slub: make ->remote_node_defrag_ratio unsigned int

->remote_node_defrag_ratio is in range 0..1000.

This also adds a check and modifies the behavior to return an error
code.  Before this patch invalid values were ignored.

Link: http://lkml.kernel.org/r/20180305200730.15812-9-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/slub_def.h

@@ -124,7 +124,7 @@ struct kmem_cache {
 	/*
 	 * Defragmentation by allocating from a remote node.
 	 */
-	int remote_node_defrag_ratio;
+	unsigned int remote_node_defrag_ratio;
 #endif
 
 #ifdef CONFIG_SLAB_FREELIST_RANDOM

mm/slub.c

@@ -5289,21 +5289,22 @@ SLAB_ATTR(shrink);
 #ifdef CONFIG_NUMA
 static ssize_t remote_node_defrag_ratio_show(struct kmem_cache *s, char *buf)
 {
-	return sprintf(buf, "%d\n", s->remote_node_defrag_ratio / 10);
+	return sprintf(buf, "%u\n", s->remote_node_defrag_ratio / 10);
 }
 
 static ssize_t remote_node_defrag_ratio_store(struct kmem_cache *s,
 				const char *buf, size_t length)
 {
-	unsigned long ratio;
+	unsigned int ratio;
 	int err;
 
-	err = kstrtoul(buf, 10, &ratio);
+	err = kstrtouint(buf, 10, &ratio);
 	if (err)
 		return err;
+	if (ratio > 100)
+		return -ERANGE;
 
-	if (ratio <= 100)
-		s->remote_node_defrag_ratio = ratio * 10;
+	s->remote_node_defrag_ratio = ratio * 10;
 
 	return length;
 }