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 0D338C7EE2E for ; Mon, 5 Jun 2023 08:59:58 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q6621-0005gJ-PE; Mon, 05 Jun 2023 04:57:41 -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 1q661s-0005bp-2a for qemu-devel@nongnu.org; Mon, 05 Jun 2023 04:57:32 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q661o-0004sU-53 for qemu-devel@nongnu.org; Mon, 05 Jun 2023 04:57:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685955447; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2mKzNMaMJeH3JwSykSj+IX99QH6A36+xK3k+tagyGoI=; b=ZY487vCg4ZX+u5Nwij0qcNJYshbe8EC4+0Zt1Q518NS0oKzt+djKkDX0Rs7z2mEpz7do1L q7Pq7FRd4p35fi0ZaVzk1mnn2lJw9dXh1N4FVvfh3GIGlUgZ0dsf3G18zedToFp1MKnhB6 4K94HDfhAdnPeCkQg43uTicnR0Uzd9E= 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-575--PCNjCZsMNOvgbkZRzNZbg-1; Mon, 05 Jun 2023 04:57:22 -0400 X-MC-Unique: -PCNjCZsMNOvgbkZRzNZbg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 24B97185A792; Mon, 5 Jun 2023 08:57:22 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.193.25]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2DFA140C6EC4; Mon, 5 Jun 2023 08:57:21 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, hreitz@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org Subject: [PATCH v2 05/11] block: Fix AioContext locking in bdrv_attach_child_common() Date: Mon, 5 Jun 2023 10:57:05 +0200 Message-Id: <20230605085711.21261-6-kwolf@redhat.com> In-Reply-To: <20230605085711.21261-1-kwolf@redhat.com> References: <20230605085711.21261-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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 The function can move the child node to a different AioContext. In this case, it also must take the AioContext lock for the new context before calling functions that require the caller to hold the AioContext for the child node. Signed-off-by: Kevin Wolf --- block.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 3ed943467a..508e0e396b 100644 --- a/block.c +++ b/block.c @@ -2989,6 +2989,10 @@ static TransactionActionDrv bdrv_attach_child_common_drv = { * Function doesn't update permissions, caller is responsible for this. * * Returns new created child. + * + * The caller must hold the AioContext lock for @child_bs. Both @parent_bs and + * @child_bs can move to a different AioContext in this function. Callers must + * make sure that their AioContext locking is still correct after this. */ static BdrvChild *bdrv_attach_child_common(BlockDriverState *child_bs, const char *child_name, @@ -2999,7 +3003,7 @@ static BdrvChild *bdrv_attach_child_common(BlockDriverState *child_bs, Transaction *tran, Error **errp) { BdrvChild *new_child; - AioContext *parent_ctx; + AioContext *parent_ctx, *new_child_ctx; AioContext *child_ctx = bdrv_get_aio_context(child_bs); assert(child_class->get_parent_desc); @@ -3050,6 +3054,12 @@ static BdrvChild *bdrv_attach_child_common(BlockDriverState *child_bs, } } + new_child_ctx = bdrv_get_aio_context(child_bs); + if (new_child_ctx != child_ctx) { + aio_context_release(child_ctx); + aio_context_acquire(new_child_ctx); + } + bdrv_ref(child_bs); /* * Let every new BdrvChild start with a drained parent. Inserting the child @@ -3079,11 +3089,20 @@ static BdrvChild *bdrv_attach_child_common(BlockDriverState *child_bs, }; tran_add(tran, &bdrv_attach_child_common_drv, s); + if (new_child_ctx != child_ctx) { + aio_context_release(new_child_ctx); + aio_context_acquire(child_ctx); + } + return new_child; } /* * Function doesn't update permissions, caller is responsible for this. + * + * The caller must hold the AioContext lock for @child_bs. Both @parent_bs and + * @child_bs can move to a different AioContext in this function. Callers must + * make sure that their AioContext locking is still correct after this. */ static BdrvChild *bdrv_attach_child_noperm(BlockDriverState *parent_bs, BlockDriverState *child_bs, -- 2.40.1