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Subject: Re: [PATCH v13 3/3] mm, powerpc, x86: introduce an additional vma bit
 for powerpc pkey
To:     Ram Pai <linuxram@us.ibm.com>
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From:   Dave Hansen <dave.hansen@intel.com>
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Date:   Fri, 4 May 2018 21:42:39 -0700
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On 05/04/2018 06:12 PM, Ram Pai wrote:
>> That new line boils down to:
>>
>> 		[ilog2(0)]	= "",
>>
>> on x86.  It wasn't *obvious* to me that it is OK to do that.  The other
>> possibly undefined bits (VM_SOFTDIRTY for instance) #ifdef themselves
>> out of this array.
>>
>> I would just be a wee bit worried that this would overwrite the 0 entry
>> ("??") with "".
> Yes it would :-( and could potentially break anything that depends on
> 0th entry being "??"
> 
> Is the following fix acceptable?
> 
> #if VM_PKEY_BIT4
>                 [ilog2(VM_PKEY_BIT4)]   = "",
> #endif

Yep, I think that works for me.