selinux: Use kmem_cache for hashtab_node

During random test as own device to check slub account,
we found some slack memory from hashtab_node(kmalloc-64).
By using kzalloc(), middle of test result like below:
allocated size 240768
request size 45144
slack size 195624
allocation count 3762

So, we want to use kmem_cache_zalloc() and that
can reduce memory size 52byte(slack size/alloc count) per each struct.
Signed-off-by: NKyeongdon Kim <kyeongdon.kim@lge.com>
Signed-off-by: NPaul Moore <paul@paul-moore.com>

security/selinux/ss/hashtab.c

@@ -9,6 +9,8 @@
 #include <linux/sched.h>
 #include "hashtab.h"
 
+static struct kmem_cache *hashtab_node_cachep;
+
 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 size)
@@ -57,7 +59,7 @@ int hashtab_insert(struct hashtab *h, void *key, void *datum)
 	if (cur && (h->keycmp(h, key, cur->key) == 0))
 		return -EEXIST;
 
-	newnode = kzalloc(sizeof(*newnode), GFP_KERNEL);
+	newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
 	if (!newnode)
 		return -ENOMEM;
 	newnode->key = key;
@@ -106,7 +108,7 @@ void hashtab_destroy(struct hashtab *h)
 		while (cur) {
 			temp = cur;
 			cur = cur->next;
-			kfree(temp);
+			kmem_cache_free(hashtab_node_cachep, temp);
 		}
 		h->htable[i] = NULL;
 	}
@@ -166,3 +168,14 @@ void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
 	info->slots_used = slots_used;
 	info->max_chain_len = max_chain_len;
 }
+void hashtab_cache_init(void)
+{
+		hashtab_node_cachep = kmem_cache_create("hashtab_node",
+			sizeof(struct hashtab_node),
+			0, SLAB_PANIC, NULL);
+}
+
+void hashtab_cache_destroy(void)
+{
+		kmem_cache_destroy(hashtab_node_cachep);
+}

security/selinux/ss/hashtab.h

@@ -84,4 +84,8 @@ int hashtab_map(struct hashtab *h,
 /* Fill info with some hash table statistics */
 void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
 
+/* Use kmem_cache for hashtab_node */
+void hashtab_cache_init(void);
+void hashtab_cache_destroy(void);
+
 #endif	/* _SS_HASHTAB_H */

security/selinux/ss/services.c

@@ -2060,10 +2060,12 @@ int security_load_policy(void *data, size_t len)
 	if (!ss_initialized) {
 		avtab_cache_init();
 		ebitmap_cache_init();
+		hashtab_cache_init();
 		rc = policydb_read(&policydb, fp);
 		if (rc) {
 			avtab_cache_destroy();
 			ebitmap_cache_destroy();
+			hashtab_cache_destroy();
 			goto out;
 		}
 
@@ -2075,6 +2077,7 @@ int security_load_policy(void *data, size_t len)
 			policydb_destroy(&policydb);
 			avtab_cache_destroy();
 			ebitmap_cache_destroy();
+			hashtab_cache_destroy();
 			goto out;
 		}
 
@@ -2083,6 +2086,7 @@ int security_load_policy(void *data, size_t len)
 			policydb_destroy(&policydb);
 			avtab_cache_destroy();
 			ebitmap_cache_destroy();
+			hashtab_cache_destroy();
 			goto out;
 		}