/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
* Copyright (C) 2006 Nick Piggin
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/radix-tree.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/gfp.h>
#include <linux/string.h>
#include <linux/bitops.h>
#include <linux/rcupdate.h>
#ifdef __KERNEL__
#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
#else
#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */
#endif
#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
#define RADIX_TREE_TAG_LONGS \
((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
struct radix_tree_node {
unsigned int height; /* Height from the bottom */
unsigned int count;
struct rcu_head rcu_head;
void *slots[RADIX_TREE_MAP_SIZE];
unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};
struct radix_tree_path {
struct radix_tree_node *node;
int offset;
};
#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
RADIX_TREE_MAP_SHIFT))
/*
* The height_to_maxindex array needs to be one deeper than the maximum
* path as height 0 holds only 1 entry.
*/
static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
/*
* Radix tree node cache.
*/
static struct kmem_cache *radix_tree_node_cachep;
/*
* Per-cpu pool of preloaded nodes
*/
struct radix_tree_preload {
int nr;
struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
};
DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
}
/*
* 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;
gfp_t gfp_mask = root_gfp_mask(root);
ret = kmem_cache_alloc(radix_tree_node_cachep,
set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
if (ret == NULL && !(gfp_mask & __GFP_WAIT)) {
struct radix_tree_preload *rtp;
rtp = &__get_cpu_var(radix_tree_preloads);
if (rtp->nr) {
ret = rtp->nodes[rtp->nr - 1];
rtp->nodes[rtp->nr - 1] = NULL;
rtp->nr--;
}
}
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);
kmem_cache_free(radix_tree_node_cachep, node);
}
static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
}
/*
* Load up this CPU's radix_tree_node buffer with sufficient objects to
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
*/
int radix_tree_preload(gfp_t gfp_mask)
{
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
int ret = -ENOMEM;
preempt_disable();
rtp = &__get_cpu_var(radix_tree_preloads);
while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
preempt_enable();
node = kmem_cache_alloc(radix_tree_node_cachep,
set_migrateflags(gfp_mask, __GFP_RECLAIMABLE));
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);
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;
}
/*
* Return the maximum key which can be store into a
* radix tree with height HEIGHT.
*/
static inline unsigned long radix_tree_maxindex(unsigned int height)
{
return height_to_maxindex[height];
}
/*
* Extend a radix tree so it can store key @index.
*/
static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
{
struct radix_tree_node *node;
unsigned int height;
int tag;
/* Figure out what the height should be. */
height = root->height + 1;
while (index > radix_tree_maxindex(height))
height++;
if (root->rnode == NULL) {
root->height = height;
goto out;
}
do {
unsigned int newheight;
if (!(node = radix_tree_node_alloc(root)))
return -ENOMEM;
/* Increase the height. */
node->slots[0] = radix_tree_indirect_to_ptr(root->rnode);
/* Propagate the aggregated tag info into the new root */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (root_tag_get(root, tag))
tag_set(node, tag, 0);
}
newheight = root->height+1;
node->height = newheight;
node->count = 1;
node = radix_tree_ptr_to_indirect(node);
rcu_assign_pointer(root->rnode, node);
root->height = newheight;
} while (height > root->height);
out:
return 0;
}
/**
* radix_tree_insert - insert into a radix tree
* @root: radix tree root
* @index: index key
* @item: item to insert
*
* Insert an item into the radix tree at position @index.
