SUNRPC: Fix a lock recursion in the auth_gss downcall

When we look up a new cred in the auth_gss downcall so that we can stuff
 the credcache, we do not want that lookup to queue up an upcall in order
 to initialise it. To do an upcall here not only redundant, but since we
 are already holding the inode->i_mutex, it will trigger a lock recursion.

 This patch allows rpcauth cache searches to indicate that they can cope
 with uninitialised credentials.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/auth.h

@@ -50,6 +50,7 @@ struct rpc_cred {
 };
 #define RPCAUTH_CRED_LOCKED	0x0001
 #define RPCAUTH_CRED_UPTODATE	0x0002
+#define RPCAUTH_CRED_NEW	0x0004
 
 #define RPCAUTH_CRED_MAGIC	0x0f4aa4f0
 
@@ -87,6 +88,10 @@ struct rpc_auth {
 						 * uid/gid, fs[ug]id, gids)
 						 */
 
+/* Flags for rpcauth_lookupcred() */
+#define RPCAUTH_LOOKUP_NEW		0x01	/* Accept an uninitialised cred */
+#define RPCAUTH_LOOKUP_ROOTCREDS	0x02	/* This really ought to go! */
+
 /*
  * Client authentication ops
  */