From: "Chuck Lever" Subject: Re: [PATCH 2/2] nfs(5): Clarify behavior of the mountproto= and proto= options Date: Tue, 23 Sep 2008 12:55:52 -0400 Message-ID: <76bd70e30809230955l66aa59abo1fa25f85994e1915@mail.gmail.com> References: <20080923161322.5119.20872.stgit@manray.1015granger.net> <20080923161641.5119.37034.stgit@manray.1015granger.net> Reply-To: chucklever@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: steved@redhat.com, linux-nfs@vger.kernel.org To: "Talpey, Thomas" Return-path: Received: from gv-out-0910.google.com ([216.239.58.185]:9701 "EHLO gv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751648AbYIWQzy (ORCPT ); Tue, 23 Sep 2008 12:55:54 -0400 Received: by gv-out-0910.google.com with SMTP id e6so162652gvc.37 for ; Tue, 23 Sep 2008 09:55:52 -0700 (PDT) In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, Sep 23, 2008 at 12:41 PM, Talpey, Thomas wrote: > One other comment... > > At 12:16 PM 9/23/2008, Chuck Lever wrote: >>Document the interaction between the mountproto= and the proto= mount >>options in a new subsection of nfs(5). >> >>Signed-off-by: Chuck Lever >>--- >> >> utils/mount/nfs.man | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 files changed, 81 insertions(+), 0 deletions(-) >> >>diff --git a/utils/mount/nfs.man b/utils/mount/nfs.man >>index b1037a8..48f2153 100644 >>--- a/utils/mount/nfs.man >>+++ b/utils/mount/nfs.man >>@@ -831,6 +831,87 @@ and >> .B wsize >> can safely be allowed to default to the largest values supported by >> both client and server, independent of the network's MTU size. >>+.SS "Interaction between the proto and mountproto options" >>+The Linux NFS client can use a different transport protocol for >>+contacting an NFS server's rpcbind service, its mountd service, >>+its NLM service, and its NFS service. >>+The exact transport protocols employed by the Linux NFS client for >>+each mount point depends on the settings of the transport protocol >>+mount options, which include >>+.BR proto , >>+.BR mountproto , >>+.BR udp ", and " tcp . >>+.P >>+The NSM protocol uses the UDP transport >>+no matter what transport specific options are specified. > > This actually isn't true - in fact the client NSM by default listens on > both UDP and TCP, as can be seen with rpcinfo -p. > > What is true is that the vast majority of NFS servers call back on UDP, > and if this fails, there is no indication at the client whatsoever. > > So the text should perhaps say "NFS servers typically choose UDP for the > NSM protocol; the client in any case accepts both UDP and TCP." Granted that this text should be tuned a bit, but... Even though rpc.statd listens on TCP as well, Linux sm-notify requests go out only on UDP; and there is no mount option to change any of this behavior. NSM is a bit of a challenge to describe because both ends act as a client and a server. -- Chuck Lever