From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C09A5C433C1 for ; Tue, 30 Mar 2021 06:27:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9263761969 for ; Tue, 30 Mar 2021 06:27:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230248AbhC3G1U (ORCPT ); Tue, 30 Mar 2021 02:27:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:42742 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230334AbhC3G0t (ORCPT ); Tue, 30 Mar 2021 02:26:49 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1F99FAE86; Tue, 30 Mar 2021 06:26:48 +0000 (UTC) Subject: Re: [PATCH V4 11/12] block: add poll_capable method to support bio-based IO polling To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org, Jeffle Xu , Mike Snitzer , dm-devel@redhat.com References: <20210329152622.173035-1-ming.lei@redhat.com> <20210329152622.173035-12-ming.lei@redhat.com> From: Hannes Reinecke Message-ID: <162f000f-7f86-8988-4a15-2c3bf70de1b7@suse.de> Date: Tue, 30 Mar 2021 08:26:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210329152622.173035-12-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 3/29/21 5:26 PM, Ming Lei wrote: > From: Jeffle Xu > > This method can be used to check if bio-based device supports IO polling > or not. For mq devices, checking for hw queue in polling mode is > adequate, while the sanity check shall be implementation specific for > bio-based devices. For example, dm device needs to check if all > underlying devices are capable of IO polling. > > Though bio-based device may have done the sanity check during the > device initialization phase, cacheing the result of this sanity check > (such as by cacheing in the queue_flags) may not work. Because for dm > devices, users could change the state of the underlying devices through > '/sys/block//io_poll', bypassing the dm device above. In this case, > the cached result of the very beginning sanity check could be > out-of-date. Thus the sanity check needs to be done every time 'io_poll' > is to be modified. > > Signed-off-by: Jeffle Xu > --- > block/blk-sysfs.c | 14 +++++++++++--- > include/linux/blkdev.h | 1 + > 2 files changed, 12 insertions(+), 3 deletions(-) > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index db3268d41274..c8e7e4af66cb 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -426,9 +426,17 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page, > unsigned long poll_on; > ssize_t ret; > > - if (!q->tag_set || q->tag_set->nr_maps <= HCTX_TYPE_POLL || > - !q->tag_set->map[HCTX_TYPE_POLL].nr_queues) > - return -EINVAL; > + if (queue_is_mq(q)) { > + if (!q->tag_set || q->tag_set->nr_maps <= HCTX_TYPE_POLL || > + !q->tag_set->map[HCTX_TYPE_POLL].nr_queues) > + return -EINVAL; > + } else { > + struct gendisk *disk = queue_to_disk(q); > + > + if (!disk->fops->poll_capable || > + !disk->fops->poll_capable(disk)) > + return -EINVAL; > + } > > ret = queue_var_store(&poll_on, page, count); > if (ret < 0) > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index bfab74b45f15..a46f975f2a2f 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1881,6 +1881,7 @@ struct block_device_operations { > int (*report_zones)(struct gendisk *, sector_t sector, > unsigned int nr_zones, report_zones_cb cb, void *data); > char *(*devnode)(struct gendisk *disk, umode_t *mode); > + bool (*poll_capable)(struct gendisk *disk); > struct module *owner; > const struct pr_ops *pr_ops; > }; > I really wonder how this would work for nvme multipath; but I guess it doesn't change the current situation. So: Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer