From: Paul Jackson <pj@sgi.com>

Backout one item from a previous "memory page_alloc minor cleanups" patch. 
Until and unless we are certain that no one can ever pass an empty zonelist
to __alloc_pages(), this check for an empty zonelist (or some BUG
equivalent) is essential.  The code in get_page_from_freelist() blow ups if
passed an empty zonelist.

Signed-off-by: Paul Jackson <pj@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/page_alloc.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff -puN mm/page_alloc.c~memory-page-alloc-minor-cleanups-fix mm/page_alloc.c
--- a/mm/page_alloc.c~memory-page-alloc-minor-cleanups-fix
+++ a/mm/page_alloc.c
@@ -994,6 +994,13 @@ __alloc_pages(gfp_t gfp_mask, unsigned i
 	might_sleep_if(wait);
 
 restart:
+	z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
+
+	if (unlikely(*z == NULL)) {
+		/* Should this ever happen?? */
+		return NULL;
+	}
+
 	page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, order,
 				zonelist, ALLOC_WMARK_LOW|ALLOC_CPUSET);
 	if (page)
_