Re: [discuss] mmap, mbind and write to mmap'ed memory crashes2.6.16-rc1[2] on 2 node X86_64

[Christoph Lameter]

On Wed, 8 Feb 2006, Andi Kleen wrote:

> > So a provisional solution would be to simply ignore empty zones in 
> > bind_zonelist?
> 
> That would likely prevent the crash yes (Bharata can you test?)
> 
> But of course it still has the problem of a lot of memory being unpolicied
> on machines with >4GB if there's both DMA32 and NORMAL.

The fix could result in a zonelist with no zones. So we can answer one 
question in __alloc_pages().

Index: linux-2.6.16-rc2/mm/page_alloc.c
===================================================================
--- linux-2.6.16-rc2.orig/mm/page_alloc.c	2006-02-08 00:05:09.000000000 -0800
+++ linux-2.6.16-rc2/mm/page_alloc.c	2006-02-08 08:18:59.000000000 -0800
@@ -913,7 +913,7 @@ restart:
 	z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
 
 	if (unlikely(*z == NULL)) {
-		/* Should this ever happen?? */
+		/* May occur if MPOL_BIND results in an empty zonelist */
 		return NULL;
 	}
 
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