[PATCH] Fix bogus get_page() calls in hugepage code

From: David Gibson <david@gibson.dropbear.id.au>

Some versions of follow_huge_addr() and follow_huge_pmd() are doing a
get_page() on the target page.  They shouldn't: follow_page() returns an
unpinned page and it is the caller's responsibility to pin the page (if
desired) before dropping page_table_lock.

arch/i386/mm/hugetlbpage.c

@@ -206,10 +206,8 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 	struct page *page;
 
 	page = pte_page(*(pte_t *)pmd);
-	if (page) {
+	if (page)
 		page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
-		get_page(page);
-	}
 	return page;
 }
 #endif

arch/ia64/mm/hugetlbpage.c

@@ -170,7 +170,6 @@ struct page *follow_huge_addr(struct mm_struct *mm, struct vm_area_struct *vma,
 	ptep = huge_pte_offset(mm, addr);
 	page = pte_page(*ptep);
 	page += ((addr & ~HPAGE_MASK) >> PAGE_SHIFT);
-	get_page(page);
 	return page;
 }
 int pmd_huge(pmd_t pmd)

arch/ppc64/mm/hugetlbpage.c

@@ -360,10 +360,8 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 	BUG_ON(! pmd_hugepage(*pmd));
 
 	page = hugepte_page(*(hugepte_t *)pmd);
-	if (page) {
+	if (page)
 		page += ((address & ~HPAGE_MASK) >> PAGE_SHIFT);
-		get_page(page);
-	}
 	return page;
 }