diff options
Diffstat (limited to '')
| -rw-r--r-- | lib/radix-tree.c | 1605 |
1 files changed, 1605 insertions, 0 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c new file mode 100644 index 000000000..cbc691525 --- /dev/null +++ b/lib/radix-tree.c @@ -0,0 +1,1605 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * 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 + * Copyright (C) 2016 Intel, Matthew Wilcox + * Copyright (C) 2016 Intel, Ross Zwisler + */ + +#include <linux/bitmap.h> +#include <linux/bitops.h> +#include <linux/bug.h> +#include <linux/cpu.h> +#include <linux/errno.h> +#include <linux/export.h> +#include <linux/idr.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/kmemleak.h> +#include <linux/percpu.h> +#include <linux/preempt.h> /* in_interrupt() */ +#include <linux/radix-tree.h> +#include <linux/rcupdate.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/xarray.h> + +/* + * Radix tree node cache. + */ +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) + +/* + * The IDR does not have to be as high as the radix tree since it uses + * signed integers, not unsigned longs. + */ +#define IDR_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(int) - 1) +#define IDR_MAX_PATH (DIV_ROUND_UP(IDR_INDEX_BITS, \ + RADIX_TREE_MAP_SHIFT)) +#define IDR_PRELOAD_SIZE (IDR_MAX_PATH * 2 - 1) + +/* + * Per-cpu pool of preloaded nodes + */ +DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { + .lock = INIT_LOCAL_LOCK(lock), +}; +EXPORT_PER_CPU_SYMBOL_GPL(radix_tree_preloads); + +static inline struct radix_tree_node *entry_to_node(void *ptr) +{ + return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE); +} + +static inline void *node_to_entry(void *ptr) +{ + return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE); +} + +#define RADIX_TREE_RETRY XA_RETRY_ENTRY + +static inline unsigned long +get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot) +{ + return parent ? slot - parent->slots : 0; +} + +static unsigned int radix_tree_descend(const struct radix_tree_node *parent, + struct radix_tree_node **nodep, unsigned long index) +{ + unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK; + void __rcu **entry = rcu_dereference_raw(parent->slots[offset]); + + *nodep = (void *)entry; + return offset; +} + +static inline gfp_t root_gfp_mask(const struct radix_tree_root *root) +{ + return root->xa_flags & (__GFP_BITS_MASK & ~GFP_ZONEMASK); +} + +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(const 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 tag) +{ + root->xa_flags |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT)); +} + +static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag) +{ + root->xa_flags &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT)); +} + +static inline void root_tag_clear_all(struct radix_tree_root *root) +{ + root->xa_flags &= (__force gfp_t)((1 << ROOT_TAG_SHIFT) - 1); +} + +static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag) +{ + return (__force int)root->xa_flags & (1 << (tag + ROOT_TAG_SHIFT)); +} + +static inline unsigned root_tags_get(const struct radix_tree_root *root) +{ + return (__force unsigned)root->xa_flags >> ROOT_TAG_SHIFT; +} + +static inline bool is_idr(const struct radix_tree_root *root) +{ + return !!(root->xa_flags & ROOT_IS_IDR); +} + +/* + * Returns 1 if any slot in the node has this tag set. + * Otherwise returns 0. + */ +static inline int any_tag_set(const struct radix_tree_node *node, + unsigned int tag) +{ + unsigned idx; + for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) { + if (node->tags[tag][idx]) + return 1; + } + return 0; +} + +static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag) +{ + bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE); +} + +/** + * 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(struct radix_tree_node *node, unsigned int tag, + unsigned long offset) +{ + const unsigned long *addr = node->tags[tag]; + + if (offset < RADIX_TREE_MAP_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 < RADIX_TREE_MAP_SIZE) { + tmp = *++addr; + if (tmp) + return __ffs(tmp) + offset; + offset += BITS_PER_LONG; + } + } + return RADIX_TREE_MAP_SIZE; +} + +static unsigned int iter_offset(const struct radix_tree_iter *iter) +{ + return iter->index & RADIX_TREE_MAP_MASK; +} + +/* + * The maximum index which can be stored in a radix tree + */ +static inline unsigned long shift_maxindex(unsigned int shift) +{ + return (RADIX_TREE_MAP_SIZE << shift) - 1; +} + +static inline unsigned long node_maxindex(const struct radix_tree_node *node) +{ + return shift_maxindex(node->shift); +} + +static unsigned long next_index(unsigned long index, + const struct radix_tree_node *node, + unsigned long offset) +{ + return (index & ~node_maxindex(node)) + (offset << node->shift); +} + +/* + * 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(gfp_t gfp_mask, struct radix_tree_node *parent, + struct radix_tree_root *root, + unsigned int shift, unsigned int offset, + unsigned int count, unsigned int nr_values) +{ + struct radix_tree_node *ret = NULL; + + /* + * Preload code isn't irq safe and it doesn't make sense to use + * preloading during an interrupt anyway as all the allocations have + * to be atomic. So just do normal allocation when in interrupt. + */ + if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) { + struct radix_tree_preload *rtp; + + /* + * Even if the caller has preloaded, try to allocate from the + * cache first for the new node to get accounted to the memory + * cgroup. + */ + ret = kmem_cache_alloc(radix_tree_node_cachep, + gfp_mask | __GFP_NOWARN); + if (ret) + goto out; + + /* + * Provided the caller has preloaded here, we will always + * succeed in getting a node here (and never reach + * kmem_cache_alloc) + */ + rtp = this_cpu_ptr(&radix_tree_preloads); + if (rtp->nr) { + ret = rtp->nodes; + rtp->nodes = ret->parent; + rtp->nr--; + } + /* + * Update the allocation stack trace as this is more useful + * for debugging. + */ + kmemleak_update_trace(ret); + goto out; + } + ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); +out: + BUG_ON(radix_tree_is_internal_node(ret)); + if (ret) { + ret->shift = shift; + ret->offset = offset; + ret->count = count; + ret->nr_values = nr_values; + ret->parent = parent; + ret->array = root; + } + return ret; +} + +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. We can be left with + * non-NULL entries by radix_tree_free_nodes, so clear the entries + * and tags here. + */ + memset(node->slots, 0, sizeof(node->slots)); + memset(node->tags, 0, sizeof(node->tags)); + INIT_LIST_HEAD(&node->private_list); + + 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_DIRECT_RECLAIM being passed to INIT_RADIX_TREE(). + */ +static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr) +{ + struct radix_tree_preload *rtp; + struct radix_tree_node *node; + int ret = -ENOMEM; + + /* + * Nodes preloaded by one cgroup can be used by another cgroup, so + * they should never be accounted to any particular memory cgroup. + */ + gfp_mask &= ~__GFP_ACCOUNT; + + local_lock(&radix_tree_preloads.lock); + rtp = this_cpu_ptr(&radix_tree_preloads); + while (rtp->nr < nr) { + local_unlock(&radix_tree_preloads.lock); + node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask); + if (node == NULL) + goto out; + local_lock(&radix_tree_preloads.lock); + rtp = this_cpu_ptr(&radix_tree_preloads); + if (rtp->nr < nr) { + node->parent = rtp->nodes; + rtp->nodes = node; + rtp->nr++; + } 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_DIRECT_RECLAIM being passed to INIT_RADIX_TREE(). + */ +int radix_tree_preload(gfp_t gfp_mask) +{ + /* Warn on non-sensical use... */ + WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask)); + return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); +} +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 (gfpflags_allow_blocking(gfp_mask)) + return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE); + /* Preloading doesn't help anything with this gfp mask, skip it */ + local_lock(&radix_tree_preloads.lock); + return 0; +} +EXPORT_SYMBOL(radix_tree_maybe_preload); + +static unsigned radix_tree_load_root(const struct radix_tree_root *root, + struct radix_tree_node **nodep, unsigned long *maxindex) +{ + struct radix_tree_node *node = rcu_dereference_raw(root->xa_head); + + *nodep = node; + + if (likely(radix_tree_is_internal_node(node))) { + node = entry_to_node(node); + *maxindex = node_maxindex(node); + return node->shift + RADIX_TREE_MAP_SHIFT; + } + + *maxindex = 0; + return 0; +} + +/* + * Extend a radix tree so it can store key @index. + */ +static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp, + unsigned long index, unsigned int shift) +{ + void *entry; + unsigned int maxshift; + int tag; + + /* Figure out what the shift should be. */ + maxshift = shift; + while (index > shift_maxindex(maxshift)) + maxshift += RADIX_TREE_MAP_SHIFT; + + entry = rcu_dereference_raw(root->xa_head); + if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE))) + goto out; + + do { + struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL, + root, shift, 0, 1, 0); + if (!node) + return -ENOMEM; + + if (is_idr(root)) { + all_tag_set(node, IDR_FREE); + if (!root_tag_get(root, IDR_FREE)) { + tag_clear(node, IDR_FREE, 0); + root_tag_set(root, IDR_FREE); + } + } else { + /* Propagate the aggregated tag info to the new child */ + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) { + if (root_tag_get(root, tag)) + tag_set(node, tag, 0); + } + } + + BUG_ON(shift > BITS_PER_LONG); + if (radix_tree_is_internal_node(entry)) { + entry_to_node(entry)->parent = node; + } else if (xa_is_value(entry)) { + /* Moving a value entry root->xa_head to a node */ + node->nr_values = 1; + } + /* + * entry was already in the radix tree, so we do not need + * rcu_assign_pointer here + */ + node->slots[0] = (void __rcu *)entry; + entry = node_to_entry(node); + rcu_assign_pointer(root->xa_head, entry); + shift += RADIX_TREE_MAP_SHIFT; + } while (shift <= maxshift); +out: + return maxshift + RADIX_TREE_MAP_SHIFT; +} + +/** + * radix_tree_shrink - shrink radix tree to minimum height + * @root radix tree root + */ +static inline bool radix_tree_shrink(struct radix_tree_root *root) +{ + bool shrunk = false; + + for (;;) { + struct radix_tree_node *node = rcu_dereference_raw(root->xa_head); + struct radix_tree_node *child; + + if (!radix_tree_is_internal_node(node)) + break; + node = entry_to_node(node); + + /* + * The candidate node has more than one child, or its child + * is not at the leftmost slot, we cannot shrink. + */ + if (node->count != 1) + break; + child = rcu_dereference_raw(node->slots[0]); + if (!child) + break; + + /* + * For an IDR, we must not shrink entry 0 into the root in + * case somebody calls idr_replace() with a pointer that + * appears to be an internal entry + */ + if (!node->shift && is_idr(root)) + break; + + if (radix_tree_is_internal_node(child)) + entry_to_node(child)->parent = NULL; + + /* + * 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 + * (node->slots[0]), it will be safe to dereference the new + * one (root->xa_head) as far as dependent read barriers go. + */ + root->xa_head = (void __rcu *)child; + if (is_idr(root) && !tag_get(node, IDR_FREE, 0)) + root_tag_clear(root, IDR_FREE); + + /* + * 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 has 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. + */ + node->count = 0; + if (!radix_tree_is_internal_node(child)) { + node->slots[0] = (void __rcu *)RADIX_TREE_RETRY; + } + + WARN_ON_ONCE(!list_empty(&node->private_list)); + radix_tree_node_free(node); + shrunk = true; + } + + return shrunk; +} + +static bool 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_to_entry(node) == + rcu_dereference_raw(root->xa_head)) + deleted |= radix_tree_shrink(root); + return deleted; + } + + parent = node->parent; + if (parent) { + parent->slots[node->offset] = NULL; + parent->count--; + } else { + /* + * Shouldn't the tags already have all been cleared + * by the caller? + */ + if (!is_idr(root)) + root_tag_clear_all(root); + root->xa_head = NULL; + } + + WARN_ON_ONCE(!list_empty(&node->private_list)); + radix_tree_node_free(node); + deleted = true; + + node = parent; + } while (node); + + return deleted; +} + +/** + * __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->xa_head 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. + */ +static int __radix_tree_create(struct radix_tree_root *root, + unsigned long index, struct radix_tree_node **nodep, + void __rcu ***slotp) +{ + struct radix_tree_node *node = NULL, *child; + void __rcu **slot = (void __rcu **)&root->xa_head; + unsigned long maxindex; + unsigned int shift, offset = 0; + unsigned long max = index; + gfp_t gfp = root_gfp_mask(root); + + shift = radix_tree_load_root(root, &child, &maxindex); + + /* Make sure the tree is high enough. */ + if (max > maxindex) { + int error = radix_tree_extend(root, gfp, max, shift); + if (error < 0) + return error; + shift = error; + child = rcu_dereference_raw(root->xa_head); + } + + while (shift > 0) { + shift -= RADIX_TREE_MAP_SHIFT; + if (child == NULL) { + /* Have to add a child node. */ + child = radix_tree_node_alloc(gfp, node, root, shift, + offset, 0, 0); + if (!child) + return -ENOMEM; + rcu_assign_pointer(*slot, node_to_entry(child)); + if (node) + node->count++; + } else if (!radix_tree_is_internal_node(child)) + break; + + /* Go a level down */ + node = entry_to_node(child); + offset = radix_tree_descend(node, &child, index); + slot = &node->slots[offset]; + } + + if (nodep) + *nodep = node; + if (slotp) + *slotp = slot; + return 0; +} + +/* + * Free any nodes below this node. The tree is presumed to not need + * shrinking, and any user data in the tree is presumed to not need a + * destructor called on it. If we need to add a destructor, we can + * add that functionality later. Note that we may not clear tags or + * slots from the tree as an RCU walker may still have a pointer into + * this subtree. We could replace the entries with RADIX_TREE_RETRY, + * but we'll still have to clear those in rcu_free. + */ +static void radix_tree_free_nodes(struct radix_tree_node *node) +{ + unsigned offset = 0; + struct radix_tree_node *child = entry_to_node(node); + + for (;;) { + void *entry = rcu_dereference_raw(child->slots[offset]); + if (xa_is_node(entry) && child->shift) { + child = entry_to_node(entry); + offset = 0; + continue; + } + offset++; + while (offset == RADIX_TREE_MAP_SIZE) { + struct radix_tree_node *old = child; + offset = child->offset + 1; + child = child->parent; + WARN_ON_ONCE(!list_empty(&old->private_list)); + radix_tree_node_free(old); + if (old == entry_to_node(node)) + return; + } + } +} + +static inline int insert_entries(struct radix_tree_node *node, + void __rcu **slot, void *item, bool replace) +{ + if (*slot) + return -EEXIST; + rcu_assign_pointer(*slot, item); + if (node) { + node->count++; + if (xa_is_value(item)) + node->nr_values++; + } + return 1; +} + +/** + * __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 __rcu **slot; + int error; + + BUG_ON(radix_tree_is_internal_node(item)); + + error = __radix_tree_create(root, index, &node, &slot); + if (error) + return error; + + error = insert_entries(node, slot, item, false); + if (error < 0) + return error; + + if (node) { + unsigned offset = get_slot_offset(node, slot); + BUG_ON(tag_get(node, 0, offset)); + BUG_ON(tag_get(node, 1, offset)); + BUG_ON(tag_get(node, 2, offset)); + } else { + BUG_ON(root_tags_get(root)); + } + + 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->xa_head is used as a direct slot instead of + * pointing to a node, in which case *@nodep will be NULL. + */ +void *__radix_tree_lookup(const struct radix_tree_root *root, + unsigned long index, struct radix_tree_node **nodep, + void __rcu ***slotp) +{ + struct radix_tree_node *node, *parent; + unsigned long maxindex; + void __rcu **slot; + + restart: + parent = NULL; + slot = (void __rcu **)&root->xa_head; + radix_tree_load_root(root, &node, &maxindex); + if (index > maxindex) + return NULL; + + while (radix_tree_is_internal_node(node)) { + unsigned offset; + + parent = entry_to_node(node); + offset = radix_tree_descend(parent, &node, index); + slot = parent->slots + offset; + if (node == RADIX_TREE_RETRY) + goto restart; + if (parent->shift == 0) + break; + } + + 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 __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root, + unsigned long index) +{ + void __rcu **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(const