Re: [PATCH v3 08/10] dm: Add support for copy offload.

[Nitesh Shetty <nj.shetty@samsung.com>]

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On Tue, Feb 22, 2022 at 11:00:31AM -0500, Mike Snitzer wrote:
> On Mon, Feb 14 2022 at  2:59P -0500,
> Nitesh Shetty <nj.shetty@samsung.com> wrote:
> 
> > Before enabling copy for dm target, check if underlying devices and
> > dm target support copy. Avoid split happening inside dm target.
> > Fail early if the request needs split, currently splitting copy
> > request is not supported.
> > 
> > Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> > ---
> >  drivers/md/dm-table.c         | 45 +++++++++++++++++++++++++++++++++++
> >  drivers/md/dm.c               |  6 +++++
> >  include/linux/device-mapper.h |  5 ++++
> >  3 files changed, 56 insertions(+)
> > 
> > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> > index e43096cfe9e2..8dc9ae6a6a86 100644
> > --- a/drivers/md/dm-table.c
> > +++ b/drivers/md/dm-table.c
> > @@ -1903,6 +1903,38 @@ static bool dm_table_supports_nowait(struct dm_table *t)
> >  	return true;
> >  }
> >  
> > +static int device_not_copy_capable(struct dm_target *ti, struct dm_dev *dev,
> > +				      sector_t start, sector_t len, void *data)
> > +{
> > +	struct request_queue *q = bdev_get_queue(dev->bdev);
> > +
> > +	return !blk_queue_copy(q);
> > +}
> > +
> > +static bool dm_table_supports_copy(struct dm_table *t)
> > +{
> > +	struct dm_target *ti;
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < dm_table_get_num_targets(t); i++) {
> > +		ti = dm_table_get_target(t, i);
> > +
> > +		if (!ti->copy_supported)
> > +			return false;
> > +
> > +		/*
> > +		 * target provides copy support (as implied by setting
> > +		 * 'copy_supported') and it relies on _all_ data devices having copy support.
> > +		 */
> > +		if (ti->copy_supported &&
> > +		    (!ti->type->iterate_devices ||
> > +		     ti->type->iterate_devices(ti, device_not_copy_capable, NULL)))
> > +			return false;
> > +	}
> > +
> > +	return true;
> > +}
> > +
> >  static int device_not_discard_capable(struct dm_target *ti, struct dm_dev *dev,
> >  				      sector_t start, sector_t len, void *data)
> >  {
> > @@ -2000,6 +2032,19 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
> >  	} else
> >  		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
> >  
> > +	if (!dm_table_supports_copy(t)) {
> > +		blk_queue_flag_clear(QUEUE_FLAG_COPY, q);
> > +		/* Must also clear discard limits... */
> 
> copy-and-paste mistake: s/discard/copy/ ^
>

acked

> > +		q->limits.max_copy_sectors = 0;
> > +		q->limits.max_hw_copy_sectors = 0;
> > +		q->limits.max_copy_range_sectors = 0;
> > +		q->limits.max_hw_copy_range_sectors = 0;
> > +		q->limits.max_copy_nr_ranges = 0;
> > +		q->limits.max_hw_copy_nr_ranges = 0;
> > +	} else {
> > +		blk_queue_flag_set(QUEUE_FLAG_COPY, q);
> > +	}
> > +
> >  	if (dm_table_supports_secure_erase(t))
> >  		blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
> >  
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index ab9cc91931f9..3b4cd49c489d 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -1372,6 +1372,12 @@ static int __split_and_process_non_flush(struct clone_info *ci)
> >  	if (__process_abnormal_io(ci, ti, &r))
> >  		return r;
> >  
> > +	if ((unlikely(op_is_copy(ci->bio->bi_opf)) &&
> > +				max_io_len(ti, ci->sector) < ci->sector_count)) {
> > +		DMERR("%s: Error IO size(%u) is greater than maximum target size(%llu)\n",
> > +				__func__, ci->sector_count, max_io_len(ti, ci->sector));
> > +		return -EIO;
> > +	}
> >  	len = min_t(sector_t, max_io_len(ti, ci->sector), ci->sector_count);
> >  
> >  	r = __clone_and_map_data_bio(ci, ti, ci->sector, &len);
> 
> There isn't a need for __func__ prefix here.
> 
> You'll also need to rebase on latest dm-5.18 (or wait until 5.18 merge
> window opens) because there has been some conflicting changes since
> you posted.
>

acked

> > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> > index b26fecf6c8e8..acfd4018125a 100644
> > --- a/include/linux/device-mapper.h
> > +++ b/include/linux/device-mapper.h
> > @@ -362,6 +362,11 @@ struct dm_target {
> >  	 * zone append operations using regular writes.
> >  	 */
> >  	bool emulate_zone_append:1;
> > +
> > +	/*
> > +	 * copy offload is supported
> > +	 */
> > +	bool copy_supported:1;
> >  };
> 
> Would prefer this be "copy_offload_supported".
> 

acked, will update in next series.

--
Nitesh Shetty

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