Merge branch 'prep-for-5level'

Merge 5-level page table prep from Kirill Shutemov:
 "Here's relatively low-risk part of 5-level paging patchset. Merging it
  now will make x86 5-level paging enabling in v4.12 easier.

  The first patch is actually x86-specific: detect 5-level paging
  support. It boils down to single define.

  The rest of patchset converts Linux MMU abstraction from 4- to 5-level
  paging.

  Enabling of new abstraction in most cases requires adding single line
  of code in arch-specific code. The rest is taken care by asm-generic/.

  Changes to mm/ code are mostly mechanical: add support for new page
  table level -- p4d_t -- where we deal with pud_t now.

  v2:
   - fix build on microblaze (Michal);
   - comment for __ARCH_HAS_5LEVEL_HACK in kasan_populate_zero_shadow();
   - acks from Michal"

* emailed patches from Kirill A Shutemov <kirill.shutemov@linux.intel.com>:
  mm: introduce __p4d_alloc()
  mm: convert generic code to 5-level paging
  asm-generic: introduce <asm-generic/pgtable-nop4d.h>
  arch, mm: convert all architectures to use 5level-fixup.h
  asm-generic: introduce __ARCH_USE_5LEVEL_HACK
  asm-generic: introduce 5level-fixup.h
  x86/cpufeature: Add 5-level paging detection

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 2bb1c72380f29..1d227b0fcf49f 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -265,6 +265,7 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
 {
 	struct mm_struct *mm = ctx->mm;
 	pgd_t *pgd;
+	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd, _pmd;
 	pte_t *pte;
@@ -275,7 +276,10 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
 	pgd = pgd_offset(mm, address);
 	if (!pgd_present(*pgd))
 		goto out;
-	pud = pud_offset(pgd, address);
+	p4d = p4d_offset(pgd, address);
+	if (!p4d_present(*p4d))
+		goto out;
+	pud = pud_offset(p4d, address);
 	if (!pud_present(*pud))
 		goto out;
 	pmd = pmd_offset(pud, address);