Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754293AbbETUS3 (ORCPT ); Wed, 20 May 2015 16:18:29 -0400 Received: from mail.kernel.org ([198.145.29.136]:43077 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752300AbbETUS1 (ORCPT ); Wed, 20 May 2015 16:18:27 -0400 MIME-Version: 1.0 In-Reply-To: References: <1430980461-5235-1-git-send-email-mlin@kernel.org> <1430980461-5235-2-git-send-email-mlin@kernel.org> Date: Wed, 20 May 2015 13:18:22 -0700 Message-ID: Subject: Re: [PATCH v3 01/11] block: make generic_make_request handle arbitrarily sized bios From: Ming Lin To: Jeff Moyer Cc: Ming Lin , lkml , Christoph Hellwig , Jens Axboe , Kent Overstreet , Dongsu Park , Christoph Hellwig , Al Viro , Ming Lei , Neil Brown , Alasdair Kergon , Mike Snitzer , dm-devel@redhat.com, Lars Ellenberg , Jiri Kosina , Geoff Levand , Jim Paris , Joshua Morris , Philip Kelleher , Minchan Kim , Nitin Gupta , Oleg Drokin , Andreas Dilger Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1726 Lines: 52 On Wed, May 20, 2015 at 11:58 AM, Jeff Moyer wrote: > Ming Lin writes: > >> On Mon, May 18, 2015 at 9:52 AM, Jeff Moyer wrote: >>> Ming Lin writes: >>> >>>> diff --git a/block/blk-core.c b/block/blk-core.c >>>> index fd154b9..909f317 100644 >>>> --- a/block/blk-core.c >>>> +++ b/block/blk-core.c >>>> @@ -617,6 +617,10 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) >>>> if (q->id < 0) >>>> goto fail_q; >>>> >>>> + q->bio_split = bioset_create(4, 0); >>>> + if (!q->bio_split) >>>> + goto fail_id; >>>> + >>> >>> Arbitrary numbers should be documented. >> >> Kent, >> >> Is there specific reason to choose number 4? >> If no, I may change it to BIO_POOL_SIZE which is 2. > > Here's what he had to say last time around: > > 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 Then I'll update it to BIO_POOL_SIZE. > bio_alloc_bioset() rescuer thing I did awhile back guarantees that. > > link: https://lkml.org/lkml/2013/11/26/47 > > Cheers, > Jeff -- 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/