mm: use for_each_online_node and node_online instead of open coding

Use more generic functions to deal with issues related to online nodes. 
The changes will make the code simplified.

Link: https://lkml.kernel.org/r/20220429030218.644635-1-liupeng256@huawei.comSigned-off-by: NPeng Liu <liupeng256@huawei.com>
Suggested-by: NDavidlohr Bueso <dave@stgolabs.net>
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Reviewed-by: NDavid Hildenbrand <david@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

arch/ia64/kernel/uncached.c

@@ -261,7 +261,7 @@ static int __init uncached_init(void)
 {
 	int nid;
 
-	for_each_node_state(nid, N_ONLINE) {
+	for_each_online_node(nid) {
 		uncached_pools[nid].pool = gen_pool_create(PAGE_SHIFT, nid);
 		mutex_init(&uncached_pools[nid].add_chunk_mutex);
 	}

mm/hugetlb.c

@@ -6971,7 +6971,7 @@ void __init hugetlb_cma_reserve(int order)
 		if (hugetlb_cma_size_in_node[nid] == 0)
 			continue;
 
-		if (!node_state(nid, N_ONLINE)) {
+		if (!node_online(nid)) {
 			pr_warn("hugetlb_cma: invalid node %d specified\n", nid);
 			hugetlb_cma_size -= hugetlb_cma_size_in_node[nid];
 			hugetlb_cma_size_in_node[nid] = 0;
@@ -7010,7 +7010,7 @@ void __init hugetlb_cma_reserve(int order)
 	}
 
 	reserved = 0;
-	for_each_node_state(nid, N_ONLINE) {
+	for_each_online_node(nid) {
 		int res;
 		char name[CMA_MAX_NAME];
 

mm/page_ext.c

@@ -320,7 +320,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
 		 * online__pages(), and start_pfn should exist.
 		 */
 		nid = pfn_to_nid(start_pfn);
-		VM_BUG_ON(!node_state(nid, N_ONLINE));
+		VM_BUG_ON(!node_online(nid));
 	}
 
 	for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)