[ 3.5.y.z extended stable ] Patch "virtio-blk: Don't free ida when disk is in use" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    virtio-blk: Don't free ida when disk is in use

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From e889d879779c6b4c241702332f29246c7cb733d4 Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf at suse.de>
Date: Wed, 2 Jan 2013 15:37:17 +1030
Subject: [PATCH] virtio-blk: Don't free ida when disk is in use

commit f4953fe6c4aeada2d5cafd78aa97587a46d2d8f9 upstream.

When a file system is mounted on a virtio-blk disk, we then remove it
and then reattach it, the reattached disk gets the same disk name and
ids as the hot removed one.

This leads to very nasty effects - mostly rendering the newly attached
device completely unusable.

Trying what happens when I do the same thing with a USB device, I saw
that the sd node simply doesn't get free'd when a device gets forcefully
removed.

Imitate the same behavior for vd devices. This way broken vd devices
simply are never free'd and newly attached ones keep working just fine.

Signed-off-by: Alexander Graf <agraf at suse.de>
Signed-off-by: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/block/virtio_blk.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 774c31d..98bb43f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -573,6 +573,7 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
 {
 	struct virtio_blk *vblk = vdev->priv;
 	int index = vblk->index;
+	int refc;

 	/* Prevent config work handler from accessing the device. */
 	mutex_lock(&vblk->config_lock);
@@ -587,11 +588,15 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)

 	flush_work(&vblk->config_work);

+	refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
 	put_disk(vblk->disk);
 	mempool_destroy(vblk->pool);
 	vdev->config->del_vqs(vdev);
 	kfree(vblk);
-	ida_simple_remove(&vd_index_ida, index);
+
+	/* Only free device id if we don't have any users */
+	if (refc == 1)
+		ida_simple_remove(&vd_index_ida, index);
 }

 #ifdef CONFIG_PM
--
1.7.9.5