From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id n0EMH0Bu004343 for ; Wed, 14 Jan 2009 16:17:01 -0600 Received: from ipmail05.adl2.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 103BD8BCE1 for ; Wed, 14 Jan 2009 14:16:59 -0800 (PST) Received: from ipmail05.adl2.internode.on.net (ipmail05.adl2.internode.on.net [203.16.214.145]) by cuda.sgi.com with ESMTP id kseRMLGZBaxlCcsF for ; Wed, 14 Jan 2009 14:16:59 -0800 (PST) Date: Thu, 15 Jan 2009 09:16:55 +1100 From: Dave Chinner Subject: Re: spurious -ENOSPC on XFS Message-ID: <20090114221655.GX8071@disturbed> References: <20090112151133.GA24852@infradead.org> <496C2D69.2010301@sgi.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <496C2D69.2010301@sgi.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Lachlan McIlroy Cc: Christoph Hellwig , Mikulas Patocka , linux-kernel@vger.kernel.org, xfs@oss.sgi.com On Tue, Jan 13, 2009 at 04:58:01PM +1100, Lachlan McIlroy wrote: > Christoph Hellwig wrote: >> On Mon, Jan 12, 2009 at 06:14:36AM -0500, Mikulas Patocka wrote: >>> Hi >>> >>> I discovered a bug in XFS in delayed allocation. >>> >>> When you take a small partition (52MB in my case) and copy many small >>> files on it (source code) that barely fits there, you get -ENOSPC. >>> Then sync the partition, some free space pops up, click "retry" in MC >>> an the copy continues. They you get again -ENOSPC, you must sync, >>> click "retry" and go on. And so on few times until the source code >>> finally fits on the XFS partition. >>> >>> This misbehavior is apparently caused by delayed allocation, delayed >>> allocation does not exactly know how much space will be occupied by >>> data, so it makes some upper bound guess. Because free space count is >>> only a guess, not the actual data being consumed, XFS should not >>> return -ENOSPC on behalf of it. When the free space overflows, XFS >>> should sync itself, retry allocation and only return -ENOSPC if it >>> fails the second time, after the sync. > This sounds like a problem with speculative allocation - delayed allocations > beyond eof. Even if we write a small file, say 4k, a 64k chunk of delayed > allocation will be credited to the file. The second retry occurs without speculative EOF allocation. That's what the BMAPI_SYNC flag does.... That being said, it can't truncate away pre-existing speculative allocations on other files, which is why there is a global flush and wait before the third retry..... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs