Re: [Xen-devel] [PATCH 2/6] xen-blkfront: handle backend CLOSED without CLOSING

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 25/09/12 18:53, David Vrabel wrote:
> On 21/09/12 17:04, David Vrabel wrote:
>> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>>
>> Backend drivers shouldn't transistion to CLOSED unless the frontend is
>> CLOSED.  If a backend does transition to CLOSED too soon then the
>> frontend may not see the CLOSING state and will not properly shutdown.
>>
>> So, treat an unexpected backend CLOSED state the same as CLOSING.
> 
> Didn't handle the frontend block device being mounted. Updated patch here.

Konrad, can you ack this updated patch if you're happy with it.

Thanks.

David

> 8<---------------------------------
> xen-blkfront: handle backend CLOSED without CLOSING
> 
> Backend drivers shouldn't transistion to CLOSED unless the frontend is
> CLOSED.  If a backend does transition to CLOSED too soon then the
> frontend may not see the CLOSING state and will not properly shutdown.
> 
> So, treat an unexpected backend CLOSED state the same as CLOSING.
> 
> If the backend is CLOSED then the frontend can't talk to it so go to
> CLOSED immediately without waiting for the block device to be closed
> or unmounted.
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  drivers/block/xen-blkfront.c |   13 +++++++++----
>  1 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 2c2d2e5..c1f5f38 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -1143,7 +1143,8 @@ static int blkfront_resume(struct xenbus_device *dev)
>  }
>  
>  static void
> -blkfront_closing(struct blkfront_info *info)
> +blkfront_closing(struct blkfront_info *info,
> +              enum xenbus_state backend_state)
>  {
>       struct xenbus_device *xbdev = info->xbdev;
>       struct block_device *bdev = NULL;
> @@ -1167,7 +1168,8 @@ blkfront_closing(struct blkfront_info *info)
>  
>       mutex_lock(&bdev->bd_mutex);
>  
> -     if (bdev->bd_openers) {
> +     /* If the backend is already CLOSED, close now. */
> +     if (bdev->bd_openers && backend_state != XenbusStateClosed) {
>               xenbus_dev_error(xbdev, -EBUSY,
>                                "Device in use; refusing to close");
>               xenbus_switch_state(xbdev, XenbusStateClosing);
> @@ -1340,15 +1342,18 @@ static void blkback_changed(struct xenbus_device *dev,
>       case XenbusStateReconfiguring:
>       case XenbusStateReconfigured:
>       case XenbusStateUnknown:
> -     case XenbusStateClosed:
>               break;
>  
>       case XenbusStateConnected:
>               blkfront_connect(info);
>               break;
>  
> +     case XenbusStateClosed:
> +             if (dev->state == XenbusStateClosed)
> +                     break;
> +             /* Missed the backend's Closing state -- fallthrough */
>       case XenbusStateClosing:
> -             blkfront_closing(info);
> +             blkfront_closing(info, backend_state);
>               break;
>       }
>  }

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