thp: consolidate code between handle_mm_fault() and do_huge_pmd_anonymous_page()

do_huge_pmd_anonymous_page() has copy-pasted piece of handle_mm_fault()
to handle fallback path.

Let's consolidate code back by introducing VM_FAULT_FALLBACK return
code.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 5ec6f199e685..ca0003947115 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3695,7 +3695,7 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
  * but allow concurrent faults), and pte mapped but not yet locked.
  * We return with mmap_sem still held, but pte unmapped and unlocked.
  */
-int handle_pte_fault(struct mm_struct *mm,
+static int handle_pte_fault(struct mm_struct *mm,
                      struct vm_area_struct *vma, unsigned long address,
                      pte_t *pte, pmd_t *pmd, unsigned int flags)
 {
@@ -3774,9 +3774,12 @@ retry:
         if (!pmd)
                 return VM_FAULT_OOM;
         if (pmd_none(*pmd) && transparent_hugepage_enabled(vma)) {
+                int ret = VM_FAULT_FALLBACK;
                 if (!vma->vm_ops)
-                        return do_huge_pmd_anonymous_page(mm, vma, address,
-                                                          pmd, flags);
+                        ret = do_huge_pmd_anonymous_page(mm, vma, address,
+                                        pmd, flags);
+                if (!(ret & VM_FAULT_FALLBACK))
+                        return ret;
         } else {
                 pmd_t orig_pmd = *pmd;
                 int ret;