Virtualization - Apr 2011 - [PATCH] virtio_blk: decrement index when blockdevice is removed

When virtio block device is removed, index does not get decremented. When 
another virtio disk is attached it uses the next device letter to the 
one that is suppose to be available. 

Signed-off-by: Takuma Umeya <tumeya at redhat.com>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6ecf89c..730e7af 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -489,6 +489,7 @@ static void __devexit virtblk_remove(struct virtio_device
*vdev)
        mempool_destroy(vblk->pool);
        vdev->config->del_vqs(vdev);
        kfree(vblk);
+       index--;
 }
 
 static const struct virtio_device_id id_table[] = {

-- 
Umeya, Takuma
Technical Account Manager
Red Hat GSS APAC
+81.3.5798.8584 (direct)
tumeya at redhat.com

On 2011-04-05 06:49, Takuma Umeya wrote:
> When virtio block device is removed, index does not get decremented. When 
> another virtio disk is attached it uses the next device letter to the 
> one that is suppose to be available. 
> 
> Signed-off-by: Takuma Umeya <tumeya at redhat.com>
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 6ecf89c..730e7af 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -489,6 +489,7 @@ static void __devexit virtblk_remove(struct
virtio_device *vdev)
>         mempool_destroy(vblk->pool);
>         vdev->config->del_vqs(vdev);
>         kfree(vblk);
> +       index--;
>  }
>  
>  static const struct virtio_device_id id_table[] = {
What happens when you delete a device that isn't the last one?

-- 
Jens Axboe

On Tue, 05 Apr 2011 07:08:12 +0200, Jens Axboe <jaxboe at fusionio.com>
wrote:
> On 2011-04-05 06:49, Takuma Umeya wrote:
> > When virtio block device is removed, index does not get decremented.
When
> > another virtio disk is attached it uses the next device letter to the 
> > one that is suppose to be available. 
> > 
> > Signed-off-by: Takuma Umeya <tumeya at redhat.com>
> > 
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 6ecf89c..730e7af 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -489,6 +489,7 @@ static void __devexit virtblk_remove(struct
virtio_device *vdev)
> >         mempool_destroy(vblk->pool);
> >         vdev->config->del_vqs(vdev);
> >         kfree(vblk);
> > +       index--;
> >  }
> >  
> >  static const struct virtio_device_id id_table[] = {
> 
> What happens when you delete a device that isn't the last one?
Obviously we should do something cleverer for assigning drives.

It might be a cute if genhd gave us a function to get the next free
index for a given major number, and format it for us, like so:

      /* Return the next available minor for a given @major, at least
       * @spacing after the previous and, and append appropriate letters
       * to @name if it's not NULL.  -ve errno on fail (-ENOSPC?). */
      int disk_next_minor(int major, unsigned spacing, char *name);

A trivial optimization would be to remember the last major and max minor
(resetting that if any disks are removed).

This could clean up other code, too.

Cheers,
Rusty.

* Takuma Umeya <tumeya at redhat.com> [2011-04-05
00:00]:
> When virtio block device is removed, index does not get decremented. When 
> another virtio disk is attached it uses the next device letter to the 
> one that is suppose to be available. 
> 
> Signed-off-by: Takuma Umeya <tumeya at redhat.com>
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 6ecf89c..730e7af 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -489,6 +489,7 @@ static void __devexit virtblk_remove(struct
virtio_device *vdev)
>         mempool_destroy(vblk->pool);
>         vdev->config->del_vqs(vdev);
>         kfree(vblk);
> +       index--;
>  }
What about referencing /dev/disk/by-id  and using drive serial numbers?
How much do we care about re-using minor numbers?  IIRC, virtio-blk can
go out to vdxxx; that's a lot of disks or add/removes.
> 
>  static const struct virtio_device_id id_table[] = {
> 
> -- 
> Umeya, Takuma
> Technical Account Manager
> Red Hat GSS APAC
> +81.3.5798.8584 (direct)
> tumeya at redhat.com
> _______________________________________________
> Virtualization mailing list
> Virtualization at lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/virtualization
-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh at us.ibm.com