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Date: Mon, 26 Jan 2015 18:13:59 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH -mm] slab: update_memcg_params: explicitly check that old
 array != NULL
Message-ID: <20150126151359.GD6507@mwanda>
References: <20150126085638.GA6507@mwanda>
 <1422266479-29098-1-git-send-email-vdavydov@parallels.com>
 <20150126101902.GC6507@mwanda>
 <20150126104534.GA28978@esperanza>
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In-Reply-To: <20150126104534.GA28978@esperanza>
Sender: owner-linux-mm@kvack.org
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To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org

On Mon, Jan 26, 2015 at 01:45:34PM +0300, Vladimir Davydov wrote:
> On Mon, Jan 26, 2015 at 01:23:05PM +0300, Dan Carpenter wrote:
> > On Mon, Jan 26, 2015 at 01:01:19PM +0300, Vladimir Davydov wrote:
> > > This warning is false-positive, because @old equals NULL iff
> > > @memcg_nr_cache_ids equals 0.
> > 
> > I don't see how it could be a false positive.  The "old" pointer is
> > dereferenced inside the call to memset() so unless memset is a macro the
> > compiler isn't going to optimize the dereference away.
> 
> old->entries is not dereferenced: memcg_cache_array->entries is not a
> pointer - it is embedded to the memcg_cache_array struct.

Ah.  Ok.  Thanks.

regards,
dan carpenter

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