From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754823Ab3KZHVB (ORCPT ); Tue, 26 Nov 2013 02:21:01 -0500 Received: from mail-pb0-f41.google.com ([209.85.160.41]:40849 "EHLO mail-pb0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753948Ab3KZHVA (ORCPT ); Tue, 26 Nov 2013 02:21:00 -0500 Date: Mon, 25 Nov 2013 23:21:28 -0800 From: Kent Overstreet To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, axboe@kernel.dk, Neil Brown , Alasdair Kergon , dm-devel@redhat.com Subject: Re: [PATCH 1/5] block: Make generic_make_request handle arbitrary sized bios Message-ID: <20131126072128.GF9244@kmo-pixel> References: <1385418633-9753-1-git-send-email-kmo@daterainc.com> <1385418633-9753-2-git-send-email-kmo@daterainc.com> <20131126060921.GB6434@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131126060921.GB6434@infradead.org> 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 On Mon, Nov 25, 2013 at 10:09:21PM -0800, Christoph Hellwig wrote: > > + q->bio_split = bioset_create(4, 0); > > + if (!q->bio_split) > > + goto fail_id; > > How did we arrive at a mempool size of 4 to make sure we can always make > progress with arbitrarily sized bios? Shouldn't we document the design > decision somewhere? It just has to be nonzero to guarantee forward progress - the bio_alloc_bioset() rescuer thing I did awhile back guarantees that. > > +static struct bio *blk_bio_discard_split(struct request_queue *q, > > + struct bio *bio, > > + struct bio_set *bs) > > +{ > > One fallout of this should be that it would allows us to impement > a range UNMAP/TRIP much more easily, which would help dramatically > with TRIM performance! Cool!