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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 3CC51C433C1 for ; Tue, 30 Mar 2021 08:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EFAA06195D for ; Tue, 30 Mar 2021 08:51:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230243AbhC3Iua (ORCPT ); Tue, 30 Mar 2021 04:50:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:27523 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229530AbhC3IuU (ORCPT ); Tue, 30 Mar 2021 04:50:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617094219; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NhqVQ817HwU5LWURD+dWlD0ONR0PaBLKta12Pq3I+u8=; b=aJckkscfWdsBItnacJAvPVzMU+AcUgitraaaMb+ZhhuYQdPVRrhOSLqmtQt3cnlcT5B/Yg z+E/iF6Bkwb2cx9GRoPtz0Krrzz701rNaJCOqMqmqQSYBk8qglHk/9ioEi6ycIJnZPAR6l e8xv/NG2Fcg16PVuehl1n3yelIrnKeI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-535-7OV1WLVsMuCpRSqrE-fwLA-1; Tue, 30 Mar 2021 04:50:15 -0400 X-MC-Unique: 7OV1WLVsMuCpRSqrE-fwLA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E0FB8801814; Tue, 30 Mar 2021 08:50:13 +0000 (UTC) Received: from T590 (ovpn-13-69.pek2.redhat.com [10.72.13.69]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3E4B754272; Tue, 30 Mar 2021 08:49:56 +0000 (UTC) Date: Tue, 30 Mar 2021 16:49:53 +0800 From: Ming Lei To: JeffleXu Cc: Hannes Reinecke , Jens Axboe , linux-block@vger.kernel.org, Mike Snitzer , dm-devel@redhat.com Subject: Re: [PATCH V4 11/12] block: add poll_capable method to support bio-based IO polling Message-ID: References: <20210329152622.173035-1-ming.lei@redhat.com> <20210329152622.173035-12-ming.lei@redhat.com> <162f000f-7f86-8988-4a15-2c3bf70de1b7@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Mar 30, 2021 at 02:50:51PM +0800, JeffleXu wrote: > > > On 3/30/21 2:26 PM, Hannes Reinecke wrote: > > 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. It should work for nvme multipath since the approach covers this case, and bio submitted to underlying NVMe is marked with REQ_HIPRI and REQ_POLL_CTX too. > > I wonder, at least, md/dm, which is built upon other devices, or > 'virtual device' in other words, should be distinguished from other > 'original' bio-based device (e.g., nvme multipath) then. Maybe one extra > flag or something. There is REQ_NVME_MPATH, but not sure we need to deal with that. Thanks, Ming