The new flag RPCAUTH_LOOKUP_RCU to credential lookup avoids locking,
does not take a reference on the returned credential, and returns
-ECHILD if a simple lookup was not possible.
The returned value can only be used within an rcu_read_lock protected
region.
The main user of this is the new rpc_lookup_cred_nonblock() which
returns a pointer to the current credential which is only rcu-safe (no
ref-count held), and might return -ECHILD if allocation was required.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
include/linux/sunrpc/auth.h | 2 ++
net/sunrpc/auth.c | 17 +++++++++++++++--
net/sunrpc/auth_generic.c | 6 ++++++
net/sunrpc/auth_null.c | 2 ++
4 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/include/linux/sunrpc/auth.h b/include/linux/sunrpc/auth.h
index 790be1472792..28ffc8476875 100644
--- a/include/linux/sunrpc/auth.h
+++ b/include/linux/sunrpc/auth.h
@@ -103,6 +103,7 @@ struct rpc_auth_create_args {
/* Flags for rpcauth_lookupcred() */
#define RPCAUTH_LOOKUP_NEW 0x01 /* Accept an uninitialised cred */
+#define RPCAUTH_LOOKUP_RCU 0x02 /* lock-less lookup */
/*
* Client authentication ops
@@ -153,6 +154,7 @@ void rpc_destroy_generic_auth(void);
void rpc_destroy_authunix(void);
struct rpc_cred * rpc_lookup_cred(void);
+struct rpc_cred * rpc_lookup_cred_nonblock(void);
struct rpc_cred * rpc_lookup_machine_cred(const char *service_name);
int rpcauth_register(const struct rpc_authops *);
int rpcauth_unregister(const struct rpc_authops *);
diff --git a/net/sunrpc/auth.c b/net/sunrpc/auth.c
index f77366717420..794fc0f4fc4c 100644
--- a/net/sunrpc/auth.c
+++ b/net/sunrpc/auth.c
@@ -523,6 +523,12 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
hlist_for_each_entry_rcu(entry, &cache->hashtable[nr], cr_hash) {
if (!entry->cr_ops->crmatch(acred, entry, flags))
continue;
+ if (flags & RPCAUTH_LOOKUP_RCU) {
+ if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) &&
+ !test_bit(RPCAUTH_CRED_NEW, &entry->cr_flags))
+ cred = entry;
+ break;
+ }
spin_lock(&cache->lock);
if (test_bit(RPCAUTH_CRED_HASHED, &entry->cr_flags) == 0) {
spin_unlock(&cache->lock);
@@ -537,6 +543,9 @@ rpcauth_lookup_credcache(struct rpc_auth *auth, struct auth_cred * acred,
if (cred != NULL)
goto found;
+ if (flags & RPCAUTH_LOOKUP_RCU)
+ return ERR_PTR(-ECHILD);
+
new = auth->au_ops->crcreate(auth, acred, flags);
if (IS_ERR(new)) {
cred = new;
@@ -586,10 +595,14 @@ rpcauth_lookupcred(struct rpc_auth *auth, int flags)
memset(&acred, 0, sizeof(acred));
acred.uid = cred->fsuid;
acred.gid = cred->fsgid;
- acred.group_info = get_group_info(((struct cred *)cred)->group_info);
+ if (flags & RPCAUTH_LOOKUP_RCU)
+ acred.group_info = rcu_dereference(cred->group_info);
+ else
+ acred.group_info = get_group_info(((struct cred *)cred)->group_info);
ret = auth->au_ops->lookup_cred(auth, &acred, flags);
- put_group_info(acred.group_info);
+ if (!(flags & RPCAUTH_LOOKUP_RCU))
+ put_group_info(acred.group_info);
return ret;
}
EXPORT_SYMBOL_GPL(rpcauth_lookupcred);
diff --git a/net/sunrpc/auth_generic.c b/net/sunrpc/auth_generic.c
index ed04869b2d4f..6f6b829c9e8e 100644
--- a/net/sunrpc/auth_generic.c
+++ b/net/sunrpc/auth_generic.c
@@ -38,6 +38,12 @@ struct rpc_cred *rpc_lookup_cred(void)
}
EXPORT_SYMBOL_GPL(rpc_lookup_cred);
+struct rpc_cred *rpc_lookup_cred_nonblock(void)
+{
+ return rpcauth_lookupcred(&generic_auth, RPCAUTH_LOOKUP_RCU);
+}
+EXPORT_SYMBOL_GPL(rpc_lookup_cred_nonblock);
+
/*
* Public call interface for looking up machine creds.
*/
diff --git a/net/sunrpc/auth_null.c b/net/sunrpc/auth_null.c
index f0ebe07978a2..712c123e04e9 100644
--- a/net/sunrpc/auth_null.c
+++ b/net/sunrpc/auth_null.c
@@ -35,6 +35,8 @@ nul_destroy(struct rpc_auth *auth)
static struct rpc_cred *
nul_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
+ if (flags & RPCAUTH_LOOKUP_RCU)
+ return &null_cred;
return get_rpccred(&null_cred);
}
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
