Slab allocators: consistent ZERO_SIZE_PTR support and NULL result semantics

Define ZERO_OR_NULL_PTR macro to be able to remove the checks from the
allocators.  Move ZERO_SIZE_PTR related stuff into slab.h.

Make ZERO_SIZE_PTR work for all slab allocators and get rid of the
WARN_ON_ONCE(size == 0) that is still remaining in SLAB.

Make slub return NULL like the other allocators if a too large memory segment
is requested via __kmalloc.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 365d036c454a..16e814ffab8d 100644
--- a/include/linux/slab_def.h
+++ b/include/linux/slab_def.h
@@ -32,6 +32,10 @@ static inline void *kmalloc(size_t size, gfp_t flags)
 {
         if (__builtin_constant_p(size)) {
                 int i = 0;
+
+                if (!size)
+                        return ZERO_SIZE_PTR;
+
 #define CACHE(x) \
                 if (size <= x) \
                         goto found; \
@@ -58,6 +62,10 @@ static inline void *kzalloc(size_t size, gfp_t flags)
 {
         if (__builtin_constant_p(size)) {
                 int i = 0;
+
+                if (!size)
+                        return ZERO_SIZE_PTR;
+
 #define CACHE(x) \
                 if (size <= x) \
                         goto found; \
@@ -88,6 +96,10 @@ static inline void *kmalloc_node(size_t size, gfp_t flags, int node)
 {
         if (__builtin_constant_p(size)) {
                 int i = 0;
+
+                if (!size)
+                        return ZERO_SIZE_PTR;
+
 #define CACHE(x) \
                 if (size <= x) \
                         goto found; \