nfs: Subsequent READDIR calls should carry non-zero cookieverifier

If the loop in nfs_readdir_xdr_to_array() runs more than once, subsequent
READDIR RPCs may wrongly carry a zero cookie verifier and non-zero cookie.
Make sure subsequent calls to READDIR carry the cookie verifier returned
by the first call.
Signed-off-by: Nagendra S Tomar <natomar@microsoft.com>
Fixes: b593c09f ("NFS: Improve handling of directory verifiers")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/dir.c

@@ -866,6 +866,8 @@ static int nfs_readdir_xdr_to_array(struct nfs_readdir_descriptor *desc,
 			break;
 		}
 
+		verf_arg = verf_res;
+
 		status = nfs_readdir_page_filler(desc, entry, pages, pglen,
 						 arrays, narrays);
 	} while (!status && nfs_readdir_page_needs_filling(page));