Re: [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer

["H. Peter Anvin" <hpa@zytor.com>]

Andrew Morton wrote:
> On Wed, 4 Oct 2006 17:56:30 -0700
> Reinette Chatre <reinette.chatre@linux.intel.com> wrote:
>
> > +			if (is_user) {
> > +				if (__get_user(c, buf++))
> > +					return -EFAULT;
> > +			}
> > +			else
> > +				c = *buf++;
>
> Is this actually needed?  __get_user(kernel_address) works OK and (believe
> it or not, given all the stuff it involves) boils down to a single instruction.		

On some architectures, kernel and user space are separate, overlapping 
address spaces.

If __bitmap_parse was an inline (and not exported), this would be okay; 
as it is, you end up doing the test dynamically under all circumstances, 
even though in most (if not all) cases the address space is know a priori.

	-hpa
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