[PATCH v2] mm/hugetlb: avoid hardcoding while checking if cma is enable

[Barry Song]

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: Roman Gushchin <g...@fb.com>
Cc: Mike Kravetz <mike.krav...@oracle.com>
Cc: Jonathan Cameron <jonathan.came...@huawei.com>
Signed-off-by: Barry Song <song.bao....@hisilicon.com>
---
 -v2: add hugetlb_cma_enabled() helper to improve readability according to Roman

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

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 57ece74e3aae..d5e98ed86bb9 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)
+{
+       if (IS_ENABLED(CONFIG_CMA)) {
+               int node;
+
+               for_each_online_node(node) {
+                       if (hugetlb_cma[node])
+                               return true;
+               }
+       }
+
+       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