> (offset % BITS_PER_LONG); + if (tmp) + return __ffs(tmp) + offset; + offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1); + while (offset < size) { + tmp = *++addr; + if (tmp) + return __ffs(tmp) + offset; + offset += BITS_PER_LONG; + } + } + return size; +} + +/* + * 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); + + /* + * Preload code isn't irq safe and it doesn't make sence to use + * preloading in the interrupt anyway as all the allocations have to + * be atomic. So just do normal allocation when in interrupt. + */ + if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) { + 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--; + } + put_cpu_var(radix_tree_preloads); + /* + * Update the allocation stack trace as this is more useful + * for debugging. + */ + kmemleak_update_trace(ret); + } + 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); + int i; + + /* + * 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. + */ + for (i = 0; i < RADIX_TREE_MAX_TAGS; i++) + tag_clear(node, i, 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); +} + +#ifndef CONFIG_PREEMPT_RT_FULL +/* + * 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. + * + * To make use of this facility, the radix tree must be initialised without + * __GFP_WAIT being passed to INIT_RADIX_TREE(). + */ +static int __radix_tree_preload(gfp_t gfp_mask) +{ + struct radix_tree_preload *rtp; + struct radix_tree_node *node; + int ret = -ENOMEM; + + preempt_disable(); + rtp = this_cpu_ptr(&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 = this_cpu_ptr(&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; +} + +/* + * 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. + * + * To make use of this facility, the radix tree must be initialised without + * __GFP_WAIT being passed to INIT_RADIX_TREE(). + */ +int radix_tree_preload(gfp_t gfp_mask) +{ + /* Warn on non-sensical use... */ + WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT)); + return __radix_tree_preload(gfp_mask); +} +EXPORT_SYMBOL(radix_tree_preload); + +/* + * The same as above function, except we don't guarantee preloading happens. + * We do it, if we decide it helps. On success, return zero with preemption + * disabled. On error, return -ENOMEM with preemption not disabled. + */ +int radix_tree_maybe_preload(gfp_t gfp_mask) +{ + if (gfp_mask & __GFP_WAIT) + return __radix_tree_preload(gfp_mask); + /* Preloading doesn't help anything with this gfp mask, skip it */ + preempt_disable(); + return 0; +} +EXPORT_SYMBOL(radix_tree_maybe_preload); +#endif + +/* + * 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; + struct radix_tree_node *slot; + 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; + + /* 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); + } + + /* Increase the height. */ + newheight = root->height+1; + BUG_ON(newheight & ~RADIX_TREE_HEIGHT_MASK); + node->path = newheight; + node->count = 1; + node->parent = NULL; + slot = root->rnode; + if (newheight > 1) { + slot = indirect_to_ptr(slot); + slot->parent = node; + } + node->slots[0] = slot; + node = ptr_to_indirect(node); + rcu_assign_pointer(root->rnode, node); + root->height = newheight; + } while (height > root->height); +out: + return 0; +} + +/** + * __radix_tree_create - create a slot in a radix tree + * @root: radix tree root + * @index: index key + * @nodep: returns node + * @slotp: returns slot + * + * Create, if necessary, and return the node and slot for an item + * at position @index in the radix tree @root. + * + * Until there is more than one item in the tree, no nodes are + * allocated and @root->rnode is used as a direct slot instead of + * pointing to a node, in which case *@nodep will be NULL. + * + * Returns -ENOMEM, or 0 for success. + */ +int __radix_tree_create(struct radix_tree_root *root, unsigned long index, + struct radix_tree_node **nodep, void ***slotp) +{ + struct radix_tree_node *node = NULL, *slot; + unsigned int height, shift, offset; + int error; + + /* 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 = 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->path = height; + slot->parent = node; + if (node) { + rcu_assign_pointer(node->slots[offset], slot); + node->count++; + slot->path |= offset << RADIX_TREE_HEIGHT_SHIFT; + } else + rcu_assign_pointer(root->rnode, 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 (nodep) + *nodep = node; + if (slotp) + *slotp = node ? node->slots + offset : (void **)&root->rnode; + 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; + void **slot; + int error; + + BUG_ON(radix_tree_is_indirect_ptr(item)); + + error = __radix_tree_create(root, index, &node, &slot); + if (error) + return error; + if (*slot != NULL) + return -EEXIST; + rcu_assign_pointer(*slot, item); + + if (node) { + node->count++; + BUG_ON(tag_get(node, 0, index & RADIX_TREE_MAP_MASK)); + BUG_ON(tag_get(node, 1, index & RADIX_TREE_MAP_MASK)); + } else { + BUG_ON(root_tag_get(root, 0)); + BUG_ON(root_tag_get(root, 1)); + } + + return 0; +} +EXPORT_SYMBOL(radix_tree_insert); + +/** + * __radix_tree_lookup - lookup an item in a radix tree + * @root: radix tree root + * @index: index key + * @nodep: returns node + * @slotp: returns slot + * + * Lookup and return the item at position @index in the radix + * tree @root. + * + * Until there is more than one item in the tree, no nodes are + * allocated and @root->rnode is used as a direct slot instead of + * pointing to a node, in which case *@nodep will be NULL. + */ +void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index, + struct radix_tree_node **nodep, void ***slotp) +{ + struct radix_tree_node *node, *parent; + unsigned int height, shift; + void **slot; + + node = rcu_dereference_raw(root->rnode); + if (node == NULL) + return NULL; + + if (!radix_tree_is_indirect_ptr(node)) { + if (index > 0) + return NULL; + + if (nodep) + *nodep = NULL; + if (slotp) + *slotp = (void **)&root->rnode; + return node; + } + node = indirect_to_ptr(node); + + height = node->path & RADIX_TREE_HEIGHT_MASK; + if (index > radix_tree_maxindex(height)) + return NULL; + + shift = (height-1) * RADIX_TREE_MAP_SHIFT; + + do { + parent = node; + slot = node->slots + ((index >> shift) & RADIX_TREE_MAP_MASK); + node = rcu_dereference_raw(*slot); + if (node == NULL) + return NULL; + + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } while (height > 0); + + if (nodep) + *nodep = parent; + if (slotp) + *slotp = slot; + return node; +} + +/** + * 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) +{ + void **slot; + + if (!__radix_tree_lookup(root, index, NULL, &slot)) + return NULL; + return 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) +{ + return __radix_tree_lookup(root, index, NULL, NULL); +} +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 = 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) +{ + struct radix_tree_node *node = NULL; + struct radix_tree_node *slot = NULL; + unsigned int height, shift; + int uninitialized_var(offset); + + height = root->height; + if (index > radix_tree_maxindex(height)) + goto out; + + shift = height * RADIX_TREE_MAP_SHIFT; + slot = indirect_to_ptr(root->rnode); + + while (shift) { + if (slot == NULL) + goto out; + + shift -= RADIX_TREE_MAP_SHIFT; + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + node = slot; + slot = slot->slots[offset]; + } + + if (slot == NULL) + goto out; + + while (node) { + if (!tag_get(node, tag, offset)) + goto out; + tag_clear(node, tag, offset); + if (any_tag_set(node, tag)) + goto out; + + index >>= RADIX_TREE_MAP_SHIFT; + offset = index & RADIX_TREE_MAP_MASK; + node = node->parent; + } + + /* 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); + +/** + * 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 + * + * Note that the return value of this function may not be relied on, even if + * the RCU lock is held, unless tag modification and node deletion are excluded + * from concurrency. + */ +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; + + /* check the root's tag bit */ + if (!root_tag_get(root, tag)) + return 0; + + node = rcu_dereference_raw(root->rnode); + if (node == NULL) + return 0; + + if (!radix_tree_is_indirect_ptr(node)) + return (index == 0); + node = indirect_to_ptr(node); + + height = node->path & RADIX_TREE_HEIGHT_MASK; + 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; + if (!tag_get(node, tag, offset)) + return 0; + if (height == 1) + return 1; + node = rcu_dereference_raw(node->slots[offset]); + shift -= RADIX_TREE_MAP_SHIFT; + height--; + } +} +EXPORT_SYMBOL(radix_tree_tag_get); + +/** + * radix_tree_next_chunk - find next chunk of slots for iteration + * + * @root: radix tree root + * @iter: iterator state + * @flags: RADIX_TREE_ITER_* flags and tag index + * Returns: pointer to chunk first slot, or NULL if iteration is over + */ +void **radix_tree_next_chunk(struct radix_tree_root *root, + struct radix_tree_iter *iter, unsigned flags) +{ + unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK; + struct radix_tree_node *rnode, *node; + unsigned long index, offset, height; + + if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag)) + return NULL; + + /* + * Catch next_index overflow after ~0UL. iter->index never overflows + * during iterating; it can be zero only at the beginning. + * And we cannot overflow iter->next_index in a single step, + * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG. + * + * This condition also used by radix_tree_next_slot() to stop + * contiguous iterating, and forbid swithing to the next chunk. + */ + index = iter->next_index; + if (!index && iter->index) + return NULL; + + rnode = rcu_dereference_raw(root->rnode); + if (radix_tree_is_indirect_ptr(rnode)) { + rnode = indirect_to_ptr(rnode); + } else if (rnode && !index) { + /* Single-slot tree */ + iter->index = 0; + iter->next_index = 1; + iter->tags = 1; + return (void **)&root->rnode; + } else + return NULL; + +restart: + height = rnode->path & RADIX_TREE_HEIGHT_MASK; + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + offset = index >> shift; + + /* Index outside of the tree */ + if (offset >= RADIX_TREE_MAP_SIZE) + return NULL; + + node = rnode; + while (1) { + if ((flags & RADIX_TREE_ITER_TAGGED) ? + !test_bit(offset, node->tags[tag]) : + !node->slots[offset]) { + /* Hole detected */ + if (flags & RADIX_TREE_ITER_CONTIG) + return NULL; + + if (flags & RADIX_TREE_ITER_TAGGED) + offset = radix_tree_find_next_bit( + node->tags[tag], + RADIX_TREE_MAP_SIZE, + offset + 1); + else + while (++offset < RADIX_TREE_MAP_SIZE) { + if (node->slots[offset]) + break; + } + index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1); + index += offset << shift; + /* Overflow after ~0UL */ + if (!index) + return NULL; + if (offset == RADIX_TREE_MAP_SIZE) + goto restart; + } + + /* This is leaf-node */ + if (!shift) + break; + + node = rcu_dereference_raw(node->slots[offset]); + if (node == NULL) + goto restart; + shift -= RADIX_TREE_MAP_SHIFT; + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + } + + /* Update the iterator state */ + iter->index = index; + iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1; + + /* Construct iter->tags bit-mask from node->tags[tag] array */ + if (flags & RADIX_TREE_ITER_TAGGED) { + unsigned tag_long, tag_bit; + + tag_long = offset / BITS_PER_LONG; + tag_bit = offset % BITS_PER_LONG; + iter->tags = node->tags[tag][tag_long] >> tag_bit; + /* This never happens if RADIX_TREE_TAG_LONGS == 1 */ + if (tag_long < RADIX_TREE_TAG_LONGS - 1) { + /* Pick tags from next element */ + if (tag_bit) + iter->tags |= node->tags[tag][tag_long + 1] << + (BITS_PER_LONG - tag_bit); + /* Clip chunk size, here only BITS_PER_LONG tags */ + iter->next_index = index + BITS_PER_LONG; + } + } + + return node->slots + offset; +} +EXPORT_SYMBOL(radix_tree_next_chunk); + +/** + * radix_tree_range_tag_if_tagged - for each item in given range set given + * tag if item has another tag set + * @root: radix tree root + * @first_indexp: pointer to a starting index of a range to scan + * @last_index: last index of a range to scan + * @nr_to_tag: maximum number items to tag + * @iftag: tag index to test + * @settag: tag index to set if tested tag is set + * + * This function scans range of radix tree from first_index to last_index + * (inclusive). For each item in the range if iftag is set, the function sets + * 