Re: [patch 1/2] mm: speculative get_page

Oleg Nesterov
2006-08-01T16:18:43Z

On 08/01, Dave Kleikamp wrote:
>
> On Tue, 2006-08-01 at 23:32 +0400, Oleg Nesterov wrote:
> > Nick Piggin wrote:
> > >
> > > --- linux-2.6.orig/mm/vmscan.c
> > > +++ linux-2.6/mm/vmscan.c
> > > @@ -380,6 +380,8 @@ int remove_mapping(struct address_space
> > > if (!mapping)
> > > return 0; /* truncate got there first */
> > >
> > > + SetPageNoNewRefs(page);
> > > + smp_wmb();
> > > write_lock_irq(&mapping->tree_lock);
> > >
> >
> > Is it enough?
> >
> > PG_nonewrefs could be already set by another add_to_page_cache()/remove_mapping(),
> > and it will be cleared when we take ->tree_lock.
>
> Isn't the page locked when calling remove_mapping()? It looks like
> SetPageNoNewRefs & ClearPageNoNewRefs are called in safe places. Either
> the page is locked, or it's newly allocated. I could have missed
> something, though.

No, I think it is I who missed something, thanks.

Oleg.