Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933320AbdCJPQb (ORCPT ); Fri, 10 Mar 2017 10:16:31 -0500 Received: from mail-wm0-f49.google.com ([74.125.82.49]:37312 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932759AbdCJPQY (ORCPT ); Fri, 10 Mar 2017 10:16:24 -0500 Subject: Re: [PATCH v2] blk: improve order of bio handling in generic_make_request() To: Mikulas Patocka , Mike Snitzer References: <87h93blz6g.fsf@notabene.neil.brown.name> <71562c2c-97f4-9a0a-32ec-30e0702ca575@profitbricks.com> <87lgsjj9w8.fsf@notabene.neil.brown.name> <87r328j00i.fsf@notabene.neil.brown.name> <87d1dphhuy.fsf@notabene.neil.brown.name> <58be6551-4aa7-72ee-1616-a1545606d029@kernel.dk> <87varhg14d.fsf@notabene.neil.brown.name> <20170310143822.GA23879@redhat.com> Cc: Lars Ellenberg , NeilBrown , Jens Axboe , LKML , Kent Overstreet , Pavel Machek , linux-raid@vger.kernel.org, device-mapper development , linux-block@vger.kernel.org From: Jack Wang Message-ID: <153a6cff-c553-0d18-e15b-4f3defc3a42b@profitbricks.com> Date: Fri, 10 Mar 2017 16:07:58 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1777 Lines: 51 On 10.03.2017 15:55, Mikulas Patocka wrote: > > > On Fri, 10 Mar 2017, Mike Snitzer wrote: > >> On Fri, Mar 10 2017 at 7:34am -0500, >> Lars Ellenberg wrote: >> >>>> --- a/block/blk-core.c >>>> +++ b/block/blk-core.c >>>> @@ -1975,7 +1975,14 @@ generic_make_request_checks(struct bio *bio) >>>> */ >>>> blk_qc_t generic_make_request(struct bio *bio) >>>> { >>>> - struct bio_list bio_list_on_stack; >>>> + /* >>>> + * bio_list_on_stack[0] contains bios submitted by the current >>>> + * make_request_fn. >>>> + * bio_list_on_stack[1] contains bios that were submitted before >>>> + * the current make_request_fn, but that haven't been processed >>>> + * yet. >>>> + */ >>>> + struct bio_list bio_list_on_stack[2]; >>>> blk_qc_t ret = BLK_QC_T_NONE; >>> >>> May I suggest that, if you intend to assign something that is not a >>> plain &(struct bio_list), but a &(struct bio_list[2]), >>> you change the task member so it is renamed (current->bio_list vs >>> current->bio_lists, plural, is what I did last year). >>> Or you will break external modules, silently, and horribly (or, >>> rather, they won't notice, but break the kernel). >>> Examples of such modules would be DRBD, ZFS, quite possibly others. >> >> drbd is upstream -- so what is the problem? (if you are having to >> distribute drbd independent of the upstream drbd then why is drbd >> upstream?) >> >> As for ZFS, worrying about ZFS kABI breakage is the last thing we should >> be doing. > > It's better to make external modules not compile than to silently > introduce bugs in them. So yes, I would rename that. > > Mikulas Agree, better rename current->bio_list to current->bio_lists Regards, Jack