/* * 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/notifier.h> #include <linux/cpu.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; union { struct radix_tree_node *parent; /* Used when ascending tree */ struct rcu_head rcu_head; /* Used when freeing node */ }; void __rcu *slots[RADIX_TREE_MAP_SIZE]; unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS]; }; #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; /* * 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); 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); 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); } /* * 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) { 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; 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; node->height = 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_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 = 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; slot->parent = node; if (node) { rcu_assign_pointer(node->slots[offset], slot); node->count++; } 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 (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); /* * is_slot == 1 : search for the slot. * is_slot == 0 : search for the node. */ static void *radix_tree_lookup_element(struct radix_tree_root *root, unsigned long index, int is_slot) { unsigned int height, shift; struct radix_tree_node *node, **slot; node = rcu_dereference_raw(root->rnode); if (node == NULL) return NULL; if (!radix_tree_is_indirect_ptr(node)) { if (index > 0) return NULL; return is_slot ? (void *)&root->rnode : node; } node = 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_raw(*slot); if (node == NULL) return NULL; shift -= RADIX_TREE_MAP_SHIFT; height--; } while (height > 0); return is_slot ? (void *)slot : indirect_to_ptr(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) { return (void **)radix_tree_lookup_element(root, index, 1); } 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_element(root, index, 0); } 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->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; 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; 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: shift = (rnode->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_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). In rare cases of index wrap-around, 0 will be returned. * * radix_tree_next_hole may be called under rcu_read_lock. However, like * radix_tree_gang_lookup, this will not atomically search a snapshot of * the tree at a single point in time. For example, if a hole is created * at index 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); /** * radix_tree_prev_hole - find the prev hole (not-present entry) * @root: tree root * @index: index key * @max_scan: maximum range to search * * Search backwards in the range [max(index-max_scan+1, 0), index] * for the first hole. * * Returns: the index of the hole if found, otherwise returns an index * outside of the set specified (in which case 'index - return >= max_scan' * will be true). In rare cases of wrap-around, ULONG_MAX will be returned. * * radix_tree_next_hole may be called under rcu_read_lock. However, like * radix_tree_gang_lookup, this will not atomically search a snapshot of * the tree at a single point in time. For example, if a hole is created * at index 10, then subsequently a hole is created at index 5, * radix_tree_prev_hole covering both indexes may return 5 if called under * rcu_read_lock. */ unsigned long radix_tree_prev_hole(struct radix_tree_root *root, unsigned long index, unsigned long max_scan) { unsigned long i; for (i = 0; i < max_scan; i++) { if (!radix_tree_lookup(root, index)) break; index--; if (index == ULONG_MAX) break; } return index; } EXPORT_SYMBOL(radix_tree_prev_hole); /** * 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->height; shift = (height-1) * RADIX_TREE_MAP_SHIFT; for ( ; height > 1; height--) { i = (index >> shift) & RADIX_TREE_MAP_MASK; for (;;) { if (slot->slots[i] != NULL) break; index &= ~((1UL << shift) - 1); index += 1UL << shift; if (index == 0) goto out; /* 32-bit wraparound */ i++; if (i == RADIX_TREE_MAP_SIZE) goto out; } shift -= RADIX_TREE_MAP_SHIFT; slot = rcu_dereference_raw(slot->slots[i]); if (slot == NULL) goto out; } /* Bottom level: check items */ for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) { if (slot->slots[i] == item) { *found_index = index + i; index = 0; goto out; } } index += RADIX_TREE_MAP_SIZE; out: return index; } /** * radix_tree_locate_item - search through radix tree for item * @root: radix tree root * @item: item to be found * * Returns index where item was found, or -1 if not found. * Caller must hold no lock (since this time-consuming function needs * to be preemptible), and must check afterwards if item is still there. */ unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) { struct radix_tree_node *node; unsigned long max_index; unsigned long cur_index = 0; unsigned long found_index = -1; do { rcu_read_lock(); node = rcu_dereference_raw(root->rnode); if (!radix_tree_is_indirect_ptr(node)) { rcu_read_unlock(); if (node == item) found_index = 0; break; } node = indirect_to_ptr(node); max_index = radix_tree_maxindex(node->height); if (cur_index > max_index) break; cur_index = __locate(node, item, cur_index, &found_index); rcu_read_unlock(); cond_resched(); } while (cur_index != 0 && cur_index <= max_index); return found_index; } #else unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item) { return -1; } #endif /* CONFIG_SHMEM && CONFIG_SWAP */ /** * radix_tree_shrink - shrink height of a radix tree to minimal * @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 - 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_node *node = NULL; struct radix_tree_node *slot = NULL; struct radix_tree_node *to_free; unsigned int height, shift; int tag; int uninitialized_var(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 = indirect_to_ptr(slot); shift = height * RADIX_TREE_MAP_SHIFT; do { if (slot == NULL) goto out; shift -= RADIX_TREE_MAP_SHIFT; offset = (index >> shift) & RADIX_TREE_MAP_MASK; node = slot; slot = slot->slots[offset]; } while (shift); if (slot == NULL) goto out; /* * 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); } to_free = NULL; /* Now free the nodes we do not need anymore */ while (node) { node->slots[offset] = NULL; 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 (node->count) { if (node == indirect_to_ptr(root->rnode)) radix_tree_shrink(root); goto out; } /* Node with zero slots in use so free it */ to_free = node; index >>= RADIX_TREE_MAP_SHIFT; offset = index & RADIX_TREE_MAP_MASK; node = node->parent; } 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); }