Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-wi0-f180.google.com ([209.85.212.180]:57407 "EHLO mail-wi0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752372Ab3D1PUu (ORCPT ); Sun, 28 Apr 2013 11:20:50 -0400 Received: by mail-wi0-f180.google.com with SMTP id h11so2023929wiv.1 for ; Sun, 28 Apr 2013 08:20:49 -0700 (PDT) Message-ID: <517D3E4D.4010607@tonian.com> Date: Sun, 28 Apr 2013 18:20:45 +0300 From: Benny Halevy MIME-Version: 1.0 To: Fred Isaman , "Myklebust, Trond" CC: "Isaman, Fred" , "linux-nfs@vger.kernel.org" Subject: Re: [PATCH] pnfs: do not reset to mds if wb_offset != wb_pgbase References: <1363617532-24172-1-git-send-email-bhalevy@tonian.com> <1363622128.4351.15.camel@leira.trondhjem.org> <51473F46.10401@tonian.com> <5148BE0B.9080802@tonian.com> <5152E3B5.8080402@tonian.com> In-Reply-To: <5152E3B5.8080402@tonian.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 2013-03-27 14:19, Benny Halevy wrote: > On 2013-03-19 22:28, Fred Isaman wrote: >> On Tue, Mar 19, 2013 at 3:35 PM, Benny Halevy wrote: >>> On 2013-03-18 19:04, Fred Isaman wrote: >>>> A problem case is if the layout ends within the page request, which >>>> can happen due to the misalignment. >>> >>> First, the file layout currently supports only whole file layouts so I don't see >>> how that's a problem. >>> Regardless, I'd rather trim the layout segment to PAGE_SIZE boundaries >>> and get a new layout from the page aligned offset and on with minlength = PAGE_SIZE >>> (as we do today). >>> >>> Benny >>> >> >> Yes, but consider.... >> >> let P = PAGE_SIZE >> >> assume you have a layout from 0 to 4P, and you try to do a WRITE from >> 2P to 6P. Now if the buffer is not page aligned, one of the nfs_page >> requests will contain the file's logical 4P offset at a random >> location within the nfs_page. What happens then? > > Fred, Can you please provide a test that reproduces this concern > so we can verify the system behavior with and without my patch? Ping... > > Benny > >> >> Fred >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-nfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >>