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radixtree.c
1717 lines (1555 loc) · 46.2 KB
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radixtree.c
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/* $NetBSD: radixtree.c,v 1.23 2020/01/28 22:20:45 ad Exp $ */
/*-
* Copyright (c)2011,2012,2013 YAMAMOTO Takashi,
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* radixtree.c
*
* Overview:
*
* This is an implementation of radix tree, whose keys are uint64_t and leafs
* are user provided pointers.
*
* Leaf nodes are just void * and this implementation doesn't care about
* what they actually point to. However, this implementation has an assumption
* about their alignment. Specifically, this implementation assumes that their
* 2 LSBs are always zero and uses them for internal accounting.
*
* Intermediate nodes and memory allocation:
*
* Intermediate nodes are automatically allocated and freed internally and
* basically users don't need to care about them. The allocation is done via
* pool_cache_get(9) for _KERNEL, malloc(3) for userland, and alloc() for
* _STANDALONE environment. Only radix_tree_insert_node function can allocate
* memory for intermediate nodes and thus can fail for ENOMEM.
*
* Memory Efficiency:
*
* It's designed to work efficiently with dense index distribution.
* The memory consumption (number of necessary intermediate nodes) heavily
* depends on the index distribution. Basically, more dense index distribution
* consumes less nodes per item. Approximately,
*
* - the best case: about RADIX_TREE_PTR_PER_NODE items per intermediate node.
* it would look like the following.
*
* root (t_height=1)
* |
* v
* [ | | | ] (intermediate node. RADIX_TREE_PTR_PER_NODE=4 in this fig)
* | | | |
* v v v v
* p p p p (items)
*
* - the worst case: RADIX_TREE_MAX_HEIGHT intermediate nodes per item.
* it would look like the following if RADIX_TREE_MAX_HEIGHT=3.
*
* root (t_height=3)
* |
* v
* [ | | | ]
* |
* v
* [ | | | ]
* |
* v
* [ | | | ]
* |
* v
* p
*
* The height of tree (t_height) is dynamic. It's smaller if only small
* index values are used. As an extreme case, if only index 0 is used,
* the corresponding value is directly stored in the root of the tree
* (struct radix_tree) without allocating any intermediate nodes. In that
* case, t_height=0.
*
* Gang lookup:
*
* This implementation provides a way to scan many nodes quickly via
* radix_tree_gang_lookup_node function and its varients.
*
* Tags:
*
* This implementation provides tagging functionality, which allows quick
* scanning of a subset of leaf nodes. Leaf nodes are untagged when inserted
* into the tree and can be tagged by radix_tree_set_tag function.
* radix_tree_gang_lookup_tagged_node function and its variants returns only
* leaf nodes with the given tag. To reduce amount of nodes to visit for
* these functions, this implementation keeps tagging information in internal
* intermediate nodes and quickly skips uninterested parts of a tree.
*
* A tree has RADIX_TREE_TAG_ID_MAX independent tag spaces, each of which are
* identified by an zero-origin numbers, tagid. For the current implementation,
* RADIX_TREE_TAG_ID_MAX is 2. A set of tags is described as a bitmask tagmask,
* which is a bitwise OR of (1 << tagid).
*/
#include <sys/cdefs.h>
#if defined(_KERNEL) || defined(_STANDALONE)
__KERNEL_RCSID(0, "$NetBSD: radixtree.c,v 1.23 2020/01/28 22:20:45 ad Exp $");
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/pool.h>
#include <sys/radixtree.h>
#include <lib/libkern/libkern.h>
#if defined(_STANDALONE)
#include <lib/libsa/stand.h>
#endif /* defined(_STANDALONE) */
#else /* defined(_KERNEL) || defined(_STANDALONE) */
__RCSID("$NetBSD: radixtree.c,v 1.23 2020/01/28 22:20:45 ad Exp $");
#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#if 1
#define KASSERT assert
#else
#define KASSERT(a) /* nothing */
#endif
#endif /* defined(_KERNEL) || defined(_STANDALONE) */
#include <sys/radixtree.h>
#define RADIX_TREE_BITS_PER_HEIGHT 4 /* XXX tune */
#define RADIX_TREE_PTR_PER_NODE (1 << RADIX_TREE_BITS_PER_HEIGHT)
#define RADIX_TREE_MAX_HEIGHT (64 / RADIX_TREE_BITS_PER_HEIGHT)
#define RADIX_TREE_INVALID_HEIGHT (RADIX_TREE_MAX_HEIGHT + 1)
__CTASSERT((64 % RADIX_TREE_BITS_PER_HEIGHT) == 0);
__CTASSERT(((1 << RADIX_TREE_TAG_ID_MAX) & (sizeof(int) - 1)) == 0);
#define RADIX_TREE_TAG_MASK ((1 << RADIX_TREE_TAG_ID_MAX) - 1)
static inline void *
entry_ptr(void *p)
{
return (void *)((uintptr_t)p & ~RADIX_TREE_TAG_MASK);
}
static inline unsigned int
entry_tagmask(void *p)
{
return (uintptr_t)p & RADIX_TREE_TAG_MASK;
}
static inline void *
entry_compose(void *p, unsigned int tagmask)
{
return (void *)((uintptr_t)p | tagmask);
}
static inline bool
entry_match_p(void *p, unsigned int tagmask)
{
KASSERT(entry_ptr(p) != NULL || entry_tagmask(p) == 0);
if (p == NULL) {
return false;
}
if (tagmask == 0) {
return true;
}
return (entry_tagmask(p) & tagmask) != 0;
}
/*
* radix_tree_node: an intermediate node
*
* we don't care the type of leaf nodes. they are just void *.
*
* we used to maintain a count of non-NULL nodes in this structure, but it
* prevented it from being aligned to a cache line boundary; the performance
* benefit from being cache friendly is greater than the benefit of having
* a dedicated count value, especially in multi-processor situations where
* we need to avoid intra-pool-page false sharing.
*/
struct radix_tree_node {
void *n_ptrs[RADIX_TREE_PTR_PER_NODE];
};
/*
* any_children_tagmask:
*
* return OR'ed tagmask of the given node's children.
*/
static unsigned int
any_children_tagmask(const struct radix_tree_node *n)
{
unsigned int mask;
int i;
mask = 0;
for (i = 0; i < RADIX_TREE_PTR_PER_NODE; i++) {
mask |= (unsigned int)(uintptr_t)n->n_ptrs[i];
}
return mask & RADIX_TREE_TAG_MASK;
}
/*
* p_refs[0].pptr == &t->t_root
* :
* p_refs[n].pptr == &(*p_refs[n-1])->n_ptrs[x]
* :
* :
* p_refs[t->t_height].pptr == &leaf_pointer
*/
struct radix_tree_path {
struct radix_tree_node_ref {
void **pptr;
} p_refs[RADIX_TREE_MAX_HEIGHT + 1]; /* +1 for the root ptr */
/*
* p_lastidx is either the index of the last valid element of p_refs[]
* or RADIX_TREE_INVALID_HEIGHT.
* RADIX_TREE_INVALID_HEIGHT means that radix_tree_lookup_ptr found
* that the height of the tree is not enough to cover the given index.
*/
unsigned int p_lastidx;
};
static inline void **
path_pptr(const struct radix_tree *t, const struct radix_tree_path *p,
unsigned int height)
{
KASSERT(height <= t->t_height);
return p->p_refs[height].pptr;
}
static inline struct radix_tree_node *
path_node(const struct radix_tree * t, const struct radix_tree_path *p,
unsigned int height)
{
KASSERT(height <= t->t_height);
return entry_ptr(*path_pptr(t, p, height));
}
/*
* radix_tree_init_tree:
*
* Initialize a tree.
*/
void
radix_tree_init_tree(struct radix_tree *t)
{
t->t_height = 0;
t->t_root = NULL;
}
/*
* radix_tree_fini_tree:
*
* Finish using a tree.
*/
void
radix_tree_fini_tree(struct radix_tree *t)
{
KASSERT(t->t_root == NULL);
KASSERT(t->t_height == 0);
}
/*
* radix_tree_empty_tree_p:
*
* Return if the tree is empty.