struct radix_tree_root *root, unsigned long index) +{ + return __radix_tree_lookup(root, index, NULL, NULL); +} +EXPORT_SYMBOL(radix_tree_lookup); + +static void replace_slot(void __rcu **slot, void *item, + struct radix_tree_node *node, int count, int values) +{ + if (node && (count || values)) { + node->count += count; + node->nr_values += values; + } + + rcu_assign_pointer(*slot, item); +} + +static bool node_tag_get(const struct radix_tree_root *root, + const struct radix_tree_node *node, + unsigned int tag, unsigned int offset) +{ + if (node) + return tag_get(node, tag, offset); + return root_tag_get(root, tag); +} + +/* + * IDR users want to be able to store NULL in the tree, so if the slot isn't + * free, don't adjust the count, even if it's transitioning between NULL and + * non-NULL. For the IDA, we mark slots as being IDR_FREE while they still + * have empty bits, but it only stores NULL in slots when they're being + * deleted. + */ +static int calculate_count(struct radix_tree_root *root, + struct radix_tree_node *node, void __rcu **slot, + void *item, void *old) +{ + if (is_idr(root)) { + unsigned offset = get_slot_offset(node, slot); + bool free = node_tag_get(root, node, IDR_FREE, offset); + if (!free) + return 0; + if (!old) + return 1; + } + return !!item - !!old; +} + +/** + * __radix_tree_replace - replace item in a slot + * @root: radix tree root + * @node: pointer to tree node + * @slot: pointer to slot in @node + * @item: new item to store in the slot. + * + * For use with __radix_tree_lookup(). Caller must hold tree write locked + * across slot lookup and replacement. + */ +void __radix_tree_replace(struct radix_tree_root *root, + struct radix_tree_node *node, + void __rcu **slot, void *item) +{ + void *old = rcu_dereference_raw(*slot); + int values = !!xa_is_value(item) - !!xa_is_value(old); + int count = calculate_count(root, node, slot, item, old); + + /* + * This function supports replacing value entries and + * deleting entries, but that needs accounting against the + * node unless the slot is root->xa_head. + */ + WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->xa_head) && + (count || values)); + replace_slot(slot, item, node, count, values); + + if (!node) + return; + + delete_node(root, node); +} + +/** + * radix_tree_replace_slot - replace item in a slot + * @root: radix tree root + * @slot: pointer to slot + * @item: new item to store in the slot. + * + * For use with radix_tree_lookup_slot() and + * radix_tree_gang_lookup_tag_slot(). Caller must hold tree write locked + * across slot lookup and replacement. + * + * NOTE: This cannot be used to switch between non-entries (empty slots), + * regular entries, and value entries, as that requires accounting + * inside the radix tree node. When switching from one type of entry or + * deleting, use __radix_tree_lookup() and __radix_tree_replace() or + * radix_tree_iter_replace(). + */ +void radix_tree_replace_slot(struct radix_tree_root *root, + void __rcu **slot, void *item) +{ + __radix_tree_replace(root, NULL, slot, item); +} +EXPORT_SYMBOL(radix_tree_replace_slot); + +/** + * radix_tree_iter_replace - replace item in a slot + * @root: radix tree root + * @slot: pointer to slot + * @item: new item to store in the slot. + * + * For use with radix_tree_for_each_slot(). + * Caller must hold tree write locked. + */ +void radix_tree_iter_replace(struct radix_tree_root *root, + const struct radix_tree_iter *iter, + void __rcu **slot, void *item) +{ + __radix_tree_replace(root, iter->node, slot, item); +} + +static void node_tag_set(struct radix_tree_root *root, + struct radix_tree_node *node, + unsigned int tag, unsigned int offset) +{ + while (node) { + if (tag_get(node, tag, offset)) + return; + tag_set(node, tag, offset); + offset = node->offset; + node = node->parent; + } + + if (!root_tag_get(root, tag)) + root_tag_set(root, tag); +} + +/** + * 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) +{ + struct radix_tree_node *node, *parent; + unsigned long maxindex; + + radix_tree_load_root(root, &node, &maxindex); + BUG_ON(index > maxindex); + + while (radix_tree_is_internal_node(node)) { + unsigned