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

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

On Friday 07 March 2008 12:38, Christoph Lameter wrote:
> On Fri, 7 Mar 2008, Nick Piggin wrote:
> > On Friday 07 March 2008 09:51, Christoph Lameter wrote:
> > > On Thu, 6 Mar 2008, Nick Piggin wrote:
> > > > >  	PG_mappedtodisk,	/* Has blocks allocated on-disk */
> > > > >  	PG_reclaim,		/* To be reclaimed asap */
> > > > > -	/* PG_readahead is only used for file reads; PG_reclaim is only
> > > > > for writes */ -	PG_readahead = PG_reclaim, /* Reminder to do async
> > > > > read-ahead */ PG_buddy,		/* Page is free, on buddy lists */
> > > >
> > > > IMO it's nice to see these alias up front.
> > >
> > > I could add a comment pointing to the aliases for those that are
> > > aliases?
> >
> > Yeah that would be better than nothing. I didn't quite
> > understand why you made this change in the first place
> > though.
>
> It avoids us having to deal with aliases in the future.

It doesn't. You still have to deal with them.


> 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.

You still have to know that checking for PG_reclaim in bad_page
can only be done if it is *also* a bug for PG_readahead to be
found set at that point too. Because it is an alias.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>