SUNRPC: Make the credential cache hashtable size configurable

This patch allows the user to configure the credential cache hashtable size
using a new module parameter: auth_hashtable_size
When set, this parameter will be rounded up to the nearest power of two,
with a maximum allowed value of 1024 elements.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 55 insertions, 5 deletions

diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index eef76a1f1dd6..d80f01725fc2 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -19,6 +19,15 @@
 # define RPCDBG_FACILITY        RPCDBG_AUTH
 #endif
 
+#define RPC_CREDCACHE_DEFAULT_HASHBITS  (4)
+struct rpc_cred_cache {
+        struct hlist_head       *hashtable;
+        unsigned int            hashbits;
+        spinlock_t              lock;
+};
+
+static unsigned int auth_hashbits = RPC_CREDCACHE_DEFAULT_HASHBITS;
+
 static DEFINE_SPINLOCK(rpc_authflavor_lock);
 static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
         &authnull_ops,          /* AUTH_NULL */
@@ -29,6 +38,42 @@ static const struct rpc_authops *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
 static LIST_HEAD(cred_unused);
 static unsigned long number_cred_unused;
 
+#define MAX_HASHTABLE_BITS (10) 
+static int param_set_hashtbl_sz(const char *val, struct kernel_param *kp)
+{
+        unsigned long num;
+        unsigned int nbits;
+        int ret;
+
+        if (!val)
+                goto out_inval;
+        ret = strict_strtoul(val, 0, &num);
+        if (ret == -EINVAL)
+                goto out_inval;
+        nbits = fls(num);
+        if (num > (1U << nbits))
+                nbits++;
+        if (nbits > MAX_HASHTABLE_BITS || nbits < 2)
+                goto out_inval;
+        *(unsigned int *)kp->arg = nbits;
+        return 0;
+out_inval:
+        return -EINVAL;
+}
+
+static int param_get_hashtbl_sz(char *buffer, struct kernel_param *kp)
+{
+        unsigned int nbits;
+
+        nbits = *(unsigned int *)kp->arg;
+        return sprintf(buffer, "%u", 1U << nbits);
+}
+
+#define param_check_hashtbl_sz(name, p) __param_check(name, p, unsigned int);
+
+module_param_named(auth_hashtable_size, auth_hashbits, hashtbl_sz, 0644);
+MODULE_PARM_DESC(auth_hashtable_size, "RPC credential cache hashtable size");
+
 static u32
 pseudoflavor_to_flavor(u32 flavor) {
         if (flavor >= RPC_AUTH_MAXFLAVOR)
@@ -146,18 +191,22 @@ rpcauth_init_credcache(struct rpc_auth *auth)
 {
         struct rpc_cred_cache *new;
         unsigned int hashsize;
-        int i;
 
         new = kmalloc(sizeof(*new), GFP_KERNEL);
         if (!new)
-                return -ENOMEM;
-        new->hashbits = RPC_CREDCACHE_HASHBITS;
+                goto out_nocache;
+        new->hashbits = auth_hashbits;
         hashsize = 1U << new->hashbits;
-        for (i = 0; i < hashsize; i++)
-                INIT_HLIST_HEAD(&new->hashtable[i]);
+        new->hashtable = kcalloc(hashsize, sizeof(new->hashtable[0]), GFP_KERNEL);
+        if (!new->hashtable)
+                goto out_nohashtbl;
         spin_lock_init(&new->lock);
         auth->au_credcache = new;
         return 0;
+out_nohashtbl:
+        kfree(new);
+out_nocache:
+        return -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(rpcauth_init_credcache);
 
@@ -220,6 +269,7 @@ rpcauth_destroy_credcache(struct rpc_auth *auth)
         if (cache) {
                 auth->au_credcache = NULL;
                 rpcauth_clear_credcache(cache);
+                kfree(cache->hashtable);
                 kfree(cache);
         }
 }