slab: make kmalloc_size() return "unsigned int"

kmalloc_size() derives size of kmalloc cache from internal index, which
can't be negative.

Propagate unsignedness a bit.

Link: http://lkml.kernel.org/r/20180305200730.15812-3-adobriyan@gmail.com
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/slab.h

@@ -522,11 +522,11 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
  * return size or 0 if a kmalloc cache for that
  * size does not exist
  */
-static __always_inline int kmalloc_size(int n)
+static __always_inline unsigned int kmalloc_size(unsigned int n)
 {
 #ifndef CONFIG_SLOB
 	if (n > 2)
-		return 1 << n;
+		return 1U << n;
 
 	if (n == 1 && KMALLOC_MIN_SIZE <= 32)
 		return 96;

mm/slab_common.c

@@ -1138,9 +1138,9 @@ void __init create_kmalloc_caches(slab_flags_t flags)
 		struct kmem_cache *s = kmalloc_caches[i];
 
 		if (s) {
-			int size = kmalloc_size(i);
+			unsigned int size = kmalloc_size(i);
 			char *n = kasprintf(GFP_NOWAIT,
-				 "dma-kmalloc-%d", size);
+				 "dma-kmalloc-%u", size);
 
 			BUG_ON(!n);
 			kmalloc_dma_caches[i] = create_kmalloc_cache(n,