slub: make ->inuse unsigned int

->inuse is "the number of bytes in actual use by the object",
can't be negative.

Link: http://lkml.kernel.org/r/20180305200730.15812-14-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>
diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
index 2a0eabe..2287b80 100644
--- a/include/linux/slub_def.h
+++ b/include/linux/slub_def.h
@@ -98,7 +98,7 @@ struct kmem_cache {
 	gfp_t allocflags;	/* gfp flags to use on each alloc */
 	int refcount;		/* Refcount for slab cache destroy */
 	void (*ctor)(void *);
-	int inuse;		/* Offset to metadata */
+	unsigned int inuse;		/* Offset to metadata */
 	unsigned int align;		/* Alignment */
 	unsigned int reserved;		/* Reserved bytes at the end of slabs */
 	unsigned int red_left_pad;	/* Left redzone padding size */