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, 7 insertions, 4 deletions

diff --git a/mm/slob.c b/mm/slob.c
index 154e7bdf3544..41d32c3c0be4 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -347,7 +347,7 @@ static void slob_free(void *block, int size)
         slobidx_t units;
         unsigned long flags;
 
-        if (!block)
+        if (ZERO_OR_NULL_PTR(block))
                 return;
         BUG_ON(!size);
 
@@ -424,10 +424,13 @@ out:
 
 void *__kmalloc_node(size_t size, gfp_t gfp, int node)
 {
+        unsigned int *m;
         int align = max(ARCH_KMALLOC_MINALIGN, ARCH_SLAB_MINALIGN);
 
         if (size < PAGE_SIZE - align) {
-                unsigned int *m;
+                if (!size)
+                        return ZERO_SIZE_PTR;
+
                 m = slob_alloc(size + align, gfp, align, node);
                 if (m)
                         *m = size;
@@ -450,7 +453,7 @@ void kfree(const void *block)
 {
         struct slob_page *sp;
 
-        if (!block)
+        if (ZERO_OR_NULL_PTR(block))
                 return;
 
         sp = (struct slob_page *)virt_to_page(block);
@@ -468,7 +471,7 @@ size_t ksize(const void *block)
 {
         struct slob_page *sp;
 
-        if (!block)
+        if (ZERO_OR_NULL_PTR(block))
                 return 0;
 
         sp = (struct slob_page *)virt_to_page(block);