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>

3 files changed, 25 insertions, 12 deletions

diff --git a/include/linux/slab.h b/include/linux/slab.h
index 27402fe..0289ec8 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -31,6 +31,19 @@
 #define SLAB_TRACE		0x00200000UL	/* Trace allocations and frees */
 
 /*
+ * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
+ *
+ * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault.
+ *
+ * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL can.
+ * Both make kfree a no-op.
+ */
+#define ZERO_SIZE_PTR ((void *)16)
+
+#define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) < \
+				(unsigned long)ZERO_SIZE_PTR)
+
+/*
  * struct kmem_cache related prototypes
  */
 void __init kmem_cache_init(void);
diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
index 365d036..16e814f 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; \
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index a582f67..579b0a2 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -159,18 +159,6 @@ static inline struct kmem_cache *kmalloc_slab(size_t size)
 #define SLUB_DMA 0
 #endif
 
-
-/*
- * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
- *
- * Dereferencing ZERO_SIZE_PTR will lead to a distinct access fault.
- *
- * ZERO_SIZE_PTR can be passed to kfree though in the same way that NULL can.
- * Both make kfree a no-op.
- */
-#define ZERO_SIZE_PTR ((void *)16)
-
-
 void *kmem_cache_alloc(struct kmem_cache *, gfp_t);
 void *__kmalloc(size_t size, gfp_t flags);