From: Hugh Dickins Subject: Re: Bug with "fix partial page writes" [3.2-rc regression] Date: Tue, 6 Dec 2011 14:47:02 -0800 (PST) Message-ID: References: <20111121165626.GD14568@thunk.org> <4EDD729E.2060402@linux.vnet.ibm.com> <4EDE85F4.4020503@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Ted Ts'o , Curt Wohlgemuth , Yongqiang Yang , Surbhi Palande , Rafael Wysocki , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: Allison Henderson Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:54340 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753919Ab1LFWrY (ORCPT ); Tue, 6 Dec 2011 17:47:24 -0500 Received: by iakc1 with SMTP id c1so4336416iak.19 for ; Tue, 06 Dec 2011 14:47:23 -0800 (PST) In-Reply-To: <4EDE85F4.4020503@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, 6 Dec 2011, Allison Henderson wrote: > On 12/06/2011 01:55 AM, Hugh Dickins wrote: > > On Mon, 5 Dec 2011, Allison Henderson wrote: > > > > > > Have you tried Yongqiang's patch "[PATCH 1/2] ext4: let mpage_submit_io > > > works well when blocksize< pagesize" ? I have tried it and it does > > > seem to > > > help, but I am still running into some failures that I am trying to > > > debug, > > > but let please let us know if it helps the issues that you are seeing. > > > Thx! > > > > That 1/2, or the 2/2 "ext4: let ext4_discard_partial_buffers handle > > pages without buffers correctly"? The latter is mostly a reversion > > of your 02fac1297eb3, so that's the one I need to fix the oops and > > rare data corruption. Perhaps you're suggesting 1/2 for fsx failures > > under memory pressure? > > > > I've now tried the fsx test on three machines, with both 1/2 and 2/2 > > applied to 3.2-rc4. On one machine, with ext2 on loop on tmpfs, the > > fsx test failed in a couple of minutes with those patches; on another > > machine, with ext2 on loop on tmpfs, it failed after about 40 minutes > > with the patches; on this laptop, with ext2 on SSD, it's just now > > failed after 35 minutes with the patches. > > > > That's not to say that Yongqiang's patches aren't good; but I cannot > > detect whether they make any improvement or not, since lasting for 2 or > > 40 minutes is typical for fsx under memory pressure with recent kernels. > > > Well, initially I meant to just try the whole set, but now that I try just > one of them, I find that I get further with only the first one. I think > Yongqiang and I have a similar set up because I get the hang if I dont have > the first patch, and I get the fsx write failure (in about 20 or so minutes) > if I have the second one. But I think Yongqiang's right, we need to figure > out why the page is uptodate when it shouldn't be. I've not seen a hang myself. I'm reluctant to drop the second patch, since it appears to fix the real problems (oops and corruption) that I have seen, and fsx fails with or without it; but I don't know whether it's any better than simply reverting yours. I would certainly like fsx under memory pressure to be reliable again - that will help all our testing of new changes; but I think it's more urgent to get normal loads to be reliable again. If you can call building on -t ext2 -b 1024 under memory pressure normal ;) Hugh