- 根目录:
- lib
- radix-tree.c
/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2005 SGI, Christoph Lameter
* Copyright (C) 2006 Nick Piggin
* Copyright (C) 2012 Konstantin Khlebnikov
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/radix-tree.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/string.h>
#include <linux/bitops.h>
#include <linux/rcupdate.h>
#include <linux/hardirq.h> /* in_interrupt() */
#ifdef __KERNEL__
#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
#else
#define RADIX_TREE_MAP_SHIFT 3 /* For more stressful testing */
#endif
#define RADIX_TREE_MAP_SIZE (1UL << RADIX_TREE_MAP_SHIFT)
#define RADIX_TREE_MAP_MASK (RADIX_TREE_MAP_SIZE-1)
#define RADIX_TREE_TAG_LONGS \
((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
struct radix_tree_node {
unsigned int height; /* Height from the bottom */
unsigned int count;
union {
struct radix_tree_node *parent; /* Used when ascending tree */
struct rcu_head rcu_head; /* Used when freeing node */
};
void __rcu *slots[RADIX_TREE_MAP_SIZE];
unsigned long tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
};
#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
RADIX_TREE_MAP_SHIFT))
/*
* The height_to_maxindex array needs to be one deeper than the maximum
* path as height 0 holds only 1 entry.
*/
static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
/*
* Radix tree node cache.
*/
static struct kmem_cache *radix_tree_node_cachep;
/*
* The radix tree is variable-height, so an insert operation not only has
* to build the branch to its corresponding item, it also has to build the
* branch to existing items if the size has to be increased (by
* radix_tree_extend).
*
* The worst case is a zero height tree with just a single item at index 0,
* and then inserting an item at index ULONG_MAX. This requires 2 new branches
* of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
* Hence:
*/
#define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
/*
* Per-cpu pool of preloaded nodes
*/
struct radix_tree_preload {
int nr;
struct radix_tree_node *nodes[RADIX_TREE_PRELOAD_SIZE];
};
static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
static inline void *ptr_to_indirect(void *ptr)
{
return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
}
static inline void *indirect_to_ptr(void *ptr)
{
return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
}
static inline gfp_t root_gfp_mask(struct radix_tree_root *root)
{
return root->gfp_mask & __GFP_BITS_MASK;
}
static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__set_bit(offset, node->tags[tag]);
}
static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__clear_bit(offset, node->tags[tag]);
}
static inline int tag_get(struct radix_tree_node *node, unsigned int tag,
int offset)
{
return test_bit(offset, node->tags[tag]);
}
static inline void root_tag_set(struct radix_tree_root *root, unsigned int tag)
{
root->gfp_mask |= (__force gfp_t)(1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear(struct radix_tree_root *root, unsigned int tag)
{
root->gfp_mask &= (__force gfp_t)~(1 << (tag + __GFP_BITS_SHIFT));
}
static inline void root_tag_clear_all(struct radix_tree_root *root)
{
root->gfp_mask &= __GFP_BITS_MASK;
}
static inline int root_tag_get(struct radix_tree_root *root, unsigned int tag)
{
return (__force unsigned)root->gfp_mask & (1 << (tag + __GFP_BITS_SHIFT));
}
/*
* Returns 1 if any slot in the node has this tag set.
* Otherwise returns 0.
*/
static inline int any_tag_set(struct radix_tree_node *node, unsigned int tag)
{
int idx;
for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
if (node->tags[tag][idx])
return 1;
}
return 0;
}
/**
* radix_tree_find_next_bit - find the next set bit in a memory region
*
* @addr: The address to base the search on
* @size: The bitmap size in bits
* @offset: The bitnumber to start searching at
*
* Unrollable variant of find_next_bit() for constant size arrays.
* Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
* Returns next bit offset, or size if nothing found.
*/
static __always_inline unsigned long
radix_tree_find_next_bit(const unsigned long *addr,
unsigned long size, unsigned long offset)
{
if (!__builtin_constant_p(size))
return find_next_bit(addr, size, offset);
if (offset < size) {
unsigned long tmp;
addr += offset / BITS_PER_LONG;
tmp = *addr >> (offset % BITS_PER_LONG);
if (tmp)
return __ffs(tmp) + offset;
offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
while (offset < size) {
tmp = *++addr;
if (tmp)
return __ffs(tmp) + offset;
offset += BITS_PER_LONG;
}
}
return size;
}
/*
* This assumes that the caller has performed appropriate preallocation, and
* that the caller has pinned this thread of control to the current CPU.
