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 B959DC433F5 for ; Fri, 12 Nov 2021 11:39:18 +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 594D760FE7 for ; Fri, 12 Nov 2021 11:39:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 594D760FE7 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]:42524 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mlUtp-0004dG-Gj for qemu-devel@archiver.kernel.org; Fri, 12 Nov 2021 06:39:17 -0500 Received: from eggs.gnu.org ([209.51.188.92]:43518) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlUt5-0003oa-TQ for qemu-devel@nongnu.org; Fri, 12 Nov 2021 06:38:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24700) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mlUt1-0001j7-LM for qemu-devel@nongnu.org; Fri, 12 Nov 2021 06:38:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636717105; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=52uo0Bxw+j8SuaLywxAcQfiO/qAfqfMRlqofKg11Y+Q=; b=XjxJ1mw+6ZSyyVsF1QTO+OPyjOnb3XqQjgHzhYWrNsQrd+hzs4O9i5IeHWBX984OBVQP4k X9wA/yIxie0ywqXv1C4kOOBSXddG6044G9OFsem0ijwfjO9FeTrOFfFtKcBQYqTnFfY+Ai 2JjSXNWpjXfE93Nsq/cHA6FcywI0BZM= 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-434-OKkQx6GYMVKaOKLIkaRNhQ-1; Fri, 12 Nov 2021 06:38:22 -0500 X-MC-Unique: OKkQx6GYMVKaOKLIkaRNhQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 50E2D1023F4E; Fri, 12 Nov 2021 11:38:21 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.237]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 1CF595C1B4; Fri, 12 Nov 2021 11:38:00 +0000 (UTC) Date: Fri, 12 Nov 2021 12:37:59 +0100 From: Kevin Wolf To: Roman Kagan , qemu-devel@nongnu.org, qemu-block@nongnu.org, "Michael S. Tsirkin" , Hanna Reitz , yc-core@yandex-team.ru, =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Paolo Bonzini Subject: Re: [PATCH 01/10] vhost-user-blk: reconnect on any error during realize Message-ID: References: <20211111153354.18807-1-rvkagan@yandex-team.ru> <20211111153354.18807-2-rvkagan@yandex-team.ru> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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=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=-0.699, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 12.11.2021 um 08:39 hat Roman Kagan geschrieben: > On Thu, Nov 11, 2021 at 06:52:30PM +0100, Kevin Wolf wrote: > > Am 11.11.2021 um 16:33 hat Roman Kagan geschrieben: > > > vhost-user-blk realize only attempts to reconnect if the previous > > > connection attempt failed on "a problem with the connection and not an > > > error related to the content (which would fail again the same way in the > > > next attempt)". > > > > > > However this distinction is very subtle, and may be inadvertently broken > > > if the code changes somewhere deep down the stack and a new error gets > > > propagated up to here. > > > > > > OTOH now that the number of reconnection attempts is limited it seems > > > harmless to try reconnecting on any error. > > > > > > So relax the condition of whether to retry connecting to check for any > > > error. > > > > > > This patch amends a527e312b5 "vhost-user-blk: Implement reconnection > > > during realize". > > > > > > Signed-off-by: Roman Kagan > > > > It results in less than perfect error messages. With a modified export > > that just crashes qemu-storage-daemon during get_features, I get: > > > > qemu-system-x86_64: -device vhost-user-blk-pci,chardev=c: Failed to read msg header. Read 0 instead of 12. Original request 1. > > qemu-system-x86_64: -device vhost-user-blk-pci,chardev=c: Reconnecting after error: vhost_backend_init failed: Protocol error > > qemu-system-x86_64: -device vhost-user-blk-pci,chardev=c: Reconnecting after error: Failed to connect to '/tmp/vsock': Connection refused > > qemu-system-x86_64: -device vhost-user-blk-pci,chardev=c: Reconnecting after error: Failed to connect to '/tmp/vsock': Connection refused > > qemu-system-x86_64: -device vhost-user-blk-pci,chardev=c: Failed to connect to '/tmp/vsock': Connection refused > > This patch doesn't change any error messages. Which ones specifically > became less than perfect as a result of this patch? But it adds error messages (for each retry), which are different from the first error message. As I said this is not the end of the world, but maybe a bit more confusing. > > I guess this might be tolerable. On the other hand, the patch doesn't > > really fix anything either, but just gets rid of possible subtleties. > > The remaining patches in the series make other errors beside -EPROTO > propagate up to this point, and some (most) of them are retryable. This > was the reason to include this patch at the beginning of the series (I > guess I should've mentioned that in the patch log). I see. I hadn't looked at the rest of the series yet because I ran out of time, but now that I'm skimming them, I see quite a few places that use non-EPROTO, but I wonder which of them actually should be reconnected. So far all I saw were presumably persistent errors where a retry won't help. Can you give me some examples? Kevin