xen/gntdev: Grant maps should not be subject to NUMA balancing

Doing so will cause the grant to be unmapped and then, during
fault handling, the fault to be mistakenly treated as NUMA hint
fault.

In addition, even if those maps could partcipate in NUMA
balancing, it wouldn't provide any benefit since we are unable
to determine physical page's node (even if/when VNUMA is
implemented).

Marking grant maps' VMAs as VM_IO will exclude them from being
part of NUMA balancing.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2ea0b3b2a91d2585a2d37f8ead07f08f32c79826..1be5dd048622f6c8c4f9aa805514b9fd5b5c5d7b 100644 (file)
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -804,7 +804,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 
        vma->vm_ops = &gntdev_vmops;
 
-       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
 
        if (use_ptemod)
                vma->vm_flags |= VM_DONTCOPY;