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=-2.6 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_NEOMUTT autolearn=ham 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 3C26DC43334 for ; Thu, 6 Sep 2018 16:14:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF33920652 for ; Thu, 6 Sep 2018 16:14:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CF33920652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=citrix.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727847AbeIFUun (ORCPT ); Thu, 6 Sep 2018 16:50:43 -0400 Received: from smtp.eu.citrix.com ([185.25.65.24]:18048 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725978AbeIFUun (ORCPT ); Thu, 6 Sep 2018 16:50:43 -0400 X-IronPort-AV: E=Sophos;i="5.53,338,1531785600"; d="scan'208";a="78657326" Date: Thu, 6 Sep 2018 18:14:21 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Valentin Vidic CC: Konrad Rzeszutek Wilk , Jens Axboe , , , , , Subject: Re: [PATCH] xen-blkback: Switch to closed state after releasing the backing device Message-ID: <20180906161421.ba35p6qx5rvktjos@mac.bytemobile.com> References: <20180829065214.23546-1-Valentin.Vidic@CARNet.hr> <20180905103649.edugijsjx4v2fbxd@mac.bytemobile.com> <20180905162756.GA26705@gavran.carpriv.carnet.hr> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180905162756.GA26705@gavran.carpriv.carnet.hr> User-Agent: NeoMutt/20180716 X-ClientProxiedBy: AMSPEX02CAS01.citrite.net (10.69.22.112) To AMSPEX02CL02.citrite.net (10.69.22.126) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 05, 2018 at 06:27:56PM +0200, Valentin Vidic wrote: > On Wed, Sep 05, 2018 at 12:36:49PM +0200, Roger Pau Monné wrote: > > On Wed, Aug 29, 2018 at 08:52:14AM +0200, Valentin Vidic wrote: > > > Switching to closed state earlier can cause the block-drbd > > > script to fail with 'Device is held open by someone': > > > > > > root: /etc/xen/scripts/block-drbd: remove XENBUS_PATH=backend/vbd/6/51712 > > > kernel: [ 2222.278235] block drbd6: State change failed: Device is held open by someone > > > kernel: [ 2222.278304] block drbd6: state = { cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate r----- } > > > kernel: [ 2222.278340] block drbd6: wanted = { cs:Connected ro:Secondary/Secondary ds:UpToDate/UpToDate r----- } > > > root: /etc/xen/scripts/block-drbd: Writing backend/vbd/6/51712/hotplug-error /etc/xen/scripts/block-drbd failed; error detected. backend/vbd/6/51712/hotplug-status error to xenstore. > > > root: /etc/xen/scripts/block-drbd: /etc/xen/scripts/block-drbd failed; error detected. > > > > > > Signed-off-by: Valentin Vidic > > > Cc: stable@vger.kernel.org > > > --- > > > drivers/block/xen-blkback/xenbus.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > > > index a4bc74e72c39..43bddc996709 100644 > > > --- a/drivers/block/xen-blkback/xenbus.c > > > +++ b/drivers/block/xen-blkback/xenbus.c > > > @@ -323,6 +323,7 @@ static void xen_blkif_free(struct xen_blkif *blkif) > > > { > > > WARN_ON(xen_blkif_disconnect(blkif)); > > > xen_vbd_free(&blkif->vbd); > > > + xenbus_switch_state(blkif->be->dev, XenbusStateClosed); > > > kfree(blkif->be->mode); > > > kfree(blkif->be); > > > > > > @@ -814,7 +815,6 @@ static void frontend_changed(struct xenbus_device *dev, > > > > > > case XenbusStateClosed: > > > xen_blkif_disconnect(be->blkif); > > > - xenbus_switch_state(dev, XenbusStateClosed); > > > if (xenbus_dev_is_online(dev)) > > > break; > > > > AFAICT, this will cause the backend to never switch to 'Closed' state > > until the toolstack sets online to 0, which is not good IMO. > > > > If for example a frontend decides to close a device, the backend will > > stay in state 'Closing' until the toolstack actually removes the disk > > by setting online to 0. > > > > This will prevent resetting blk connections, as blkback will refuse to > > switch to state XenbusStateInitWait unless it's at XenbusStateClosed > > (see the XenbusStateInitialising case in frontend_changed), which will > > never be reached with your patch. > > Ok, is it possible to test this somehow? Yes, you can try booting a PV guest with pvgrub, that will cause pvgrub to open a blk connection, then close it and afterwards the OS kernel will start a new connection. Thanks, Roger.