Re: [PATCH] v2.5.1-pre9-00_kvec.diff

[Roman Zippel]

Hi,

On Tue, 11 Dec 2001, Benjamin LaHaise wrote:

> On Tue, Dec 11, 2001 at 09:35:15PM -0600, Steven Walter wrote:
> > > +	nr_pages = (ptr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
> > > +	nr_pages -= ptr >> PAGE_SHIFT;
> >
> > Isn't this the same as
> > 	nr_pages = (len + PAGE_SIZE -1) >> PAGE_SHIFT;
>
> No.

But this is:

	nr_pages = ((ptr & ~PAGE_MASK) + len + PAGE_SIZE - 1) >> PAGE_SHIFT;

and this even slightly better (at least on ia32):

	mask = PAGE_SIZE - 1;
	nr_pages = ((ptr & mask) + len + mask) >> PAGE_SHIFT;

bye, Roman