percpu: fix static checker warnings in pcpu_destroy_chunk

From 5021b97f4026334d2c8dfad80797dd1028cddd73 Mon Sep 17 00:00:00 2001
From: Dennis Zhou <dennisz@fb.com>
Date: Thu, 29 Jun 2017 07:11:41 -0700

Add NULL check in pcpu_destroy_chunk to correct static checker warnings.
Signed-off-by: Dennis Zhou <dennisz@fb.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/percpu-km.c

@@ -82,10 +82,13 @@ static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
 {
 	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
 
+	if (!chunk)
+		return;
+
 	pcpu_stats_chunk_dealloc();
 	trace_percpu_destroy_chunk(chunk->base_addr);
 
-	if (chunk && chunk->data)
+	if (chunk->data)
 		__free_pages(chunk->data, order_base_2(nr_pages));
 	pcpu_free_chunk(chunk);
 }

mm/percpu-vm.c

@@ -352,10 +352,13 @@ static struct pcpu_chunk *pcpu_create_chunk(void)
 
 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
 {
+	if (!chunk)
+		return;
+
 	pcpu_stats_chunk_dealloc();
 	trace_percpu_destroy_chunk(chunk->base_addr);
 
-	if (chunk && chunk->data)
+	if (chunk->data)
 		pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
 	pcpu_free_chunk(chunk);
 }