*/
int radix_tree_insert(struct radix_tree_root *root,
unsigned long index, void *item)
{
struct radix_tree_node *node = NULL, *slot;
unsigned int height, shift;
int offset;
int error;
BUG_ON(radix_tree_is_indirect_ptr(item));
/* Make sure the tree is high enough. */
if (index > radix_tree_maxindex(root->height)) {
error = radix_tree_extend(root, index);
if (error)
return error;
}
slot = radix_tree_indirect_to_ptr(root->rnode);
height = root->height;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
offset = 0; /* uninitialised var warning */
while (height > 0) {
if (slot == NULL) {
/* Have to add a child node. */
if (!(slot = radix_tree_node_alloc(root)))
return -ENOMEM;
slot->height = height;
if (node) {
rcu_assign_pointer(node->slots[offset], slot);
node->count++;
} else
rcu_assign_pointer(root->rnode,
radix_tree_ptr_to_indirect(slot));
}
/* Go a level down */
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
node = slot;
slot = node->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
if (slot != NULL)
return -EEXIST;
if (node) {
node->count++;
rcu_assign_pointer(node->slots[offset], item);
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
} else {
rcu_assign_pointer(root->rnode, item);
BUG_ON(root_tag_get(root, 0));
BUG_ON(root_tag_get(root, 1));
}
return 0;
}
EXPORT_SYMBOL(radix_tree_insert);
/**
* radix_tree_lookup_slot - lookup a slot in a radix tree
* @root: radix tree root
* @index: index key
*
* Returns: the slot corresponding to the position @index in the
* radix tree @root. This is useful for update-if-exists operations.
*
* This function cannot be called under rcu_read_lock, it must be
* excluded from writers, as must the returned slot for subsequent
* use by radix_tree_deref_slot() and radix_tree_replace slot.
* Caller must hold tree write locked across slot lookup and
* replace.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
unsigned int height, shift;
struct radix_tree_node *node, **slot;
node = root->rnode;
if (node == NULL)
return NULL;
if (!radix_tree_is_indirect_ptr(node)) {
if (index > 0)
return NULL;
return (void **)&root->rnode;
}
node = radix_tree_indirect_to_ptr(node);
height = node->height;
if (index > radix_tree_maxindex(height))
return NULL;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
do {
slot = (struct radix_tree_node **)
(node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
node = *slot;
if (node == NULL)
return NULL;
shift -= RADIX_TREE_MAP_SHIFT;
height--;
} while (height > 0);
return (void **)slot;
}
EXPORT_SYMBOL(radix_tree_lookup_slot);
/**
* radix_tree_lookup - perform lookup operation on a radix tree
* @root: radix tree root
* @index: index key
*
* Lookup the item at the position @index in the radix tree @root.
*
* This function can be called under rcu_read_lock, however the caller
* must manage lifetimes of leaf nodes (eg. RCU may also be used to free
* them safely). No RCU barriers are required to access or modify the
* returned item, however.
*/
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
unsigned int height, shift;
struct radix_tree_node *node, **slot;
node = rcu_dereference(root->rnode);
if (node == NULL)
return NULL;
if (!radix_tree_is_indirect_ptr(node)) {
if (index > 0)
return NULL;
return node;
}
node = radix_tree_indirect_to_ptr(node);
height = node->height;
if (index > radix_tree_maxindex(height))
return NULL;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
do {
slot = (struct radix_tree_node **)
(node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
node = rcu_dereference(*slot);
if (node == NULL)
return NULL;
shift -= RADIX_TREE_MAP_SHIFT;
height--;
} while (height > 0);
return node;
}
EXPORT_SYMBOL(radix_tree_lookup);
/**
* radix_tree_tag_set - set a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. From
* the root all the way down to the leaf node.
*
* Returns the address of the tagged item. Setting a tag on a not-present
* item is a bug.
*/
void *radix_tree_tag_set(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
unsigned int height, shift;
struct radix_tree_node *slot;
height = root->height;
BUG_ON(index > radix_tree_maxindex(height));
slot = radix_tree_indirect_to_ptr(root->rnode);
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
while (height > 0) {
int offset;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
if (!tag_get(slot, tag, offset))
tag_set(slot, tag, offset);
slot = slot->slots[offset];
BUG_ON(slot == NULL);
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
/* set the root's tag bit */
if (slot && !root_tag_get(root, tag))
root_tag_set(root, tag);
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_set);
/**
* radix_tree_tag_clear - clear a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. If
* this causes the leaf node to have no tags set then clear the tag in the
* next-to-leaf node, etc.
