linux/fs/btrfs/radix-tree.c
Chris Mason eb60ceac0e Btrfs: Add backing store, memory management
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2007-02-02 09:18:22 -05:00

836 lines
20 KiB
C

/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
* Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
*
* 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 "kerncompat.h"
#include "radix-tree.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 count;
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 (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
/*
* Per-cpu pool of preloaded nodes
*/
struct radix_tree_preload {
int nr;
struct radix_tree_node *nodes[RADIX_TREE_MAX_PATH];
};
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;
}
static int internal_nodes = 0;
/*
* 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;
ret = malloc(sizeof(struct radix_tree_node));
if (ret) {
memset(ret, 0, sizeof(struct radix_tree_node));
internal_nodes++;
}
return ret;
}
static inline void
radix_tree_node_free(struct radix_tree_node *node)
{
internal_nodes--;
free(node);
}
/*
* 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 = radix_tree_node_alloc(NULL);
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
radix_tree_node_free(node);
}
ret = 0;
out:
return ret;
}
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 {
if (!(node = radix_tree_node_alloc(root)))
return -ENOMEM;
/* Increase the height. */
node->slots[0] = 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);
}
node->count = 1;
root->rnode = node;
root->height++;
} 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;
/* 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 = 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;
if (node) {
node->slots[offset] = slot;
node->count++;
} else
root->rnode = 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++;
node->slots[offset] = item;
BUG_ON(tag_get(node, 0, offset));
BUG_ON(tag_get(node, 1, offset));
} else {
root->rnode = item;
BUG_ON(root_tag_get(root, 0));
BUG_ON(root_tag_get(root, 1));
}
return 0;
}
static inline void **__lookup_slot(struct radix_tree_root *root,
unsigned long index)
{
unsigned int height, shift;
struct radix_tree_node **slot;
height = root->height;
if (index > radix_tree_maxindex(height))
return NULL;
if (height == 0 && root->rnode)
return (void **)&root->rnode;
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
slot = &root->rnode;
while (height > 0) {
if (*slot == NULL)
return NULL;
slot = (struct radix_tree_node **)
((*slot)->slots +
((index >> shift) & RADIX_TREE_MAP_MASK));
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
return (void **)slot;
}
/**
* radix_tree_lookup_slot - lookup a slot in a radix tree
* @root: radix tree root
* @index: index key
*
* Lookup the slot corresponding to the position @index in the radix tree
* @root. This is useful for update-if-exists operations.
*/
void **radix_tree_lookup_slot(struct radix_tree_root *root, unsigned long index)
{
return __lookup_slot(root, index);
}
/**
* 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.
*/
void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
{
void **slot;
slot = __lookup_slot(root, index);
return slot != NULL ? *slot : NULL;
}
/**
* 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 = 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;
}
/**
* 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_path path[RADIX_TREE_MAX_PATH], *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 = 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;
}
#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 *slot;
int saw_unset_tag = 0;
height = root->height;
if (index > radix_tree_maxindex(height))
return 0;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 0;
if (height == 0)
return 1;
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
for ( ; ; ) {
int offset;
if (slot == 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(slot, tag, offset))
saw_unset_tag = 1;
if (height == 1) {
int ret = tag_get(slot, tag, offset);
BUG_ON(ret && saw_unset_tag);
return !!ret;
}
slot = slot->slots[offset];
shift -= RADIX_TREE_MAP_SHIFT;
height--;
}
}
#endif
static unsigned int
__lookup(struct radix_tree_root *root, void **results, unsigned long index,
unsigned int max_items, unsigned long *next_index)
{
unsigned int nr_found = 0;
unsigned int shift, height;
struct radix_tree_node *slot;
unsigned long i;
height = root->height;
if (height == 0) {
if (root->rnode && index == 0)
results[nr_found++] = root->rnode;
goto out;
}
shift = (height-1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
for ( ; height > 1; height--) {
for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
i < RADIX_TREE_MAP_SIZE; i++) {
if (slot->slots[i] != NULL)
break;
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
}
if (i == RADIX_TREE_MAP_SIZE)
goto out;
shift -= RADIX_TREE_MAP_SHIFT;
slot = slot->slots[i];
}
/* Bottom level: grab some items */
for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
index++;
if (slot->slots[i]) {
results[nr_found++] = slot->slots[i];
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.
*/
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items)
{
const unsigned long max_index = radix_tree_maxindex(root->height);
unsigned long cur_index = first_index;
unsigned int 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(root, results + ret, cur_index,
max_items - ret, &next_index);
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
return ret;
}
/*
* 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_root *root, void **results, unsigned long index,
unsigned int max_items, unsigned long *next_index, unsigned int tag)
{
unsigned int nr_found = 0;
unsigned int shift;
unsigned int height = root->height;
struct radix_tree_node *slot;
if (height == 0) {
if (root->rnode && index == 0)
results[nr_found++] = root->rnode;
goto out;
}
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = root->rnode;
do {
unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
if (tag_get(slot, tag, i)) {
BUG_ON(slot->slots[i] == NULL);
break;
}
index &= ~((1UL << shift) - 1);
index += 1UL << shift;
if (index == 0)
goto out; /* 32-bit wraparound */
}
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++) {
index++;
if (tag_get(slot, tag, j)) {
BUG_ON(slot->slots[j] == NULL);
results[nr_found++] = slot->slots[j];
if (nr_found == max_items)
goto out;
}
}
}
shift -= RADIX_TREE_MAP_SHIFT;
slot = slot->slots[i];
} while (height > 0);
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)
{
const unsigned long max_index = radix_tree_maxindex(root->height);
unsigned long cur_index = first_index;
unsigned int ret = 0;
/* check the root's tag bit */
if (!root_tag_get(root, tag))
return 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(root, results + ret, cur_index,
max_items - ret, &next_index, tag);
ret += nr_found;
if (next_index == 0)
break;
cur_index = next_index;
}
return ret;
}
/**
* 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 &&
root->rnode->count == 1 &&
root->rnode->slots[0]) {
struct radix_tree_node *to_free = root->rnode;
root->rnode = to_free->slots[0];
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)
{
struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
struct radix_tree_node *slot = NULL;
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->rnode) {
root_tag_clear_all(root);
root->rnode = NULL;
goto out;
}
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);
}
/* Now free the nodes we do not need anymore */
while (pathp->node) {
pathp->node->slots[pathp->offset] = NULL;
pathp->node->count--;
if (pathp->node->count) {
if (pathp->node == root->rnode)
radix_tree_shrink(root);
goto out;
}
/* Node with zero slots in use so free it */
radix_tree_node_free(pathp->node);
pathp--;
}
root_tag_clear_all(root);
root->height = 0;
root->rnode = NULL;
out:
return slot;
}
/**
* 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);
}
static unsigned long __maxindex(unsigned int height)
{
unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
if (tmp >= RADIX_TREE_INDEX_BITS)
index = ~0UL;
return index;
}
static 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);
}
void radix_tree_init(void)
{
radix_tree_init_maxindex();
}