On Mon, Jul 21, 2014 at 03:11:41PM -0400, Trond Myklebust wrote:
> In some cases where the credentials are not often reused, we may want
> to limit their total number just in order to make the negative lookups
> in the hash table more manageable.
Out of curiosity--how would somebody know that might need to set this?
--b.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> net/sunrpc/auth.c | 44 +++++++++++++++++++++++++++++++++++---------
> 1 file changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
> index 2bc7bb82b162..360decdddc78 100644
> --- a/net/sunrpc/auth.c
> +++ b/net/sunrpc/auth.c
> @@ -80,6 +80,10 @@ static struct kernel_param_ops param_ops_hashtbl_sz = {
> module_param_named(auth_hashtable_size, auth_hashbits, hashtbl_sz, 0644);
> MODULE_PARM_DESC(auth_hashtable_size, "RPC credential cache hashtable size");
>
> +static unsigned long auth_max_cred_cachesize = ULONG_MAX;
> +module_param(auth_max_cred_cachesize, ulong, 0644);
> +MODULE_PARM_DESC(auth_max_cred_cachesize, "RPC credential maximum total cache size");
> +
> static u32
> pseudoflavor_to_flavor(u32 flavor) {
> if (flavor > RPC_AUTH_MAXFLAVOR)
> @@ -481,6 +485,20 @@ rpcauth_prune_expired(struct list_head *free, int nr_to_scan)
> return freed;
> }
>
> +static unsigned long
> +rpcauth_cache_do_shrink(int nr_to_scan)
> +{
> + LIST_HEAD(free);
> + unsigned long freed;
> +
> + spin_lock(&rpc_credcache_lock);
> + freed = rpcauth_prune_expired(&free, nr_to_scan);
> + spin_unlock(&rpc_credcache_lock);
> + rpcauth_destroy_credlist(&free);
> +
> + return freed;
> +}
> +
> /*
> * Run memory cache shrinker.
> */
> @@ -488,9 +506,6 @@ static unsigned long
> rpcauth_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
>
> {
> - LIST_HEAD(free);
> - unsigned long freed;
> -
> if ((sc->gfp_mask & GFP_KERNEL) != GFP_KERNEL)
> return SHRINK_STOP;
>
> @@ -498,12 +513,7 @@ rpcauth_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
> if (list_empty(&cred_unused))
> return SHRINK_STOP;
>
> - spin_lock(&rpc_credcache_lock);
> - freed = rpcauth_prune_expired(&free, sc->nr_to_scan);
> - spin_unlock(&rpc_credcache_lock);
> - rpcauth_destroy_credlist(&free);
> -
> - return freed;
> + return rpcauth_cache_do_shrink(sc->nr_to_scan);
> }
>
> static unsigned long
> @@ -513,6 +523,21 @@ rpcauth_cache_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
> return (number_cred_unused / 100) * sysctl_vfs_cache_pressure;
> }
>
> +static void
> +rpcauth_cache_enforce_limit(void)
> +{
> + unsigned long diff;
> + unsigned int nr_to_scan;
> +
> + if (number_cred_unused <= auth_max_cred_cachesize)
> + return;
> + diff = number_cred_unused - auth_max_cred_cachesize;
> + nr_to_scan = 100;
> + if (diff < nr_to_scan)
> + nr_to_scan = diff;
> + rpcauth_cache_do_shrink(nr_to_scan);
> +}
> +
> /*
> * Look up a process' credentials in the authentication cache
> */
> @@ -566,6 +591,7 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
> } else
> list_add_tail(&new->cr_lru, &free);
> spin_unlock(&cache->lock);
> + rpcauth_cache_enforce_limit();
> found:
> if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags) &&
> cred->cr_ops->cr_init != NULL &&
> --
> 1.9.3
>
> --
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