Re: [PATCH v7 6/6] xfs: disable map_sync for async flush

[Dan Williams <dan.j.williams@intel.com>]

On Thu, Apr 25, 2019 at 10:03 PM Pankaj Gupta <pagupta@redhat.com> wrote:
>
> Dont support 'MAP_SYNC' with non-DAX files and DAX files
> with asynchronous dax_device. Virtio pmem provides
> asynchronous host page cache flush mechanism. We don't
> support 'MAP_SYNC' with virtio pmem and xfs.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  fs/xfs/xfs_file.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)

Darrick, does this look ok to take through the nvdimm tree?

>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a7ceae90110e..f17652cca5ff 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1203,11 +1203,14 @@ xfs_file_mmap(
>         struct file     *filp,
>         struct vm_area_struct *vma)
>  {
> +       struct dax_device       *dax_dev;
> +
> +       dax_dev = xfs_find_daxdev_for_inode(file_inode(filp));
>         /*
> -        * We don't support synchronous mappings for non-DAX files. At least
> -        * until someone comes with a sensible use case.
> +        * We don't support synchronous mappings for non-DAX files and
> +        * for DAX files if underneath dax_device is not synchronous.
>          */
> -       if (!IS_DAX(file_inode(filp)) && (vma->vm_flags & VM_SYNC))
> +       if (!daxdev_mapping_supported(vma, dax_dev))
>                 return -EOPNOTSUPP;
>
>         file_accessed(filp);
> --
> 2.20.1
>