From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: Ext4 and xfs problems in dm-thin on allocation and discard Date: Tue, 19 Jun 2012 14:20:29 +0200 (CEST) Message-ID: References: <4FDF9EBE.2030809@shiftmail.org> <20120619015745.GJ25389@dastard> <20120619031241.GA3884@redhat.com> <4FE062B3.7080702@shiftmail.org> Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="571144193-1915489382-1340108483=:21961" Cc: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= , Mike Snitzer , Dave Chinner , device-mapper development , linux-ext4@vger.kernel.org, xfs@oss.sgi.com To: Spelic Return-path: Received: from mx1.redhat.com ([209.132.183.28]:11588 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753163Ab2FSMVg (ORCPT ); Tue, 19 Jun 2012 08:21:36 -0400 In-Reply-To: <4FE062B3.7080702@shiftmail.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --571144193-1915489382-1340108483=:21961 Content-Type: TEXT/PLAIN; charset=windows-1252 Content-Transfer-Encoding: 8BIT On Tue, 19 Jun 2012, Spelic wrote: > Date: Tue, 19 Jun 2012 13:29:55 +0200 > From: Spelic > To: Luk?? Czerner > Cc: Mike Snitzer , Dave Chinner , > Spelic , > device-mapper development , > linux-ext4@vger.kernel.org, xfs@oss.sgi.com > Subject: Re: Ext4 and xfs problems in dm-thin on allocation and discard > > On 06/19/12 08:32, Luk?? Czerner wrote: > > > > So do I understand correctly that even though the discard came > > through and thinp took advantage of it it still returns EOPNOTSUPP ? > > This seems rather suboptimal. IIRC there was a discussion to add an > > option to enable/disable sending discard in thinp target down > > to the device. > > I'll ask this too... > do I understand correctly that dm-thin returns EOPNOTSUPP to the filesystem > layer even though it is using the discard to unmap blocks, and at that point > XFS stops sending discards down there (while ext4 keeps sending them)? > > This looks like a bug of dm-thin to me. Discards are "supported" in such a > scenario. > > Do you have a patch for dm-thin so to prevent it sending EOPTNOTSUPP ? Yes, definitely this behaviour need to change in dm-thin. I do not have a path, it was merely a proposal how thing could be done. Not sure what Mike and rest of the dm folks think about this. -Lukas > > Thank you > S. > --571144193-1915489382-1340108483=:21961--