mm: hugetlb: fix the name of hugetlb CMA

Once we enable CMA_DEBUGFS, we will get the below errors: directory
'cma-hugetlb' with parent 'cma' already present.

We should have different names for different CMA areas.
Signed-off-by: NBarry Song <song.bao.hua@hisilicon.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NMike Kravetz <mike.kravetz@oracle.com>
Acked-by: NRoman Gushchin <guro@fb.com>
Link: http://lkml.kernel.org/r/20200616223131.33828-3-song.bao.hua@hisilicon.comSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -5707,12 +5707,14 @@ void __init hugetlb_cma_reserve(int order)
 	reserved = 0;
 	for_each_node_state(nid, N_ONLINE) {
 		int res;
+		char name[20];
 
 		size = min(per_node, hugetlb_cma_size - reserved);
 		size = round_up(size, PAGE_SIZE << order);
 
+		snprintf(name, 20, "hugetlb%d", nid);
 		res = cma_declare_contiguous_nid(0, size, 0, PAGE_SIZE << order,
-						 0, false, "hugetlb",
+						 0, false, name,
 						 &hugetlb_cma[nid], nid);
 		if (res) {
 			pr_warn("hugetlb_cma: reservation failed: err %d, node %d",