Messages in this thread | | | Subject | Re: [patch 1/2] mm: speculative get_page | From | Dave Kleikamp <> | Date | Tue, 01 Aug 2006 10:55:29 -0500 |
| |
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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |