Re: [Xen-devel] [PATCH] xen/blkback: prevent repeated backend_changed invocations

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2012-12-12 at 09:42 +0000, Jan Beulich wrote:
> >>> On 11.12.12 at 21:50, Olaf Hering <olaf@aepfle.de> wrote:
> > backend_changed might be called multiple times, which will leak
> > be->mode. Make sure it will be called only once. Remove some unneeded
> > checks. Also the be->mode string was leaked, release the memory on
> > device shutdown.
> 
> So did I miss some discussion here? I haven't seen any
> confirmation of this function indeed being supposed to be called
> just once.
> 
> Also, as said previously, if indeed it is to be called just once,
> removing the watch during/after the first invocation would seem
> to be the more appropriate thing to do.

The watch fires (often needlessly) when you first register it so in the
common case it is going to be called twice. Of course that first time
should abort early on so perhaps that's a moot point.

Ian.