Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:9302 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937008Ab0COWrL (ORCPT ); Mon, 15 Mar 2010 18:47:11 -0400 Date: Mon, 15 Mar 2010 18:47:02 -0400 From: Jeff Layton To: Trond Myklebust Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH] vfs: pass struct file to do_truncate on O_TRUNC opens Message-ID: <20100315184702.35c4d140@tlielax.poochiereds.net> In-Reply-To: <1268692288.3040.2.camel@localhost.localdomain> References: <1268689152-19168-1-git-send-email-jlayton@redhat.com> <1268692288.3040.2.camel@localhost.localdomain> Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Mon, 15 Mar 2010 18:31:28 -0400 Trond Myklebust wrote: > On Mon, 2010-03-15 at 17:39 -0400, Jeff Layton wrote: > > When a file is opened with O_TRUNC, the truncate processing is handled > > by handle_truncate(). This function however doesn't receive any info > > about the newly instantiated filp, and therefore can't pass that info > > along so that the setattr can use it. > > > > This makes NFSv4 misbehave. The client does an open and gets a valid > > stateid, and then doesn't use that stateid on the subsequent truncate. > > It uses the zero-stateid instead. Most servers ignore this fact and > > just do the truncate anyway, but some don't like it (notably, RHEL4). > > > > It seems more correct that since we have a fully instantiated file at > > the time that handle_truncate is called, that we pass that along so > > that the truncate operation can properly use it. > > At least in the O_CREAT|O_TRUNC case, we really should modify > nfs4_opendata_alloc() to set the attrs.ia_size to zero, so that the > server does an atomic open(O_CREAT|O_TRUNC) for us (see the DESCRIPTION > paragraph in RFC3530 section 14.2.16). There shouldn't be any need for > an extra truncate RPC call. > > Plain open(O_TRUNC) probably does need something along the lines of what > you propose, however. > Yeah that would be cleaner on the wire for the create case. It's not clear to me how to implement that though. There doesn't appear to be a straightforward way to tell the VFS to skip the truncate. -- Jeff Layton