*/
bool
radix_tree_empty_tree_p(struct radix_tree *t)
{
return t->t_root == NULL;
}
/*
* radix_tree_empty_tree_p:
*
* Return true if the tree has any nodes with the given tag. Otherwise
* return false.
*
* It's illegal to call this function with tagmask 0.
*/
bool
radix_tree_empty_tagged_tree_p(struct radix_tree *t, unsigned int tagmask)
{
KASSERT(tagmask != 0);
return (entry_tagmask(t->t_root) & tagmask) == 0;
}
static void
radix_tree_node_init(struct radix_tree_node *n)
{
memset(n, 0, sizeof(*n));
}
#if defined(_KERNEL)
pool_cache_t radix_tree_node_cache __read_mostly;
static int
radix_tree_node_ctor(void *dummy, void *item, int flags)
{
struct radix_tree_node *n = item;
KASSERT(dummy == NULL);
radix_tree_node_init(n);
return 0;
}
/*
* radix_tree_init:
*
* initialize the subsystem.
*/
void
radix_tree_init(void)
{
radix_tree_node_cache = pool_cache_init(sizeof(struct radix_tree_node),
coherency_unit, 0, PR_LARGECACHE, "radixnode", NULL, IPL_NONE,
radix_tree_node_ctor, NULL, NULL);
KASSERT(radix_tree_node_cache != NULL);
}
/*
* radix_tree_await_memory:
*
* after an insert has failed with ENOMEM, wait for memory to become
* available, so the caller can retry.
*/
void
radix_tree_await_memory(void)
{
struct radix_tree_node *n;
n = pool_cache_get(radix_tree_node_cache, PR_WAITOK);
pool_cache_put(radix_tree_node_cache, n);
}
#endif /* defined(_KERNEL) */
static bool __unused
radix_tree_node_clean_p(const struct radix_tree_node *n)
{
#if RADIX_TREE_PTR_PER_NODE > 16
unsigned int i;
for (i = 0; i < RADIX_TREE_PTR_PER_NODE; i++) {
if (n->n_ptrs[i] != NULL) {
return false;
}
}
return true;
#else /* RADIX_TREE_PTR_PER_NODE > 16 */
uintptr_t sum;
/*
* Unrolling the above is much better than a tight loop with two
* test+branch pairs. On x86 with gcc 5.5.0 this compiles into 19
* deterministic instructions including the "return" and prologue &
* epilogue.
*/
sum = (uintptr_t)n->n_ptrs[0];
sum |= (uintptr_t)n->n_ptrs[1];
sum |= (uintptr_t)n->n_ptrs[2];
sum |= (uintptr_t)n->n_ptrs[3];
#if RADIX_TREE_PTR_PER_NODE > 4
sum |= (uintptr_t)n->n_ptrs[4];
sum |= (uintptr_t)n->n_ptrs[5];
sum |= (uintptr_t)n->n_ptrs[6];
sum |= (uintptr_t)n->n_ptrs[7];
#endif
#if RADIX_TREE_PTR_PER_NODE > 8
sum |= (uintptr_t)n->n_ptrs[8];
sum |= (uintptr_t)n->n_ptrs[9];
sum |= (uintptr_t)n->n_ptrs[10];
sum |= (uintptr_t)n->n_ptrs[11];
sum |= (uintptr_t)n->n_ptrs[12];
sum |= (uintptr_t)n->n_ptrs[13];
sum |= (uintptr_t)n->n_ptrs[14];
sum |= (uintptr_t)n->n_ptrs[15];
#endif
return sum == 0;
#endif /* RADIX_TREE_PTR_PER_NODE > 16 */
}
static int __unused
radix_tree_node_count_ptrs(const struct radix_tree_node *n)
{
unsigned int i, c;
for (i = c = 0; i < RADIX_TREE_PTR_PER_NODE; i++) {
c += (n->n_ptrs[i] != NULL);
}
return c;
}
static struct radix_tree_node *
radix_tree_alloc_node(void)
{
struct radix_tree_node *n;
#if defined(_KERNEL)
/*
* note that pool_cache_get can block.
*/
n = pool_cache_get(radix_tree_node_cache, PR_NOWAIT);
#else /* defined(_KERNEL) */
#if defined(_STANDALONE)
n = alloc(sizeof(*n));
#else /* defined(_STANDALONE) */
n = malloc(sizeof(*n));
#endif /* defined(_STANDALONE) */
if (n != NULL) {
radix_tree_node_init(n);
}
#endif /* defined(_KERNEL) */
KASSERT(n == NULL || radix_tree_node_clean_p(n));
return n;
}
static void
radix_tree_free_node(struct radix_tree_node *n)
{
KASSERT(radix_tree_node_clean_p(n));
#if defined(_KERNEL)
pool_cache_put(radix_tree_node_cache, n);
#elif defined(_STANDALONE)
dealloc(n, sizeof(*n));
#else
free(n);
#endif
}
static int
radix_tree_grow(struct radix_tree *t, unsigned int newheight)
{
const unsigned int tagmask = entry_tagmask(t->t_root);
KASSERT(newheight <= 64 / RADIX_TREE_BITS_PER_HEIGHT);
if (t->t_root == NULL) {
t->t_height = newheight;
return 0;
}
while (t->t_height < newheight) {
struct radix_tree_node *n;
n = radix_tree_alloc_node();
if (n == NULL) {
/*
* don't bother to revert our changes.
* the caller will likely retry.
*/
return ENOMEM;
}
n->n_ptrs[0] = t->t_root;
t->t_root = entry_compose(n, tagmask);
t->t_height++;
}
return 0;
}
/*
* radix_tree_lookup_ptr:
*
* an internal helper function used for various exported functions.
*
* return the pointer to store the node for the given index.
*
* if alloc is true, try to allocate the storage. (note for _KERNEL:
* in that case, this function can block.) if the allocation failed or
* alloc is false, return NULL.
*
* if path is not NULL, fill it for the caller's investigation.
*
* if tagmask is not zero, search only for nodes with the tag set.
* note that, however, this function doesn't check the tagmask for the leaf
* pointer. it's a caller's responsibility to investigate the value which
* is pointed by the returned pointer if necessary.
*
* while this function is a bit large, as it's called with some constant
* arguments, inlining might have benefits. anyway, a compiler will decide.
*/
static inline void **
radix_tree_lookup_ptr(struct radix_tree *t, uint64_t idx,
struct radix_tree_path *path, bool alloc, const unsigned int tagmask)
{
struct radix_tree_node *n;
int hshift = RADIX_TREE_BITS_PER_HEIGHT * t->t_height;
int shift;
void **vpp;
const uint64_t mask = (UINT64_C(1) << RADIX_TREE_BITS_PER_HEIGHT) - 1;
struct radix_tree_node_ref *refs = NULL;
/*
* check unsupported combinations
*/
KASSERT(tagmask == 0 || !alloc);
KASSERT(path == NULL || !alloc);
vpp = &t->t_root;
if (path != NULL) {
refs = path->p_refs;
refs->pptr = vpp;
}
n = NULL;
for (shift = 64 - RADIX_TREE_BITS_PER_HEIGHT; shift >= 0;) {
struct radix_tree_node *c;
void *entry;
const uint64_t i = (idx >> shift) & mask;
if (shift >= hshift) {
unsigned int newheight;
KASSERT(vpp == &t->t_root);
if (i == 0) {
shift -= RADIX_TREE_BITS_PER_HEIGHT;
continue;
}
if (!alloc) {
if (path != NULL) {
KASSERT((refs - path->p_refs) == 0);
path->p_lastidx =
RADIX_TREE_INVALID_HEIGHT;
}
return NULL;
}
newheight = shift / RADIX_TREE_BITS_PER_HEIGHT + 1;
if (radix_tree_grow(t, newheight)) {
return NULL;
}
hshift = RADIX_TREE_BITS_PER_HEIGHT * t->t_height;
}
entry = *vpp;
c = entry_ptr(entry);
if (c == NULL ||
(tagmask != 0 &&
(entry_tagmask(entry) & tagmask) == 0)) {
if (!alloc) {
if (path != NULL) {
path->p_lastidx = refs - path->p_refs;
}
return NULL;
}
c = radix_tree_alloc_node();
if (c == NULL) {
return NULL;
}
*vpp = c;
}
n = c;
vpp = &n->n_ptrs[i];
if (path != NULL) {
refs++;
refs->pptr = vpp;
}
shift -= RADIX_TREE_BITS_PER_HEIGHT;
}
if (alloc) {
KASSERT(*vpp == NULL);
}
if (path != NULL) {
path->p_lastidx = refs - path->p_refs;
}
return vpp;
}
/*
* radix_tree_insert_node:
*
* Insert the node at the given index.
