SUNRPC: Add a backpointer from the struct rpc_cred to the rpc_auth

Cleans up an issue whereby rpcsec_gss uses the rpc_clnt->cl_auth. If we want
to be able to add several rpc_auths to a single rpc_clnt, then this abuse
must go.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/auth.h

@@ -30,8 +30,11 @@ struct auth_cred {
 /*
  * Client user credentials
  */
+struct rpc_auth;
+struct rpc_credops;
 struct rpc_cred {
 	struct hlist_node	cr_hash;	/* hash chain */
+	struct rpc_auth *	cr_auth;
 	struct rpc_credops *	cr_ops;
 	unsigned long		cr_expire;	/* when to gc */
 	atomic_t		cr_count;	/* ref count */
@@ -60,6 +63,7 @@ struct rpc_cred_cache {
 	unsigned long		expire;		/* cache expiry interval */
 };
 
+struct rpc_authops;
 struct rpc_auth {
 	unsigned int		au_cslack;	/* call cred size estimate */
 				/* guess at number of u32's auth adds before

net/sunrpc/auth_gss/auth_gss.c

@@ -386,7 +386,7 @@ static inline int
 gss_refresh_upcall(struct rpc_task *task)
 {
 	struct rpc_cred *cred = task->tk_msg.rpc_cred;
-	struct gss_auth *gss_auth = container_of(task->tk_client->cl_auth,
+	struct gss_auth *gss_auth = container_of(cred->cr_auth,
 			struct gss_auth, rpc_auth);
 	struct gss_cred *gss_cred = container_of(cred,
 			struct gss_cred, gc_base);
@@ -741,6 +741,7 @@ gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
 	 * fail to flag the credential as RPCAUTH_CRED_UPTODATE.
 	 */
 	cred->gc_flags = 0;
+	cred->gc_base.cr_auth = auth;
 	cred->gc_base.cr_ops = &gss_credops;
 	cred->gc_base.cr_flags = RPCAUTH_CRED_NEW;
 	cred->gc_service = gss_auth->service;

net/sunrpc/auth_null.c

@@ -133,6 +133,7 @@ struct rpc_credops	null_credops = {
 
 static
 struct rpc_cred null_cred = {
+	.cr_auth	= &null_auth,
 	.cr_ops		= &null_credops,
 	.cr_count	= ATOMIC_INIT(1),
 	.cr_flags	= RPCAUTH_CRED_UPTODATE,

net/sunrpc/auth_unix.c

@@ -92,6 +92,7 @@ unx_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
 		if (i < NFS_NGROUPS)
 		  cred->uc_gids[i] = NOGROUP;
 	}
+	cred->uc_base.cr_auth = &unix_auth;
 	cred->uc_base.cr_ops = &unix_credops;
 
 	return (struct rpc_cred *) cred;