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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Fri, 31 May 2019 23:28:56 -0700
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Subject: Re: [PATCH v10 4/7] dm: enable synchronous dax
To:     Pankaj Gupta <pagupta@redhat.com>
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On Tue, May 21, 2019 at 6:43 AM Pankaj Gupta <pagupta@redhat.com> wrote:
>
>  This patch sets dax device 'DAXDEV_SYNC' flag if all the target
>  devices of device mapper support synchrononous DAX. If device
>  mapper consists of both synchronous and asynchronous dax devices,
>  we don't set 'DAXDEV_SYNC' flag.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> ---
>  drivers/md/dm-table.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index cde3b49b2a91..1cce626ff576 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -886,10 +886,17 @@ static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
>         return bdev_dax_supported(dev->bdev, PAGE_SIZE);
>  }
>
> +static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
> +                              sector_t start, sector_t len, void *data)
> +{
> +       return dax_synchronous(dev->dax_dev);
> +}
> +
>  static bool dm_table_supports_dax(struct dm_table *t)
>  {
>         struct dm_target *ti;
>         unsigned i;
> +       bool dax_sync = true;
>
>         /* Ensure that all targets support DAX. */
>         for (i = 0; i < dm_table_get_num_targets(t); i++) {
> @@ -901,7 +908,14 @@ static bool dm_table_supports_dax(struct dm_table *t)
>                 if (!ti->type->iterate_devices ||
>                     !ti->type->iterate_devices(ti, device_supports_dax, NULL))
>                         return false;
> +
> +               /* Check devices support synchronous DAX */
> +               if (dax_sync &&
> +                   !ti->type->iterate_devices(ti, device_synchronous, NULL))
> +                       dax_sync = false;

Looks like this needs to be rebased on the current state of v5.2-rc,
and then we can nudge Mike for an ack.