Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-we0-f171.google.com ([74.125.82.171]:46575 "EHLO mail-we0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750822Ab3C0MTG (ORCPT ); Wed, 27 Mar 2013 08:19:06 -0400 Received: by mail-we0-f171.google.com with SMTP id d46so5428046wer.16 for ; Wed, 27 Mar 2013 05:19:04 -0700 (PDT) Message-ID: <5152E3B5.8080402@tonian.com> Date: Wed, 27 Mar 2013 14:19:01 +0200 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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: 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? 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 >