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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91EA5C433F5 for ; Thu, 11 Nov 2021 17:27:38 +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 2A7C96103A for ; Thu, 11 Nov 2021 17:27:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2A7C96103A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:47496 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mlDrN-0003yL-1H for qemu-devel@archiver.kernel.org; Thu, 11 Nov 2021 12:27:37 -0500 Received: from eggs.gnu.org ([209.51.188.92]:42872) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlDqb-0002kz-A0 for qemu-devel@nongnu.org; Thu, 11 Nov 2021 12:26:49 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:29399) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlDqY-0004I2-GF for qemu-devel@nongnu.org; Thu, 11 Nov 2021 12:26:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636651605; 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=B8rLN0gSGi4UfsrJ05a+dEpSFWQQDZKLFWdyWmisvKE=; b=JkbW0GpF2c1QMJSJWBxuY3aRPlfzgkqaNryavfWORZwNs8TOwALZq/sHS1PPyF2WWI6arR TrJJmNDihARHVOpCWqo+6RsjCfQLi7W/fLd2YYq7Y9xnRS0JT8qB/WLRVeet7bNKPICzEL lkkPa0qz71wjeL+IGif449ipLVFmkdE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-416-BQosaLHUNKaCORn0dahE_Q-1; Thu, 11 Nov 2021 12:26:43 -0500 X-MC-Unique: BQosaLHUNKaCORn0dahE_Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C941118125F1; Thu, 11 Nov 2021 17:26:06 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.238]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 96161380; Thu, 11 Nov 2021 17:25:59 +0000 (UTC) Date: Thu, 11 Nov 2021 18:25:57 +0100 From: Kevin Wolf To: Hanna Reitz Subject: Re: [PATCH v2 00/10] block: Attempt on fixing 030-reported errors Message-ID: References: <20211111120829.81329-1-hreitz@redhat.com> MIME-Version: 1.0 In-Reply-To: <20211111120829.81329-1-hreitz@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, 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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 11.11.2021 um 13:08 hat Hanna Reitz geschrieben: > Hi, > > v1 cover letter: > https://lists.nongnu.org/archive/html/qemu-devel/2021-11/msg01287.html > > In v2 I’ve addressed the comments I’ve received from Kevin and Vladimir. > To this end, I’ve retained only the non-controversial part in patch 5, > and split everything else (i.e. the stuff relating to > bdrv_replace_child_tran()) into the dedicated patches 6 and 8. > > Kevin’s most important comments (to my understanding) were that: > > (A) When bdrv_remove_file_or_backing_child() uses > bdrv_replace_child_tran(), we have to ensure that the BDS lives as > long as the transaction does. This is solved by keeping a strong > reference to it that’s released only when the transaction is cleaned > up (and the new patch 7 ensures that the .clean() handler will be > invoked after all .commit()/.abort() handlers, so the reference will > really live as long as the transaction does). > > (B) bdrv_replace_node_noperm() passes a pointer to loop-local variable, > which is a really bad idea considering the transaction lives much > longer than one loop iteration. > Luckily, the new_bs it passes is always non-NULL, and so > bdrv_replace_child_tran() actually doesn’t need to store the > BdrvChild ** pointer, because for a non-NULL new_bs, there is > nothing to revert in the abort handler. We just need to clarify > this, not store the pointer in case of a non-NULL new_bs, and assert > that bdrv_replace_node_noperm() and its relatives are only used to > replace an existing node by some other existing (i.e. non-NULL) > node. Thanks, applied to the block branch. Kevin