Re: [patch fixup] memcg: remove direct page_cgroup-to-page pointer fix

[Randy Dunlap <randy.dunlap@oracle.com>]

On 02/05/11 01:04, Johannes Weiner wrote:
> On Fri, Feb 04, 2011 at 06:38:10PM -0800, Randy Dunlap wrote:
>> On Fri, 04 Feb 2011 15:15:17 -0800 akpm@linux-foundation.org wrote:
>>
>>> The mm-of-the-moment snapshot 2011-02-04-15-15 has been uploaded to
>>>
>>>    http://userweb.kernel.org/~akpm/mmotm/
>>>
>>> and will soon be available at
>>>
>>>    git://zen-kernel.org/kernel/mmotm.git
>>>
>>> It contains the following patches against 2.6.38-rc3:
>>
>>
>> Lots of these warnings in some kernel configs:
>>
>> mmotm-2011-0204-1515/include/linux/page_cgroup.h:144: warning: left shift count >= width of type
>> mmotm-2011-0204-1515/include/linux/page_cgroup.h:145: warning: left shift count >= width of type
>> mmotm-2011-0204-1515/include/linux/page_cgroup.h:150: warning: right shift count >= width of type
> 
> Thanks for the report, Randy, and sorry for the breakage.  Here is the
> fixup:
> 
> ---
> Since the non-flags field for pc array ids in pc->flags is offset from
> the end of the word, we end up with a shift count of BITS_PER_LONG in
> case the field width is zero.
> 
> This results in a compiler warning as we shift in both directions a
> long int by BITS_PER_LONG.
> 
> There is no real harm -- the mask is zero -- but fix up the compiler
> warning by also making the shift count zero for a non-existant field.
> 
> Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> ---

Acked-by: Randy Dunlap <randy.dunlap@oracle.com>

Thanks.

-- 
~Randy
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