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=-3.8 required=3.0 tests=BAYES_00, 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 84D3EC433ED for ; Mon, 12 Apr 2021 09:40:08 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 1F6B661248 for ; Mon, 12 Apr 2021 09:40:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F6B661248 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=tempfail smtp.mailfrom=dm-devel-bounces@redhat.com 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-468-1PLPc3fENB2PkpNcMNDWCg-1; Mon, 12 Apr 2021 05:40:05 -0400 X-MC-Unique: 1PLPc3fENB2PkpNcMNDWCg-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 D1C278030CA; Mon, 12 Apr 2021 09:39:59 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A38905D6DC; Mon, 12 Apr 2021 09:39:59 +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 AA50918095C9; Mon, 12 Apr 2021 09:39:58 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 13C9dMhe027182 for ; Mon, 12 Apr 2021 05:39:23 -0400 Received: by smtp.corp.redhat.com (Postfix) id 5CA7F43697; Mon, 12 Apr 2021 09:39:22 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast02.extmail.prod.ext.rdu2.redhat.com [10.11.55.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 572EC43685 for ; Mon, 12 Apr 2021 09:39:19 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D4121802BEE for ; Mon, 12 Apr 2021 09:39:19 +0000 (UTC) Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-265-ONoSo4q8MHKHc4_5OFQlfg-1; Mon, 12 Apr 2021 05:39:18 -0400 X-MC-Unique: ONoSo4q8MHKHc4_5OFQlfg-1 Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lVt20-00474E-Sm; Mon, 12 Apr 2021 09:39:04 +0000 Date: Mon, 12 Apr 2021 10:38:56 +0100 From: Christoph Hellwig To: Ming Lei Message-ID: <20210412093856.GA978201@infradead.org> References: <20210401021927.343727-1-ming.lei@redhat.com> <20210401021927.343727-12-ming.lei@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210401021927.343727-12-ming.lei@redhat.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 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] [PATCH V5 11/12] block: add poll_capable method to support bio-based IO polling 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 10.5.11.15 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 Thu, Apr 01, 2021 at 10:19:26AM +0800, 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. I really don't think thi should be a method, and I really do dislike how we have all this "if (is_mq)" junk. Why can't we have a flag on the gendisk that signals if the device can support polling that is autoamtically set for blk-mq and as-needed by bio based drivers? And please move everything that significantly hanges things for the mq based path to separate prep patches early in th series. -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel 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=-5.8 required=3.0 tests=BAYES_00,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 2683FC433ED for ; Mon, 12 Apr 2021 09:46:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E67E561278 for ; Mon, 12 Apr 2021 09:46:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238467AbhDLJqj (ORCPT ); Mon, 12 Apr 2021 05:46:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243542AbhDLJmY (ORCPT ); Mon, 12 Apr 2021 05:42:24 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8058AC061372 for ; Mon, 12 Apr 2021 02:39:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Wc1obG7oQbtBmhuM6MkYMF2AyXJCF0Lo7DtwxbYymnc=; b=dtx3FFSEYJm1Xg5VsOVvMt/Wak H8EwQiZNLXMGvg7sPm6yH/jqE/f23LM4nDa+vxHyzj6a2L9h3UmRQLrPbQRkzCMuJ6emjiz/TYdRq ob9YluiFNQzRG9ySFkiXq0N0NiGBt2EwPg9fPqAtlrec+cfME7ZhnrwIfbL1yFcfhHja/EzEvXkb4 ehTPBtP+N4ww756oEaJLxaCdxFuqfU4EgzJ8uvMSgsxGDFAO2bi7e6KPrHcP+QXPDd83iCx+CLrBb pbPk6oRyJYyfM9Wb20pmuBSTji/C1jJ6WPkJWU9Ijzg9/1y2Cz1AL9ePIaT/jTUMBOS6Y7MQNGbM4 U652BXpg==; Received: from hch by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lVt20-00474E-Sm; Mon, 12 Apr 2021 09:39:04 +0000 Date: Mon, 12 Apr 2021 10:38:56 +0100 From: Christoph Hellwig To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Jeffle Xu , Mike Snitzer , dm-devel@redhat.com, Hannes Reinecke Subject: Re: [PATCH V5 11/12] block: add poll_capable method to support bio-based IO polling Message-ID: <20210412093856.GA978201@infradead.org> References: <20210401021927.343727-1-ming.lei@redhat.com> <20210401021927.343727-12-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210401021927.343727-12-ming.lei@redhat.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Apr 01, 2021 at 10:19:26AM +0800, 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. I really don't think thi should be a method, and I really do dislike how we have all this "if (is_mq)" junk. Why can't we have a flag on the gendisk that signals if the device can support polling that is autoamtically set for blk-mq and as-needed by bio based drivers? And please move everything that significantly hanges things for the mq based path to separate prep patches early in th series.