1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Implementation of the hash table type.
4 *
5 * Author : Stephen Smalley, <sds@tycho.nsa.gov>
6 */
7#include <linux/kernel.h>
8#include <linux/slab.h>
9#include <linux/errno.h>
10#include "hashtab.h"
11
12static struct kmem_cache *hashtab_node_cachep;
13
14/*
15 * Here we simply round the number of elements up to the nearest power of two.
16 * I tried also other options like rouding down or rounding to the closest
17 * power of two (up or down based on which is closer), but I was unable to
18 * find any significant difference in lookup/insert performance that would
19 * justify switching to a different (less intuitive) formula. It could be that
20 * a different formula is actually more optimal, but any future changes here
21 * should be supported with performance/memory usage data.
22 *
23 * The total memory used by the htable arrays (only) with Fedora policy loaded
24 * is approximately 163 KB at the time of writing.
25 */
26static u32 hashtab_compute_size(u32 nel)
27{
28	return nel == 0 ? 0 : roundup_pow_of_two(nel);
29}
30
31int hashtab_init(struct hashtab *h, u32 nel_hint)
32{
33	u32 size = hashtab_compute_size(nel_hint);
34
35	/* should already be zeroed, but better be safe */
36	h->nel = 0;
37	h->size = 0;
38	h->htable = NULL;
39
40	if (size) {
41		h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL);
42		if (!h->htable)
43			return -ENOMEM;
44		h->size = size;
45	}
46	return 0;
47}
48
49int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
50		     void *key, void *datum)
51{
52	struct hashtab_node *newnode;
53
54	newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
55	if (!newnode)
56		return -ENOMEM;
57	newnode->key = key;
58	newnode->datum = datum;
59	newnode->next = *dst;
60	*dst = newnode;
61
62	h->nel++;
63	return 0;
64}
65
66void hashtab_destroy(struct hashtab *h)
67{
68	u32 i;
69	struct hashtab_node *cur, *temp;
70
71	for (i = 0; i < h->size; i++) {
72		cur = h->htable[i];
73		while (cur) {
74			temp = cur;
75			cur = cur->next;
76			kmem_cache_free(hashtab_node_cachep, temp);
77		}
78		h->htable[i] = NULL;
79	}
80
81	kfree(h->htable);
82	h->htable = NULL;
83}
84
85int hashtab_map(struct hashtab *h,
86		int (*apply)(void *k, void *d, void *args),
87		void *args)
88{
89	u32 i;
90	int ret;
91	struct hashtab_node *cur;
92
93	for (i = 0; i < h->size; i++) {
94		cur = h->htable[i];
95		while (cur) {
96			ret = apply(cur->key, cur->datum, args);
97			if (ret)
98				return ret;
99			cur = cur->next;
100		}
101	}
102	return 0;
103}
104
105
106void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
107{
108	u32 i, chain_len, slots_used, max_chain_len;
109	struct hashtab_node *cur;
110
111	slots_used = 0;
112	max_chain_len = 0;
113	for (i = 0; i < h->size; i++) {
114		cur = h->htable[i];
115		if (cur) {
116			slots_used++;
117			chain_len = 0;
118			while (cur) {
119				chain_len++;
120				cur = cur->next;
121			}
122
123			if (chain_len > max_chain_len)
124				max_chain_len = chain_len;
125		}
126	}
127
128	info->slots_used = slots_used;
129	info->max_chain_len = max_chain_len;
130}
131
132int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
133		int (*copy)(struct hashtab_node *new,
134			struct hashtab_node *orig, void *args),
135		int (*destroy)(void *k, void *d, void *args),
136		void *args)
137{
138	struct hashtab_node *cur, *tmp, *tail;
139	int i, rc;
140
141	memset(new, 0, sizeof(*new));
142
143	new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
144	if (!new->htable)
145		return -ENOMEM;
146
147	new->size = orig->size;
148
149	for (i = 0; i < orig->size; i++) {
150		tail = NULL;
151		for (cur = orig->htable[i]; cur; cur = cur->next) {
152			tmp = kmem_cache_zalloc(hashtab_node_cachep,
153						GFP_KERNEL);
154			if (!tmp)
155				goto error;
156			rc = copy(tmp, cur, args);
157			if (rc) {
158				kmem_cache_free(hashtab_node_cachep, tmp);
159				goto error;
160			}
161			tmp->next = NULL;
162			if (!tail)
163				new->htable[i] = tmp;
164			else
165				tail->next = tmp;
166			tail = tmp;
167			new->nel++;
168		}
169	}
170
171	return 0;
172
173 error:
174	for (i = 0; i < new->size; i++) {
175		for (cur = new->htable[i]; cur; cur = tmp) {
176			tmp = cur->next;
177			destroy(cur->key, cur->datum, args);
178			kmem_cache_free(hashtab_node_cachep, cur);
179		}
180	}
181	kfree(new->htable);
182	memset(new, 0, sizeof(*new));
183	return -ENOMEM;
184}
185
186void __init hashtab_cache_init(void)
187{
188		hashtab_node_cachep = kmem_cache_create("hashtab_node",
189			sizeof(struct hashtab_node),
190			0, SLAB_PANIC, NULL);
191}
192