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. + * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must + * be prepared to handle that. + */ +unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, + unsigned long *first_indexp, unsigned long last_index, + unsigned long nr_to_tag, + unsigned int iftag, unsigned int settag) +{ + unsigned int height = root->height; + struct radix_tree_node *node = NULL; + 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) + return 0; + if (!nr_to_tag) + return 0; + if (!root_tag_get(root, iftag)) { + *first_indexp = last_index + 1; + return 0; + } + if (height == 0) { + *first_indexp = last_index + 1; + root_tag_set(root, settag); + return 1; + } + + shift = (height - 1) * RADIX_TREE_MAP_SHIFT; + slot = indirect_to_ptr(root->rnode); + + for (;;) { + unsigned long upindex; + int offset; + + offset = (index >> shift) & RADIX_TREE_MAP_MASK; + if (!slot->slots[offset]) + goto next; + if (!tag_get(slot, iftag, offset)) + goto next; + if (shift) { + /* Go down one level */ + shift -= RADIX_TREE_MAP_SHIFT; + node = slot; + slot = slot->slots[offset]; + continue; + } + + /* tag the leaf */ + tagged++; + tag_set(slot, settag, offset); + + /* walk back up the path tagging interior nodes */ + upindex = index; + while (node) { + upindex >>= RADIX_TREE_MAP_SHIFT; + offset = upindex & RADIX_TREE_MAP_MASK; + + /* stop if we find a node with the tag already set */ + if (tag_get(node, settag, offset)) + break; + tag_set(node, settag, offset); + node = node->parent; + } + + /* + * Small optimization: now clear that node pointer. + * Since all of this slot's ancestors now have the tag set + * from setting it above, we have no further need to walk + * back up the tree setting tags, until we update slot to + * point to another radix_tree_node. + */ + node = NULL; + +next: + /* Go to next item at level determined by 'shift' */ + index = ((index >> shift) + 1) << shift; + /* Overflow can happen when last_index is ~0UL... */ + if (index > last_index || !index) + break; + if (tagged >= nr_to_tag) + break; + while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) { + /* + * We've fully scanned this node. Go up. Because + * last_index is guaranteed to be in the tree, what + * we do below cannot wander astray. + */ + slot = slot->parent; + shift += RADIX_TREE_MAP_SHIFT; + } + } + /* + * We need not to tag the root tag if there is no tag which is set with + * settag within the range from *first_indexp to last_index. + */ + if (tagged > 0) + root_tag_set(root, settag); + *first_indexp = index; + + return tagged; +} +EXPORT_SYMBOL(radix_tree_range_tag_if_tagged); + +/** + * 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) +{ + struct radix_tree_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_slot(slot, root, &iter, first_index) { + results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); + if (!results[ret]) + continue; + if (++ret == max_items) + break; + } + + 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 + * @indices: where their indices should be placed (but usually NULL) + * @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 *indices, + unsigned long first_index, unsigned int max_items) +{ + struct radix_tree_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_slot(slot, root, &iter, first_index) { + results[ret] = slot; + if (indices) + indices[ret] = iter.index; + if (++ret == max_items) + break; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup_slot); + +/** + * 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_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { + results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot)); + if (!results[ret]) + continue; + if (++ret == max_items) + break; + } + + 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_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { + results[ret] = slot; + if (++ret == max_items) + break; + } + + return ret; +} +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->path & RADIX_TREE_HEIGHT_MASK; + 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->path & + RADIX_TREE_HEIGHT_MASK); + if (cur_index > max_index) { + rcu_read_unlock(); + 