From: Spelic Subject: Re: Ext4 and xfs problems in dm-thin on allocation and discard Date: Tue, 19 Jun 2012 15:52:15 +0200 Message-ID: <4FE0840F.2050704@shiftmail.org> References: <4FDF9EBE.2030809@shiftmail.org> <20120619015745.GJ25389@dastard> <20120619031241.GA3884@redhat.com> <20120619131649.GA6811@redhat.com> <20120619133041.GB6811@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: =?UTF-8?B?THVrw6HFoSBDemVybmVy?= , Dave Chinner , Spelic , device-mapper development , linux-ext4@vger.kernel.org, xfs@oss.sgi.com To: Mike Snitzer Return-path: Received: from blade3.isti.cnr.it ([194.119.192.19]:1105 "EHLO blade3.isti.cnr.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752353Ab2FSNwf (ORCPT ); Tue, 19 Jun 2012 09:52:35 -0400 Received: from [192.168.6.232] ([155.253.6.254]) by mx.isti.cnr.it (PMDF V6.5-x6 #31988) with ESMTPSA id <01OGVIYF00W4ODSR3C@mx.isti.cnr.it> for linux-ext4@vger.kernel.org; Tue, 19 Jun 2012 15:51:39 +0200 (MEST) In-reply-to: <20120619133041.GB6811@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 06/19/12 15:30, Mike Snitzer wrote: > I don't recall Spelic saying anything about EOPNOTSUPP. So what has > made you zero in on an -EOPNOTSUPP return (which should not be > happening)? Exactly: I do not know if EOPNOTSUPP is being returned or not. If this helps, I have configured dm-thin via lvm2 LVM version: 2.02.95(2) (2012-03-06) Library version: 1.02.74 (2012-03-06) Driver version: 4.22.0 from dmsetup table I only see one option : "skip_block_zeroing", if and only if I configure it with -Zn . I do not see anything regarding ignore_discard vg1-pooltry1-tpool: 0 20971520 thin-pool 252:1 252:2 2048 0 1 skip_block_zeroing vg1-pooltry1_tdata: 0 20971520 linear 9:20 62922752 vg1-pooltry1_tmeta: 0 8192 linear 9:20 83894272 vg1-thinlv1: 0 31457280 thin 252:3 1 and in dmesg: [ 33.685200] device-mapper: thin: Discard unsupported by data device (dm-2): Disabling discard passdown. [ 33.709586] device-mapper: thin: Discard unsupported by data device (dm-6): Disabling discard passdown. I do not know what is the mechanism for which xfs cannot unmap blocks from dm-thin, but it really can't. If anyone has dm-thin installed he can try. This is 100% reproducible for me.