*/
static struct radix_tree_node *
radix_tree_node_alloc(struct radix_tree_root *root)
{
struct radix_tree_node *ret = NULL;
gfp_t gfp_mask = root_gfp_mask(root);
/*
* Preload code isn't irq safe and it doesn't make sence to use
* preloading in the interrupt anyway as all the allocations have to
* be atomic. So just do normal allocation when in interrupt.
*/
if (!(gfp_mask & __GFP_WAIT) && !in_interrupt()) {
struct radix_tree_preload *rtp;
/*
* Provided the caller has preloaded here, we will always
* succeed in getting a node here (and never reach
* kmem_cache_alloc)
*/
rtp = &__get_cpu_var(radix_tree_preloads);
if (rtp->nr) {
ret = rtp->nodes[rtp->nr - 1];
rtp->nodes[rtp->nr - 1] = NULL;
rtp->nr--;
}
}
if (ret == NULL)
ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
BUG_ON(radix_tree_is_indirect_ptr(ret));
return ret;
}
static void radix_tree_node_rcu_free(struct rcu_head *head)
{
struct radix_tree_node *node =
container_of(head, struct radix_tree_node, rcu_head);
int i;
/*
* must only free zeroed nodes into the slab. radix_tree_shrink
* can leave us with a non-NULL entry in the first slot, so clear
* that here to make sure.
*/
for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
tag_clear(node, i, 0);
node->slots[0] = NULL;
node->count = 0;
kmem_cache_free(radix_tree_node_cachep, node);
}
static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
}
/*
* Load up this CPU's radix_tree_node buffer with sufficient objects to
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
*
* To make use of this facility, the radix tree must be initialised without
* __GFP_WAIT being passed to INIT_RADIX_TREE().
*/
static int __radix_tree_preload(gfp_t gfp_mask)
{
struct radix_tree_preload *rtp;
struct radix_tree_node *node;
int ret = -ENOMEM;
preempt_disable();
rtp = &__get_cpu_var(radix_tree_preloads);
while (rtp->nr < ARRAY_SIZE(rtp->nodes)) {
preempt_enable();
node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
if (node == NULL)
goto out;
preempt_disable();
rtp = &__get_cpu_var(radix_tree_preloads);
if (rtp->nr < ARRAY_SIZE(rtp->nodes))
rtp->nodes[rtp->nr++] = node;
else
kmem_cache_free(radix_tree_node_cachep, node);
}
ret = 0;
out:
return ret;
}
/*
* Load up this CPU's radix_tree_node buffer with sufficient objects to
* ensure that the addition of a single element in the tree cannot fail. On
* success, return zero, with preemption disabled. On error, return -ENOMEM
* with preemption not disabled.
*
* To make use of this facility, the radix tree must be initialised without
* __GFP_WAIT being passed to INIT_RADIX_TREE().
*/
int radix_tree_preload(gfp_t gfp_mask)
{
/* Warn on non-sensical use... */
WARN_ON_ONCE(!(gfp_mask & __GFP_WAIT));
return __radix_tree_preload(gfp_mask);
}
EXPORT_SYMBOL(radix_tree_preload);
/*
* The same as above function, except we don't guarantee preloading happens.
* We do it, if we decide it helps. On success, return zero with preemption
* disabled. On error, return -ENOMEM with preemption not disabled.
*/
int radix_tree_maybe_preload(gfp_t gfp_mask)
{
if (gfp_mask & __GFP_WAIT)
return __radix_tree_preload(gfp_mask);
/* Preloading doesn't help anything with this gfp mask, skip it */
preempt_disable();
return 0;
}
EXPORT_SYMBOL(radix_tree_maybe_preload);
/*
* Return the maximum key which can be store into a
* radix tree with height HEIGHT.
*/
static inline unsigned long radix_tree_maxindex(unsigned int height)
{
return height_to_maxindex[height];
}
/*
* Extend a radix tree so it can store key @index.
*/
static int radix_tree_extend(struct radix_tree_root *root, unsigned long index)
{
struct radix_tree_node *node;
struct radix_tree_node *slot;
unsigned int height;
int tag;
/* Figure out what the height should be. */
height = root->height + 1;
while (index > radix_tree_maxindex(height))
height++;
if (root->rnode == NULL) {
root->height = height;
goto out;
}
do {
unsigned int newheight;
if (!(node = radix_tree_node_alloc(root)))
return -ENOMEM;
/* Propagate the aggregated tag info into the new root */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (root_tag_get(root, tag))
tag_set(node, tag, 0);
}
/* Increase the height. */
newheight = root->height+1;
node->height = newheight;
node->count = 1;
node->parent = NULL;
slot = root->rnode;
if (newheight > 1) {
slot = indirect_to_ptr(slot);
slot->parent = node;
}
node->slots[0] = slot;
node = ptr_to_indirect(node);
rcu_assign_pointer(root->rnode, node);
root->height = newheight;
} while (height > root->height);
out:
return 0;
}
/**
* radix_tree_insert - insert into a radix tree
* @root: radix tree root
* @index: index key
* @item: item to insert
*
* Insert an item into the radix tree at position @index.
*/
int radix_tree_insert(struct radix_tree_root *root,
unsigned long index, void *item)
{
struct radix_tree_node *node = NULL, *slot;
unsigned int height, shift;
int offset;
int error;
BUG_ON(radix_tree_is_indirect_ptr(item));
/* Make sure the tree is high enough. */
if (index > radix_tree_maxindex(root->height)) {
error = radix_tree_extend(root, index);
if (error)
return error;
}
slot = indirect_to_ptr(root->rnode);
height = root->height;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
offset = 0; /* uninitialised var warning */
while (height > 0) {
if (slot == NULL) {
/* Have to add a child node. */
if (!(slot = radix_tree_node_alloc(root)))
return -ENOMEM;
slot->height = height;
slot->parent = node;
if (node) {
rcu_assign_pointer(node->slots[offset], slot);
node->count++;
} else
rcu_assign_pointer(root->rnode, ptr_to_indirect(slot));
}
/* Go a level down */
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
node = slot;
slot = node->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
if (slot != NULL)
return -EEXIST;
if (node) {
node->count++;
rcu_assign_pointer(node->slots[offset], item);
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
} else {
rcu_assign_pointer(root->rnode, item);
BUG_ON(root_tag_get(root, 0));
BUG_ON(root_tag_get(root, 1));
}
return 0;
}
EXPORT_SYMBOL(radix_tree_insert);
/*
* is_slot == 1 : search for the slot.
* is_slot == 0 : search for the node.
*/
static void *radix_tree_lookup_element(struct radix_tree_root *root,
unsigned long index, int is_slot)
{
unsigned int height, shift;
struct radix_tree_node *node, **slot;
node = rcu_dereference_raw(root->rnode);
if (node == NULL)
return NULL;
if (!radix_tree_is_indirect_ptr(node)) {
if (index > 0)
return NULL;
return is_slot ? (void *)&root->rnode : node;
}
node = indirect_to_ptr(node);
height = node->height;
if (index > radix_tree_maxindex(height))
return NULL;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
do {
slot = (struct radix_tree_node **)
(node->slots + ((index>>shift) & RADIX_TREE_MAP_MASK));
node = rcu_dereference_raw(*slot);
if (node == NULL)
return NULL;
shift -= RADIX_TREE_MAP_SHIFT;
height--;
} while (height > 0);
return is_slot ? (void *)slot : indirect_to_ptr(node);
}
/**
* radix_tree_lookup_slot - lookup a slot in a radix tree
* @root: radix tree root
* @index: index key
*
* Returns: the slot corresponding to the position @index in the
* radix tree @root. This is useful for update-if-exists operations.
*
* This function can be called under rcu_read_lock iff the slot is not
* modified by radix_tree_replace_slot, otherwise it must be called
* exclusive from other writers. Any dereference of the slot must be done
* using radix_tree_deref_slot.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
return (void **)radix_tree_lookup_element(root, index, 1);
}
EXPORT_SYMBOL(radix_tree_lookup_slot);
/**
* radix_tree_lookup - perform lookup operation on a radix tree
* @root: radix tree root
* @index: index key
*
* Lookup the item at the position @index in the radix tree @root.
*
* This function can be called under rcu_read_lock, however the caller
* must manage lifetimes of leaf nodes (eg. RCU may also be used to free
* them safely). No RCU barriers are required to access or modify the
* returned item, however.
*/
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
return radix_tree_lookup_element(root, index, 0);
}
EXPORT_SYMBOL(radix_tree_lookup);
/**
* radix_tree_tag_set - set a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. From
* the root all the way down to the leaf node.
*
* Returns the address of the tagged item. Setting a tag on a not-present
* item is a bug.
*/
void *radix_tree_tag_set(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
unsigned int height, shift;
struct radix_tree_node *slot;
height = root->height;
BUG_ON(index > radix_tree_maxindex(height));
slot = indirect_to_ptr(root->rnode);
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
while (height > 0) {
int offset;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
if (!tag_get(slot, tag, offset))
tag_set(slot, tag, offset);
slot = slot->slots[offset];
BUG_ON(slot == NULL);
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
/* set the root's tag bit */
if (slot && !root_tag_get(root, tag))
root_tag_set(root, tag);
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_set);
/**
* radix_tree_tag_clear - clear a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index
*
* Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
* corresponding to @index in the radix tree. If
* this causes the leaf node to have no tags set then clear the tag in the
* next-to-leaf node, etc.
*
* Returns the address of the tagged item on success, else NULL. ie:
* has the same return value and semantics as radix_tree_lookup().
*/
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
struct radix_tree_node *node = NULL;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
int uninitialized_var(offset);
height = root->height;
if (index > radix_tree_maxindex(height))
goto out;
shift = height * RADIX_TREE_MAP_SHIFT;
slot = indirect_to_ptr(root->rnode);
while (shift) {
if (slot == NULL)
goto out;
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
node = slot;
slot = slot->slots[offset];
}
if (slot == NULL)
goto out;
while (node) {
if (!tag_get(node, tag, offset))
goto out;
tag_clear(node, tag, offset);
if (any_tag_set(node, tag))
goto out;
index >>= RADIX_TREE_MAP_SHIFT;
offset = index & RADIX_TREE_MAP_MASK;
node = node->parent;
}
/* clear the root's tag bit */
if (root_tag_get(root, tag))
root_tag_clear(root, tag);
out:
return slot;
}
EXPORT_SYMBOL(radix_tree_tag_clear);
/**
* radix_tree_tag_get - get a tag on a radix tree node
* @root: radix tree root
* @index: index key
* @tag: tag index (< RADIX_TREE_MAX_TAGS)
*
* Return values:
*
* 0: tag not present or not set
* 1: tag set
*
* Note that the return value of this function may not be relied on, even if
* the RCU lock is held, unless tag modification and node deletion are excluded
* from concurrency.
*/
int radix_tree_tag_get(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
unsigned int height, shift;
struct radix_tree_node *node;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
node = rcu_dereference_raw(root->rnode);
if (node == NULL)
return 0;
if (!radix_tree_is_indirect_ptr(node))
return (index == 0);
node = indirect_to_ptr(node);
height = node->height;
if (index > radix_tree_maxindex(height))
return 0;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
for ( ; ; ) {
int offset;
if (node == NULL)
return 0;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
if (!tag_get(node, tag, offset))
return 0;
if (height == 1)
return 1;
node = rcu_dereference_raw(node->slots[offset]);
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
}
EXPORT_SYMBOL(radix_tree_tag_get);
/**
* radix_tree_next_chunk - find next chunk of slots for iteration
*
* @root: radix tree root
* @iter: iterator state
* @flags: RADIX_TREE_ITER_* flags and tag index
* Returns: pointer to chunk first slot, or NULL if iteration is over
*/
void **radix_tree_next_chunk(struct radix_tree_root *root,
struct radix_tree_iter *iter, unsigned flags)
{
unsigned shift, tag = flags & RADIX_TREE_ITER_TAG_MASK;
struct radix_tree_node *rnode, *node;
unsigned long index, offset;
if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
return NULL;
/*
* Catch next_index overflow after ~0UL. iter->index never overflows
* during iterating; it can be zero only at the beginning.
* And we cannot overflow iter->next_index in a single step,
* because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
*
* This condition also used by radix_tree_next_slot() to stop
* contiguous iterating, and forbid swithing to the next chunk.
*/
index = iter->next_index;
if (!index && iter->index)
return NULL;
rnode = rcu_dereference_raw(root->rnode);
if (radix_tree_is_indirect_ptr(rnode)) {
rnode = indirect_to_ptr(rnode);
} else if (rnode && !index) {
/* Single-slot tree */
iter->index = 0;
iter->next_index = 1;
iter->tags = 1;
return (void **)&root->rnode;
} else
return NULL;
restart:
shift = (rnode->height - 1) * RADIX_TREE_MAP_SHIFT;
offset = index >> shift;
/* Index outside of the tree */
if (offset >= RADIX_TREE_MAP_SIZE)
return NULL;
node = rnode;
while (1) {
if ((flags & RADIX_TREE_ITER_TAGGED) ?
!test_bit(offset, node->tags[tag]) :
!node->slots[offset]) {
/* Hole detected */
if (flags & RADIX_TREE_ITER_CONTIG)
return NULL;
if (flags & RADIX_TREE_ITER_TAGGED)
offset = radix_tree_find_next_bit(
node->tags[tag],
RADIX_TREE_MAP_SIZE,
offset + 1);
else
while (++offset < RADIX_TREE_MAP_SIZE) {
if (node->slots[offset])
break;
}
index &= ~((RADIX_TREE_MAP_SIZE << shift) - 1);
index += offset << shift;
/* Overflow after ~0UL */
if (!index)
return NULL;
if (offset == RADIX_TREE_MAP_SIZE)
goto restart;
}
/* This is leaf-node */
if (!shift)
break;
node = rcu_dereference_raw(node->slots[offset]);
if (node == NULL)
goto restart;
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
}
/* Update the iterator state */
iter->index = index;
iter->next_index = (index | RADIX_TREE_MAP_MASK) + 1;
/* Construct iter->tags bit-mask from node->tags[tag] array */
if (flags & RADIX_TREE_ITER_TAGGED) {
unsigned tag_long, tag_bit;
tag_long = offset / BITS_PER_LONG;
tag_bit = offset % BITS_PER_LONG;
iter->tags = node->tags[tag][tag_long] >> tag_bit;
/* This never happens if RADIX_TREE_TAG_LONGS == 1 */
if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
/* Pick tags from next element */
if (tag_bit)
iter->tags |= node->tags[tag][tag_long + 1] <<
(BITS_PER_LONG - tag_bit);
/* Clip chunk size, here only BITS_PER_LONG tags */
iter->next_index = index + BITS_PER_LONG;
}
}
return node->slots + offset;
}
EXPORT_SYMBOL(radix_tree_next_chunk);
/**
* radix_tree_range_tag_if_tagged - for each item in given range set given
* tag if item has another tag set
* @root: radix tree root
* @first_indexp: pointer to a starting index of a range to scan
* @last_index: last index of a range to scan
* @nr_to_tag: maximum number items to tag
* @iftag: tag index to test
* @settag: tag index to set if tested tag is set
*
* This function scans range of radix tree from first_index to last_index
* (inclusive). For each item in the range if iftag is set, the function sets
* also settag. The function stops either after tagging nr_to_tag items or
* after reaching last_index.
*
* The tags must be set from the leaf level only and propagated back up the
* path to the root. We must do this so that we resolve the full path before
* setting any tags on intermediate nodes. If we set tags as we descend, then
* we can get to the leaf node and find that the index that has the iftag
* set is outside the range we are scanning. This reults in dangling tags and
* can lead to problems with later tag operations (e.g. livelocks on lookups).
*
* The function returns number of leaves where the tag was set and sets
* *first_indexp to the first unscanned index.
* WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
* be prepared to handle that.
*/
unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
unsigned long *first_indexp, unsigned long last_index,
unsigned long nr_to_tag,
unsigned int iftag, unsigned int settag)
{
unsigned int height = root->height;
struct radix_tree_node *node = NULL;
struct radix_tree_node *slot;
unsigned int shift;
unsigned long tagged = 0;
unsigned long index = *first_indexp;
last_index = min(last_index, radix_tree_maxindex(height));
if (index > last_index)
return 0;
if (!nr_to_tag)
return 0;
if (!root_tag_get(root, iftag)) {
*first_indexp = last_index + 1;
return 0;
}
if (height == 0) {
*first_indexp = last_index + 1;
root_tag_set(root, settag);
return 1;
}
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = indirect_to_ptr(root->rnode);
for (;;) {
unsigned long upindex;
int offset;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
if (!slot->slots[offset])
goto next;
if (!tag_get(slot, iftag, offset))
goto next;
if (shift) {
/* Go down one level */
shift -= RADIX_TREE_MAP_SHIFT;
node = slot;
slot = slot->slots[offset];
continue;
}
/* tag the leaf */
tagged++;
tag_set(slot, settag, offset);
/* walk back up the path tagging interior nodes */
upindex = index;
while (node) {
upindex >>= RADIX_TREE_MAP_SHIFT;
offset = upindex & RADIX_TREE_MAP_MASK;
/* stop if we find a node with the tag already set */
if (tag_get(node, settag, offset))
break;
tag_set(node, settag, offset);
node = node->parent;
}
/*
* Small optimization: now clear that node pointer.
* Since all of this slot's ancestors now have the tag set
* from setting it above, we have no further need to walk
* back up the tree setting tags, until we update slot to
* point to another radix_tree_node.
