From: Trond Myklebust Subject: Re: [NFS] blocks of zeros (NULLs) in NFS files in kernels >= 2.6.20 Date: Mon, 22 Sep 2008 12:35:22 -0400 Message-ID: <1222101322.7615.6.camel@localhost> References: <20080905191939.GG22796@merfinllc.com> <56258A29-95D5-4A8C-A097-014B8FEDFB8F@oracle.com> <20080911184951.GB19054@merfinllc.com> <200809221805.48463.hpj@urpla.net> Mime-Version: 1.0 Content-Type: text/plain Cc: linux-kernel@vger.kernel.org, Aaron Straus , Chuck Lever , Neil Brown , Linux NFS Mailing List To: Hans-Peter Jansen Return-path: Received: from mail-out2.uio.no ([129.240.10.58]:41825 "EHLO mail-out2.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751011AbYIVQf2 (ORCPT ); Mon, 22 Sep 2008 12:35:28 -0400 In-Reply-To: <200809221805.48463.hpj-2x7n3sizJbFeoWH0uzbU5w@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, 2008-09-22 at 18:05 +0200, Hans-Peter Jansen wrote: > For what is worth, this behavior is visible in bog standard writing/reading > files, (log files in my case, via the python logging package). It obviously > deviates from local filesystem behavior, and former state of the linux > nfs-client. Should we add patches to less, tail, and all other instruments > for watching/analysing log files (just to pick the tip of the ice rock) in > order to throw away runs of zeros, when reading from nfs mounted files? Or > should we ask their maintainers to add locking code for the nfs "read > files, which are written at the same time" case, just to work around > __some__ of the consequences of this bug? Imagine, how ugly this is going > to look! > > The whole issue is what I call a major regression, thus I strongly ask for a > reply from Trond on this matter. > > I even vote for sending a revert request for this hunk to the stable team, > where it is applicable, after Trond sorted it out (for 2.6.27?). > > Thanks, Aaron and Chuck for the detailed analysis - it demystified a wired > behavior, I observed here. When you're in a process to get real work done > in a fixed timeline, such things could make you mad.. Revert _what_ exactly? Please assume that I've been travelling for the past 5 weeks, and have only a sketchy idea of what has been going on. My understanding was that this is a consequence of unordered writes causing the file to be extended while some other task is reading. AFAICS, this sort of behaviour has _always_ been possible. I can't see how reverting anything will fix it. Trond