[PATCH] memory page_alloc revert empty zonelist check

[PATCH] memory page_alloc revert empty zonelist check

[Paul Jackson, Paul Jackson]

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

---

Andrew - applies on top of my "memory page_alloc minor cleanups"
patch.  -pj

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

--- 2.6.18-mm3.orig/mm/page_alloc.c	2006-10-10 00:25:31.751908557 -0700
+++ 2.6.18-mm3/mm/page_alloc.c	2006-10-10 00:25:32.567919262 -0700
@@ -1057,6 +1057,13 @@ __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)

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373

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