*/
node = NULL;
next:
/* Go to next item at level determined by 'shift' */
index = ((index >> shift) + 1) << shift;
/* Overflow can happen when last_index is ~0UL... */
if (index > last_index || !index)
break;
if (tagged >= nr_to_tag)
break;
while (((index >> shift) & RADIX_TREE_MAP_MASK) == 0) {
/*
* We've fully scanned this node. Go up. Because
* last_index is guaranteed to be in the tree, what
* we do below cannot wander astray.
*/
slot = slot->parent;
shift += RADIX_TREE_MAP_SHIFT;
}
}
/*
* We need not to tag the root tag if there is no tag which is set with
* settag within the range from *first_indexp to last_index.
*/
if (tagged > 0)
root_tag_set(root, settag);
*first_indexp = index;
return tagged;
}
EXPORT_SYMBOL(radix_tree_range_tag_if_tagged);
/**
* radix_tree_next_hole - find the next hole (not-present entry)
* @root: tree root
* @index: index key
* @max_scan: maximum range to search
*
* Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the lowest
* indexed hole.
*
* Returns: the index of the hole if found, otherwise returns an index
* outside of the set specified (in which case 'return - index >= max_scan'
* will be true). In rare cases of index wrap-around, 0 will be returned.
*
* radix_tree_next_hole may be called under rcu_read_lock. However, like
* radix_tree_gang_lookup, this will not atomically search a snapshot of
* the tree at a single point in time. For example, if a hole is created
* at index 5, then subsequently a hole is created at index 10,
* radix_tree_next_hole covering both indexes may return 10 if called
* under rcu_read_lock.
*/
unsigned long radix_tree_next_hole(struct radix_tree_root *root,
unsigned long index, unsigned long max_scan)
{
unsigned long i;
for (i = 0; i < max_scan; i++) {
if (!radix_tree_lookup(root, index))
break;
index++;
if (index == 0)
break;
}
return index;
}
EXPORT_SYMBOL(radix_tree_next_hole);
/**
* radix_tree_prev_hole - find the prev hole (not-present entry)
* @root: tree root
* @index: index key
* @max_scan: maximum range to search
*
* Search backwards in the range [max(index-max_scan+1, 0), index]
* for the first hole.
*
* Returns: the index of the hole if found, otherwise returns an index
* outside of the set specified (in which case 'index - return >= max_scan'
* will be true). In rare cases of wrap-around, ULONG_MAX will be returned.
*
* radix_tree_next_hole may be called under rcu_read_lock. However, like
* radix_tree_gang_lookup, this will not atomically search a snapshot of
* the tree at a single point in time. For example, if a hole is created
* at index 10, then subsequently a hole is created at index 5,
* radix_tree_prev_hole covering both indexes may return 5 if called under
* rcu_read_lock.
*/
unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
unsigned long index, unsigned long max_scan)
{
unsigned long i;
for (i = 0; i < max_scan; i++) {
if (!radix_tree_lookup(root, index))
break;
index--;
if (index == ULONG_MAX)
break;
}
return index;
}
EXPORT_SYMBOL(radix_tree_prev_hole);
/**
* radix_tree_gang_lookup - perform multiple lookup on a radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
*
* Performs an index-ascending scan of the tree for present items. Places
* them at *@results and returns the number of items which were placed at
* *@results.
*
* The implementation is naive.
*
* Like radix_tree_lookup, radix_tree_gang_lookup may be called under
* rcu_read_lock. In this case, rather than the returned results being
* an atomic snapshot of the tree at a single point in time, the semantics
* of an RCU protected gang lookup are as though multiple radix_tree_lookups
* have been issued in individual locks, and results stored in 'results'.
*/
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_slot(slot, root, &iter, first_index) {
results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
if (!results[ret])
continue;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup);
/**
* radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
* @root: radix tree root
* @results: where the results of the lookup are placed
* @indices: where their indices should be placed (but usually NULL)
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
*
* Performs an index-ascending scan of the tree for present items. Places
* their slots at *@results and returns the number of items which were
* placed at *@results.
*
* The implementation is naive.
*
* Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
* be dereferenced with radix_tree_deref_slot, and if using only RCU
* protection, radix_tree_deref_slot may fail requiring a retry.
