mm/hugetlb: move page order check inside hugetlb_cma_reserve()

All platforms could benefit from page order check against MAX_PAGE_ORDER
before allocating a CMA area for gigantic hugetlb pages.  Let's move this
check from individual platforms to generic hugetlb.

Link: https://lkml.kernel.org/r/20240209054221.1403364-1-anshuman.khandual@arm.comSigned-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/arm64/mm/hugetlbpage.c

@@ -45,13 +45,6 @@ void __init arm64_hugetlb_cma_reserve(void)
 	else
 		order = CONT_PMD_SHIFT - PAGE_SHIFT;
 
-	/*
-	 * HugeTLB CMA reservation is required for gigantic
-	 * huge pages which could not be allocated via the
-	 * page allocator. Just warn if there is any change
-	 * breaking this assumption.
-	 */
-	WARN_ON(order <= MAX_PAGE_ORDER);
 	hugetlb_cma_reserve(order);
 }
 #endif /* CONFIG_CMA */

arch/powerpc/mm/hugetlbpage.c

@@ -614,8 +614,6 @@ void __init gigantic_hugetlb_cma_reserve(void)
 		 */
 		order = mmu_psize_to_shift(MMU_PAGE_16G) - PAGE_SHIFT;
 
-	if (order) {
-		VM_WARN_ON(order <= MAX_PAGE_ORDER);
+	if (order)
 		hugetlb_cma_reserve(order);
-	}
 }

mm/hugetlb.c

@@ -7720,6 +7720,13 @@ void __init hugetlb_cma_reserve(int order)
 	bool node_specific_cma_alloc = false;
 	int nid;
 
+	/*
+	 * HugeTLB CMA reservation is required for gigantic
+	 * huge pages which could not be allocated via the
+	 * page allocator. Just warn if there is any change
+	 * breaking this assumption.
+	 */
+	VM_WARN_ON(order <= MAX_PAGE_ORDER);
 	cma_reserve_called = true;
 
 	if (!hugetlb_cma_size)