dax: revert userfaultfd change

Orabug: 21685254

Undo the change which "userfaultfd: call handle_userfault() for
userfaultfd_missing() faults" made to set_huge_zero_page().  DAX will
need that return value.

Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 7c414164593514f76b422faae0824bdd3754209b)
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Dhaval Giani <dhaval.giani@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index c02a2d0afc2aa167eb8407afb600ec59c37313c0..0028ba2c9cc8adb4fd78a6f93031d23cf3c350f2 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -794,16 +794,19 @@ static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
 }
 
 /* Caller must hold page table lock. */
-static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
+static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
                struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
                struct page *zero_page)
 {
        pmd_t entry;
+       if (!pmd_none(*pmd))
+               return false;
        entry = mk_pmd(zero_page, vma->vm_page_prot);
        entry = pmd_mkhuge(entry);
        pgtable_trans_huge_deposit(mm, pmd, pgtable);
        set_pmd_at(mm, haddr, pmd, entry);
        atomic_long_inc(&mm->nr_ptes);
+       return true;
 }
 
 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,