NFS/NFSD/SUNRPC: replace generic creds with 'struct cred'.

SUNRPC has two sorts of credentials, both of which appear as
"struct rpc_cred".
There are "generic credentials" which are supplied by clients
such as NFS and passed in 'struct rpc_message' to indicate
which user should be used to authorize the request, and there
are low-level credentials such as AUTH_NULL, AUTH_UNIX, AUTH_GSS
which describe the credential to be sent over the wires.

This patch replaces all the generic credentials by 'struct cred'
pointers - the credential structure used throughout Linux.

For machine credentials, there is a special 'struct cred *' pointer
which is statically allocated and recognized where needed as
having a special meaning.  A look-up of a low-level cred will
map this to a machine credential.

Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index de50a34..c2626ba 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -81,8 +81,8 @@
 	u32				fh_versions_cnt;
 	struct nfs_fh			*fh_versions;
 	nfs4_stateid			stateid;
-	struct rpc_cred	__rcu		*ro_cred;
-	struct rpc_cred	__rcu		*rw_cred;
+	const struct cred __rcu		*ro_cred;
+	const struct cred __rcu		*rw_cred;
 	refcount_t			ref;
 	spinlock_t			lock;
 	unsigned long			flags;
@@ -229,8 +229,8 @@
 				 u32 ds_idx,
 				 struct nfs_client *ds_clp,
 				 struct inode *inode);
-struct rpc_cred *ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg,
-				       u32 ds_idx, struct rpc_cred *mdscred);
+const struct cred *ff_layout_get_ds_cred(struct pnfs_layout_segment *lseg,
+				       u32 ds_idx, const struct cred *mdscred);
 bool ff_layout_avoid_mds_available_ds(struct pnfs_layout_segment *lseg);
 bool ff_layout_avoid_read_on_rw(struct pnfs_layout_segment *lseg);