pagemap: add #ifdefs CONFIG_HUGETLB_PAGE on code walking hugetlb vma

If !CONFIG_HUGETLB_PAGE, pagemap_hugetlb_range() is never called.  So put
it (and its calling function) into #ifdef block.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/task_mmu.c

@@ -634,6 +634,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	return err;
 }
 
+#ifdef CONFIG_HUGETLB_PAGE
 static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
 {
 	u64 pme = 0;
@@ -664,6 +665,7 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
 
 	return err;
 }
+#endif /* HUGETLB_PAGE */
 
 /*
  * /proc/pid/pagemap - an array mapping virtual pages to pfns
@@ -733,7 +735,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
 
 	pagemap_walk.pmd_entry = pagemap_pte_range;
 	pagemap_walk.pte_hole = pagemap_pte_hole;
+#ifdef CONFIG_HUGETLB_PAGE
 	pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
+#endif
 	pagemap_walk.mm = mm;
 	pagemap_walk.private = ±