From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756151Ab2IIXd3 (ORCPT ); Sun, 9 Sep 2012 19:33:29 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51173 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755823Ab2IIXQJ (ORCPT ); Sun, 9 Sep 2012 19:16:09 -0400 Message-Id: <20120909224202.499750447@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 09 Sep 2012 23:43:17 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Asias He , "Michael S. Tsirkin" , Rusty Russell Subject: [ 87/95] virtio-blk: Call del_gendisk() before disable guest kick In-Reply-To: <20120909224150.641491654@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Asias He commit 02e2b124943648fba0a2ccee5c3656a5653e0151 upstream. del_gendisk() might not return due to failing to remove the /sys/block/vda/serial sysfs entry when another thread (udev) is trying to read it. virtblk_remove() vdev->config->reset() : guest will not kick us through interrupt del_gendisk() device_del() kobject_del(): got stuck, sysfs entry ref count non zero sysfs_open_file(): user space process read /sys/block/vda/serial sysfs_get_active() : got sysfs entry ref count dev_attr_show() virtblk_serial_show() blk_execute_rq() : got stuck, interrupt is disabled request cannot be finished This patch fixes it by calling del_gendisk() before we disable guest's interrupt so that the request sent in virtblk_serial_show() will be finished and del_gendisk() will success. This fixes another race in hot-unplug process. It is save to call del_gendisk(vblk->disk) before flush_work(&vblk->config_work) which might access vblk->disk, because vblk->disk is not freed until put_disk(vblk->disk). Cc: virtualization@lists.linux-foundation.org Cc: kvm@vger.kernel.org Signed-off-by: Asias He Acked-by: Michael S. Tsirkin Signed-off-by: Rusty Russell Signed-off-by: Ben Hutchings --- drivers/block/virtio_blk.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 693187d..1bed517 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -584,13 +584,13 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) vblk->config_enable = false; mutex_unlock(&vblk->config_lock); + del_gendisk(vblk->disk); + /* Stop all the virtqueues. */ vdev->config->reset(vdev); flush_work(&vblk->config_work); - del_gendisk(vblk->disk); - /* Abort requests dispatched to driver. */ spin_lock_irqsave(&vblk->lock, flags); while ((vbr = virtqueue_detach_unused_buf(vblk->vq))) {