linux-kernel - RE: [PATCH 02/10] zcache: fix refcount leak

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Date:	Tue, 19 Jun 2012 12:49:13 -0700 (PDT)
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Konrad Wilk <konrad.wilk@...cle.com>,
	Nitin Gupta <ngupta@...are.org>
Subject: RE: [PATCH 02/10] zcache: fix refcount leak

> From: Seth Jennings [mailto:sjenning@...ux.vnet.ibm.com]
> Sent: Tuesday, June 19, 2012 8:29 AM
> To: Xiao Guangrong
> Cc: Andrew Morton; Dan Magenheimer; LKML; linux-mm@...ck.org
> Subject: Re: [PATCH 02/10] zcache: fix refcount leak
> 
> On 06/19/2012 03:33 AM, Xiao Guangrong wrote:
> 
> > In zcache_get_pool_by_id, the refcount of zcache_host is not increased, but
> > it is always decreased in zcache_put_pool
> >
> > Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> 
> Acked-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>

(Nitin Gupta and Konrad Wilk cc'ed to call their attention
to this patch sequence...)

My preference would be to fix it the opposite way, by
checking and ignoring zcache_host in zcache_put_pool.
The ref-counting is to ensure that a client isn't
accidentally destroyed while in use (for multiple-client
users such as ramster and kvm) and since zcache_host is a static
struct, it should never be deleted so need not be ref-counted.

Dan
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