From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753115AbaE0Pml (ORCPT ); Tue, 27 May 2014 11:42:41 -0400 Received: from mail-pb0-f45.google.com ([209.85.160.45]:63430 "EHLO mail-pb0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752154AbaE0Pmk (ORCPT ); Tue, 27 May 2014 11:42:40 -0400 Message-ID: <5384B26D.1000703@kernel.dk> Date: Tue, 27 May 2014 09:42:37 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Mikulas Patocka CC: Kent Overstreet , linux-kernel@vger.kernel.org, dm-devel@redhat.com, "Alasdair G. Kergon" , Mike Snitzer Subject: Re: [PATCH] block: flush queued bios when the process blocks References: <5384AA79.4010206@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-05-27 09:23, Mikulas Patocka wrote: > > > On Tue, 27 May 2014, Jens Axboe wrote: > >> On 2014-05-27 09:03, Mikulas Patocka wrote: >>> The block layer uses per-process bio list to avoid recursion in >>> generic_make_request. When generic_make_request is called recursively, the >>> bio is added to current->bio_list and the function returns immediatelly. >>> The top-level instance of generic_make_requests takes bios from >>> current->bio_list and processes them. >> >> This really begs the question of why we just don't use the per-process plugs >> for this. We already have scheduler hooks in place to flush those at the >> appropriate time. Why are we reinventing something for essentially the same >> thing? >> >> -- >> Jens Axboe > > Plugs work with requests, this patch works with bios. They are different > structures, so you can't use one infrastructure to process them. Yes... I realize the list and plugs are for requests. But there's nothing preventing a non-rq hook, we have uses like that too. And it could easily be extended to handle bio lists, too. > The patch adds bio list flushing to the scheduler just besides plug > flushsing. ... which is exactly why I'm commenting. It'd be great to avoid yet one more scheduler hook for this sort of thing. -- Jens Axboe