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=-7.2 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 76A82C4361A for ; Fri, 4 Dec 2020 01:13:17 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E5526224B1 for ; Fri, 4 Dec 2020 01:13:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E5526224B1 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=1607044395; 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=gL8XAJ+FVZKtVNYxSEQzOlICl4y+GAEJ1x9/TWhN3HY=; b=ZeigcQhmnJdzhugE1znhWHMwJ+dYuT5GqDkxTxU1cESHCQaCkDiGaH2C6bDxwx1cYGQ20N ARlOQfgmcYci6KY5Cj2ELrEy8GjU/wxvWjIw3dSHzWjSoquu047MNo9gw+ozUj7itPC0aB ulnxpy7hYIjTcNqt2/qKhvaTNXcfQUU= 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-584-C98g7zUEN9yK7k9wofx6rw-1; Thu, 03 Dec 2020 20:13:13 -0500 X-MC-Unique: C98g7zUEN9yK7k9wofx6rw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2D4239CC09; Fri, 4 Dec 2020 01:13:09 +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 9BDC31A8A9; Fri, 4 Dec 2020 01:13:08 +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 950D74A7C6; Fri, 4 Dec 2020 01:13:06 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 0B41D4Oa028465 for ; Thu, 3 Dec 2020 20:13:04 -0500 Received: by smtp.corp.redhat.com (Postfix) id 33393189B6; Fri, 4 Dec 2020 01:13:04 +0000 (UTC) Received: from T590 (ovpn-12-155.pek2.redhat.com [10.72.12.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AB8FB189B8; Fri, 4 Dec 2020 01:12:47 +0000 (UTC) Date: Fri, 4 Dec 2020 09:12:43 +0800 From: Ming Lei To: Mike Snitzer Message-ID: <20201204011243.GB661914@T590> References: <20201130171805.77712-1-snitzer@redhat.com> <20201201160709.31748-1-snitzer@redhat.com> <20201203032608.GD540033@T590> <20201203143359.GA29261@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201203143359.GA29261@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-loop: dm-devel@redhat.com Cc: axboe@kernel.dk, martin.petersen@oracle.com, jdorminy@redhat.com, bjohnsto@redhat.com, linux-block@vger.kernel.org, dm-devel@redhat.com Subject: Re: [dm-devel] [PATCH v2] block: use gcd() to fix chunk_sectors limit stacking 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 2.84 on 10.5.11.23 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, Dec 03, 2020 at 09:33:59AM -0500, Mike Snitzer wrote: > On Wed, Dec 02 2020 at 10:26pm -0500, > Ming Lei wrote: > > > On Tue, Dec 01, 2020 at 11:07:09AM -0500, Mike Snitzer wrote: > > > commit 22ada802ede8 ("block: use lcm_not_zero() when stacking > > > chunk_sectors") broke chunk_sectors limit stacking. chunk_sectors must > > > reflect the most limited of all devices in the IO stack. > > > > > > Otherwise malformed IO may result. E.g.: prior to this fix, > > > ->chunk_sectors = lcm_not_zero(8, 128) would result in > > > blk_max_size_offset() splitting IO at 128 sectors rather than the > > > required more restrictive 8 sectors. > > > > What is the user-visible result of splitting IO at 128 sectors? > > The VDO dm target fails because it requires IO it receives to be split > as it advertised (8 sectors). OK, looks VDO's chunk_sector limit is one hard constraint, even though it is one DM device, so I guess you are talking about DM over VDO? Another reason should be that VDO doesn't use blk_queue_split(), otherwise it won't be a trouble, right? Frankly speaking, if the stacking driver/device has its own hard queue limit like normal hardware drive, the driver should be responsible for the splitting. > > > I understand it isn't related with correctness, because the underlying > > queue can split by its own chunk_sectors limit further. So is the issue > > too many further-splitting on queue with chunk_sectors 8? then CPU > > utilization is increased? Or other issue? > > No, this is all about correctness. > > Seems you're confining the definition of the possible stacking so that > the top-level device isn't allowed to have its own hard requirements on I just don't know this story, thanks for your clarification. As I mentioned above, if the stacking driver has its own hard queue limit, it should be the driver's responsibility to respect it via blk_queue_split() or whatever. Thanks, Ming -- dm-devel mailing list dm-devel@redhat.com https://www.