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// SPDX-License-Identifier: GPL-2.0
/*
* Implementation of the hash table type.
*
* Author : Stephen Smalley, <sds@tycho.nsa.gov>
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include "hashtab.h"
static struct kmem_cache *hashtab_node_cachep;
/*
* Here we simply round the number of elements up to the nearest power of two.
* I tried also other options like rouding down or rounding to the closest
* power of two (up or down based on which is closer), but I was unable to
* find any significant difference in lookup/insert performance that would
* justify switching to a different (less intuitive) formula. It could be that
* a different formula is actually more optimal, but any future changes here
* should be supported with performance/memory usage data.
*
* The total memory used by the htable arrays (only) with Fedora policy loaded
* is approximately 163 KB at the time of writing.
*/
static u32 hashtab_compute_size(u32 nel)
{
return nel == 0 ? 0 : roundup_pow_of_two(nel);
}
struct hashtab *hashtab_create(u32 (*hash_value)(struct hashtab *h, const void *key),
int (*keycmp)(struct hashtab *h, const void *key1, const void *key2),
u32 nel_hint)
{
struct hashtab *p;
u32 i, size = hashtab_compute_size(nel_hint);
p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p)
return p;
p->size = size;
p->nel = 0;
p->hash_value = hash_value;
p->keycmp = keycmp;
if (!size)
return p;
p->htable = kmalloc_array(size, sizeof(*p->htable), GFP_KERNEL);
if (!p->htable) {
kfree(p);
return NULL;
}
for (i = 0; i < size; i++)
p->htable[i] = NULL;
return p;
}
int hashtab_insert(struct hashtab *h, void *key, void *datum)
{
u32 hvalue;
struct hashtab_node *prev, *cur, *newnode;
cond_resched();
if (!h || !h->size || h->nel == HASHTAB_MAX_NODES)
return -EINVAL;
hvalue = h->hash_value(h, key);
prev = NULL;
cur = h->htable[hvalue];
while (cur && h->keycmp(h, key, cur->key) > 0) {
prev = cur;
cur = cur->next;
}
if (cur && (h->keycmp(h, key, cur->key) == 0))
return -EEXIST;
newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
if (!newnode)
return -ENOMEM;
newnode->key = key;
newnode->datum = datum;
if (prev) {
newnode->next = prev->next;
prev->next = newnode;
} else {
newnode->next = h->htable[hvalue];
h->htable[hvalue] = newnode;
}
h->nel++;
return 0;
}
void *hashtab_search(struct hashtab *h, const void *key)
{
u32 hvalue;
struct hashtab_node *cur;
if (!h || !h->size)
return NULL;
hvalue = h->hash_value(h, key);
cur = h->htable[hvalue];
while (cur && h->keycmp(h, key, cur->key) > 0)
cur = cur->next;
if (!cur || (h->keycmp(h, key, cur->key) != 0))
return NULL;
return cur->datum;
}
void hashtab_destroy(struct hashtab *h)
{
u32 i;
struct hashtab_node *cur, *temp;
if (!h)
return;
for (i = 0; i < h->size; i++) {
cur = h->htable[i];
while (cur) {
temp = cur;
cur = cur->next;
kmem_cache_free(hashtab_node_cachep, temp);
}
h->htable[i] = NULL;
}
kfree(h->htable);
h->htable = NULL;
kfree(h);
}
int hashtab_map(struct hashtab *h,
int (*apply)(void *k, void *d, void *args),
void *args)
{
u32 i;
int ret;
struct hashtab_node *cur;
if (!h)
return 0;
for (i = 0; i < h->size; i++) {
cur = h->htable[i];
while (cur) {
ret = apply(cur->key, cur->datum, args);
if (ret)
return ret;
cur = cur->next;
}
}
return 0;
}
void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
{
u32 i, chain_len, slots_used, max_chain_len;
struct hashtab_node *cur;
slots_used = 0;
max_chain_len = 0;
for (i = 0; i < h->size; i++) {
cur = h->htable[i];
if (cur) {
slots_used++;
chain_len = 0;
while (cur) {
chain_len++;
cur = cur->next;
}
if (chain_len > max_chain_len)
max_chain_len = chain_len;
}
}
info->slots_used = slots_used;
info->max_chain_len = max_chain_len;
}
void __init hashtab_cache_init(void)
{
hashtab_node_cachep = kmem_cache_create("hashtab_node",
sizeof(struct hashtab_node),
0, SLAB_PANIC, NULL);
}
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