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Date: Sun, 09 Sep 2012 23:43:17 +0100
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
alan@...rguk.ukuu.org.uk, Asias He <asias@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Rusty Russell <rusty@...tcorp.com.au>
Subject: [ 87/95] virtio-blk: Call del_gendisk() before disable guest kick
3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Asias He <asias@...hat.com>
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@...ts.linux-foundation.org
Cc: kvm@...r.kernel.org
Signed-off-by: Asias He <asias@...hat.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
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))) {
--
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