Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757878Ab2HXKiN (ORCPT ); Fri, 24 Aug 2012 06:38:13 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:41716 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754396Ab2HXKiI (ORCPT ); Fri, 24 Aug 2012 06:38:08 -0400 Date: Fri, 24 Aug 2012 03:37:34 -0700 From: Kent Overstreet To: "Martin K. Petersen" Cc: Tejun Heo , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, vgoyal@redhat.com, mpatocka@redhat.com, bharrosh@panasas.com, Jens Axboe , NeilBrown , Lars Ellenberg , Peter Osterlund , Sage Weil Subject: Re: [PATCH v6 11/13] block: Rework bio_pair_split() Message-ID: <20120824103734.GH11977@moria.home.lan> References: <1345655050-28199-1-git-send-email-koverstreet@google.com> <1345655050-28199-12-git-send-email-koverstreet@google.com> <20120822210410.GL19212@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1930 Lines: 38 On Thu, Aug 23, 2012 at 10:25:47PM -0400, Martin K. Petersen wrote: > >>>>> "Tejun" == Tejun Heo writes: > > Tejun> I complained about this in the last posting and in the previous > Tejun> patch. Please respond. Martin, are you okay with these > Tejun> integrity changes? > > I missed the first several iterations of all this while I was out on > vacation. I'll have to try to wrap my head around the new approach. > > However, I'm not sure I like the overall approach of the new splitting. > Instead of all this cloning, slicing and dicing of bio_vecs I'd rather > we bit the bullet and had an offset + length for the vector inside each > bio. That way we could keep the bio_vec immutable and make clones more > lightweight since their vecs would always point to the parent. This also > makes it trivial to split I/Os in the stacking drivers and removes evils > in the partial completion code path. It would also allow to sever the > ties between "size of block range operated on" vs. bi_size which we need > for copy offload, discard, etc. Agree 110% - making bio_vecs immutable and keeping the offset in the bio is something I've been talking about for ages, I'd love to see it happen. But that's going to be a much more invasive change so if I'm going to do it (and I am willing to work on it) it's just going to be a bit. This is really a stopgap solution. As far as the integrity splitting, it's similar to what the existing dm code does (main difference is dm already has the bio cloned, my bio_split() doesn't assume anything about the bio being split). Not sure how that affects ownership of the integrity data, honestly that part kind of confuses me. -- 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/