powerpc: function to allocate gigantic hugepages

The 16G page locations have been saved during early boot in an array.  The
alloc_bootmem_huge_page() function adds a page from here to the
huge_boot_pages list.
Acked-by: Adam Litke <agl@us.ibm.com>
Signed-off-by: Jon Tollefson <kniht@linux.vnet.ibm.com>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/mm/hugetlbpage.c

@@ -29,6 +29,12 @@
 
 #define NUM_LOW_AREAS	(0x100000000UL >> SID_SHIFT)
 #define NUM_HIGH_AREAS	(PGTABLE_RANGE >> HTLB_AREA_SHIFT)
+#define MAX_NUMBER_GPAGES	1024
+
+/* Tracks the 16G pages after the device tree is scanned and before the
+ * huge_boot_pages list is ready.  */
+static unsigned long gpage_freearray[MAX_NUMBER_GPAGES];
+static unsigned nr_gpages;
 
 unsigned int hugepte_shift;
 #define PTRS_PER_HUGEPTE	(1 << hugepte_shift)
@@ -104,6 +110,21 @@ pmd_t *hpmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long addr)
 }
 #endif
 
+/* Moves the gigantic page addresses from the temporary list to the
+ * huge_boot_pages list.  */
+int alloc_bootmem_huge_page(struct hstate *h)
+{
+	struct huge_bootmem_page *m;
+	if (nr_gpages == 0)
+		return 0;
+	m = phys_to_virt(gpage_freearray[--nr_gpages]);
+	gpage_freearray[nr_gpages] = 0;
+	list_add(&m->list, &huge_boot_pages);
+	m->hstate = h;
+	return 1;
+}
+
+
 /* Modelled after find_linux_pte() */
 pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 {