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 A4399C4361A for ; Fri, 4 Dec 2020 03:59:55 +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 16CD22220F for ; Fri, 4 Dec 2020 03:59:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16CD22220F 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=1607054393; 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=4DwNfF0ZaIEBYnjQdW4uRxMBqgIU42XfNFgsMrc+YAg=; b=gqBHg/YjCsFooyAIu8KFIsFzPEq0bLWXaSfKxKgn3fOOOSA1q9uDS/VlLkPLuPA2FOPXEB yboCsj+dWbK3Oc5P8P/HlixFcT86Nzag1WsK01TB5z3WUtg5BWA/UPYbFFG0MMNBIp38AZ 4A91KbQ7emxQOkHFV6ZG2fSPINxlwhE= 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-228-cKTbMGsBPZ-6ZFMK99B3eQ-1; Thu, 03 Dec 2020 22:59:51 -0500 X-MC-Unique: cKTbMGsBPZ-6ZFMK99B3eQ-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 55E5A80EF81; Fri, 4 Dec 2020 03:59:47 +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 0D72D60854; Fri, 4 Dec 2020 03:59:47 +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 72CF74E58E; Fri, 4 Dec 2020 03:59:46 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 0B43xiO5014595 for ; Thu, 3 Dec 2020 22:59:44 -0500 Received: by smtp.corp.redhat.com (Postfix) id 87E955C1D5; Fri, 4 Dec 2020 03:59:44 +0000 (UTC) Received: from T590 (ovpn-12-155.pek2.redhat.com [10.72.12.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 244A05C1CF; Fri, 4 Dec 2020 03:59:28 +0000 (UTC) Date: Fri, 4 Dec 2020 11:59:24 +0800 From: Ming Lei To: Mike Snitzer Message-ID: <20201204035924.GD661914@T590> References: <20201130171805.77712-1-snitzer@redhat.com> <20201201160709.31748-1-snitzer@redhat.com> <20201203032608.GD540033@T590> <20201203143359.GA29261@redhat.com> <20201204011243.GB661914@T590> <20201204020343.GA32150@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201204020343.GA32150@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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 2.79 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 Thu, Dec 03, 2020 at 09:03:43PM -0500, Mike Snitzer wrote: > On Thu, Dec 03 2020 at 8:12pm -0500, > Ming Lei wrote: > > > 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. > > DM core does the splitting for VDO (just like any other DM target). > In 5.9 I updated DM to use chunk_sectors, use blk_stack_limits() > stacking of it, and also use blk_max_size_offset(). > > But all that block core code has shown itself to be too rigid for DM. I > tried to force the issue by stacking DM targets' ti->max_io_len with > chunk_sectors. But really I'd need to be able to pass in the per-target > max_io_len to blk_max_size_offset() to salvage using it. > > Stacking chunk_sectors seems ill-conceived. One size-fits-all splitting > is too rigid. DM/VDO knows exactly it is one hard chunk_sectors limit, and DM shouldn't play the stacking trick on VDO's chunk_sectors limit, should it? Thanks, Ming -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel