{slub, slob}: use unlikely() for kfree(ZERO_OR_NULL_PTR) check

Considering kfree(NULL) would normally occur only in error paths and
kfree(ZERO_SIZE_PTR) is uncommon as well, so let's use unlikely() for the
condition check in SLUB's and SLOB's kfree() to optimize for the common
case.  SLAB has this already.
Signed-off-by: Satyam Sharma <satyam@infradead.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slob.c

@@ -360,7 +360,7 @@ static void slob_free(void *block, int size)
 	slobidx_t units;
 	unsigned long flags;
 
-	if (ZERO_OR_NULL_PTR(block))
+	if (unlikely(ZERO_OR_NULL_PTR(block)))
 		return;
 	BUG_ON(!size);
 
@@ -466,7 +466,7 @@ void kfree(const void *block)
 {
 	struct slob_page *sp;
 
-	if (ZERO_OR_NULL_PTR(block))
+	if (unlikely(ZERO_OR_NULL_PTR(block)))
 		return;
 
 	sp = (struct slob_page *)virt_to_page(block);
@@ -484,7 +484,7 @@ size_t ksize(const void *block)
 {
 	struct slob_page *sp;
 
-	if (ZERO_OR_NULL_PTR(block))
+	if (unlikely(ZERO_OR_NULL_PTR(block)))
 		return 0;
 
 	sp = (struct slob_page *)virt_to_page(block);

mm/slub.c

@@ -2449,7 +2449,7 @@ size_t ksize(const void *object)
 	struct page *page;
 	struct kmem_cache *s;
 
-	if (ZERO_OR_NULL_PTR(object))
+	if (unlikely(ZERO_OR_NULL_PTR(object)))
 		return 0;
 
 	page = get_object_page(object);
@@ -2483,7 +2483,7 @@ void kfree(const void *x)
 {
 	struct page *page;
 
-	if (ZERO_OR_NULL_PTR(x))
+	if (unlikely(ZERO_OR_NULL_PTR(x)))
 		return;
 
 	page = virt_to_head_page(x);
@@ -2800,7 +2800,7 @@ void *__kmalloc_track_caller(size_t size, gfp_t gfpflags, void *caller)
 							get_order(size));
 	s = get_slab(size, gfpflags);
 
-	if (ZERO_OR_NULL_PTR(s))
+	if (unlikely(ZERO_OR_NULL_PTR(s)))
 		return s;
 
 	return slab_alloc(s, gfpflags, -1, caller);
@@ -2816,7 +2816,7 @@ void *__kmalloc_node_track_caller(size_t size, gfp_t gfpflags,
 							get_order(size));
 	s = get_slab(size, gfpflags);
 
-	if (ZERO_OR_NULL_PTR(s))
+	if (unlikely(ZERO_OR_NULL_PTR(s)))
 		return s;
 
 	return slab_alloc(s, gfpflags, node, caller);