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 3FE45C7EE23 for ; Mon, 5 Jun 2023 08:58:03 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q661w-0005dY-OE; Mon, 05 Jun 2023 04:57:36 -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-0005br-37 for qemu-devel@nongnu.org; Mon, 05 Jun 2023 04:57:32 -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 1q661o-0004sQ-4A 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=ZXzk+wTY/wPTx+vScZUjOzTefhoJYcLpzD/2LCLqaO0=; b=Atf5efkJrpdj84gAegSc0HBtfCJ1F5m+8XYDExuiz2b8MNQMY5P7Wrk3wX2SjuVgVljK5J eU3Fk8mCecT3c6YJG/BGqTdEbgkX7ZYdYL37LXc7Bm4EtV3WGIAOC2NJ85bmEZByIg7HZC ZpkBToKl+GZ2p91EkSiGkebsiraMoxY= 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-50-59H5fcNUNU6i6KKEsUfiTQ-1; Mon, 05 Jun 2023 04:57:23 -0400 X-MC-Unique: 59H5fcNUNU6i6KKEsUfiTQ-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 5E1DE8037AB; Mon, 5 Jun 2023 08:57:23 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.193.25]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5C97840C6EC4; Mon, 5 Jun 2023 08:57:22 +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 06/11] block: Fix AioContext locking in bdrv_reopen_parse_file_or_backing() Date: Mon, 5 Jun 2023 10:57:06 +0200 Message-Id: <20230605085711.21261-7-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=170.10.133.124; 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=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org bdrv_set_file_or_backing_noperm() requires the caller to hold the AioContext lock for the child node, but we hold the one for the parent node in bdrv_reopen_parse_file_or_backing(). Take the other one temporarily. Signed-off-by: Kevin Wolf --- block.c | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index 508e0e396b..a0793b6435 100644 --- a/block.c +++ b/block.c @@ -3366,6 +3366,10 @@ static BdrvChildRole bdrv_backing_role(BlockDriverState *bs) * callers which don't need their own reference any more must call bdrv_unref(). * * 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 int bdrv_set_file_or_backing_noperm(BlockDriverState *parent_bs, BlockDriverState *child_bs, @@ -3454,6 +3458,11 @@ out: return 0; } +/* + * The caller must hold the AioContext lock for @backing_hd. Both @bs and + * @backing_hd can move to a different AioContext in this function. Callers must + * make sure that their AioContext locking is still correct after this. + */ static int bdrv_set_backing_noperm(BlockDriverState *bs, BlockDriverState *backing_hd, Transaction *tran, Error **errp) @@ -4606,6 +4615,11 @@ int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only, * backing BlockDriverState (or NULL). * * Return 0 on success, otherwise return < 0 and set @errp. + * + * The caller must hold the AioContext lock of @reopen_state->bs. + * @reopen_state->bs can move to a different AioContext in this function. + * Callers must make sure that their AioContext locking is still correct after + * this. */ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state, bool is_backing, Transaction *tran, @@ -4618,6 +4632,8 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state, const char *child_name = is_backing ? "backing" : "file"; QObject *value; const char *str; + AioContext *ctx, *old_ctx; + int ret; GLOBAL_STATE_CODE(); @@ -4682,8 +4698,22 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state, reopen_state->old_file_bs = old_child_bs; } - return bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing, - tran, errp); + old_ctx = bdrv_get_aio_context(bs); + ctx = bdrv_get_aio_context(new_child_bs); + if (old_ctx != ctx) { + aio_context_release(old_ctx); + aio_context_acquire(ctx); + } + + ret = bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing, + tran, errp); + + if (old_ctx != ctx) { + aio_context_release(ctx); + aio_context_acquire(old_ctx); + } + + return ret; } /* @@ -4702,6 +4732,7 @@ static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state, * It is the responsibility of the caller to then call the abort() or * commit() for any other BDS that have been left in a prepare() state * + * The caller must hold the AioContext lock of @reopen_state->bs. */ static int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, -- 2.40.1