thp: introduce hugepage_vma_check()

commit fa475e51 upstream.

Multiple places do the same check.
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Ni zhan Chen <nizhan.chen@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2:
 - Also move the is_linear_pfn_mapping() test
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

mm/huge_memory.c

@@ -1817,6 +1817,24 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
 	}
 }
 
+static bool hugepage_vma_check(struct vm_area_struct *vma)
+{
+	if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
+	    (vma->vm_flags & VM_NOHUGEPAGE))
+		return false;
+
+	if (!vma->anon_vma || vma->vm_ops)
+		return false;
+	if (is_vma_temporary_stack(vma))
+		return false;
+	/*
+	 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
+	 * true too, verify it here.
+	 */
+	VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
+	return true;
+}
+
 static void collapse_huge_page(struct mm_struct *mm,
 			       unsigned long address,
 			       struct page **hpage,
@@ -1889,21 +1907,8 @@ static void collapse_huge_page(struct mm_struct *mm,
 	hend = vma->vm_end & HPAGE_PMD_MASK;
 	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
 		goto out;
-
-	if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
-	    (vma->vm_flags & VM_NOHUGEPAGE))
+	if (!hugepage_vma_check(vma))
 		goto out;
-
-	if (!vma->anon_vma || vma->vm_ops)
-		goto out;
-	if (is_vma_temporary_stack(vma))
-		goto out;
-	/*
-	 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
-	 * true too, verify it here.
-	 */
-	VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
-
 	pgd = pgd_offset(mm, address);
 	if (!pgd_present(*pgd))
 		goto out;
@@ -2133,25 +2138,11 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
 			progress++;
 			break;
 		}
-
-		if ((!(vma->vm_flags & VM_HUGEPAGE) &&
-		     !khugepaged_always()) ||
-		    (vma->vm_flags & VM_NOHUGEPAGE)) {
-		skip:
+		if (!hugepage_vma_check(vma)) {
+skip:
 			progress++;
 			continue;
 		}
-		if (!vma->anon_vma || vma->vm_ops)
-			goto skip;
-		if (is_vma_temporary_stack(vma))
-			goto skip;
-		/*
-		 * If is_pfn_mapping() is true is_learn_pfn_mapping()
-		 * must be true too, verify it here.
-		 */
-		VM_BUG_ON(is_linear_pfn_mapping(vma) ||
-			  vma->vm_flags & VM_NO_THP);
-
 		hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
 		hend = vma->vm_end & HPAGE_PMD_MASK;
 		if (hstart >= hend)