*/
unsigned int
radix_tree_gang_lookup_slot(struct radix_tree_root *root,
void ***results, unsigned long *indices,
unsigned long first_index, unsigned int max_items)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_slot(slot, root, &iter, first_index) {
results[ret] = slot;
if (indices)
indices[ret] = iter.index;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
/**
* radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
* based on a tag
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
* @tag: the tag index (< RADIX_TREE_MAX_TAGS)
*
* Performs an index-ascending scan of the tree for present items which
* have the tag indexed by @tag set. Places the items at *@results and
* returns the number of items which were placed at *@results.
*/
unsigned int
radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items,
unsigned int tag)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
results[ret] = indirect_to_ptr(rcu_dereference_raw(*slot));
if (!results[ret])
continue;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
/**
* radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
* radix tree based on a tag
* @root: radix tree root
* @results: where the results of the lookup are placed
* @first_index: start the lookup from this key
* @max_items: place up to this many items at *results
* @tag: the tag index (< RADIX_TREE_MAX_TAGS)
*
* Performs an index-ascending scan of the tree for present items which
* have the tag indexed by @tag set. Places the slots at *@results and
* returns the number of slots which were placed at *@results.
*/
unsigned int
radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
unsigned long first_index, unsigned int max_items,
unsigned int tag)
{
struct radix_tree_iter iter;
void **slot;
unsigned int ret = 0;
if (unlikely(!max_items))
return 0;
radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
results[ret] = slot;
if (++ret == max_items)
break;
}
return ret;
}
EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
#include <linux/sched.h> /* for cond_resched() */
/*
* This linear search is at present only useful to shmem_unuse_inode().
*/
static unsigned long __locate(struct radix_tree_node *slot, void *item,
unsigned long index, unsigned long *found_index)
{
unsigned int shift, height;
unsigned long i;
height = slot->height;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
for ( ; height > 1; height--) {
i = (index >> shift) & RADIX_TREE_MAP_MASK;
for (;;) {
if (slot->slots[i] != NULL)
break;
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
i++;
if (i == RADIX_TREE_MAP_SIZE)
goto out;
}
shift -= RADIX_TREE_MAP_SHIFT;
slot = rcu_dereference_raw(slot->slots[i]);
if (slot == NULL)
goto out;
}
/* Bottom level: check items */
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
if (slot->slots[i] == item) {
*found_index = index + i;
index = 0;
goto out;
}
}
index += RADIX_TREE_MAP_SIZE;
out:
return index;
}
/**
* radix_tree_locate_item - search through radix tree for item
* @root: radix tree root
* @item: item to be found
*
* Returns index where item was found, or -1 if not found.
* Caller must hold no lock (since this time-consuming function needs
* to be preemptible), and must check afterwards if item is still there.
*/
unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
{
struct radix_tree_node *node;
unsigned long max_index;
unsigned long cur_index = 0;
unsigned long found_index = -1;
do {
rcu_read_lock();
node = rcu_dereference_raw(root->rnode);
if (!radix_tree_is_indirect_ptr(node)) {
rcu_read_unlock();
if (node == item)
found_index = 0;
break;
}
node = indirect_to_ptr(node);
max_index = radix_tree_maxindex(node->height);
if (cur_index > max_index) {
rcu_read_unlock();
break;
}
cur_index = __locate(node, item, cur_index, &found_index);
rcu_read_unlock();
cond_resched();
} while (cur_index != 0 && cur_index <= max_index);
return found_index;
}
#else
unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
{
return -1;
}
#endif /* CONFIG_SHMEM && CONFIG_SWAP */
/**
* radix_tree_shrink - shrink height of a radix tree to minimal
* @root radix tree root
*/
static inline void radix_tree_shrink(struct radix_tree_root *root)
{
/* try to shrink tree height */
while (root->height > 0) {
struct radix_tree_node *to_free = root->rnode;
struct radix_tree_node *slot;
BUG_ON(!radix_tree_is_indirect_ptr(to_free));
to_free = indirect_to_ptr(to_free);
/*
* The candidate node has more than one child, or its child
* is not at the leftmost slot, we cannot shrink.
*/
if (to_free->count != 1)
break;
if (!to_free->slots[0])
break;
/*
* We don't need rcu_assign_pointer(), since we are simply
* moving the node from one part of the tree to another: if it
* was safe to dereference the old pointer to it
* (to_free->slots[0]), it will be safe to dereference the new
* one (root->rnode) as far as dependent read barriers go.
