[RFC 7/9] powerpc/hugetlb: Change follow_huge_* routines for BOOK3S 64K

[Anshuman Khandual]

With this change, BOOK3S 64K platforms will not use 'follow_huge_addr'
function any more and always return ERR_PTR(-ENIVAL), hence skipping
the BUG_ON(flags & FOLL_GET) test in 'follow_page_mask' function. These
platforms will then fall back on generic follow_huge_* functions for
everything else. While being here, also added 'follow_huge_pgd' function
which was missing earlier.

Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/mm/hugetlbpage.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index f6e4712..89b748a 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -631,6 +631,10 @@ follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 	unsigned long mask, flags;
 	struct page *page = ERR_PTR(-EINVAL);
 
+#if defined(CONFIG_PPC_64K_PAGES) && defined(CONFIG_PPC_BOOK3S_64)
+	return ERR_PTR(-EINVAL);
+#endif
+
 	local_irq_save(flags);
 	ptep = find_linux_pte_or_hugepte(mm->pgd, address, &is_thp, &shift);
 	if (!ptep)
@@ -658,6 +662,7 @@ no_page:
 	return page;
 }
 
+#if !defined(CONFIG_PPC_64K_PAGES) || !defined(CONFIG_PPC_BOOK3S_64)
 struct page *
 follow_huge_pmd(struct mm_struct *mm, unsigned long address,
 		pmd_t *pmd, int write)
@@ -674,6 +679,15 @@ follow_huge_pud(struct mm_struct *mm, unsigned long address,
 	return NULL;
 }
 
+struct page *
+follow_huge_pgd(struct mm_struct *mm, unsigned long address,
+		pgd_t *pgd, int write)
+{
+	BUG();
+	return NULL;
+}
+#endif /* !defined(CONFIG_PPC_64K_PAGE) || !defined(CONFIG_BOOK3S_64) */
+
 static unsigned long hugepte_addr_end(unsigned long addr, unsigned long end,
 				      unsigned long sz)
 {
-- 
2.1.0