slub: fix handling of oversized slabs

I'm getting zillions of undefined references to __kmalloc_size_too_large on
alpha.  For some reason alpha is building out-of-line copies of kmalloc_slab()
into lots of compilation units.

It turns out that gcc just isn't smart enough to work out that
__builtin_contant_p(size)==true implies that __builtin_contant_p(index)==true.

So let's give it a bit of help.

Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 5e2e7297dfaa..a9fb92862aaa 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -145,7 +145,12 @@ static inline struct kmem_cache *kmalloc_slab(size_t size)
         if (index == 0)
                 return NULL;
 
-        if (index < 0) {
+        /*
+         * This function only gets expanded if __builtin_constant_p(size), so
+         * testing it here shouldn't be needed.  But some versions of gcc need
+         * help.
+         */
+        if (__builtin_constant_p(size) && index < 0) {
                 /*
                  * Generate a link failure. Would be great if we could
                  * do something to stop the compile here.