mm/hugetlb: Allow arch to override and call the weak function

When running in guest mode ppc64 supports a different mechanism for hugetlb
allocation/reservation. The LPAR management application called HMC can
be used to reserve a set of hugepages and we pass the details of
reserved pages via device tree to the guest. (more details in
htab_dt_scan_hugepage_blocks()) . We do the memblock_reserve of the range
and later in the boot sequence, we add the reserved range to huge_boot_pages.

But to enable 16G hugetlb on baremetal config (when we are not running as guest)
we want to do memblock reservation during boot. Generic code already does this

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

include/linux/hugetlb.h

@@ -358,6 +358,7 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
 			pgoff_t idx);
 
 /* arch callback */
+int __init __alloc_bootmem_huge_page(struct hstate *h);
 int __init alloc_bootmem_huge_page(struct hstate *h);
 
 void __init hugetlb_bad_size(void);

mm/hugetlb.c

@@ -2083,7 +2083,9 @@ struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
 	return page;
 }
 
-int __weak alloc_bootmem_huge_page(struct hstate *h)
+int alloc_bootmem_huge_page(struct hstate *h)
+	__attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
+int __alloc_bootmem_huge_page(struct hstate *h)
 {
 	struct huge_bootmem_page *m;
 	int nr_nodes, node;