From patchwork Tue May 30 16:32:13 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 13260745 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 8B85DC77B7A for ; Tue, 30 May 2023 16:38:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q42IC-0007jo-2W; Tue, 30 May 2023 12:33:52 -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 1q42HO-0006Wr-GC for qemu-devel@nongnu.org; Tue, 30 May 2023 12:33:04 -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 1q42HK-0008GS-Fo for qemu-devel@nongnu.org; Tue, 30 May 2023 12:33:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685464377; 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=unXlMObQwr/nXbipsntQnoRogAjP6neXdOKypzUgOjw=; b=hU1Mh+sJ4sDmj6TM9nnChxYftmDU1dh0RSoD8q7+anwVKvkVa4Ha5yfMTKHSxFTIdBe38+ kMlz4x/uUMMHJi16bQmu9e0i1ifRD3ESdFJc/gc8rS/KVnAfpU9pqPaSLkKecmVulV9Azn icFe+BRib65XM3EzkNMQd1UweQwSd/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-423-t2DWfS0ANRWF2YyElO654g-1; Tue, 30 May 2023 12:32:53 -0400 X-MC-Unique: t2DWfS0ANRWF2YyElO654g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B805A8032FA; Tue, 30 May 2023 16:32:52 +0000 (UTC) Received: from merkur.redhat.com (unknown [10.39.194.4]) by smtp.corp.redhat.com (Postfix) with ESMTP id 09FFFC15612; Tue, 30 May 2023 16:32:51 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org Subject: [PULL 06/32] qcow2: Fix open with 'file' in iothread Date: Tue, 30 May 2023 18:32:13 +0200 Message-Id: <20230530163239.576632-7-kwolf@redhat.com> In-Reply-To: <20230530163239.576632-1-kwolf@redhat.com> References: <20230530163239.576632-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 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: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.167, 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 qcow2_open() doesn't work correctly when opening the 'file' child moves bs to an iothread, for several reasons: - It uses BDRV_POLL_WHILE() to wait for the qcow2_open_entry() coroutine, which involves dropping the AioContext lock for bs when it is not in the main context - but we don't hold it, so this crashes. - It runs the qcow2_open_entry() coroutine in the current thread instead of the new AioContext of bs. - qcow2_open_entry() doesn't notify the main loop when it's done. This patches fixes these issues around delegating work to a coroutine. Temporarily dropping the main AioContext lock is not necessary because we know we run in the main thread. Signed-off-by: Kevin Wolf Message-Id: <20230525124713.401149-7-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block.c | 6 ++++++ block/qcow2.c | 8 ++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index be9ae364fb..178ece2fa9 100644 --- a/block.c +++ b/block.c @@ -3646,6 +3646,9 @@ done: * BlockdevRef. * * The BlockdevRef will be removed from the options QDict. + * + * @parent can move to a different AioContext in this function. Callers must + * make sure that their AioContext locking is still correct after this. */ BdrvChild *bdrv_open_child(const char *filename, QDict *options, const char *bdref_key, @@ -3670,6 +3673,9 @@ BdrvChild *bdrv_open_child(const char *filename, /* * Wrapper on bdrv_open_child() for most popular case: open primary child of bs. + * + * @parent can move to a different AioContext in this function. Callers must + * make sure that their AioContext locking is still correct after this. */ int bdrv_open_file_child(const char *filename, QDict *options, const char *bdref_key, diff --git a/block/qcow2.c b/block/qcow2.c index b00b4e7575..7f3948360d 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1904,6 +1904,8 @@ static void coroutine_fn qcow2_open_entry(void *opaque) qoc->ret = qcow2_do_open(qoc->bs, qoc->options, qoc->flags, true, qoc->errp); qemu_co_mutex_unlock(&s->lock); + + aio_wait_kick(); } static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, @@ -1929,8 +1931,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags, assert(!qemu_in_coroutine()); assert(qemu_get_current_aio_context() == qemu_get_aio_context()); - qemu_coroutine_enter(qemu_coroutine_create(qcow2_open_entry, &qoc)); - BDRV_POLL_WHILE(bs, qoc.ret == -EINPROGRESS); + + aio_co_enter(bdrv_get_aio_context(bs), + qemu_coroutine_create(qcow2_open_entry, &qoc)); + AIO_WAIT_WHILE_UNLOCKED(NULL, qoc.ret == -EINPROGRESS); return qoc.ret; }