Module removal is RCU safe by design, so we really have no need to
lock the auth_flavors[] array. Substitute a lockless scheme to
add/remove entries in the array, and then use rcu.
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
net/sunrpc/auth.c | 128 ++++++++++++++++++++++------------------------
1 file changed, 62 insertions(+), 66 deletions(-)
diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index 59df5cdba0ac..32985aa515be 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -30,10 +30,9 @@ struct rpc_cred_cache {
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 */
- &authunix_ops, /* AUTH_UNIX */
+static const struct rpc_authops __rcu *auth_flavors[RPC_AUTH_MAXFLAVOR] = {
+ [RPC_AUTH_NULL] = (const struct rpc_authops __force __rcu *)&authnull_ops,
+ [RPC_AUTH_UNIX] = (const struct rpc_authops __force __rcu *)&authunix_ops,
NULL, /* others can be loadable modules */
};
@@ -93,39 +92,65 @@ pseudoflavor_to_flavor(u32 flavor) {
int
rpcauth_register(const struct rpc_authops *ops)
{
+ const struct rpc_authops *old;
rpc_authflavor_t flavor;
- int ret = -EPERM;
if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
return -EINVAL;
- spin_lock(&rpc_authflavor_lock);
- if (auth_flavors[flavor] == NULL) {
- auth_flavors[flavor] = ops;
- ret = 0;
- }
- spin_unlock(&rpc_authflavor_lock);
- return ret;
+ old = cmpxchg((const struct rpc_authops ** __force)&auth_flavors[flavor], NULL, ops);
+ if (old == NULL || old == ops)
+ return 0;
+ return -EPERM;
}
EXPORT_SYMBOL_GPL(rpcauth_register);
int
rpcauth_unregister(const struct rpc_authops *ops)
{
+ const struct rpc_authops *old;
rpc_authflavor_t flavor;
- int ret = -EPERM;
if ((flavor = ops->au_flavor) >= RPC_AUTH_MAXFLAVOR)
return -EINVAL;
- spin_lock(&rpc_authflavor_lock);
- if (auth_flavors[flavor] == ops) {
- auth_flavors[flavor] = NULL;
- ret = 0;
- }
- spin_unlock(&rpc_authflavor_lock);
- return ret;
+
+ old = cmpxchg((const struct rpc_authops ** __force)&auth_flavors[flavor], ops, NULL);
+ if (old == ops || old == NULL)
+ return 0;
+ return -EPERM;
}
EXPORT_SYMBOL_GPL(rpcauth_unregister);
+static const struct rpc_authops *
+rpcauth_get_authops(rpc_authflavor_t flavor)
+{
+ const struct rpc_authops *ops;
+
+ if (flavor >= RPC_AUTH_MAXFLAVOR)
+ return NULL;
+
+ rcu_read_lock();
+ ops = rcu_dereference(auth_flavors[flavor]);
+ if (ops == NULL) {
+ rcu_read_unlock();
+ request_module("rpc-auth-%u", flavor);
+ rcu_read_lock();
+ ops = rcu_dereference(auth_flavors[flavor]);
+ if (ops == NULL)
+ goto out;
+ }
+ if (!try_module_get(ops->owner))
+ ops = NULL;
+out:
+ rcu_read_unlock();
+ return ops;
+}
+
+static void
+rpcauth_put_authops(const struct rpc_authops *ops)
+{
+ module_put(ops->owner);
+}
+
/**
* rpcauth_get_pseudoflavor - check if security flavor is supported
* @flavor: a security flavor
@@ -138,25 +163,16 @@ EXPORT_SYMBOL_GPL(rpcauth_unregister);
rpc_authflavor_t
rpcauth_get_pseudoflavor(rpc_authflavor_t flavor, struct rpcsec_gss_info *info)
{
- const struct rpc_authops *ops;
+ const struct rpc_authops *ops = rpcauth_get_authops(flavor);
