thp, dax: do not try to withdraw pgtable from non-anon VMA

DAX doesn't deposit pgtables when it maps huge pages: nothing to
withdraw. It can lead to crash.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 08fc0ba2207e..722546dcfb7e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1700,7 +1700,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
                 VM_BUG_ON(!pmd_none(*new_pmd));
 
-                if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
+                if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
+                                vma_is_anonymous(vma)) {
                         pgtable_t pgtable;
                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);