Re: [patch 8/8] Pageflags: Eliminate PG_xxx aliases

[Nick Piggin <nickpiggin@yahoo.com.au>]

On Friday 07 March 2008 14:53, Christoph Lameter wrote:
> On Fri, 7 Mar 2008, Nick Piggin wrote:
> > > It avoids us having to deal with aliases in the future.
> >
> > It doesn't. You still have to deal with them.
>
> Sortof.
>
> You do not have to deal with it on the level of the PG_xxx enum constant.

But that's the easy part, and the part that I think is actually
useful because you get to explicitly see the aliases.


> Yes you will have to deal with the aliases at the level of the
> functions.

Which is the hard part.


> > > PG_xx at this
> > > point is not unique which can be confusing. See the PG_reclaim in
> > > mm/page_alloc.c. It also means PG_readahead. If I look for
> > > handling of PG_readahead then I wont find it.
> >
> > You can't just pretend not to deal with aliases at that point
> > in mm/page_alloc.c just becuase you only have one name for the
> > bit position.
>
> If you only have one name for the bit position the you can localize the
> aliases and uses of that bit. This means you can go from a bit that you
> see set while debugging to the PG_xxx flag and then look for uses. Which
> will turn up aliases.

I don't understand how this would be any different from the current
code except with the curent code, you only have to look for aliases
in one place (ie. the PG_ definitions).


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