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 393F7C2D0A8 for ; Mon, 28 Sep 2020 10:59:27 +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 D69F42074F for ; Mon, 28 Sep 2020 10:59:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Ddc6udEc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D69F42074F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50360 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kMqsP-0000Gj-PA for qemu-devel@archiver.kernel.org; Mon, 28 Sep 2020 06:59:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:47222) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kMqrH-000888-0K for qemu-devel@nongnu.org; Mon, 28 Sep 2020 06:58:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:31048) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kMqqN-00084p-0C for qemu-devel@nongnu.org; Mon, 28 Sep 2020 06:58:13 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601290637; 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: in-reply-to:in-reply-to:references:references; bh=SGCxguFyh/Ui2C8+N8jFiAjBheF8ptz38fY8joy7zz4=; b=Ddc6udEc/DSfIQfm+ZAfmdakfBH+y1X47iGvaLBmaDaFHJV2XjiEaakv+XW0KVu16lDC5Q 5p+u1dkkIB3ie6XcL8mwqikXsxlL+v9vS2hR8p7bzexeQ3QXw3j7HfvpOT7OqbAGh5h1Bs V5lfFL8rmqQtRPuoycYQz0kdrQVxmUw= 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-548-l34VLxV5OkeGySpesX5f9g-1; Mon, 28 Sep 2020 06:57:15 -0400 X-MC-Unique: l34VLxV5OkeGySpesX5f9g-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 53A048015A4; Mon, 28 Sep 2020 10:57:14 +0000 (UTC) Received: from linux.fritz.box (ovpn-114-193.ams2.redhat.com [10.36.114.193]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5B9D678437; Mon, 28 Sep 2020 10:57:13 +0000 (UTC) Date: Mon, 28 Sep 2020 12:57:11 +0200 From: Kevin Wolf To: Ying Fang Subject: Re: [RFC PATCH 0/7] block-backend: Introduce I/O hang Message-ID: <20200928105711.GF5451@linux.fritz.box> References: <20200927130420.1095-1-fangying1@huawei.com> MIME-Version: 1.0 In-Reply-To: <20200927130420.1095-1-fangying1@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 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=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/28 03:47:08 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.687, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: zhang.zhanghailiang@huawei.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 27.09.2020 um 15:04 hat Ying Fang geschrieben: > A VM in the cloud environment may use a virutal disk as the backend storage, > and there are usually filesystems on the virtual block device. When backend > storage is temporarily down, any I/O issued to the virtual block device will > cause an error. For example, an error occurred in ext4 filesystem would make > the filesystem readonly. However a cloud backend storage can be soon recovered. > For example, an IP-SAN may be down due to network failure and will be online > soon after network is recovered. The error in the filesystem may not be > recovered unless a device reattach or system restart. So an I/O rehandle is > in need to implement a self-healing mechanism. > > This patch series propose a feature called I/O hang. It can rehandle AIOs > with EIO error without sending error back to guest. From guest's perspective > of view it is just like an IO is hanging and not returned. Guest can get > back running smoothly when I/O is recovred with this feature enabled. What is the problem with setting werror=stop and rerror=stop for the device? Is it that QEMU won't automatically retry, but management tool interaction is required to resume the guest? I haven't checked your patches in detail yet, but implementing this functionality in the backend means that blk_drain() will hang (or if it doesn't hang, it doesn't do what it's supposed to do), making the whole QEMU process unresponsive until the I/O succeeds again. Amongst others, this would make it impossible to migrate away from a host with storage problems. Kevin