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=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 B4E94C48BE5 for ; Mon, 21 Jun 2021 08:42:14 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 417BB611C1 for ; Mon, 21 Jun 2021 08:42:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 417BB611C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=dm-devel-bounces@redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624264933; h=from:from:sender:sender: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:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=XmSvTwtfzKhxUdd+NornCQSSbOXisOtXe4myobwwkbA=; b=PMVWcAqAjlZSztKpO9ZJc2/T7pFHwccANR++V9EY/DHoJL9qjK3jOkVp9R38ryRfxxKub9 qOnxvctvuGfi2mhg/v8BWB1+g56IYprL7/6tYE+G3pbYI3NiAlgxY2pHYD2qPcWC4l4hWg ObRDVuPf6mlUirlNXiSICH/z0nTjaKo= 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-543-VI3wRXaSNTGeFXrDO-wyNQ-1; Mon, 21 Jun 2021 04:42:11 -0400 X-MC-Unique: VI3wRXaSNTGeFXrDO-wyNQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B7B8F802C88; Mon, 21 Jun 2021 08:42:06 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9ED5060938; Mon, 21 Jun 2021 08:42:06 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 374C14EA29; Mon, 21 Jun 2021 08:42:06 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 15L8g3tF023891 for ; Mon, 21 Jun 2021 04:42:04 -0400 Received: by smtp.corp.redhat.com (Postfix) id EF4085D703; Mon, 21 Jun 2021 08:42:03 +0000 (UTC) Received: from T590 (ovpn-13-237.pek2.redhat.com [10.72.13.237]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 514791ABD4; Mon, 21 Jun 2021 08:41:50 +0000 (UTC) Date: Mon, 21 Jun 2021 16:41:33 +0800 From: Ming Lei To: Christoph Hellwig Message-ID: References: <20210617103549.930311-1-ming.lei@redhat.com> <20210617103549.930311-3-ming.lei@redhat.com> <20210621072502.GC6651@lst.de> MIME-Version: 1.0 In-Reply-To: <20210621072502.GC6651@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-loop: dm-devel@redhat.com Cc: Jens Axboe , Mike Snitzer , linux-block@vger.kernel.org, dm-devel@redhat.com, Jeffle Xu Subject: Re: [dm-devel] [RFC PATCH V2 2/3] block: add ->poll_bio to block_device_operations X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Mon, Jun 21, 2021 at 09:25:02AM +0200, Christoph Hellwig wrote: > > + struct gendisk *disk = bio->bi_bdev->bd_disk; > > + struct request_queue *q = disk->queue; > > blk_qc_t cookie = READ_ONCE(bio->bi_cookie); > > int ret; > > > > - if (cookie == BLK_QC_T_NONE || !blk_queue_poll(q)) > > + if ((queue_is_mq(q) && cookie == BLK_QC_T_NONE) || > > + !blk_queue_poll(q)) > > return 0; > > How does polling for a bio without a cookie make sense even when > polling bio based? It isn't necessary to use bio->bi_cookie, that is why I doesn't use it, which actually provides one free 32bit in bio for bio based driver. > > But if we come up for a good rationale for this I'd really > split the conditions to make them more readable: > > if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > return 0; > if (queue_is_mq(q) && cookie == BLK_QC_T_NONE) > return 0; OK. > > > + if (!queue_is_mq(q)) { > > + if (disk->fops->poll_bio) { > > + ret = disk->fops->poll_bio(bio, flags); > > + } else { > > + WARN_ON_ONCE(1); > > + ret = 0; > > + } > > + } else { > > ret = blk_mq_poll(q, cookie, flags); > > I'd go for someting like: > > if (queue_is_mq(q)) > ret = blk_mq_poll(q, cookie, flags); > else if (disk->fops->poll_bio) > ret = disk->fops->poll_bio(bio, flags); > else > WARN_ON_ONCE(1); > > with ret initialized to 0 at declaration time. Fine. > > > struct block_device_operations { > > void (*submit_bio)(struct bio *bio); > > + /* ->poll_bio is for bio driver only */ > > I'd drop the comment, this is already nicely documented in add_disk > together with the actual check. We also don't note this for submit_bio > here. OK. thanks, Ming -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel