Messages in this thread | | | Date | Wed, 15 May 2013 16:20:54 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v3 3/4] memory_hotplug: use pgdat_resize_lock() in online_pages() |
| |
On Mon, 13 May 2013 16:13:06 -0700 Cody P Schafer <cody@linux.vnet.ibm.com> wrote:
> mmzone.h documents node_size_lock (which pgdat_resize_lock() locks) as > follows: > > * Must be held any time you expect node_start_pfn, node_present_pages > * or node_spanned_pages stay constant. [...]
Yeah, I suppose so. Although no present code sites actually do that.
> So actually hold it when we update node_present_pages in online_pages(). > > ... > > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -915,6 +915,7 @@ static void node_states_set_node(int node, struct memory_notify *arg) > > int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type) > { > + unsigned long flags; > unsigned long onlined_pages = 0; > struct zone *zone; > int need_zonelists_rebuild = 0; > @@ -993,7 +994,11 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ > > zone->managed_pages += onlined_pages; > zone->present_pages += onlined_pages; > + > + pgdat_resize_lock(zone->zone_pgdat, &flags); > zone->zone_pgdat->node_present_pages += onlined_pages; > + pgdat_resize_unlock(zone->zone_pgdat, &flags); > + > if (onlined_pages) { > node_states_set_node(zone_to_nid(zone), &arg); > if (need_zonelists_rebuild)
afaict the only benefits of making this change are
a) so that code which does
a = p->node_present_pages; ... b = p->node_present_pages;
can ensure that `a' and `b' are equal, by taking pgdat_resize_lock().
Which is somewhat odd, and
b) to make the comment truthful ;)
| |