offset; + + parent = entry_to_node(node); + offset = radix_tree_descend(parent, &node, index); + BUG_ON(!node); + + if (!tag_get(parent, tag, offset)) + tag_set(parent, tag, offset); + } + + /* set the root's tag bit */ + if (!root_tag_get(root, tag)) + root_tag_set(root, tag); + + return node; +} +EXPORT_SYMBOL(radix_tree_tag_set); + +static void node_tag_clear(struct radix_tree_root *root, + struct radix_tree_node *node, + unsigned int tag, unsigned int offset) +{ + while (node) { + if (!tag_get(node, tag, offset)) + return; + tag_clear(node, tag, offset); + if (any_tag_set(node, tag)) + return; + + offset = node->offset; + node = node->parent; + } + + /* clear the root's tag bit */ + if (root_tag_get(root, tag)) + root_tag_clear(root, tag); +} + +/** + * 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, *parent; + unsigned long maxindex; + int offset; + + radix_tree_load_root(root, &node, &maxindex); + if (index > maxindex) + return NULL; + + parent = NULL; + + while (radix_tree_is_internal_node(node)) { + parent = entry_to_node(node); + offset = radix_tree_descend(parent, &node, index); + } + + if (node) + node_tag_clear(root, parent, tag, offset); + + return node; +} +EXPORT_SYMBOL(radix_tree_tag_clear); + +/** + * radix_tree_iter_tag_clear - clear a tag on the current iterator entry + * @root: radix tree root + * @iter: iterator state + * @tag: tag to clear + */ +void radix_tree_iter_tag_clear(struct radix_tree_root *root, + const struct radix_tree_iter *iter, unsigned int tag) +{ + node_tag_clear(root, iter->node, tag, iter_offset(iter)); +} + +/** + * 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(const struct radix_tree_root *root, + unsigned long index, unsigned int tag) +{ + struct radix_tree_node *node, *parent; + unsigned long maxindex; + + if (!root_tag_get(root, tag)) + return 0; + + radix_tree_load_root(root, &node, &maxindex); + if (index > maxindex) + return 0; + + while (radix_tree_is_internal_node(node)) { + unsigned offset; + + parent = entry_to_node(node); + offset = radix_tree_descend(parent, &node, index); + + if (!tag_get(parent, tag, offset)) + return 0; + if (node == RADIX_TREE_RETRY) + break; + } + + return 1; +} +EXPORT_SYMBOL(radix_tree_tag_get); + +/* Construct iter->tags bit-mask from node->tags[tag] array */ +static void set_iter_tags(struct radix_tree_iter *iter, + struct radix_tree_node *node, unsigned offset, + unsigned tag) +{ + unsigned tag_long = offset / BITS_PER_LONG; + unsigned tag_bit = offset % BITS_PER_LONG; + + if (!node) { + iter->tags = 1; + return; + } + + 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 = __radix_tree_iter_add(iter, BITS_PER_LONG); + } +} + +void __rcu **radix_tree_iter_resume(void __rcu **slot, + struct radix_tree_iter *iter) +{ + iter->index = __radix_tree_iter_add(iter, 1); + iter->next_index = iter->index; + iter->tags = 0; + return NULL; +} +EXPORT_SYMBOL(radix_tree_iter_resume); + +/** + * 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 __rcu **radix_tree_next_chunk(const struct radix_tree_root *root, + struct radix_tree_iter *iter, unsigned flags) +{ + unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK; + struct radix_tree_node *node, *child; + unsigned long index, offset, maxindex; + + 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 switching to the next chunk. + */ + index = iter->next_index; + if (!index && iter->index) + return NULL; + + restart: + radix_tree_load_root(root, &child, &maxindex); + if (index > maxindex) + return NULL; + if (!child) + return NULL; + + if (!radix_tree_is_internal_node(child)) { + /* Single-slot tree */ + iter->index = index; + iter->next_index = maxindex + 1; + iter->tags = 1; + iter->node = NULL; + return (void __rcu **)&root->xa_head; + } + + do { + node = entry_to_node(child); + offset = radix_tree_descend(node, &child, index); + + if ((flags & RADIX_TREE_ITER_TAGGED) ? + !tag_get(node, tag, offset) : !child) { + /* Hole detected */ + if (flags & RADIX_TREE_ITER_CONTIG) + return NULL; + + if (flags & RADIX_TREE_ITER_TAGGED) + offset = radix_tree_find_next_bit(node, tag, + offset + 1); + else + while (++offset < RADIX_TREE_MAP_SIZE) { + void *slot = rcu_dereference_raw( + node->slots[offset]); + if (slot) + break; + } + index &= ~node_maxindex(node); + index += offset << node->shift; + /* Overflow after ~0UL */ + if (!index) + return NULL; + if (offset == RADIX_TREE_MAP_SIZE) + goto restart; + child = rcu_dereference_raw(node->slots[offset]); + } + + if (!child) + goto restart; + if (child == RADIX_TREE_RETRY) + break; + } while (node->shift && radix_tree_is_internal_node(child)); + + /* Update the iterator state */ + iter->index = (index &~ node_maxindex(node)) | offset; + iter->next_index = (index | node_maxindex(node)) + 1; + iter->node = node; + + if (flags & RADIX_TREE_ITER_TAGGED) + set_iter_tags(iter, node, offset, tag); + + return node->slots + offset; +} +EXPORT_SYMBOL(radix_tree_next_chunk); + +/** + * 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(const struct radix_tree_root *root, void **results, + unsigned long first_index, unsigned int max_items) +{ + struct radix_tree_iter iter; + void __rcu **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_slot(slot, root, &iter, first_index) { + results[ret] = rcu_dereference_raw(*slot); + if (!results[ret]) + continue; + if (radix_tree_is_internal_node(results[ret])) { + slot = radix_tree_iter_retry(&iter); + continue; + } + if (++ret == max_items) + break; + } + + return ret; +} +EXPORT_SYMBOL(radix_tree_gang_lookup); + +/** + * 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(const struct radix_tree_root *root, void **results, + unsigned long first_index, unsigned int max_items, + unsigned int tag) +{ + struct radix_tree_iter iter; + void __rcu **slot; + unsigned int ret = 0; + + if (unlikely(!max_items)) + return 0; + + radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) { + results[ret] = rcu_dereference_raw(*slot); + if (!results[ret]) + continue; + if (radix_tree_is_internal_node(results[ret])) { + slot = radix_tree_iter_retry(&iter); + 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(const struct radix_tree_root *root, + void __rcu ***results, unsigned long first_index, + unsigned int max_items, unsigned int tag) +{ + struct radix_tree_iter iter; + void __rcu **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); + +static bool __radix_tree_delete(struct radix_tree_root *root, + struct radix_tree_node *node, void __rcu **slot) +{ + void *old = rcu_dereference_raw(*slot); + int values = xa_is_value(old) ? -1 : 0; + unsigned offset = get_slot_offset(node, slot); + int tag; + + if (is_idr(root)) + node_tag_set(root, node, IDR_FREE, offset); + else + for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) + node_tag_clear(root, node, tag, offset); + + replace_slot(slot, NULL, node, -1, values); + return node && delete_node(root, node); +} + +/** + * radix_tree_iter_delete - delete the entry at this iterator position + * @root: radix tree root + * @iter: iterator state + * @slot: pointer to slot + * + * Delete the entry at the position currently pointed to by the iterator. + * This may result in the current node being freed; if it is, the iterator + * is advanced so that it will not reference the freed memory. This + * function may be called without any locking if there are no other threads + * which can access this tree. + */ +void radix_tree_iter_delete(struct radix_tree_root *root, + struct radix_tree_iter *iter, void __rcu **slot) +{ + if (__radix_tree_delete(root, iter->node, slot)) + iter->index = iter->next_index; +} +EXPORT_SYMBOL(radix_tree_iter_delete); + +/** + * 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. + * + * Return: the deleted entry, 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 = NULL; + void __rcu **slot = NULL; + void *entry; + + entry = __radix_tree_lookup(root, index, &node, &slot); + if (!slot) + return NULL; + if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE, + get_slot_offset(node, slot)))) + return NULL; + + if (item && entry != item) + return NULL; + + __radix_tree_delete(root, node, slot); + + return entry; +} +EXPORT_SYMBOL(radix_tree_delete_item); + +/** + * radix_tree_delete - delete an entry from a radix tree + * @root: radix tree root + * @index: index