*
* It's illegal to insert NULL. It's illegal to insert a non-aligned pointer.
*
* This function returns ENOMEM if necessary memory allocation failed.
* Otherwise, this function returns 0.
*
* Note that inserting a node can involves memory allocation for intermediate
* nodes. If _KERNEL, it's done with no-sleep IPL_NONE memory allocation.
*
* For the newly inserted node, all tags are cleared.
*/
int
radix_tree_insert_node(struct radix_tree *t, uint64_t idx, void *p)
{
void **vpp;
KASSERT(p != NULL);
KASSERT(entry_tagmask(entry_compose(p, 0)) == 0);
vpp = radix_tree_lookup_ptr(t, idx, NULL, true, 0);
if (vpp == NULL) {
return ENOMEM;
}
KASSERT(*vpp == NULL);
*vpp = p;
return 0;
}
/*
* radix_tree_replace_node:
*
* Replace a node at the given index with the given node and return the
* replaced one.
*
* It's illegal to try to replace a node which has not been inserted.
*
* This function keeps tags intact.
*/
void *
radix_tree_replace_node(struct radix_tree *t, uint64_t idx, void *p)
{
void **vpp;
void *oldp;
KASSERT(p != NULL);
KASSERT(entry_tagmask(entry_compose(p, 0)) == 0);
vpp = radix_tree_lookup_ptr(t, idx, NULL, false, 0);
KASSERT(vpp != NULL);
oldp = *vpp;
KASSERT(oldp != NULL);
*vpp = entry_compose(p, entry_tagmask(*vpp));
return entry_ptr(oldp);
}
/*
* radix_tree_remove_node:
*
* Remove the node at the given index.
*
* It's illegal to try to remove a node which has not been inserted.
*/
void *
radix_tree_remove_node(struct radix_tree *t, uint64_t idx)
{
struct radix_tree_path path;
void **vpp;
void *oldp;
int i;
vpp = radix_tree_lookup_ptr(t, idx, &path, false, 0);
KASSERT(vpp != NULL);
oldp = *vpp;
KASSERT(oldp != NULL);
KASSERT(path.p_lastidx == t->t_height);
KASSERT(vpp == path_pptr(t, &path, path.p_lastidx));
*vpp = NULL;
for (i = t->t_height - 1; i >= 0; i--) {
void *entry;
struct radix_tree_node ** const pptr =
(struct radix_tree_node **)path_pptr(t, &path, i);
struct radix_tree_node *n;
KASSERT(pptr != NULL);
entry = *pptr;
n = entry_ptr(entry);
KASSERT(n != NULL);
if (!radix_tree_node_clean_p(n)) {
break;
}
radix_tree_free_node(n);
*pptr = NULL;
}
/*
* fix up height
*/
if (i < 0) {
KASSERT(t->t_root == NULL);
t->t_height = 0;
}
/*
* update tags
*/
for (; i >= 0; i--) {
void *entry;
struct radix_tree_node ** const pptr =
(struct radix_tree_node **)path_pptr(t, &path, i);
struct radix_tree_node *n;
unsigned int newmask;
KASSERT(pptr != NULL);
entry = *pptr;
n = entry_ptr(entry);
KASSERT(n != NULL);
KASSERT(!radix_tree_node_clean_p(n));
newmask = any_children_tagmask(n);
if (newmask == entry_tagmask(entry)) {
break;
}
*pptr = entry_compose(n, newmask);
}
/*
* XXX is it worth to try to reduce height?
* if we do that, make radix_tree_grow rollback its change as well.
