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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D0BD0C83038 for ; Tue, 1 Jul 2025 17:36:14 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uWeqZ-0008WT-3b; Tue, 01 Jul 2025 13:32:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uWeqN-00086I-At for qemu-devel@nongnu.org; Tue, 01 Jul 2025 13:32:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uWeqJ-0007mq-Un for qemu-devel@nongnu.org; Tue, 01 Jul 2025 13:32:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1751391146; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VoFn0RB4KSTG4vLlw/0Pdh/GkxQugPFiMH/x+lHcwFQ=; b=R9S4Sa7tXDB1Tm0RRamRY2q4tisP8068NUiLJ6PcrAEOAYMg/ESS9wpkWpoWemtWVBuJlU lM2P9LgWVDS8Rzv29KY+ph2ZZzgQuA+6DKdPdEuSVUTDgH+y5l071uPaDMIdfRVt5kE5nU QjcnDEJdz8+QBJ68dQiMvMN+XehqkP8= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-494-WCG4TOuNNVWy_HRf4kNwTw-1; Tue, 01 Jul 2025 13:32:23 -0400 X-MC-Unique: WCG4TOuNNVWy_HRf4kNwTw-1 X-Mimecast-MFC-AGG-ID: WCG4TOuNNVWy_HRf4kNwTw_1751391142 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 2E696195FCC2; Tue, 1 Jul 2025 17:32:22 +0000 (UTC) Received: from redhat.com (unknown [10.44.34.118]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 468AE19560A7; Tue, 1 Jul 2025 17:32:19 +0000 (UTC) Date: Tue, 1 Jul 2025 19:32:16 +0200 From: Kevin Wolf To: Hanna Czenczek Cc: Fiona Ebner , qemu-block@nongnu.org, qemu-devel@nongnu.org, stefanha@redhat.com, fam@euphon.net Subject: Re: [PATCH 3/4] block: implement 'resize' callback for child_of_bds class Message-ID: References: <20250630113035.820557-1-f.ebner@proxmox.com> <20250630113035.820557-4-f.ebner@proxmox.com> <18f6275a-dee0-4df4-85e3-efaf81a7724d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <18f6275a-dee0-4df4-85e3-efaf81a7724d@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 01.07.2025 um 16:46 hat Hanna Czenczek geschrieben: > On 30.06.25 13:27, Fiona Ebner wrote: > > If a node below a filter node is resized, the size of the filter node > > is now also refreshed (recursively for filter parents). > > > > Signed-off-by: Fiona Ebner > > --- > > block.c | 12 ++++++++++++ > > include/block/block_int-common.h | 2 +- > > 2 files changed, 13 insertions(+), 1 deletion(-) > > What does this do for block job filter nodes, like mirror?  If they changed > their length, we might have to consider whether the job also needs to be > amended somehow. mirror doesn't share BLK_PERM_RESIZE in its block_job_create() call, so can this even happen? (If yes, that sounds bad.) > However, I assume it’s a safe (conservative) change for them because such > drivers don’t implement bdrv_co_getlength(), so > bdrv_co_refresh_total_sectors() will not change anything.  Is that right and > intended? > > Reviewed-by: Hanna Czenczek > > (Babbling below.) > > > diff --git a/block.c b/block.c > > index bfd4340b24..449f814ebe 100644 > > --- a/block.c > > +++ b/block.c > > @@ -1497,6 +1497,17 @@ static void GRAPH_WRLOCK bdrv_child_cb_detach(BdrvChild *child) > > } > > } > > +static void coroutine_fn GRAPH_RDLOCK bdrv_child_cb_resize(BdrvChild *child) > > +{ > > + BlockDriverState *bs = child->opaque; > > + > > + if (bs->drv && bs->drv->is_filter) { > > Checking the role for BDRV_CHILD_FILTERED would be more generic; but it > would cause 'raw' nodes to be updated, too.  But I don’t know whether we > want that or not, and excluding raw (i.e. not changing behavior there) is > certainly the safe option. If the size is not explicitly overridden in the node configuration, I would certainly expect that a raw node reflects the size of its file node. Seems this is exactly the condition that makes it use BDRV_CHILD_FILTERED, so it would probably be a good change? > > + /* Best effort, ignore errors. */ > > + bdrv_co_refresh_total_sectors(bs, bs->total_sectors); > > + bdrv_co_parent_cb_resize(bs); > > This makes me wonder whether bdrv_co_refresh_total_sectors() should itself > call bdrv_co_parent_cb_resize().  Still not quite sure; if the underlying > image file is resized by an external party (and we notice this by accident, > more or less), maybe the guest device should be informed. > > (One thing to consider, maybe, are nodes that unshare the resize permission > for a child.  It’s probably not clever to call the resize CB if that > permission is unshared, so maybe just from that perspective, we should keep > that CB strictly inside of that explicit truncate path that checks that > permission (at least when growing images...).) > > Anyway, again, this is the safe option. The traditional solution for nodes that unshare resize, but get resized in the background anyway would be bs->drv = NULL, and we probably still aren't certain what happens after that. :-) Kevin