[PATCH v3] mm/hugetlb: avoid hardcoding while checking if cma is enable

[Barry Song <song.bao.hua@hisilicon.com>]

hugetlb_cma[0] can be NULL due to various reasons, for example, node0 has
no memory. so NULL hugetlb_cma[0] doesn't necessarily mean cma is not
enabled. gigantic pages might have been reserved on other nodes.

Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jonathan Cameron <jonathan.cameron@huawei.com>
Acked-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
---
 -v3: add acked-by; make code more canonical 

 mm/hugetlb.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 57ece74e3aae..d293c823121e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2546,6 +2546,20 @@ static void __init gather_bootmem_prealloc(void)
 	}
 }
 
+bool __init hugetlb_cma_enabled(void)
+{
+#ifdef CONFIG_CMA
+	int node;
+
+	for_each_online_node(node) {
+		if (hugetlb_cma[node])
+			return true;
+	}
+#endif
+
+	return false;
+}
+
 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 {
 	unsigned long i;
@@ -2571,7 +2585,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 
 	for (i = 0; i < h->max_huge_pages; ++i) {
 		if (hstate_is_gigantic(h)) {
-			if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) {
+			if (hugetlb_cma_enabled()) {
 				pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
 				break;
 			}
-- 
2.27.0