From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> commit 30faaafdfa0c754c91bac60f216c9f34a2bfdf7e upstream. Commit 9c17d96500f7 ("xen/gntdev: Grant maps should not be subject to NUMA balancing") set VM_IO flag to prevent grant maps from being subjected to NUMA balancing. It was discovered recently that this flag causes get_user_pages() to always fail with -EFAULT. check_vma_flags __get_user_pages __get_user_pages_locked __get_user_pages_unlocked get_user_pages_fast iov_iter_get_pages dio_refill_pages do_direct_IO do_blockdev_direct_IO do_blockdev_direct_IO ext4_direct_IO_read generic_file_read_iter aio_run_iocb (which can happen if guest's vdisk has direct-io-safe option). To avoid this let's use VM_MIXEDMAP flag instead --- it prevents NUMA balancing just as VM_IO does and has no effect on check_vma_flags(). Reported-by: Olaf Hering <olaf@xxxxxxxxx> Suggested-by: Hugh Dickins <hughd@xxxxxxxxxx> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Tested-by: Olaf Hering <olaf@xxxxxxxxx> Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Signed-off-by: Willy Tarreau <w@xxxxxx> --- drivers/xen/gntdev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 3d8e609..6c6d253 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -770,7 +770,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) vma->vm_ops = &gntdev_vmops; - vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO; + vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_MIXEDMAP; if (use_ptemod) vma->vm_flags |= VM_DONTCOPY; -- 2.8.0.rc2.1.gbe9624a