[PATCH 0/5] drivers: xen frontend devices should handle missed backend CLOSING

[PATCH 0/5] drivers: xen frontend devices should handle missed backend CLOSING

[David Vrabel]

Subsystem maintainers, you can either pick up the relevant driver patch
or ack it to go via Konrad's Xen tree.

The series makes all the Xen frontend drivers handle the backend
transitioning to CLOSED without the frontend having previously seen
the backend in the CLOSING state.

Backends shouldn't do this but some do.  e.g., if the host is
XenServer and the toolstack decides to do a forced shutdown of a VBD,
then the blkfront may miss the CLOSING transition and the /dev/xvdX
device will not be destroyed which prevents it being reused.

I have seen systems that ended up in this state but it's not clear if
this was the actual cause.  However, I think in general it's a good
thing to thing to improve the handling of unexpected state
transitions.

David

[PATCH 5/5] xen-kbdfront: handle backend CLOSED without CLOSING

[David Vrabel]

From: David Vrabel <david.vrabel@citrix.com>

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.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
Cc: linux-input@vger.kernel.org
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/misc/xen-kbdfront.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index 02ca868..6f7d990 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -311,7 +311,6 @@ static void xenkbd_backend_changed(struct xenbus_device *dev,
 	case XenbusStateReconfiguring:
 	case XenbusStateReconfigured:
 	case XenbusStateUnknown:
-	case XenbusStateClosed:
 		break;
 
 	case XenbusStateInitWait:
@@ -350,6 +349,10 @@ InitWait:
 
 		break;
 
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's CLOSING state -- fallthrough */
 	case XenbusStateClosing:
 		xenbus_frontend_closed(dev);
 		break;
-- 
1.7.2.5

Re: [PATCH 5/5] xen-kbdfront: handle backend CLOSED without CLOSING

[Konrad Rzeszutek Wilk]

On Thu, Oct 18, 2012 at 11:03:38AM +0100, David Vrabel wrote:
> From: David Vrabel <david.vrabel@citrix.com>
> 
> 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.
> 
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> Cc: linux-input@vger.kernel.org
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Hey Dmitry,

Should I prep a git pull for you for this or are you OK giving
an Ack for me to put this patch in my git pull for Linus?

Thx.
> ---
>  drivers/input/misc/xen-kbdfront.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> index 02ca868..6f7d990 100644
> --- a/drivers/input/misc/xen-kbdfront.c
> +++ b/drivers/input/misc/xen-kbdfront.c
> @@ -311,7 +311,6 @@ static void xenkbd_backend_changed(struct xenbus_device *dev,
>  	case XenbusStateReconfiguring:
>  	case XenbusStateReconfigured:
>  	case XenbusStateUnknown:
> -	case XenbusStateClosed:
>  		break;
>  
>  	case XenbusStateInitWait:
> @@ -350,6 +349,10 @@ InitWait:
>  
>  		break;
>  
> +	case XenbusStateClosed:
> +		if (dev->state == XenbusStateClosed)
> +			break;
> +		/* Missed the backend's CLOSING state -- fallthrough */
>  	case XenbusStateClosing:
>  		xenbus_frontend_closed(dev);
>  		break;
> -- 
> 1.7.2.5

Re: [PATCH 5/5] xen-kbdfront: handle backend CLOSED without CLOSING

[Dmitry Torokhov]

On Fri, Oct 19, 2012 at 09:00:59AM -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Oct 18, 2012 at 11:03:38AM +0100, David Vrabel wrote:
> > From: David Vrabel <david.vrabel@citrix.com>
> > 
> > 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.
> > 
> > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> > Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> > Cc: linux-input@vger.kernel.org
> > Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> 
> Hey Dmitry,
> 
> Should I prep a git pull for you for this or are you OK giving
> an Ack for me to put this patch in my git pull for Linus?

Sure, please merge with the rest through your tree.

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Thanks!

> 
> Thx.
> > ---
> >  drivers/input/misc/xen-kbdfront.c |    5 ++++-
> >  1 files changed, 4 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> > index 02ca868..6f7d990 100644
> > --- a/drivers/input/misc/xen-kbdfront.c
> > +++ b/drivers/input/misc/xen-kbdfront.c
> > @@ -311,7 +311,6 @@ static void xenkbd_backend_changed(struct xenbus_device *dev,
> >  	case XenbusStateReconfiguring:
> >  	case XenbusStateReconfigured:
> >  	case XenbusStateUnknown:
> > -	case XenbusStateClosed:
> >  		break;
> >  
> >  	case XenbusStateInitWait:
> > @@ -350,6 +349,10 @@ InitWait:
> >  
> >  		break;
> >  
> > +	case XenbusStateClosed:
> > +		if (dev->state == XenbusStateClosed)
> > +			break;
> > +		/* Missed the backend's CLOSING state -- fallthrough */
> >  	case XenbusStateClosing:
> >  		xenbus_frontend_closed(dev);
> >  		break;
> > -- 
> > 1.7.2.5

-- 
Dmitry