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>
(cherry picked from commit 9c17d96500f78d7ecdb71ca6942830158bc75a2b)
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 0dbb222daaf1c694b1f073f3e206f755f5f77cc6..3dcc16e6d0bf85df97253afce371349e37ef3158 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;