*/
slot = to_free->slots[0];
if (root->height > 1) {
slot->parent = NULL;
slot = ptr_to_indirect(slot);
}
root->rnode = slot;
root->height--;
/*
* We have a dilemma here. The node's slot[0] must not be
* NULLed in case there are concurrent lookups expecting to
* find the item. However if this was a bottom-level node,
* then it may be subject to the slot pointer being visible
* to callers dereferencing it. If item corresponding to
* slot[0] is subsequently deleted, these callers would expect
* their slot to become empty sooner or later.
*
* For example, lockless pagecache will look up a slot, deref
* the page pointer, and if the page is 0 refcount it means it
* was concurrently deleted from pagecache so try the deref
* again. Fortunately there is already a requirement for logic
* to retry the entire slot lookup -- the indirect pointer
* problem (replacing direct root node with an indirect pointer
* also results in a stale slot). So tag the slot as indirect
* to force callers to retry.
*/
if (root->height == 0)
*((unsigned long *)&to_free->slots[0]) |=
RADIX_TREE_INDIRECT_PTR;
radix_tree_node_free(to_free);
}
}
/**
* radix_tree_delete - delete an item from a radix tree
* @root: radix tree root
* @index: index key
*
* Remove the item at @index from the radix tree rooted at @root.
*
* Returns the address of the deleted item, or NULL if it was not present.
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
struct radix_tree_node *node = NULL;
struct radix_tree_node *slot = NULL;
struct radix_tree_node *to_free;
unsigned int height, shift;
int tag;
int uninitialized_var(offset);
height = root->height;
if (index > radix_tree_maxindex(height))
goto out;
slot = root->rnode;
if (height == 0) {
root_tag_clear_all(root);
root->rnode = NULL;
goto out;
}
slot = indirect_to_ptr(slot);
shift = height * RADIX_TREE_MAP_SHIFT;
do {
if (slot == NULL)
goto out;
shift -= RADIX_TREE_MAP_SHIFT;
offset = (index >> shift) & RADIX_TREE_MAP_MASK;
node = slot;
slot = slot->slots[offset];
} while (shift);
if (slot == NULL)
goto out;
/*
* Clear all tags associated with the item to be deleted.
* This way of doing it would be inefficient, but seldom is any set.
*/
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (tag_get(node, tag, offset))
radix_tree_tag_clear(root, index, tag);
}
to_free = NULL;
/* Now free the nodes we do not need anymore */
while (node) {
node->slots[offset] = NULL;
node->count--;
/*
* Queue the node for deferred freeing after the
* last reference to it disappears (set NULL, above).
*/
if (to_free)
radix_tree_node_free(to_free);
if (node->count) {
if (node == indirect_to_ptr(root->rnode))
radix_tree_shrink(root);
goto out;
}
/* Node with zero slots in use so free it */
to_free = node;
index >>= RADIX_TREE_MAP_SHIFT;
offset = index & RADIX_TREE_MAP_MASK;
node = node->parent;
}
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
if (to_free)
radix_tree_node_free(to_free);
out:
return slot;
}
EXPORT_SYMBOL(radix_tree_delete);
/**
* radix_tree_tagged - test whether any items in the tree are tagged
* @root: radix tree root
* @tag: tag to test
*/
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
{
return root_tag_get(root, tag);
}
EXPORT_SYMBOL(radix_tree_tagged);
static void
radix_tree_node_ctor(void *node)
{
memset(node, 0, sizeof(struct radix_tree_node));
}
static __init unsigned long __maxindex(unsigned int height)
{
unsigned int width = height * RADIX_TREE_MAP_SHIFT;
int shift = RADIX_TREE_INDEX_BITS - width;
if (shift < 0)
return ~0UL;
if (shift >= BITS_PER_LONG)
return 0UL;
return ~0UL >> shift;
}
static __init void radix_tree_init_maxindex(void)
{
unsigned int i;
for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
height_to_maxindex[i] = __maxindex(i);
}
static int radix_tree_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
int cpu = (long)hcpu;
struct radix_tree_preload *rtp;
/* Free per-cpu pool of perloaded nodes */
if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
rtp = &per_cpu(radix_tree_preloads, cpu);
while (rtp->nr) {
kmem_cache_free(radix_tree_node_cachep,
rtp->nodes[rtp->nr-1]);
rtp->nodes[rtp->nr-1] = NULL;
rtp->nr--;
}
}
return NOTIFY_OK;
}
void __init radix_tree_init(void)
{
radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
sizeof(struct radix_tree_node), 0,
SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
radix_tree_node_ctor);
radix_tree_init_maxindex();
hotcpu_notifier(radix_tree_callback, 0);
}