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.
> For example:
>
> CPU_0 CPU_1 CPU_3
>
> add_to_page_cache:
>
> SetPageNoNewRefs();
> write_lock_irq(->tree_lock);
SetPageLocked(page);
> ...
> write_unlock_irq(->tree_lock);
>
> remove_mapping:
>
> SetPageNoNewRefs();
>
> ClearPageNoNewRefs();
> write_lock_irq(->tree_lock);
>
> check page_count()
>
> page_cache_get_speculative:
>
> increment page_count()
>
> no PG_nonewrefs => return
>
> Oleg.
Shaggy
--
David Kleikamp
IBM Linux Technology Center
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
