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SUNRPC: Remove rpc_authflavor_lock in favour of RCU locking

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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@hammerspace.com>
This commit is contained in:
Trond Myklebust 2018-09-27 13:12:44 -04:00
parent 1c6c4b740d
commit 4e4c3bef44
1 changed files with 62 additions and 66 deletions
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128
net/sunrpc/auth.c
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@ -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)