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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79D00C6FD1F for ; Wed, 22 Mar 2023 16:10:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229747AbjCVQKQ (ORCPT ); Wed, 22 Mar 2023 12:10:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229524AbjCVQKF (ORCPT ); Wed, 22 Mar 2023 12:10:05 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 494455982B for ; Wed, 22 Mar 2023 09:09:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679501349; 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=1bX4swPuNAE8QO6vwyly7Hj41GaBwCiM8/ocxk1BKj4=; b=bhZRxNTE5zKfTGiSXyOud5qqUZckc8u+UI3Xpq3mX3tsx93CbTirLiHMllK5VDUBTRcNV0 wlT8npDLQeg51CN0aauUYlpb6BsB7PRkBRuvbJIHWMrWv4gk2OWHnh1vaXkv9ZoWu0p/Dg V6Cz0tQwVT+L5JnzMulivpRplH5hHh8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-240-ZxPoGhpZNJi8CF_LsICsCw-1; Wed, 22 Mar 2023 12:09:05 -0400 X-MC-Unique: ZxPoGhpZNJi8CF_LsICsCw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4F5C68030D6; Wed, 22 Mar 2023 16:09:04 +0000 (UTC) Received: from ovpn-8-17.pek2.redhat.com (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A89D41410F1E; Wed, 22 Mar 2023 16:08:57 +0000 (UTC) Date: Thu, 23 Mar 2023 00:08:51 +0800 From: Ming Lei To: Jan Kara Cc: Yu Kuai , hch@infradead.org, axboe@kernel.dk, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, Xiao Ni , linux-raid@vger.kernel.org, ming.lei@redhat.com Subject: Re: [PATCH] block: don't set GD_NEED_PART_SCAN if scan partition failed Message-ID: References: <20230322035926.1791317-1-yukuai1@huaweicloud.com> <20230322094707.7xsexupiijmxxlom@quack3> <20230322130709.7zp7spmhcmjbfjvm@quack3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230322130709.7zp7spmhcmjbfjvm@quack3> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Mar 22, 2023 at 02:07:09PM +0100, Jan Kara wrote: > On Wed 22-03-23 19:34:30, Ming Lei wrote: > > On Wed, Mar 22, 2023 at 10:47:07AM +0100, Jan Kara wrote: > > > On Wed 22-03-23 15:58:35, Ming Lei wrote: > > > > On Wed, Mar 22, 2023 at 11:59:26AM +0800, Yu Kuai wrote: > > > > > From: Yu Kuai > > > > > > > > > > Currently if disk_scan_partitions() failed, GD_NEED_PART_SCAN will still > > > > > set, and partition scan will be proceed again when blkdev_get_by_dev() > > > > > is called. However, this will cause a problem that re-assemble partitioned > > > > > raid device will creat partition for underlying disk. > > > > > > > > > > Test procedure: > > > > > > > > > > mdadm -CR /dev/md0 -l 1 -n 2 /dev/sda /dev/sdb -e 1.0 > > > > > sgdisk -n 0:0:+100MiB /dev/md0 > > > > > blockdev --rereadpt /dev/sda > > > > > blockdev --rereadpt /dev/sdb > > > > > mdadm -S /dev/md0 > > > > > mdadm -A /dev/md0 /dev/sda /dev/sdb > > > > > > > > > > Test result: underlying disk partition and raid partition can be > > > > > observed at the same time > > > > > > > > > > Note that this can still happen in come corner cases that > > > > > GD_NEED_PART_SCAN can be set for underlying disk while re-assemble raid > > > > > device. > > > > > > > > > > Fixes: e5cfefa97bcc ("block: fix scan partition for exclusively open device again") > > > > > Signed-off-by: Yu Kuai > > > > > > > > The issue still can't be avoided completely, such as, after rebooting, > > > > /dev/sda1 & /dev/md0p1 can be observed at the same time. And this one > > > > should be underlying partitions scanned before re-assembling raid, I > > > > guess it may not be easy to avoid. > > > > > > So this was always happening (before my patches, after my patches, and now > > > after Yu's patches) and kernel does not have enough information to know > > > that sda will become part of md0 device in the future. But mdadm actually > > > deals with this as far as I remember and deletes partitions for all devices > > > it is assembling the array from (and quick tracing experiment I did > > > supports this). > > > > I am testing on Fedora 37, so mdadm v4.2 doesn't delete underlying > > partitions before re-assemble. > > Strange, I'm on openSUSE Leap 15.4 and mdadm v4.1 deletes these partitions > (at least I can see mdadm do BLKPG_DEL_PARTITION ioctls). And checking > mdadm sources I can see calls to remove_partitions() from start_array() > function in Assemble.c so I'm not sure why this is not working for you... I added dump_stack() in delete_partition() for partition 1, not observe stack trace during booting. > > > Also given mdadm or related userspace has to change for avoiding > > to scan underlying partitions, just wondering why not let userspace > > to tell kernel not do it explicitly? > > Well, those userspace changes are long deployed, now you would introduce > new API that needs to proliferate again. Not very nice. Also how would that > exactly work? I mean once mdadm has underlying device open, the current > logic makes sure we do not create partitions anymore. But there's no way > how mdadm could possibly prevent creation of partitions for devices it > doesn't know about yet so it still has to delete existing partitions... I meant if mdadm has to change to delete existed partitions, why not add one ioctl to disable partition scan for this disk when deleting partitions/re-assemble, and re-enable scan after stopping array. But looks it isn't so, since you mentioned that remove_partitions is supposed to be called before starting array, however I didn't observe this behavior. I am worrying if the current approach may cause regression, one concern is that ioctl(BLKRRPART) needs exclusive open now, such as: 1) mount /dev/vdb1 /mnt 2) ioctl(BLKRRPART) may fail after removing /dev/vdb3 thanks, Ming