Re: [discuss] mmap, mbind and write to mmap'ed memory crashes 2.6.16-rc1[2] on 2 node X86_64

[Christoph Lameter <clameter@engr.sgi.com>]

On Wed, 8 Feb 2006, Andi Kleen wrote:

> On Wednesday 08 February 2006 16:42, Christoph Lameter wrote:
> 
> > However, this has implications for policy_zone. This variable should store
> > the zone that policies apply to. However, in your case this zone will vary 
> > which may lead to all sorts of weird behavior even if we fix 
> > bind_zonelist. To which zone does policy apply? ZONE_NORMAL or ZONE_DMA32?
> 
> It really needs to apply to both (currently you can't police 4GB of your 
> memory on x86-64) But I haven't worked out a good design how to implement it yet.

So a provisional solution would be to simply ignore empty zones in 
bind_zonelist? Or fall back to earlier zones (which includes unpolicied 
zones in the bind zone list?)

Index: linux-2.6.16-rc2/mm/mempolicy.c
===================================================================
--- linux-2.6.16-rc2.orig/mm/mempolicy.c	2006-02-02 22:03:08.000000000 -0800
+++ linux-2.6.16-rc2/mm/mempolicy.c	2006-02-08 07:55:29.000000000 -0800
@@ -143,8 +143,12 @@ static struct zonelist *bind_zonelist(no
 	if (!zl)
 		return NULL;
 	num = 0;
-	for_each_node_mask(nd, *nodes)
-		zl->zones[num++] = &NODE_DATA(nd)->node_zones[policy_zone];
+	for_each_node_mask(nd, *nodes) {
+		struct zone *zone = &NODE_DATA(nd)->node_zones[policy_zone];
+
+		if (zone->present_pages)
+			zl->zones[num++] = &NODE_DATA(nd)->node_zones[policy_zone];
+	}
 	zl->zones[num] = NULL;
 	return zl;
 }
-
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