mm: vmpressure: don't need call kfree if kstrndup fails

When kstrndup fails, no memory was allocated and we can exit directly.

[david@redhat.com: reword changelog]
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1581398649-125989-1-git-send-email-yang.shi@linux.alibaba.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmpressure.c

@@ -371,10 +371,8 @@ int vmpressure_register_event(struct mem_cgroup *memcg,
 	int ret = 0;
 
 	spec_orig = spec = kstrndup(args, MAX_VMPRESSURE_ARGS_LEN, GFP_KERNEL);
-	if (!spec) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (!spec)
+		return -ENOMEM;
 
 	/* Find required level */
 	token = strsep(&spec, ",");