Merge branch 'akpm' (patches from Andrew)

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - v9fs updates

 - MM

 - procfs updates

 - lib/ updates

 - autofs updates

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (118 commits)
  autofs: small cleanup in autofs_getpath()
  autofs: clean up includes
  autofs: comment on selinux changes needed for module autoload
  autofs: update MAINTAINERS entry for autofs
  autofs: use autofs instead of autofs4 in documentation
  autofs: rename autofs documentation files
  autofs: create autofs Kconfig and Makefile
  autofs: delete fs/autofs4 source files
  autofs: update fs/autofs4/Makefile
  autofs: update fs/autofs4/Kconfig
  autofs: copy autofs4 to autofs
  autofs4: use autofs instead of autofs4 everywhere
  autofs4: merge auto_fs.h and auto_fs4.h
  fs/binfmt_misc.c: do not allow offset overflow
  checkpatch: improve patch recognition
  lib/ucs2_string.c: add MODULE_LICENSE()
  lib/mpi: headers cleanup
  lib/percpu_ida.c: use _irqsave() instead of local_irq_save() + spin_lock
  lib/idr.c: remove simple_ida_lock
  lib/bitmap.c: micro-optimization for __bitmap_complement()
  ...

1 files changed, 29 insertions, 13 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 541904a7c60f..1020c7f8f5ee 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -212,53 +212,69 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
 				    unsigned long address, pud_t *pudp,
 				    unsigned int flags, unsigned int *page_mask)
 {
-	pmd_t *pmd;
+	pmd_t *pmd, pmdval;
 	spinlock_t *ptl;
 	struct page *page;
 	struct mm_struct *mm = vma->vm_mm;
 
 	pmd = pmd_offset(pudp, address);
-	if (pmd_none(*pmd))
+	/*
+	 * The READ_ONCE() will stabilize the pmdval in a register or
+	 * on the stack so that it will stop changing under the code.
+	 */
+	pmdval = READ_ONCE(*pmd);
+	if (pmd_none(pmdval))
 		return no_page_table(vma, flags);
-	if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
+	if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
 		page = follow_huge_pmd(mm, address, pmd, flags);
 		if (page)
 			return page;
 		return no_page_table(vma, flags);
 	}
-	if (is_hugepd(__hugepd(pmd_val(*pmd)))) {
+	if (is_hugepd(__hugepd(pmd_val(pmdval)))) {
 		page = follow_huge_pd(vma, address,
-				      __hugepd(pmd_val(*pmd)), flags,
+				      __hugepd(pmd_val(pmdval)), flags,
 				      PMD_SHIFT);
 		if (page)
 			return page;
 		return no_page_table(vma, flags);
 	}
 retry:
-	if (!pmd_present(*pmd)) {
+	if (!pmd_present(pmdval)) {
 		if (likely(!(flags & FOLL_MIGRATION)))
 			return no_page_table(vma, flags);
 		VM_BUG_ON(thp_migration_supported() &&
-				  !is_pmd_migration_entry(*pmd));
-		if (is_pmd_migration_entry(*pmd))
+				  !is_pmd_migration_entry(pmdval));
+		if (is_pmd_migration_entry(pmdval))
 			pmd_migration_entry_wait(mm, pmd);
+		pmdval = READ_ONCE(*pmd);
+		/*
+		 * MADV_DONTNEED may convert the pmd to null because
+		 * mmap_sem is held in read mode
+		 */
+		if (pmd_none(pmdval))
+			return no_page_table(vma, flags);
 		goto retry;
 	}
-	if (pmd_devmap(*pmd)) {
+	if (pmd_devmap(pmdval)) {
 		ptl = pmd_lock(mm, pmd);
 		page = follow_devmap_pmd(vma, address, pmd, flags);
 		spin_unlock(ptl);
 		if (page)
 			return page;
 	}
-	if (likely(!pmd_trans_huge(*pmd)))
+	if (likely(!pmd_trans_huge(pmdval)))
 		return follow_page_pte(vma, address, pmd, flags);
 
-	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
+	if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
 		return no_page_table(vma, flags);
 
 retry_locked:
 	ptl = pmd_lock(mm, pmd);
+	if (unlikely(pmd_none(*pmd))) {
+		spin_unlock(ptl);
+		return no_page_table(vma, flags);
+	}
 	if (unlikely(!pmd_present(*pmd))) {
 		spin_unlock(ptl);
 		if (likely(!(flags & FOLL_MIGRATION)))
@@ -1354,7 +1370,7 @@ static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
 	}
 }
 
-#ifdef __HAVE_ARCH_PTE_SPECIAL
+#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
 static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 			 int write, struct page **pages, int *nr)
 {
@@ -1430,7 +1446,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 {
 	return 0;
 }
-#endif /* __HAVE_ARCH_PTE_SPECIAL */
+#endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */
 
 #if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static int __gup_device_huge(unsigned long pfn, unsigned long addr,