From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:56844 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756239AbcHBHHV (ORCPT ); Tue, 2 Aug 2016 03:07:21 -0400 Subject: Patch "xen-blkfront: don't call talk_to_blkback when already connected to blkback" has been added to the 4.6-stable tree To: bob.liu@oracle.com Cc: , From: Date: Tue, 02 Aug 2016 09:04:51 +0200 Message-ID: <1470121491217159@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled xen-blkfront: don't call talk_to_blkback when already connected to blkback to the 4.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: xen-blkfront-don-t-call-talk_to_blkback-when-already-connected-to-blkback.patch and it can be found in the queue-4.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From efd1535270c1deb0487527bf0c3c827301a69c93 Mon Sep 17 00:00:00 2001 From: Bob Liu Date: Tue, 7 Jun 2016 10:43:15 -0400 Subject: xen-blkfront: don't call talk_to_blkback when already connected to blkback From: Bob Liu commit efd1535270c1deb0487527bf0c3c827301a69c93 upstream. Sometimes blkfront may twice receive blkback_changed() notification (XenbusStateConnected) after migration, which will cause talk_to_blkback() to be called twice too and confuse xen-blkback. The flow is as follow: blkfront blkback blkfront_resume() > talk_to_blkback() > Set blkfront to XenbusStateInitialised front changed() > Connect() > Set blkback to XenbusStateConnected blkback_changed() > Skip talk_to_blkback() because frontstate == XenbusStateInitialised > blkfront_connect() > Set blkfront to XenbusStateConnected ----- And here we get another XenbusStateConnected notification leading to: ----- blkback_changed() > because now frontstate != XenbusStateInitialised talk_to_blkback() is also called again > blkfront state changed from XenbusStateConnected to XenbusStateInitialised (Which is not correct!) front_changed(): > Do nothing because blkback already in XenbusStateConnected Now blkback is in XenbusStateConnected but blkfront is still in XenbusStateInitialised - leading to no disks. Poking of the XenbusStateConnected state is allowed (to deal with block disk change) and has to be dealt with. The most likely cause of this bug are custom udev scripts hooking up the disks and then validating the size. Signed-off-by: Bob Liu Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Greg Kroah-Hartman --- drivers/block/xen-blkfront.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -2469,10 +2469,23 @@ static void blkback_changed(struct xenbu break; case XenbusStateConnected: - if (dev->state != XenbusStateInitialised) { + /* + * talk_to_blkback sets state to XenbusStateInitialised + * and blkfront_connect sets it to XenbusStateConnected + * (if connection went OK). + * + * If the backend (or toolstack) decides to poke at backend + * state (and re-trigger the watch by setting the state repeatedly + * to XenbusStateConnected (4)) we need to deal with this. + * This is allowed as this is used to communicate to the guest + * that the size of disk has changed! + */ + if ((dev->state != XenbusStateInitialised) && + (dev->state != XenbusStateConnected)) { if (talk_to_blkback(dev, info)) break; } + blkfront_connect(info); break; Patches currently in stable-queue which might be from bob.liu@oracle.com are queue-4.6/xen-blkfront-don-t-call-talk_to_blkback-when-already-connected-to-blkback.patch queue-4.6/xen-blkfront-save-uncompleted-reqs-in-blkfront_resume.patch queue-4.6/xen-blkfront-fix-resume-issues-after-a-migration.patch