*
* Returns the address of the tagged item on success, else NULL. ie:
* has the same return value and semantics as radix_tree_lookup().
*/
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
/*
* The radix tree path needs to be one longer than the maximum path
* since the "list" is null terminated.
*/
struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
height = root->height;
if (index > radix_tree_maxindex(height))
goto out;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
pathp->node = NULL;
slot = radix_tree_indirect_to_ptr(root->rnode);
while (height > 0) {
int offset;
if (slot == NULL)
goto out;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
pathp[1].offset = offset;
pathp[1].node = slot;
slot = slot->slots[offset];
pathp++;
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
if (slot == NULL)
goto out;
while (pathp->node) {
if (!tag_get(pathp->node, tag, pathp->offset))
goto out;
tag_clear(pathp->node, tag, pathp->offset);
if (any_tag_set(pathp->node, tag))
goto out;
pathp--;
}
/* clear the root's tag bit */
if (root_tag_get(root, tag))
root_tag_clear(root, tag);
out:
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_clear);
#ifndef __KERNEL__ /* Only the test harness uses this at present */
/**
* radix_tree_tag_get - get a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index (< RADIX_TREE_MAX_TAGS)
*
* Return values:
*
* 0: tag not present or not set
* 1: tag set
*/
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
unsigned int height, shift;
struct radix_tree_node *node;
int saw_unset_tag = 0;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
node = rcu_dereference(root->rnode);
if (node == NULL)
return 0;
if (!radix_tree_is_indirect_ptr(node))
return (index == 0);
node = radix_tree_indirect_to_ptr(node);
height = node->height;
if (index > radix_tree_maxindex(height))
return 0;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
for ( ; ; ) {
int offset;
if (node == NULL)
return 0;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
/*
* This is just a debug check. Later, we can bale as soon as
* we see an unset tag.
*/
if (!tag_get(node, tag, offset))
saw_unset_tag = 1;
if (height == 1) {
int ret = tag_get(node, tag, offset);
BUG_ON(ret && saw_unset_tag);
return !!ret;
}
node = rcu_dereference(node->slots[offset]);
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
}
EXPORT_SYMBOL(radix_tree_tag_get);
#endif
/**
* radix_tree_next_hole - find the next hole (not-present entry)
* @root: tree root
* @index: index key
* @max_scan: maximum range to search
*
* Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
* indexed hole.
*
* Returns: the index of the hole if found, otherwise returns an index
* outside of the set specified (in which case 'return - index >= max_scan'
* will be true).
*
* radix_tree_next_hole may be called under rcu_read_lock. However, like
* radix_tree_gang_lookup, this will not atomically search a snapshot of the
* tree at a single point in time. For example, if a hole is created at index
* 5, then subsequently a hole is created at index 10, radix_tree_next_hole
* covering both indexes may return 10 if called under rcu_read_lock.
*/
unsigned long radix_tree_next_hole(struct radix_tree_root *root,
unsigned long index, unsigned long max_scan)
{
unsigned long i;
for (i = 0; i < max_scan; i++) {
if (!radix_tree_lookup(root, index))
break;
index++;
if (index == 0)
break;
}
return index;
}
EXPORT_SYMBOL(radix_tree_next_hole);
static unsigned int
__lookup(struct radix_tree_node *slot, void **results, unsigned long index,
unsigned int max_items, unsigned long *next_index)
{
unsigned int nr_found = 0;
unsigned int shift, height;
unsigned long i;
height = slot->height;
if (height == 0)
goto out;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
for ( ; height > 1; height--) {
i = (index >> shift) & RADIX_TREE_MAP_MASK;
for (;;) {
if (slot->slots[i] != NULL)
break;
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
i++;
if (i == RADIX_TREE_MAP_SIZE)
goto out;
}
shift -= RADIX_TREE_MAP_SHIFT;
slot = rcu_dereference(slot->slots[i]);
if (slot == NULL)
goto out;
}
/* Bottom level: grab some items */
for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
struct radix_tree_node *node;
index++;
node = slot->slots[i];
if (node) {
results[nr_found++] = rcu_dereference(node);
if (nr_found == max_items)
goto out;
}
}
out:
*next_index = index;
return nr_found;
}
/**
* radix_tree_gang_lookup - perform multiple lookup on a radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
*
* Performs an index-ascending scan of the tree for present items. Places
* them at *@results and returns the number of items which were placed at
* *@results.
