nfs: allow to specify cred in nfs_initiate_pgio

so that flexfile layout client can pass in DS credential instead of
using user cred, which will be done in the next patch.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Tom Haynes <Thomas.Haynes@primarydata.com>
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 35a2626..c4d1758 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -597,14 +597,14 @@
 }
 
 int nfs_initiate_pgio(struct rpc_clnt *clnt, struct nfs_pgio_header *hdr,
-		      const struct nfs_rpc_ops *rpc_ops,
+		      struct rpc_cred *cred, const struct nfs_rpc_ops *rpc_ops,
 		      const struct rpc_call_ops *call_ops, int how, int flags)
 {
 	struct rpc_task *task;
 	struct rpc_message msg = {
 		.rpc_argp = &hdr->args,
 		.rpc_resp = &hdr->res,
-		.rpc_cred = hdr->cred,
+		.rpc_cred = cred,
 	};
 	struct rpc_task_setup task_setup_data = {
 		.rpc_client = clnt,
@@ -793,7 +793,9 @@
 	ret = nfs_generic_pgio(desc, hdr);
 	if (ret == 0)
 		ret = nfs_initiate_pgio(NFS_CLIENT(hdr->inode),
-					hdr, NFS_PROTO(hdr->inode),
+					hdr,
+					hdr->cred,
+					NFS_PROTO(hdr->inode),
 					desc->pg_rpc_callops,
 					desc->pg_ioflags, 0);
 	return ret;