From patchwork Mon Mar 14 13:18:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 12780151 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 6B116C433EF for ; Mon, 14 Mar 2022 13:26:57 +0000 (UTC) Received: from localhost ([::1]:42942 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nTkit-0000X1-F8 for qemu-devel@archiver.kernel.org; Mon, 14 Mar 2022 09:26:55 -0400 Received: from eggs.gnu.org ([209.51.188.92]:38016) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTkbQ-0001KU-Mi for qemu-devel@nongnu.org; Mon, 14 Mar 2022 09:19:12 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:22602) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nTkbN-0006Yb-NO for qemu-devel@nongnu.org; Mon, 14 Mar 2022 09:19:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1647263949; 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=nwA26UkG2+owWpWiI3GVGo6wBUh4XDA2BdTeqN1ous8=; b=TZpUAVOUDhwsY9YsQDUccb77UgcYhSudrjT16zPXJpLKgYcRcoIeDdYu5/ZhF/GGa7Z5Gr TM4GVuOYXdYAHSuoTZqnk85QKD3zEmedmaUHXa9qBCaFgxVQEf/e+SWxWL4t4mBBbitsr0 R6nBKzHcAlR8syfgs8P1KaBFo+LIR/g= 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-668-zmIC4VtjOq-gW49lpS37mg-1; Mon, 14 Mar 2022 09:19:06 -0400 X-MC-Unique: zmIC4VtjOq-gW49lpS37mg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AF2A9811E75; Mon, 14 Mar 2022 13:19:05 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6D0FC2EF83; Mon, 14 Mar 2022 13:19:05 +0000 (UTC) From: Emanuele Giuseppe Esposito To: qemu-block@nongnu.org Subject: [PATCH v2 05/10] block.c: bdrv_replace_child_noperm: first call ->attach(), and then add child Date: Mon, 14 Mar 2022 09:18:49 -0400 Message-Id: <20220314131854.2202651-6-eesposit@redhat.com> In-Reply-To: <20220314131854.2202651-1-eesposit@redhat.com> References: <20220314131854.2202651-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eesposit@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=170.10.133.124; envelope-from=eesposit@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Cc: Kevin Wolf , Fam Zheng , Vladimir Sementsov-Ogievskiy , Emanuele Giuseppe Esposito , qemu-devel@nongnu.org, Hanna Reitz , Stefan Hajnoczi , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Doing the opposite can make adding the child node to a non-drained node, as apply_subtree_drain is only done in ->attach() and thus make assert_bdrv_graph_writable fail. This can happen for example during a transaction rollback (test 245, test_io_with_graph_changes): 1. a node is removed from the graph, thus it is undrained 2. then something happens, and we need to roll back the transactions through tran_abort() 3. at this point, the current code would first attach the undrained node to the graph via QLIST_INSERT_HEAD, and then call ->attach() that will take care of restoring the drain with apply_subtree_drain(), leaving the node undrained between the two operations. Signed-off-by: Emanuele Giuseppe Esposito --- block.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/block.c b/block.c index d870ba5393..c6a550f9c6 100644 --- a/block.c +++ b/block.c @@ -1434,6 +1434,11 @@ static void bdrv_inherited_options(BdrvChildRole role, bool parent_is_format, *child_flags = flags; } +/* + * Add the child node to child->opaque->children list, + * and then apply the drain to the whole child subtree, + * so that the drain count matches with the parent. + */ static void bdrv_child_cb_attach(BdrvChild *child) { BlockDriverState *bs = child->opaque; @@ -2889,8 +2894,6 @@ static void bdrv_replace_child_noperm(BdrvChild **childp, } if (new_bs) { - assert_bdrv_graph_writable(new_bs); - QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent); /* * Detaching the old node may have led to the new node's @@ -2901,12 +2904,19 @@ static void bdrv_replace_child_noperm(BdrvChild **childp, assert(new_bs->quiesce_counter <= new_bs_quiesce_counter); drain_saldo += new_bs->quiesce_counter - new_bs_quiesce_counter; - /* Attach only after starting new drained sections, so that recursive - * drain sections coming from @child don't get an extra .drained_begin - * callback. */ + /* + * First call ->attach() cb. + * In child_of_bds case, add child to the parent + * (child->opaque) ->children list and if + * necessary add missing drains in the child subtree. + */ if (child->klass->attach) { child->klass->attach(child); } + + /* Then add child to new_bs->parents list */ + assert_bdrv_graph_writable(new_bs); + QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent); } /*