userfaultfd: use mmgrab instead of open-coded increment of mm_count
Link: http://lkml.kernel.org/r/1508132478-7738-1-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index f46d133..ac9a4e6 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -668,7 +668,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
ctx->features = octx->features;
ctx->released = false;
ctx->mm = vma->vm_mm;
- atomic_inc(&ctx->mm->mm_count);
+ mmgrab(ctx->mm);
userfaultfd_ctx_get(octx);
fctx->orig = octx;