*/
return entry_ptr(oldp);
}
/*
* radix_tree_lookup_node:
*
* Returns the node at the given index.
* Returns NULL if nothing is found at the given index.
*/
void *
radix_tree_lookup_node(struct radix_tree *t, uint64_t idx)
{
void **vpp;
vpp = radix_tree_lookup_ptr(t, idx, NULL, false, 0);
if (vpp == NULL) {
return NULL;
}
return entry_ptr(*vpp);
}
static inline void
gang_lookup_init(struct radix_tree *t, uint64_t idx,
struct radix_tree_path *path, const unsigned int tagmask)
{
void **vpp __unused;
vpp = radix_tree_lookup_ptr(t, idx, path, false, tagmask);
KASSERT(vpp == NULL ||
vpp == path_pptr(t, path, path->p_lastidx));
KASSERT(&t->t_root == path_pptr(t, path, 0));
KASSERT(path->p_lastidx == RADIX_TREE_INVALID_HEIGHT ||
path->p_lastidx == t->t_height ||
!entry_match_p(*path_pptr(t, path, path->p_lastidx), tagmask));
}
/*
* gang_lookup_scan:
*
* a helper routine for radix_tree_gang_lookup_node and its variants.
*/
static inline unsigned int
__attribute__((__always_inline__))
gang_lookup_scan(struct radix_tree *t, struct radix_tree_path *path,
void **results, const unsigned int maxresults, const unsigned int tagmask,
const bool reverse, const bool dense)
{
/*
* we keep the path updated only for lastidx-1.
* vpp is what path_pptr(t, path, lastidx) would be.
*/
void **vpp;
unsigned int nfound;
unsigned int lastidx;
/*
* set up scan direction dependant constants so that we can iterate
* n_ptrs as the following.
*
* for (i = first; i != guard; i += step)
* visit n->n_ptrs[i];
*/
const int step = reverse ? -1 : 1;
const unsigned int first = reverse ? RADIX_TREE_PTR_PER_NODE - 1 : 0;
const unsigned int last = reverse ? 0 : RADIX_TREE_PTR_PER_NODE - 1;
const unsigned int guard = last + step;
KASSERT(maxresults > 0);
KASSERT(&t->t_root == path_pptr(t, path, 0));
lastidx = path->p_lastidx;
KASSERT(lastidx == RADIX_TREE_INVALID_HEIGHT ||
lastidx == t->t_height ||
!entry_match_p(*path_pptr(t, path, lastidx), tagmask));
nfound = 0;
if (lastidx == RADIX_TREE_INVALID_HEIGHT) {
/*
* requested idx is beyond the right-most node.
*/
if (reverse && !dense) {
lastidx = 0;
vpp = path_pptr(t, path, lastidx);
goto descend;
}
return 0;
}
vpp = path_pptr(t, path, lastidx);
while (/*CONSTCOND*/true) {
struct radix_tree_node *n;
unsigned int i;
if (entry_match_p(*vpp, tagmask)) {
KASSERT(lastidx == t->t_height);
/*
* record the matching non-NULL leaf.
*/
results[nfound] = entry_ptr(*vpp);
nfound++;
if (nfound == maxresults) {
return nfound;
}
} else if (dense) {
return nfound;
}
scan_siblings:
/*
* try to find the next matching non-NULL sibling.
*/
if (lastidx == 0) {
/*
* the root has no siblings.
* we've done.
*/
KASSERT(vpp == &t->t_root);
break;
}
n = path_node(t, path, lastidx - 1);
for (i = vpp - n->n_ptrs + step; i != guard; i += step) {
KASSERT(i < RADIX_TREE_PTR_PER_NODE);
if (entry_match_p(n->n_ptrs[i], tagmask)) {
vpp = &n->n_ptrs[i];
break;
} else if (dense) {
return nfound;
}
}
if (i == guard) {
/*
* not found. go to parent.
*/
lastidx--;
vpp = path_pptr(t, path, lastidx);
goto scan_siblings;
}
descend:
/*
* following the left-most (or right-most in the case of
* reverse scan) child node, decend until reaching the leaf or
* an non-matching entry.
