Re: [RFC v2 2/2] pmem: device flush over VIRTIO

[Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wed, Apr 25, 2018 at 4:24 AM, Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> This patch adds functionality to perform
> flush from guest to hosy over VIRTIO
> when 'ND_REGION_VIRTIO'flag is set on
> nd_negion. Flag is set by 'virtio-pmem'
> driver.
>
> Signed-off-by: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/nvdimm/region_devs.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index a612be6..6c6454e 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -20,6 +20,7 @@
>  #include <linux/nd.h>
>  #include "nd-core.h"
>  #include "nd.h"
> +#include <linux/virtio_pmem.h>
>
>  /*
>   * For readq() and writeq() on 32-bit builds, the hi-lo, lo-hi order is
> @@ -1074,6 +1075,12 @@ void nvdimm_flush(struct nd_region *nd_region)
>         struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
>         int i, idx;
>
> +       /* call PV device flush */
> +       if (test_bit(ND_REGION_VIRTIO, &nd_region->flags)) {
> +               virtio_pmem_flush(&nd_region->dev);
> +               return;
> +       }
> +

I'd rather introduce a ->flush() operation hanging off of 'struct
nd_region' so that this multiplexing can be a static setting.