NFSv4.1: Ensure that layoutget is called using the layout credential

Ensure that we use the same credential for layoutget, layoutcommit and
layoutreturn.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -6348,6 +6348,7 @@ nfs4_proc_layoutget(struct nfs4_layoutget *lgp, gfp_t gfp_flags)
 		.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_LAYOUTGET],
 		.rpc_argp = &lgp->args,
 		.rpc_resp = &lgp->res,
+		.rpc_cred = lgp->cred,
 	};
 	struct rpc_task_setup task_setup_data = {
 		.rpc_client = server->client,

fs/nfs/pnfs.c

@@ -766,6 +766,7 @@ send_layoutget(struct pnfs_layout_hdr *lo,
 	lgp->args.inode = ino;
 	lgp->args.ctx = get_nfs_open_context(ctx);
 	lgp->gfp_flags = gfp_flags;
+	lgp->cred = lo->plh_lc_cred;
 
 	/* Synchronously retrieve layout information from server and
 	 * store in lseg.

include/linux/nfs_xdr.h

@@ -246,6 +246,7 @@ struct nfs4_layoutget_res {
 struct nfs4_layoutget {
 	struct nfs4_layoutget_args args;
 	struct nfs4_layoutget_res res;
+	struct rpc_cred *cred;
 	gfp_t gfp_flags;
 };