From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753920AbaKLBXt (ORCPT <rfc822;w@1wt.eu>);
	Tue, 11 Nov 2014 20:23:49 -0500
Received: from mail.linuxfoundation.org ([140.211.169.12]:58684 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753872AbaKLBXq (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 11 Nov 2014 20:23:46 -0500
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: [PATCH 3.17 086/319] xen/blkback: unmap all persistent grants when frontend gets disconnected
Date: Wed, 12 Nov 2014 10:13:44 +0900
Message-Id: <20141112011006.836787628@linuxfoundation.org>
X-Mailer: git-send-email 2.1.3
In-Reply-To: <20141112010952.553519040@linuxfoundation.org>
References: <20141112010952.553519040@linuxfoundation.org>
User-Agent: quilt/0.63-1
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-15
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

3.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vitaly Kuznetsov <vkuznets@redhat.com>

commit 12ea729645ace01e08f9654df155622898d3aae6 upstream.

blkback does not unmap persistent grants when frontend goes to Closed
state (e.g. when blkfront module is being removed). This leads to the
following in guest's dmesg:

[  343.243825] xen:grant_table: WARNING: g.e. 0x445 still in use!
[  343.243825] xen:grant_table: WARNING: g.e. 0x42a still in use!
...

When load module -> use device -> unload module sequence is performed multiple times
it is possible to hit BUG() condition in blkfront module:

[  343.243825] kernel BUG at drivers/block/xen-blkfront.c:954!
[  343.243825] invalid opcode: 0000 [#1] SMP
[  343.243825] Modules linked in: xen_blkfront(-) ata_generic pata_acpi [last unloaded: xen_blkfront]
...
[  343.243825] Call Trace:
[  343.243825]  [<ffffffff814111ef>] ? unregister_xenbus_watch+0x16f/0x1e0
[  343.243825]  [<ffffffffa0016fbf>] blkfront_remove+0x3f/0x140 [xen_blkfront]
...
[  343.243825] RIP  [<ffffffffa0016aae>] blkif_free+0x34e/0x360 [xen_blkfront]
[  343.243825]  RSP <ffff88001eb8fdc0>

We don't need to keep these grants if we're disconnecting as frontend might already
forgot about them. Solve the issue by moving xen_blkbk_free_caches() call from
xen_blkif_free() to xen_blkif_disconnect().

Now we can see the following:
[  928.590893] xen:grant_table: WARNING: g.e. 0x587 still in use!
[  928.591861] xen:grant_table: WARNING: g.e. 0x372 still in use!
...
[  929.592146] xen:grant_table: freeing g.e. 0x587
[  929.597174] xen:grant_table: freeing g.e. 0x372
...

Backend does not keep persistent grants any more, reconnect works fine.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/block/xen-blkback/xenbus.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -270,6 +270,9 @@ static int xen_blkif_disconnect(struct x
 		blkif->blk_rings.common.sring = NULL;
 	}
 
+	/* Remove all persistent grants and the cache of ballooned pages. */
+	xen_blkbk_free_caches(blkif);
+
 	return 0;
 }
 
@@ -281,9 +284,6 @@ static void xen_blkif_free(struct xen_bl
 	xen_blkif_disconnect(blkif);
 	xen_vbd_free(&blkif->vbd);
 
-	/* Remove all persistent grants and the cache of ballooned pages. */
-	xen_blkbk_free_caches(blkif);
-
 	/* Make sure everything is drained before shutting down */
 	BUG_ON(blkif->persistent_gnt_c != 0);
 	BUG_ON(atomic_read(&blkif->persistent_gnt_in_use) != 0);