From: Christoph Hellwig 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 04:19:25 -0400 Message-ID: <20110502081925.GA11312@infradead.org> References: <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> <20110502081308.GC8642@agk-dp.fab.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: device-mapper development , Alasdair G Kergon , sandeen@redhat.com, Mike Snitzer , Christoph Hellwig , Dark Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:54326 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920Ab1EBITb (ORCPT ); Mon, 2 May 2011 04:19:31 -0400 Content-Disposition: inline In-Reply-To: <20110502081308.GC8642@agk-dp.fab.redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, May 02, 2011 at 09:13:08AM +0100, Alasdair G Kergon wrote: > 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. Exactly. We already have the information in the queue limits to tell the filesystem if discard is supported at all or not.