Re: [PATCH v11 4/7] dm: enable synchronous dax

[Mike Snitzer <snitzer@redhat.com>]

On Tue, Jun 11 2019 at  9:10am -0400,
Pankaj Gupta <pagupta@redhat.com> wrote:

> Hi Mike,
> 
> Thanks for the review Please find my reply inline.
> 
> > 
> > dm_table_supports_dax() is called multiple times (from
> > dm_table_set_restrictions and dm_table_determine_type).  It is strange
> > to have a getter have a side-effect of being a setter too.  Overloading
> > like this could get you in trouble in the future.
> > 
> > Are you certain this is what you want?
> 
> I agree with you.
> 
> > 
> > Or would it be better to refactor dm_table_supports_dax() to take an
> > iterate_devices_fn arg and have callers pass the appropriate function?
> > Then have dm_table_set_restrictions() caller do:
> > 
> >      if (dm_table_supports_dax(t, device_synchronous, NULL))
> >                set_dax_synchronous(t->md->dax_dev);
> > 
> > (NULL arg implies dm_table_supports_dax() refactoring would take a int
> > *data pointer rather than int type).
> > 
> > Mike
> > 
> 
> I am sending below patch as per your suggestion. Does it look
> near to what you have in mind?

Yes, it does.. just one nit I noticed inlined below.

> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 350cf0451456..8d89acc8b8c2 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c

...

> @@ -1910,8 +1919,13 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
>         }
>         blk_queue_write_cache(q, wc, fua);
> 
> -       if (dm_table_supports_dax(t, PAGE_SIZE))
> +       if (dm_table_supports_dax(t, device_supports_dax, &page_size)) {
> +

No need for an empty newline here ^

>                 blk_queue_flag_set(QUEUE_FLAG_DAX, q);
> +               if (dm_table_supports_dax(t, device_synchronous, NULL))
> +                       set_dax_synchronous(t->md->dax_dev);
> +       }
>         else
>                 blk_queue_flag_clear(QUEUE_FLAG_DAX, q);
> 

Thanks,
Mike