Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756898AbcJMVAE (ORCPT ); Thu, 13 Oct 2016 17:00:04 -0400 Received: from mail-oi0-f54.google.com ([209.85.218.54]:34719 "EHLO mail-oi0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754956AbcJMU7w (ORCPT ); Thu, 13 Oct 2016 16:59:52 -0400 MIME-Version: 1.0 In-Reply-To: <094ff78d-b410-b2ac-ad60-2af09cf47523@kernel.dk> References: <1476388433-2539-1-git-send-email-adam.manzanares@hgst.com> <1476388433-2539-2-git-send-email-adam.manzanares@hgst.com> <068e03c4-3558-a6b1-2008-d13bde4958a1@kernel.dk> <094ff78d-b410-b2ac-ad60-2af09cf47523@kernel.dk> From: Dan Williams Date: Thu, 13 Oct 2016 13:59:15 -0700 Message-ID: Subject: Re: [PATCH v4 1/4] block: Add iocontext priority to request To: Jens Axboe Cc: Adam Manzanares , Tejun Heo , Hannes Reinecke , "Martin K. Petersen" , mchristi@redhat.com, Toshi Kani , Ming Lei , sathya.prakash@broadcom.com, chaitra.basappa@broadcom.com, suganath-prabu.subramani@broadcom.com, linux-block@vger.kernel.org, "IDE/ATA development list" , "linux-kernel@vger.kernel.org" , MPT-FusionLinux.pdl@broadcom.com, linux-scsi , Adam Manzananares 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: 2760 Lines: 73 On Thu, Oct 13, 2016 at 1:24 PM, Jens Axboe wrote: > On 10/13/2016 02:19 PM, Dan Williams wrote: >> >> On Thu, Oct 13, 2016 at 1:09 PM, Jens Axboe wrote: >>> >>> On 10/13/2016 02:06 PM, Dan Williams wrote: >>>> >>>> >>>> On Thu, Oct 13, 2016 at 12:53 PM, Adam Manzanares >>>> wrote: >>>>> >>>>> >>>>> Patch adds an association between iocontext ioprio and the ioprio of a >>>>> request. This value is set in blk_rq_set_prio which takes the request >>>>> and >>>>> the ioc as arguments. If the ioc is valid in blk_rq_set_prio then the >>>>> iopriority of the request is set as the iopriority of the ioc. In >>>>> init_request_from_bio a check is made to see if the ioprio of the bio >>>>> is >>>>> valid and if so then the request prio comes from the bio. >>>>> >>>>> Signed-off-by: Adam Manzananares >>>>> --- >>>>> block/blk-core.c | 4 +++- >>>>> include/linux/blkdev.h | 14 ++++++++++++++ >>>>> 2 files changed, 17 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/block/blk-core.c b/block/blk-core.c >>>>> index 14d7c07..361b1b9 100644 >>>>> --- a/block/blk-core.c >>>>> +++ b/block/blk-core.c >>>>> @@ -1153,6 +1153,7 @@ static struct request *__get_request(struct >>>>> request_list *rl, int op, >>>>> >>>>> blk_rq_init(q, rq); >>>>> blk_rq_set_rl(rq, rl); >>>>> + blk_rq_set_prio(rq, ioc); >>>>> req_set_op_attrs(rq, op, op_flags | REQ_ALLOCED); >>>>> >>>>> /* init elvpriv */ >>>>> @@ -1656,7 +1657,8 @@ void init_request_from_bio(struct request *req, >>>>> struct bio *bio) >>>>> >>>>> req->errors = 0; >>>>> req->__sector = bio->bi_iter.bi_sector; >>>>> - req->ioprio = bio_prio(bio); >>>>> + if (ioprio_valid(bio_prio(bio))) >>>>> + req->ioprio = bio_prio(bio); >>>> >>>> >>>> >>>> Should we use ioprio_best() here? If req->ioprio and bio_prio() >>>> disagree one side has explicitly asked for a higher priority. >>> >>> >>> >>> It's a good question - but if priority has been set in the bio, it makes >>> sense that that would take priority over the general setting for the >>> task/io context. So I think the patch is correct as-is. >> >> >> Assuming you always trust the kernel to know the right priority... > > > If it set it in the bio, it better know what it's doing. Besides, > there's nothing stopping the caller from checking the task priority when > it sets it. If we do ioprio_best(), then we are effectively preventing > anyone from submitting a bio with a lower priority than the task has > generally set. Ah, that makes sense. Move the ioprio_best() decision out to whatever code is setting bio_prio() to allow for cases where the kernel knows best.