From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755074AbZCEC4F (ORCPT ); Wed, 4 Mar 2009 21:56:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752600AbZCECzy (ORCPT ); Wed, 4 Mar 2009 21:55:54 -0500 Received: from smtp105.mail.mud.yahoo.com ([209.191.85.215]:48231 "HELO smtp105.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752254AbZCECzy (ORCPT ); Wed, 4 Mar 2009 21:55:54 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:X-Yahoo-Newman-Property:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=VfldiinwgvO2/XALGtU2Z2MMa21Ln1WGI/MgCRqUUu9wUKO+Z/TO9QivEYGvaVKc3HVdhX0qcnsCLtqAOOwg/Xb0RUm/AOQsjVh7qq/k2QCW98C7+Px81zUihzjt2vO7GkkXIGp5QyXNWy5Y2FwMidl29gRehnXFZXBwGIdXKQg= ; X-YMail-OSG: lRKMl38VM1lB4r2PVGt0x88kL8OqTmNTlT0iGtAt9xxnK2_pzLBgorqnbUpCQUFO_ytP9xVvwVcq4XU8FHvfiFIotO4JJfz2Y0.lL7OJ8LTGT4gW0WjrqIpRSL.FdRoDEwkH45gsF9TEorWiRlFAp7TG14oqdBZrEFeZzKrCHYYvxGwxvSGlCAGq0ZCfhw-- X-Yahoo-Newman-Property: ymail-3 From: Nick Piggin To: Jan Kara , Andrew Morton Subject: Re: fsx-linux loosing mmap() writes under memory pressure Date: Thu, 5 Mar 2009 13:55:43 +1100 User-Agent: KMail/1.9.51 (KDE/4.0.4; ; ) Cc: linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org References: <20090304145109.GA7140@duck.suse.cz> <20090304155535.GA23108@duck.suse.cz> <20090304175031.GA24730@duck.suse.cz> In-Reply-To: <20090304175031.GA24730@duck.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200903051355.43909.nickpiggin@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 05 March 2009 04:50:31 Jan Kara wrote: > On Wed 04-03-09 16:55:35, Jan Kara wrote: > > On Wed 04-03-09 15:51:09, Jan Kara wrote: > > > first, I'd like to point out that this has happened under UML so it > > > can be just some obscure bug in that architecture but I belive it's > > > worth debugging anyway. Now to the problem: > > > This has happened with today Linus's git snapshot. The filesystem is > > > ext3 with *1KB* blocksize. I booted UML with 64MB of memory and run > > > (these are test's from Andrew Morton's torture tests): > > > fsx-linux -l 8000000 /mnt/testfile > > > bash-shared-mapping -t 8 /mnt/bashfile 50000000 > > > (the second test just makes the UML under memory pressure and stresses > > > the filesystem, otherwise it does not interact with fsx-linux in any > > > way). After some time (like an hour) fsx-linux reported the file is > > > corrupted. I tried again and it happened again so probably some > > > debugging should be possible. > > > Both times it seems we've simply completely lost a write which > > > happened through mmap (2 pages in the first case, 3 pages in the second > > > case). Also I've checked and in the first case no blocks are allocated > > > for the offsets where the data should be so most probably we've lost > > > the write before block_write_full_page() called get_block(). > > > I'll debug this further but I wanted let people know there's some > > > problem and maybe somebody has some bright idea :). I'm attaching the > > > log from fsx if someone is interested. > > > > Testing a bit more, I managed to reproduce the problem on ext2 and > > what's more strange, now the lost page was written via ordinary write() > > (fsxlog attached). So I believe this is more likely to be UML specific... > > And to add even more information, this also happens on ext2 with 4KB > blocksize (although much more rarely it seems). Again the data was written > by an extending write() but the block for it was not even allocated... What block device driver are you using? Can it be reproduced without mapped reads and writes completely? (-W -R)