Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423522Ab3CVXQN (ORCPT ); Fri, 22 Mar 2013 19:16:13 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:27255 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423395Ab3CVXQM (ORCPT ); Fri, 22 Mar 2013 19:16:12 -0400 Date: Fri, 22 Mar 2013 16:16:00 -0700 From: "Darrick J. Wong" To: device-mapper development Cc: Heinz Mauelshagen , Randy Dunlap , linux-kernel@vger.kernel.org, Mikulas Patocka , Paul Taysom , Linus Torvalds , Joe Thornber Subject: Re: [dm-devel] dm: dm-cache fails to write the cache device in writethrough mode Message-ID: <20130322231600.GD5357@blackbox.djwong.org> References: <20130322201151.GB5357@blackbox.djwong.org> <20130322223425.GA5638@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130322223425.GA5638@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2790 Lines: 76 On Fri, Mar 22, 2013 at 06:34:28PM -0400, Mike Snitzer wrote: > On Fri, Mar 22 2013 at 4:11pm -0400, > Darrick J. Wong wrote: > > > The new writethrough strategy for dm-cache issues a bio to the origin device, > > remaps the bio to the cache device, and issues the bio to the cache device. > > However, the block layer modifies bi_sector and bi_size, so we need to preserve > > these or else nothing gets written to the cache (bi_size == 0). This fixes the > > problem where someone writes a block through the cache, but a subsequent reread > > (from the cache) returns old contents. > > Your writethrough blkid test results are certainly strange. But I'm not > aware of where the block layer would modify bi_size and bi_sector; > please elaborate. > > I cannot reproduce your original report. I developed > 'test_writethrough_ext4_uuids_match', apologies for the ruby code: Hmm... I'm building my kernels off 0a7e453103b9718d357688b83bb968ee108cc874 in Linus' tree (post 3.9-rc3). This is the full output of dmsetup table: moocache-blocks: 0 1039360 linear 8:16 9088 moocache-metadata: 0 8704 linear 8:16 384 moocache: 0 67108864 cache 253:0 253:1 8:0 512 1 writethrough default 4 random_threshold 4 sequential_threshold 32768 253:0 -> moocache-metadata and 253:1 -> moocache-blocks. I'm curious what your setup is... --D > > def test_writethrough_ext4_uuids_match > size = meg(10) > > # wipe the origin to ensure we don't accidentally have the same > # data on it. > with_standard_linear(:data_size => size) do |origin| > wipe_device(origin) > end > > uuid = "deadbeef-cafe-dead-beef-cafedeadbeef" > > # format the cache device with a specific uuid > with_standard_cache(:format => true, > :io_mode => :writethrough, > :data_size => size) do |cache| > fs = FS::file_system(:ext4, cache) > fs.format(:uuid => uuid) > FS::assert_fs_uuid(uuid, cache) > end > > # origin should have the same uuid as the cache > with_standard_linear(:data_size => size) do |origin| > FS::assert_fs_uuid(uuid, origin) > end > end > > This test was committed to the 'devel' branch of my thinp-test-suite > tree: git://github.com/snitm/thinp-test-suite.git > > Also the existing 'test_writethrough' test works fine. > > So for now: > > Nacked-by: Mike Snitzer > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/