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=-7.2 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 E033BC4361A for ; Fri, 4 Dec 2020 01:14:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85578224B1 for ; Fri, 4 Dec 2020 01:14:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726627AbgLDBOd (ORCPT ); Thu, 3 Dec 2020 20:14:33 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32179 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbgLDBOd (ORCPT ); Thu, 3 Dec 2020 20:14:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607044386; 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: in-reply-to:in-reply-to:references:references; bh=Z7Z9NtqyWore2TZh7acZMcCHbvHNtwcOtzYttc8TGdc=; b=Md/4wFlGT5IsVIp0CwcGLIMKN6ggmnWeiFl1nsIlTHMDY9PpiqPwVnU8JTliIXY5hBMH/9 lBlRWHazEK+1cD1nwx9GZZaHk6sLHIY9n07pfnhYf1Ea6OdHphzZURZkEqnX1rfF9tWefr 3iyzdpnMwHxT47RlxASTZOYoMy1hgoo= 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-245-Qe3d7IsgPvO4dCbYZQ0ZnA-1; Thu, 03 Dec 2020 20:13:05 -0500 X-MC-Unique: Qe3d7IsgPvO4dCbYZQ0ZnA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 357E6800D55; Fri, 4 Dec 2020 01:13:04 +0000 (UTC) Received: from T590 (ovpn-12-155.pek2.redhat.com [10.72.12.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AB8FB189B8; Fri, 4 Dec 2020 01:12:47 +0000 (UTC) Date: Fri, 4 Dec 2020 09:12:43 +0800 From: Ming Lei To: Mike Snitzer Cc: axboe@kernel.dk, martin.petersen@oracle.com, linux-block@vger.kernel.org, dm-devel@redhat.com, jdorminy@redhat.com, bjohnsto@redhat.com Subject: Re: [PATCH v2] block: use gcd() to fix chunk_sectors limit stacking Message-ID: <20201204011243.GB661914@T590> References: <20201130171805.77712-1-snitzer@redhat.com> <20201201160709.31748-1-snitzer@redhat.com> <20201203032608.GD540033@T590> <20201203143359.GA29261@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201203143359.GA29261@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Dec 03, 2020 at 09:33:59AM -0500, Mike Snitzer wrote: > On Wed, Dec 02 2020 at 10:26pm -0500, > Ming Lei wrote: > > > On Tue, Dec 01, 2020 at 11:07:09AM -0500, Mike Snitzer wrote: > > > commit 22ada802ede8 ("block: use lcm_not_zero() when stacking > > > chunk_sectors") broke chunk_sectors limit stacking. chunk_sectors must > > > reflect the most limited of all devices in the IO stack. > > > > > > Otherwise malformed IO may result. E.g.: prior to this fix, > > > ->chunk_sectors = lcm_not_zero(8, 128) would result in > > > blk_max_size_offset() splitting IO at 128 sectors rather than the > > > required more restrictive 8 sectors. > > > > What is the user-visible result of splitting IO at 128 sectors? > > The VDO dm target fails because it requires IO it receives to be split > as it advertised (8 sectors). OK, looks VDO's chunk_sector limit is one hard constraint, even though it is one DM device, so I guess you are talking about DM over VDO? Another reason should be that VDO doesn't use blk_queue_split(), otherwise it won't be a trouble, right? Frankly speaking, if the stacking driver/device has its own hard queue limit like normal hardware drive, the driver should be responsible for the splitting. > > > I understand it isn't related with correctness, because the underlying > > queue can split by its own chunk_sectors limit further. So is the issue > > too many further-splitting on queue with chunk_sectors 8? then CPU > > utilization is increased? Or other issue? > > No, this is all about correctness. > > Seems you're confining the definition of the possible stacking so that > the top-level device isn't allowed to have its own hard requirements on I just don't know this story, thanks for your clarification. As I mentioned above, if the stacking driver has its own hard queue limit, it should be the driver's responsibility to respect it via blk_queue_split() or whatever. Thanks, Ming