Re: [PATCH 00/16] mm: prepare for converting vm->vm_flags to 64-bit

[KOSAKI Motohiro]

On 3/22/2012 5:28 PM, Al Viro wrote:
> On Thu, Mar 22, 2012 at 02:26:47PM -0700, Andrew Morton wrote:
>> It would be nice to find some way of triggering compiler warnings or
>> sparse warnings if someone mixes a 32-bit type with a vm_flags_t.  Any
>> thoughts on this?
>>
>> (Maybe that's what __nocast does, but Documentation/sparse.txt doesn't
>> describe it)
> 
> Use __bitwise for that - check how gfp_t is handled.

Hmm..

If now we activate __bitwise, really plenty driver start create lots warnings.
Does it make sense?

In fact, x86-32 keep 32bit vma_t forever. thus all x86 specific driver don't
need any change. Moreover many ancient drivers has no maintainer and I can't
expect such driver will be fixed even though a warning occur.

So, I think __nocast weakness is better than strict __bitwise annotation for
this situation.
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