From: Alasdair G Kergon Subject: Re: [dm-devel] do not disable ext4 discards on first discard failure? [was: Re: dm snapshot: ignore discards issued to the snapshot-origin target] Date: Mon, 2 May 2011 09:13:08 +0100 Message-ID: <20110502081308.GC8642@agk-dp.fab.redhat.com> References: <20cf301cbef67d323104a0c2ff52@google.com> <20110413224025.GA18589@redhat.com> <20110413234854.GA19793@redhat.com> <20110426173213.GA19604@redhat.com> <20110428001912.GA14659@redhat.com> <20110428075355.GA2190@infradead.org> <20110428205935.GA24979@redhat.com> <20110429122454.GL32370@agk-dp.fab.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Alasdair G Kergon , sandeen@redhat.com, Mike Snitzer , Christoph Hellwig , DarkNovaNick@gmail.com, linux-lvm@redhat.com, Lukas Czerner , linux-ext4@vger.kernel.org To: device-mapper development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36391 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752596Ab1EBINX (ORCPT ); Mon, 2 May 2011 04:13:23 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, May 02, 2011 at 09:16:21AM +0200, Lukas Czerner wrote: > However when we have dm device where part of the device supports > discard due to underlying hardware capability we just can not return > EOPNOTSUPP from blkdev_issue_discard, because it is just not true! EOPNOTSUPP from dm means the operation was not supported on that *one* bio. It does *not* tell you anything in general about the device, or whether you'd get the same error from different bios in future. Alasdair