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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 450CEC433E0 for ; Tue, 19 Jan 2021 11:47:26 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 633C123104 for ; Tue, 19 Jan 2021 11:47:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 633C123104 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46854 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l1pTn-0004Vx-UY for qemu-devel@archiver.kernel.org; Tue, 19 Jan 2021 06:47:23 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:50650) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l1pT9-00042p-Fd; Tue, 19 Jan 2021 06:46:43 -0500 Received: from fanzine.igalia.com ([178.60.130.6]:42604) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1l1pT4-0001dK-9F; Tue, 19 Jan 2021 06:46:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Type:MIME-Version:Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From; bh=9afYoKOMwbkVbABp5rjwwi9lY4aYcR9LFT5DTSU5b18=; b=CczVlMAGz0HalxBNVQxPFMoKsRqrYx2daLcQMLfXjU6jN/o4v6m5GCIk9dMIM9hg+a1H6BJ5iRFCeQ/jYwgs9jonTLGELs9IhvjZbYVUTa9mJWV8MWDFDOe++P5a0awMu9MtgbsAQIU7CXwwT6DZjZKchu/rZ2/Y31OXU05nsXs7o2hg+8gI5CkZl4NLwMdApagYf0MGI8azufGxTcKwAhIERAZ6QUS0NN1MYQuhCH69pGYkwEZh7AMTGHRz93X5Iurrwr939vbFsxMAjyPDAMTZwafTtrB5AnsPTU08dNlwIosEjf1g7iAaoiTpUwxkGKdvMTRsB3q9IsM5Gir+/w==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine.igalia.com with esmtps (Cipher TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim) id 1l1pSh-0007b0-03; Tue, 19 Jan 2021 12:46:15 +0100 Received: from berto by mail.igalia.com with local (Exim) id 1l1pSg-0007KB-N8; Tue, 19 Jan 2021 12:46:14 +0100 From: Alberto Garcia To: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org Subject: Re: [RFC PATCH 1/2] block: Allow changing bs->file on reopen In-Reply-To: <53852b77-1b29-0c27-0083-ac6e263b560e@virtuozzo.com> References: <1a9b457d93c0732e8e4785a0cc4b5f3b935f2cf6.1610715661.git.berto@igalia.com> <53852b77-1b29-0c27-0083-ac6e263b560e@virtuozzo.com> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Tue, 19 Jan 2021 12:46:14 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=178.60.130.6; envelope-from=berto@igalia.com; helo=fanzine.igalia.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Kashyap Chamarthy , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon 18 Jan 2021 11:15:17 AM CET, Vladimir Sementsov-Ogievskiy wrote: >> +static int bdrv_reopen_parse_file(BDRVReopenState *reopen_state, >> + GSList **tran, >> + Error **errp) >> +{ >> + BlockDriverState *bs = reopen_state->bs; >> + BlockDriverState *new_file_bs; >> + QObject *value; >> + const char *str; >> + >> + value = qdict_get(reopen_state->options, "file"); >> + if (value == NULL) { >> + return 0; >> + } >> + >> + /* The 'file' option only allows strings */ >> + assert(qobject_type(value) == QTYPE_QSTRING); >> + >> + str = qobject_get_try_str(value); >> + new_file_bs = bdrv_lookup_bs(NULL, str, errp); >> + if (new_file_bs == NULL) { >> + return -EINVAL; >> + } else if (bdrv_recurse_has_child(new_file_bs, bs)) { >> + error_setg(errp, "Making '%s' a file of '%s' " >> + "would create a cycle", str, bs->node_name); >> + return -EINVAL; >> + } >> + >> + assert(bs->file && bs->file->bs); > > why are we sure at this point? Probably, we should just return an > error.. Unlike 'backing', 'file' is a BlockdevRef and it is not optional, so block devices that accept that parameter must have it set. >> + /* At the moment only backing links are frozen */ >> + assert(!bs->file->frozen); > > I think it can: file-child based filters can be a part of frozen > backing chain currently. You're right, since 7b99a26600e bdrv_freeze_backing_chain() uses bdrv_filter_or_cow_child(). Berto