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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 BA8C0C5517A for ; Tue, 10 Nov 2020 07:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6505320674 for ; Tue, 10 Nov 2020 07:00:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731729AbgKJHAb (ORCPT ); Tue, 10 Nov 2020 02:00:31 -0500 Received: from mx2.suse.de ([195.135.220.15]:42430 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731231AbgKJHAb (ORCPT ); Tue, 10 Nov 2020 02:00:31 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4ADE6ABCC; Tue, 10 Nov 2020 07:00:29 +0000 (UTC) Subject: Re: [PATCH 03/24] nvme: let set_capacity_revalidate_and_notify update the bdev size To: Sagi Grimberg , Christoph Hellwig Cc: Jens Axboe , Justin Sanders , Josef Bacik , Ilya Dryomov , Jack Wang , "Michael S. Tsirkin" , Jason Wang , Paolo Bonzini , Stefan Hajnoczi , Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Minchan Kim , Mike Snitzer , Song Liu , "Martin K. Petersen" , dm-devel@redhat.com, linux-block@vger.kernel.org, drbd-dev@lists.linbit.com, nbd@other.debian.org, ceph-devel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-raid@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20201106190337.1973127-1-hch@lst.de> <20201106190337.1973127-4-hch@lst.de> <1d06cdfa-a904-30be-f3ec-08ae2fa85cbd@suse.de> <20201109085340.GB27483@lst.de> From: Hannes Reinecke Message-ID: Date: Tue, 10 Nov 2020 08:00:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 11/10/20 12:28 AM, Sagi Grimberg wrote: > >> [ .. ] >>>> Originally nvme multipath would update/change the size of the multipath >>>> device according to the underlying path devices. >>>> With this patch the size of the multipath device will _not_ change >>>> if there >>>> is a change on the underlying devices. >>> >>> Yes, it will.  Take a close look at nvme_update_disk_info and how it is >>> called. >>> >> Okay, then: What would be the correct way of handling a size update >> for NVMe multipath? >> Assuming we're getting an AEN for each path signalling the size change >> (or a controller reset leading to a size change). >> So if we're updating the size of the multipath device together with >> the path device at the first AEN/reset we'll end up with the other >> paths having a different size than the multipath device (and the path >> we've just been updating). >> - Do we care, or cross fingers and hope for the best? >> - Shouldn't we detect the case where we won't get a size update for >> the other paths, or, indeed, we have a genuine device size mismatch >> due to a misconfiguration on the target? >> >> IE shouldn't we have a flag 'size update pending' for the other >> paths,, to take them out ouf use temporarily until the other >> AENs/resets have been processed? > > the mpath device will take the minimum size from all the paths, that is > what blk_stack_limits does. When the AEN for all the paths will arrive > the mpath size will update. > But that's precisely my point; there won't be an AEN for _all_ paths, but rather one AEN per path. Which will be processed separately, leading to the issue described above. > Not sure how this is different than what we have today... Oh, that is a problem even today. So we should probably move it to a different thread... Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer