Re: [PATCH 11/14] mm, memory_hotplug: do not associate hotadded memory to zones until online

[Michal Hocko]

On Fri 16-06-17 16:11:42, Wei Yang wrote:
> Well, I love this patch a lot. We don't need to put the hotadd memory in one
> zone and move it to another. This looks great!
> 
> On Mon, May 15, 2017 at 10:58:24AM +0200, Michal Hocko wrote:
> >From: Michal Hocko <mhocko@xxxxxxxx>
> >
> [...]
> +
> >+void move_pfn_range_to_zone(struct zone *zone,
> >+		unsigned long start_pfn, unsigned long nr_pages)
> >+{
> >+	struct pglist_data *pgdat = zone->zone_pgdat;
> >+	int nid = pgdat->node_id;
> >+	unsigned long flags;
> >+	unsigned long i;
> >+
> >+	if (zone_is_empty(zone))
> >+		init_currently_empty_zone(zone, start_pfn, nr_pages);
> >+
> >+	clear_zone_contiguous(zone);
> >+
> >+	/* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */
> >+	pgdat_resize_lock(pgdat, &flags);
> >+	zone_span_writelock(zone);
> >+	resize_zone_range(zone, start_pfn, nr_pages);
> >+	zone_span_writeunlock(zone);
> >+	resize_pgdat_range(pgdat, start_pfn, nr_pages);
> >+	pgdat_resize_unlock(pgdat, &flags);
> >+
> >+	/*
> >+	 * TODO now we have a visible range of pages which are not associated
> >+	 * with their zone properly. Not nice but set_pfnblock_flags_mask
> >+	 * expects the zone spans the pfn range. All the pages in the range
> >+	 * are reserved so nobody should be touching them so we should be safe
> >+	 */
> >+	memmap_init_zone(nr_pages, nid, zone_idx(zone), start_pfn, MEMMAP_HOTPLUG);
> >+	for (i = 0; i < nr_pages; i++) {
> >+		unsigned long pfn = start_pfn + i;
> >+		set_page_links(pfn_to_page(pfn), zone_idx(zone), nid, pfn);
> > 	}
> 
> memmap_init_zone()->__init_single_page()->set_page_links()
> 
> Do I miss something that you call set_page_links() explicitly here?

I guess you are right. Not sure why I've done this explicitly. I've most
probably just missed that. Could you post a patch that removes the for
loop.

Thanks!
-- 
Michal Hocko
SUSE Labs