Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761334AbZCXOQu (ORCPT ); Tue, 24 Mar 2009 10:16:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757963AbZCXOH2 (ORCPT ); Tue, 24 Mar 2009 10:07:28 -0400 Received: from cantor2.suse.de ([195.135.220.15]:54869 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758256AbZCXOHZ (ORCPT ); Tue, 24 Mar 2009 10:07:25 -0400 Date: Tue, 24 Mar 2009 15:07:21 +0100 From: Jan Kara To: Chris Mason Cc: Jan Kara , Nick Piggin , "Martin J. Bligh" , linux-ext4@vger.kernel.org, Ying Han , Linus Torvalds , Andrew Morton , linux-kernel , linux-mm , guichaz@gmail.com, Alex Khesin , Mike Waychison , Rohit Seth , Peter Zijlstra Subject: Re: ftruncate-mmap: pages are lost after writing to mmaped file. Message-ID: <20090324140720.GE23439@duck.suse.cz> References: <604427e00903181244w360c5519k9179d5c3e5cd6ab3@mail.gmail.com> <200903200248.22623.nickpiggin@yahoo.com.au> <20090319164638.GB3899@duck.suse.cz> <200903241844.22851.nickpiggin@yahoo.com.au> <20090324123935.GD23439@duck.suse.cz> <20090324125510.GA9434@duck.suse.cz> <20090324132637.GA14607@duck.suse.cz> <1237903305.17910.4.camel@think.oraclecorp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1237903305.17910.4.camel@think.oraclecorp.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1542 Lines: 32 On Tue 24-03-09 10:01:45, Chris Mason wrote: > On Tue, 2009-03-24 at 14:26 +0100, Jan Kara wrote: > > On Tue 24-03-09 13:55:10, Jan Kara wrote: > > > > And one more interesting thing I don't yet fully understand - I see pages > > > having PageError() set when they are removed from page cache (and they have > > > been faulted in before). It's probably some interaction with pagecache > > > readahead... > > Argh... So the problem seems to be that get_block() occasionally returns > > ENOSPC and we then discard the dirty data (hmm, we could give at least a > > warning for that). I'm not yet sure why getblock behaves like this because > > the filesystem seems to have enough space but anyway this seems to be some > > strange fs trouble as well. > > > > Ouch. Perhaps the free space is waiting on a journal commit? Yes, exactly. I've already found there's lot of space hold by the committing transaction (it can easily hold a few hundred megs or a few gigs with larger journal and my UML images aren't that big...). And writepage() implementation in ext3 does not have a logic to retry. Also block_write_full_page() clears buffers dirty bits so it's not easy to retry even if we did it. I'm now looking into how to fix this... Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/