mm/memory_hotplug: clean up try_offline_node

We can use helper macro node_spanned_pages to check whether node spans
pages.  And we can change the parameter of check_cpu_on_node to nid as
that's what it really cares.  Thus we can further get rid of the local
variable pgdat and improve the readability a bit.

Link: https://lkml.kernel.org/r/20220207133643.23427-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -2005,12 +2005,12 @@ static int get_nr_vmemmap_pages_cb(struct memory_block *mem, void *arg)
 	return mem->nr_vmemmap_pages;
 }
 
-static int check_cpu_on_node(pg_data_t *pgdat)
+static int check_cpu_on_node(int nid)
 {
 	int cpu;
 
 	for_each_present_cpu(cpu) {
-		if (cpu_to_node(cpu) == pgdat->node_id)
+		if (cpu_to_node(cpu) == nid)
 			/*
 			 * the cpu on this node isn't removed, and we can't
 			 * offline this node.
@@ -2044,7 +2044,6 @@ static int check_no_memblock_for_node_cb(struct memory_block *mem, void *arg)
  */
 void try_offline_node(int nid)
 {
-	pg_data_t *pgdat = NODE_DATA(nid);
 	int rc;
 
 	/*
@@ -2052,7 +2051,7 @@ void try_offline_node(int nid)
 	 * offline it. A node spans memory after move_pfn_range_to_zone(),
 	 * e.g., after the memory block was onlined.
 	 */
-	if (pgdat->node_spanned_pages)
+	if (node_spanned_pages(nid))
 		return;
 
 	/*
@@ -2064,7 +2063,7 @@ void try_offline_node(int nid)
 	if (rc)
 		return;
 
-	if (check_cpu_on_node(pgdat))
+	if (check_cpu_on_node(nid))
 		return;
 
 	/*