*/
while (entry_match_p(*vpp, tagmask) && lastidx < t->t_height) {
/*
* save vpp in the path so that we can come back to this
* node after finishing visiting children.
*/
path->p_refs[lastidx].pptr = vpp;
n = entry_ptr(*vpp);
vpp = &n->n_ptrs[first];
lastidx++;
}
}
return nfound;
}
/*
* radix_tree_gang_lookup_node:
*
* Scan the tree starting from the given index in the ascending order and
* return found nodes.
*
* results should be an array large enough to hold maxresults pointers.
* This function returns the number of nodes found, up to maxresults.
* Returning less than maxresults means there are no more nodes in the tree.
*
* If dense == true, this function stops scanning when it founds a hole of
* indexes. I.e. an index for which radix_tree_lookup_node would returns NULL.
* If dense == false, this function skips holes and continue scanning until
* maxresults nodes are found or it reaches the limit of the index range.
*
* The result of this function is semantically equivalent to what could be
* obtained by repeated calls of radix_tree_lookup_node with increasing index.
* but this function is expected to be computationally cheaper when looking up
* multiple nodes at once. Especially, it's expected to be much cheaper when
* node indexes are distributed sparsely.
*
* Note that this function doesn't return index values of found nodes.
* Thus, in the case of dense == false, if index values are important for
* a caller, it's the caller's responsibility to check them, typically
* by examinining the returned nodes using some caller-specific knowledge
* about them.
* In the case of dense == true, a node returned via results[N] is always for
* the index (idx + N).
*/
unsigned int
radix_tree_gang_lookup_node(struct radix_tree *t, uint64_t idx,
void **results, unsigned int maxresults, bool dense)
{
struct radix_tree_path path;
gang_lookup_init(t, idx, &path, 0);
return gang_lookup_scan(t, &path, results, maxresults, 0, false, dense);
}
/*
* radix_tree_gang_lookup_node_reverse:
*
* Same as radix_tree_gang_lookup_node except that this one scans the
* tree in the reverse order. I.e. descending index values.
*/
unsigned int
radix_tree_gang_lookup_node_reverse(struct radix_tree *t, uint64_t idx,
void **results, unsigned int maxresults, bool dense)
{
struct radix_tree_path path;
gang_lookup_init(t, idx, &path, 0);
return gang_lookup_scan(t, &path, results, maxresults, 0, true, dense);
}
/*
* radix_tree_gang_lookup_tagged_node:
*
* Same as radix_tree_gang_lookup_node except that this one only returns
* nodes tagged with tagid.
*
* It's illegal to call this function with tagmask 0.
*/
unsigned int
radix_tree_gang_lookup_tagged_node(struct radix_tree *t, uint64_t idx,
void **results, unsigned int maxresults, bool dense, unsigned int tagmask)
{
struct radix_tree_path path;
KASSERT(tagmask != 0);
gang_lookup_init(t, idx, &path, tagmask);
return gang_lookup_scan(t, &path, results, maxresults, tagmask, false,
dense);
}
/*
* radix_tree_gang_lookup_tagged_node_reverse:
*
* Same as radix_tree_gang_lookup_tagged_node except that this one scans the
* tree in the reverse order. I.e. descending index values.
*/
unsigned int
radix_tree_gang_lookup_tagged_node_reverse(struct radix_tree *t, uint64_t idx,
void **results, unsigned int maxresults, bool dense, unsigned int tagmask)
{
struct radix_tree_path path;
KASSERT(tagmask != 0);
gang_lookup_init(t, idx, &path, tagmask);
return gang_lookup_scan(t, &path, results, maxresults, tagmask, true,
dense);
}
/*
* radix_tree_get_tag:
*
* Return the tagmask for the node at the given index.
*
* It's illegal to call this function for a node which has not been inserted.
*/
unsigned int
radix_tree_get_tag(struct radix_tree *t, uint64_t idx, unsigned int tagmask)
{
/*
* the following two implementations should behave same.
* the former one was chosen because it seems faster.
*/
#if 1
void **vpp;
vpp = radix_tree_lookup_ptr(t, idx, NULL, false, tagmask);
if (vpp == NULL) {
return false;