rpc_authflavor_t pseudoflavor;
- ops = auth_flavors[flavor];
- if (ops == NULL)
- request_module("rpc-auth-%u", flavor);
- spin_lock(&rpc_authflavor_lock);
- ops = auth_flavors[flavor];
- if (ops == NULL || !try_module_get(ops->owner)) {
- spin_unlock(&rpc_authflavor_lock);
+ if (!ops)
return RPC_AUTH_MAXFLAVOR;
- }
- spin_unlock(&rpc_authflavor_lock);
-
pseudoflavor = flavor;
if (ops->info2flavor != NULL)
pseudoflavor = ops->info2flavor(info);
- module_put(ops->owner);
+ rpcauth_put_authops(ops);
return pseudoflavor;
}
EXPORT_SYMBOL_GPL(rpcauth_get_pseudoflavor);
@@ -176,25 +192,15 @@ rpcauth_get_gssinfo(rpc_authflavor_t pseudoflavor, struct rpcsec_gss_info *info)
const struct rpc_authops *ops;
int result;
- if (flavor >= RPC_AUTH_MAXFLAVOR)
- return -EINVAL;
-
- ops = auth_flavors[flavor];
+ ops = rpcauth_get_authops(flavor);
if (ops == NULL)
- request_module("rpc-auth-%u", flavor);
- spin_lock(&rpc_authflavor_lock);
- ops = auth_flavors[flavor];
- if (ops == NULL || !try_module_get(ops->owner)) {
- spin_unlock(&rpc_authflavor_lock);
return -ENOENT;
- }
- spin_unlock(&rpc_authflavor_lock);
result = -ENOENT;
if (ops->flavor2info != NULL)
result = ops->flavor2info(pseudoflavor, info);
- module_put(ops->owner);
+ rpcauth_put_authops(ops);
return result;
}
EXPORT_SYMBOL_GPL(rpcauth_get_gssinfo);
@@ -212,15 +218,13 @@ EXPORT_SYMBOL_GPL(rpcauth_get_gssinfo);
int
rpcauth_list_flavors(rpc_authflavor_t *array, int size)
{
- rpc_authflavor_t flavor;
- int result = 0;
+ const struct rpc_authops *ops;
+ rpc_authflavor_t flavor, pseudos[4];
+ int i, len, result = 0;
- spin_lock(&rpc_authflavor_lock);
+ rcu_read_lock();
for (flavor = 0; flavor < RPC_AUTH_MAXFLAVOR; flavor++) {
- const struct rpc_authops *ops = auth_flavors[flavor];
- rpc_authflavor_t pseudos[4];
- int i, len;
-
+ ops = rcu_dereference(auth_flavors[flavor]);
if (result >= size) {
result = -ENOMEM;
break;
@@ -245,7 +249,7 @@ rpcauth_list_flavors(rpc_authflavor_t *array, int size)
array[result++] = pseudos[i];
}
}
- spin_unlock(&rpc_authflavor_lock);
+ rcu_read_unlock();
dprintk("RPC: %s returns %d\n", __func__, result);
return result;
@@ -255,25 +259,17 @@ EXPORT_SYMBOL_GPL(rpcauth_list_flavors);
struct rpc_auth *
rpcauth_create(const struct rpc_auth_create_args *args, struct rpc_clnt *clnt)
{
- struct rpc_auth *auth;
+ struct rpc_auth *auth = ERR_PTR(-EINVAL);
const struct rpc_authops *ops;
- u32 flavor = pseudoflavor_to_flavor(args->pseudoflavor);
+ u32 flavor = pseudoflavor_to_flavor(args->pseudoflavor);
- auth = ERR_PTR(-EINVAL);
- if (flavor >= RPC_AUTH_MAXFLAVOR)
+ ops = rpcauth_get_authops(flavor);
+ if (ops == NULL)
goto out;
- if ((ops = auth_flavors[flavor]) == NULL)
- request_module("rpc-auth-%u", flavor);
- spin_lock(&rpc_authflavor_lock);
- ops = auth_flavors[flavor];
- if (ops == NULL || !try_module_get(ops->owner)) {
- spin_unlock(&rpc_authflavor_lock);
- goto out;
- }
- spin_unlock(&rpc_authflavor_lock);
auth = ops->create(args, clnt);
- module_put(ops->owner);
+
+ rpcauth_put_authops(ops);
if (IS_ERR(auth))
return auth;
if (clnt->cl_auth)
--
2.17.1
