// 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>
#include "radix-tree.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
*
* @node: where to begin the search
* @tag: the tag index
* @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)
{
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);
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
* @iter: iterator state
* @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 = 0;
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);
}
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