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 + * @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; + struct radix_tree_node *slot; + + BUG_ON(!radix_tree_is_indirect_ptr(to_free)); + to_free = 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) as far as dependent read barriers go. + */ + slot = to_free->slots[0]; + if (root->height > 1) { + slot->parent = NULL; + slot = ptr_to_indirect(slot); + } + root->rnode = slot; + root->height--; + + /* + * We have a dilemma here. The node's slot[0] must not be + * NULLed in case there are concurrent lookups expecting to + * find the item. However if this was a bottom-level node, + * then it may be subject to the slot pointer being visible + * to callers dereferencing it. If item corresponding to + * slot[0] is subsequently deleted, these callers would expect + * their slot to become empty sooner or later. + * + * For example, lockless pagecache will look up a slot, deref + * the page pointer, and if the page is 0 refcount it means it + * was concurrently deleted from pagecache so try the deref + * again. Fortunately there is already a requirement for logic + * to retry the entire slot lookup -- the indirect pointer + * problem (replacing direct root node with an indirect pointer + * also results in a stale slot). So tag the slot as indirect + * to force callers to retry. + */ + if (root->height == 0) + *((unsigned long *)&to_free->slots[0]) |= + RADIX_TREE_INDIRECT_PTR; + + radix_tree_node_free(to_free); + } +} + +/** + * __radix_tree_delete_node - try to free node after clearing a slot + * @root: radix tree root + * @node: node containing @index + * + * After clearing the slot at @index in @node from radix tree + * rooted at @root, call this function to attempt freeing the + * node and shrinking the tree. + * + * Returns %true if @node was freed, %false otherwise. + */ +bool __radix_tree_delete_node(struct radix_tree_root *root, + struct radix_tree_node *node) +{ + bool deleted = false; + + do { + struct radix_tree_node *parent; + + if (node->count) { + if (node == indirect_to_ptr(root->rnode)) { + radix_tree_shrink(root); + if (root->height == 0) + deleted = true; + } + return deleted; + } + + parent = node->parent; + if (parent) { + unsigned int offset; + + offset = node->path >> RADIX_TREE_HEIGHT_SHIFT; + parent->slots[offset] = NULL; + parent->count--; + } else { + root_tag_clear_all(root); + root->height = 0; + root->rnode = NULL; + } + + radix_tree_node_free(node); + deleted = true; + + node = parent; + } while (node); + + return deleted; +} + +/** + * radix_tree_delete_item - delete an item from a radix tree + * @root: radix tree root + * @index: index key + * @item: expected item + * + * Remove @item at @index from the radix tree rooted at @root. + * + * Returns the address of the deleted item, or NULL if it was not present + * or the entry at the given @index was not @item. + */ +void *radix_tree_delete_item(struct radix_tree_root *root, + unsigned long index, void *item) +{ + struct radix_tree_node *node; + unsigned int offset; + void **slot; + void *entry; + int tag; + + entry = __radix_tree_lookup(root, index, &node, &slot); + if (!entry) + return NULL; + + if (item && entry != item) + return NULL; + + if (!node) { + root_tag_clear_all(root); + root->rnode = NULL; + return entry; + } + + offset = index & RADIX_TREE_MAP_MASK; + + /* + * Clear all tags associated with the item to be deleted. + * This way of doing it would be inefficient, but seldom is any set. + */ + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { + if (tag_get(node, tag, offset)) + radix_tree_tag_clear(root, index, tag); + } + + node->slots[offset] = NULL; + node->count--; + + __radix_tree_delete_node(root, node); + + return entry; +} +EXPORT_SYMBOL(radix_tree_delete_item); + +/** + * 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) +{ + return radix_tree_delete_item(root, index, NULL); +} +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 *arg) +{ + struct radix_tree_node *node = arg; + + memset(node, 0, sizeof(*node)); + INIT_LIST_HEAD(&node->private_list); +} + +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); +} |