key + * + * Remove the entry at @index from the radix tree rooted at @root. + * + * Return: The deleted entry, 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(const struct radix_tree_root *root, unsigned int tag) +{ + return root_tag_get(root, tag); +} +EXPORT_SYMBOL(radix_tree_tagged); + +/** + * idr_preload - preload for idr_alloc() + * @gfp_mask: allocation mask to use for preloading + * + * Preallocate memory to use for the next call to idr_alloc(). This function + * returns with preemption disabled. It will be enabled by idr_preload_end(). + */ +void idr_preload(gfp_t gfp_mask) +{ + if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE)) + local_lock(&radix_tree_preloads.lock); +} +EXPORT_SYMBOL(idr_preload); + +void __rcu **idr_get_free(struct radix_tree_root *root, + struct radix_tree_iter *iter, gfp_t gfp, + unsigned long max) +{ + struct radix_tree_node *node = NULL, *child; + void __rcu **slot = (void __rcu **)&root->xa_head; + unsigned long maxindex, start = iter->next_index; + unsigned int shift, offset = 0; + + grow: + shift = radix_tree_load_root(root, &child, &maxindex); + if (!radix_tree_tagged(root, IDR_FREE)) + start = max(start, maxindex + 1); + if (start > max) + return ERR_PTR(-ENOSPC); + + if (start > maxindex) { + int error = radix_tree_extend(root, gfp, start, shift); + if (error < 0) + return ERR_PTR(error); + shift = error; + child = rcu_dereference_raw(root->xa_head); + } + if (start == 0 && shift == 0) + shift = RADIX_TREE_MAP_SHIFT; + + while (shift) { + shift -= RADIX_TREE_MAP_SHIFT; + if (child == NULL) { + /* Have to add a child node. */ + child = radix_tree_node_alloc(gfp, node, root, shift, + offset, 0, 0); + if (!child) + return ERR_PTR(-ENOMEM); + all_tag_set(child, IDR_FREE); + rcu_assign_pointer(*slot, node_to_entry(child)); + if (node) + node->count++; + } else if (!radix_tree_is_internal_node(child)) + break; + + node = entry_to_node(child); + offset = radix_tree_descend(node, &child, start); + if (!tag_get(node, IDR_FREE, offset)) { + offset = radix_tree_find_next_bit(node, IDR_FREE, + offset + 1); + start = next_index(start, node, offset); + if (start > max || start == 0) + return ERR_PTR(-ENOSPC); + while (offset == RADIX_TREE_MAP_SIZE) { + offset = node->offset + 1; + node = node->parent; + if (!node) + goto grow; + shift = node->shift; + } + child = rcu_dereference_raw(node->slots[offset]); + } + slot = &node->slots[offset]; + } + + iter->index = start; + if (node) + iter->next_index = 1 + min(max, (start | node_maxindex(node))); + else + iter->next_index = 1; + iter->node = node; + set_iter_tags(iter, node, offset, IDR_FREE); + + return slot; +} + +/** + * idr_destroy - release all internal memory from an IDR + * @idr: idr handle + * + * After this function is called, the IDR is empty, and may be reused or + * the data structure containing it may be freed. + * + * A typical clean-up sequence for objects stored in an idr tree will use + * idr_for_each() to free all objects, if necessary, then idr_destroy() to + * free the memory used to keep track of those objects. + */ +void idr_destroy(struct idr *idr) +{ + struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.xa_head); + if (radix_tree_is_internal_node(node)) + radix_tree_free_nodes(node); + idr->idr_rt.xa_head = NULL; + root_tag_set(&idr->idr_rt, IDR_FREE); +} +EXPORT_SYMBOL(idr_destroy); + +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 int radix_tree_cpu_dead(unsigned int cpu) +{ + struct radix_tree_preload *rtp; + struct radix_tree_node *node; + + /* Free per-cpu pool of preloaded nodes */ + rtp = &per_cpu(radix_tree_preloads, cpu); + while (rtp->nr) { + node = rtp->nodes; + rtp->nodes = node->parent; + kmem_cache_free(radix_tree_node_cachep, node); + rtp->nr--; + } + return 0; +} + +void __init radix_tree_init(void) +{ + int ret; + + BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32); + BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK); + BUILD_BUG_ON(XA_CHUNK_SIZE > 255); + 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); + ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead", + NULL, radix_tree_cpu_dead); + WARN_ON(ret < 0); +} |