Skip to content

Commit

Permalink
SUNRPC: Remove rpc_authflavor_lock in favour of RCU locking
Browse files Browse the repository at this point in the history 
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>
  • Loading branch information
Trond Myklebust committed Sep 30, 2018
1 parent 1c6c4b7 commit 4e4c3be
Showing 1 changed file with 62 additions and 66 deletions.
128 changes: 62 additions & 66 deletions net/sunrpc/auth.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
};

Expand Down Expand Up @@ -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
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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;
Expand All @@ -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;
Expand All @@ -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)
Expand Down

0 comments on commit 4e4c3be

Please sign in to comment.