From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Patterson Subject: Re: [dm-devel] [PATCH] block: silently error unsupported empty barriers too Date: Wed, 28 Oct 2009 20:19:01 +0000 Message-ID: <1256761141.5830.79.camel@grinch> References: <1249557257.3721.55.camel@blaa> <20090806114550.GL29899@agk-dp.fab.redhat.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mikulas Patocka Cc: Alasdair G Kergon , Mark McLoughlin , device-mapper development , Jens Axboe , Rusty Russell , linux-kernel , virtualization , ". troy.heber"@hp.com List-Id: dm-devel.ids On Thu, 2009-08-06 at 21:50 -0400, Mikulas Patocka wrote: > On Thu, 6 Aug 2009, Alasdair G Kergon wrote: > > > On Thu, Aug 06, 2009 at 12:14:17PM +0100, Mark McLoughlin wrote: > > > We should error all barriers, even empty barriers, on devices like > > > virtio_blk which don't support them. > > > > Have you considered whether or not virtio_blk actually needs to > > support empty barriers? > > > > Alasdair > > This is only for request-based drivers, where it is the responsibility of > blk-core to translate barriers. I think the empty barrier request anyway > in blk_do_ordered, but with an error message. So the patch changes it to > discard it early and queitly. It seems ok. > > Mikulas > -- This patch seems to have been dropped. I can reproduce the error using the following: 1. Create an LVM logical volume on top of a cciss device (note that the cciss driver does not support barriers) 2. Create an ext3 file system on top of the logical volume 3. Mount the file-system using -obarrier=1 4. Copy some files onto the file-system 5. Run sync (dm_flush is called) If I apply the patch (with some munging), the "end_request: I/O error, dev cciss/cXdY, sector 0" messages go away. This is not strictly a regression, given that the problem was introduced in 2.6.31, but I think it should still be fixed for 2.6.32. Andrew -- Andrew Patterson Hewlett-Packard