*
* The implementation is naive.
*
* Like radix_tree_lookup, radix_tree_gang_lookup may be called under
* rcu_read_lock. In this case, rather than the returned results being
* an atomic snapshot of the tree at a single point in time, the semantics
* of an RCU protected gang lookup are as though multiple radix_tree_lookups
* have been issued in individual locks, and results stored in 'results'.
*/
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items)
{
unsigned long max_index;
struct radix_tree_node *node;
unsigned long cur_index = first_index;
unsigned int ret;
node = rcu_dereference(root->rnode);
if (!node)
return 0;
if (!radix_tree_is_indirect_ptr(node)) {
if (first_index > 0)
return 0;
results[0] = node;
return 1;
}
node = radix_tree_indirect_to_ptr(node);
max_index = radix_tree_maxindex(node->height);
ret = 0;
while (ret < max_items) {
unsigned int nr_found;
unsigned long next_index; /* Index of next search */
if (cur_index > max_index)
break;
nr_found = __lookup(node, results + ret, cur_index,
max_items - ret, &next_index);
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup);
/*
* FIXME: the two tag_get()s here should use find_next_bit() instead of
* open-coding the search.
*/
static unsigned int
__lookup_tag(struct radix_tree_node *slot, void **results, unsigned long index,
unsigned int max_items, unsigned long *next_index, unsigned int tag)
{
unsigned int nr_found = 0;
unsigned int shift, height;
height = slot->height;
if (height == 0)
goto out;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
while (height > 0) {
unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK ;
for (;;) {
if (tag_get(slot, tag, i))
break;
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
i++;
if (i == RADIX_TREE_MAP_SIZE)
goto out;
}
height--;
if (height == 0) { /* Bottom level: grab some items */
unsigned long j = index & RADIX_TREE_MAP_MASK;
for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
struct radix_tree_node *node;
index++;
if (!tag_get(slot, tag, j))
continue;
node = slot->slots[j];
/*
* Even though the tag was found set, we need to
* recheck that we have a non-NULL node, because
* if this lookup is lockless, it may have been
* subsequently deleted.
*
* Similar care must be taken in any place that
* lookup ->slots[x] without a lock (ie. can't
* rely on its value remaining the same).
*/
if (node) {
node = rcu_dereference(node);
results[nr_found++] = node;
if (nr_found == max_items)
goto out;
}
}
}
shift -= RADIX_TREE_MAP_SHIFT;
slot = rcu_dereference(slot->slots[i]);
if (slot == NULL)
break;
}
out:
*next_index = index;
return nr_found;
}
/**
* radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
* based on a tag
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
* @tag: the tag index (< RADIX_TREE_MAX_TAGS)
*
* Performs an index-ascending scan of the tree for present items which
* have the tag indexed by @tag set. Places the items at *@results and
* returns the number of items which were placed at *@results.
*/
unsigned int
radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items,
unsigned int tag)
{
struct radix_tree_node *node;
unsigned long max_index;
unsigned long cur_index = first_index;
unsigned int ret;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
node = rcu_dereference(root->rnode);
if (!node)
return 0;
if (!radix_tree_is_indirect_ptr(node)) {
if (first_index > 0)
return 0;
results[0] = node;
return 1;
}
node = radix_tree_indirect_to_ptr(node);
max_index = radix_tree_maxindex(node->height);
ret = 0;
while (ret < max_items) {
unsigned int nr_found;
unsigned long next_index; /* Index of next search */
if (cur_index > max_index)
break;
nr_found = __lookup_tag(node, results + ret, cur_index,
max_items - ret, &next_index, tag);
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
/**
* radix_tree_shrink - shrink height of a radix tree to minimal
* @root radix tree root
*/
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
/* try to shrink tree height */
while (root->height > 0) {
struct radix_tree_node *to_free = root->rnode;
void *newptr;
BUG_ON(!radix_tree_is_indirect_ptr(to_free));
to_free = radix_tree_indirect_to_ptr(to_free);
/*
* The candidate node has more than one child, or its child
* is not at the leftmost slot, we cannot shrink.
*/
if (to_free->count != 1)
break;
if (!to_free->slots[0])
break;
/*
* We don't need rcu_assign_pointer(), since we are simply
* moving the node from one part of the tree to another. If
* it was safe to dereference the old pointer to it
* (to_free->slots[0]), it will be safe to dereference the new
* one (root->rnode).
*/
newptr = to_free->slots[0];
if (root->height > 1)
newptr = radix_tree_ptr_to_indirect(newptr);
root->rnode = newptr;
root->height--;
/* must only free zeroed nodes into the slab */
tag_clear(to_free, 0, 0);
tag_clear(to_free, 1, 0);
to_free->slots[0] = NULL;
to_free->count = 0;
radix_tree_node_free(to_free);
}
}
/**
* radix_tree_delete - delete an item from a radix tree
* @root: radix tree root
* @index: index key
*
* Remove the item at @index from the radix tree rooted at @root.
*
* Returns the address of the deleted item, or NULL if it was not present.
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
/*
* The radix tree path needs to be one longer than the maximum path
* since the "list" is null terminated.
*/
struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
struct radix_tree_node *to_free;
unsigned int height, shift;
int tag;
int offset;
height = root->height;
if (index > radix_tree_maxindex(height))
goto out;
slot = root->rnode;
if (height == 0) {
root_tag_clear_all(root);
root->rnode = NULL;
goto out;
}
slot = radix_tree_indirect_to_ptr(slot);
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
pathp->node = NULL;
do {
if (slot == NULL)
goto out;
pathp++;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
pathp->offset = offset;
pathp->node = slot;
slot = slot->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
} while (height > 0);
if (slot == NULL)
goto out;
/*
* Clear all tags associated with the just-deleted item
*/
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (tag_get(pathp->node, tag, pathp->offset))
radix_tree_tag_clear(root, index, tag);
}
to_free = NULL;
/* Now free the nodes we do not need anymore */
while (pathp->node) {
pathp->node->slots[pathp->offset] = NULL;
pathp->node->count--;
/*
* Queue the node for deferred freeing after the
* last reference to it disappears (set NULL, above).
*/
if (to_free)
radix_tree_node_free(to_free);
if (pathp->node->count) {
if (pathp->node ==
radix_tree_indirect_to_ptr(root->rnode))
radix_tree_shrink(root);
goto out;
}
/* Node with zero slots in use so free it */
to_free = pathp->node;
pathp--;
}
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
if (to_free)
radix_tree_node_free(to_free);
out:
return slot;
}
EXPORT_SYMBOL(radix_tree_delete);
/**
* radix_tree_tagged - test whether any items in the tree are tagged
* @root: radix tree root
* @tag: tag to test
*/
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
{
return root_tag_get(root, tag);
}
EXPORT_SYMBOL(radix_tree_tagged);
static void
radix_tree_node_ctor(struct kmem_cache *cachep, 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, radix_tree_node_ctor);
radix_tree_init_maxindex();
hotcpu_notifier(radix_tree_callback, 0);
}
