Re: [PATCH 25/27] block: remove the discard_zeroes_data flag

[Mike Snitzer <snitzer@redhat.com>]

On Tue, May 02 2017 at 11:33pm -0400,
Nicholas A. Bellinger <nab@linux-iscsi.org> wrote:

> On Tue, 2017-05-02 at 09:23 +0200, hch@lst.de wrote:
> > On Tue, May 02, 2017 at 12:16:13AM -0700, Nicholas A. Bellinger wrote:
> > > Or, another options is use bdev_write_zeroes_sectors() to determine when
> > > dev_attrib->unmap_zeroes_data should be set.
> > 
> > Yes, that in combination with your patch to use bdev_write_zeroes_sectors
> > for zeroing from write same seems like the right fix.
> 
> The larger target/iblock conversion patch looks like post v4.12 material
> at this point, so to avoid breakage wrt to existing LBPRZ behavior, I'll
> plan to push the following patch post -rc1.
> 
> diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
> index d2f089c..e7caf78 100644
> --- a/drivers/target/target_core_device.c
> +++ b/drivers/target/target_core_device.c
> @@ -851,7 +851,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
>         attrib->unmap_granularity = q->limits.discard_granularity / block_size;
>         attrib->unmap_granularity_alignment = q->limits.discard_alignment /
>                                                                 block_size;
> -       attrib->unmap_zeroes_data = 0;
> +       attrib->unmap_zeroes_data = (q->limits.max_write_zeroes_sectors);
>         return true;
>  }
>  EXPORT_SYMBOL(target_configure_unmap_from_queue);
> 

Completely a nit but: why the extra parenthesis?