mm/hugetlb: pass correct order_per_bit to cma_declare_contiguous_nid

commit 55d134a7b499c77e7cfd0ee41046f3c376e791e5 upstream.

The hugetlb_cma code passes 0 in the order_per_bit argument to
cma_declare_contiguous_nid (the alignment, computed using the page order,
is correctly passed in).

This causes a bit in the cma allocation bitmap to always represent a 4k
page, making the bitmaps potentially very large, and slower.

It would create bitmaps that would be pretty big.  E.g.  for a 4k page
size on x86, hugetlb_cma=64G would mean a bitmap size of (64G / 4k) / 8
== 2M.  With HUGETLB_PAGE_ORDER as order_per_bit, as intended, this
would be (64G / 2M) / 8 == 4k.  So, that's quite a difference.

Also, this restricted the hugetlb_cma area to ((PAGE_SIZE <<
MAX_PAGE_ORDER) * 8) * PAGE_SIZE (e.g.  128G on x86) , since
bitmap_alloc uses normal page allocation, and is thus restricted by
MAX_PAGE_ORDER.  Specifying anything about that would fail the CMA
initialization.

So, correctly pass in the order instead.

Link: https://lkml.kernel.org/r/20240404162515.527802-2-fvdl@google.com
Fixes: cf11e85fc0 ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
Signed-off-by: Frank van der Linden <fvdl@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

mm/hugetlb.c

@@ -7464,9 +7464,9 @@ void __init hugetlb_cma_reserve(int order)
 		 * huge page demotion.
 		 */
 		res = cma_declare_contiguous_nid(0, size, 0,
-						PAGE_SIZE << HUGETLB_PAGE_ORDER,
-						 0, false, name,
-						 &hugetlb_cma[nid], nid);
+					PAGE_SIZE << HUGETLB_PAGE_ORDER,
+					HUGETLB_PAGE_ORDER, false, name,
+					&hugetlb_cma[nid], nid);
 		if (res) {
 			pr_warn("hugetlb_cma: reservation failed: err %d, node %d",
 				res, nid);