// 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 "hashtab.h"

static struct kmem_cache *hashtab_node_cachep __ro_after_init;

/*
 * Here we simply round the number of elements up to the nearest power of two.
 * I tried also other options like rounding 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);
}

int hashtab_init(struct hashtab *h, u32 nel_hint)
{
        h->size = hashtab_compute_size(nel_hint);
        h->nel = 0;
        if (!h->size)
                return 0;

        h->htable = kcalloc(h->size, sizeof(*h->htable), GFP_KERNEL);
        return h->htable ? 0 : -ENOMEM;
}

int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
                     void *key, void *datum)
{
        struct hashtab_node *newnode;

        newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
        if (!newnode)
                return -ENOMEM;
        newnode->key = key;
        newnode->datum = datum;
        newnode->next = *dst;
        *dst = newnode;

        h->nel++;
        return 0;
}

void hashtab_destroy(struct hashtab *h)
{
        u32 i;
        struct hashtab_node *cur, *temp;

        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;
}

int hashtab_map(struct hashtab *h,
                int (*apply)(void *k, void *d, void *args),
                void *args)
{
        u32 i;
        int ret;
        struct hashtab_node *cur;

        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;
}

int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
                int (*copy)(struct hashtab_node *new,
                        struct hashtab_node *orig, void *args),
                int (*destroy)(void *k, void *d, void *args),
                void *args)
{
        struct hashtab_node *cur, *tmp, *tail;
        int i, rc;

        memset(new, 0, sizeof(*new));

        new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
        if (!new->htable)
                return -ENOMEM;

        new->size = orig->size;

        for (i = 0; i < orig->size; i++) {
                tail = NULL;
                for (cur = orig->htable[i]; cur; cur = cur->next) {
                        tmp = kmem_cache_zalloc(hashtab_node_cachep,
                                                GFP_KERNEL);
                        if (!tmp)
                                goto error;
                        rc = copy(tmp, cur, args);
                        if (rc) {
                                kmem_cache_free(hashtab_node_cachep, tmp);
                                goto error;
                        }
                        tmp->next = NULL;
                        if (!tail)
                                new->htable[i] = tmp;
                        else
                                tail->next = tmp;
                        tail = tmp;
                        new->nel++;
                }
        }

        return 0;

 error:
        for (i = 0; i < new->size; i++) {
                for (cur = new->htable[i]; cur; cur = tmp) {
                        tmp = cur->next;
                        destroy(cur->key, cur->datum, args);
                        kmem_cache_free(hashtab_node_cachep, cur);
                }
        }
        kmem_cache_free(hashtab_node_cachep, new);
        return -ENOMEM;
}

void __init hashtab_cache_init(void)
{
                hashtab_node_cachep = kmem_cache_create("hashtab_node",
                        sizeof(struct hashtab_node),
                        0, SLAB_PANIC, NULL);
}