linux-kernel - Re: [Xen-devel] [PATCH] xen/blkback: prevent repeated backend

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Date:	Wed, 12 Dec 2012 11:45:00 +0100
From:	Olaf Hering <olaf@...fle.de>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	Jan Beulich <JBeulich@...e.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>
Subject: Re: [Xen-devel] [PATCH] xen/blkback: prevent repeated
 backend_changed invocations

On Wed, Dec 12, Ian Campbell wrote:

> On Wed, 2012-12-12 at 09:42 +0000, Jan Beulich wrote:
> > >>> On 11.12.12 at 21:50, Olaf Hering <olaf@...fle.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.

The current code handles that, if a property does not exist the function
will exit early.

Olaf
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