linux-kernel - Re: [PATCH v8 7/9] dm: Add support for copy offload.

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Message-ID: <20230329121257.GC11932@green5>
Date:   Wed, 29 Mar 2023 17:42:57 +0530
From:   Nitesh Shetty <nj.shetty@...sung.com>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Anuj Gupta <anuj20.g@...sung.com>, Jens Axboe <axboe@...nel.dk>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...nel.org>, dm-devel@...hat.com,
        Keith Busch <kbusch@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        James Smart <james.smart@...adcom.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, bvanassche@....org,
        hare@...e.de, ming.lei@...hat.com, joshi.k@...sung.com,
        nitheshshetty@...il.com, gost.dev@...sung.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v8 7/9] dm: Add support for copy offload.

On Wed, Mar 29, 2023 at 05:59:49PM +0900, Damien Le Moal wrote:
> On 3/27/23 17:40, Anuj Gupta wrote:
> > From: Nitesh Shetty <nj.shetty@...sung.com>
> > 
> 
> Drop the period at the end of the patch title.


Acked

> 
> > 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@...sung.com>
> > ---
> >  drivers/md/dm-table.c         | 42 +++++++++++++++++++++++++++++++++++
> >  drivers/md/dm.c               |  7 ++++++
> >  include/linux/device-mapper.h |  5 +++++
> >  3 files changed, 54 insertions(+)
> > 
> > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> > index 7899f5fb4c13..45e894b9e3be 100644
> > --- a/drivers/md/dm-table.c
> > +++ b/drivers/md/dm-table.c
> > @@ -1863,6 +1863,39 @@ 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 < t->num_targets; i++) {
> > +		ti = dm_table_get_target(t, i);
> > +
> > +		if (!ti->copy_offload_supported)
> > +			return false;
> > +
> > +		/*
> > +		 * target provides copy support (as implied by setting
> > +		 * 'copy_offload_supported')
> > +		 * and it relies on _all_ data devices having copy support.
> > +		 */
> > +		if (!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)
> >  {
> > @@ -1945,6 +1978,15 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
> >  		q->limits.discard_misaligned = 0;
> >  	}
> >  
> > +	if (!dm_table_supports_copy(t)) {
> > +		blk_queue_flag_clear(QUEUE_FLAG_COPY, q);
> > +		/* Must also clear copy limits... */
> 
> Not a useful comment. The code is clear.

Acked

> 
> > +		q->limits.max_copy_sectors = 0;
> > +		q->limits.max_copy_sectors_hw = 0;
> > +	} else {
> > +		blk_queue_flag_set(QUEUE_FLAG_COPY, q);
> > +	}
> > +
> >  	if (!dm_table_supports_secure_erase(t))
> >  		q->limits.max_secure_erase_sectors = 0;
> >  
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index 2d0f934ba6e6..08ec51000af8 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -1693,6 +1693,13 @@ static blk_status_t __split_and_process_bio(struct clone_info *ci)
> >  	if (unlikely(ci->is_abnormal_io))
> >  		return __process_abnormal_io(ci, ti);
> >  
> > +	if ((unlikely(op_is_copy(ci->bio->bi_opf)) &&
> > +			max_io_len(ti, ci->sector) < ci->sector_count)) {
> > +		DMERR("Error, IO size(%u) > max target size(%llu)\n",
> > +			ci->sector_count, max_io_len(ti, ci->sector));
> > +		return BLK_STS_IOERR;
> > +	}
> > +
> >  	/*
> >  	 * Only support bio polling for normal IO, and the target io is
> >  	 * exactly inside the dm_io instance (verified in dm_poll_dm_io)
> > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> > index 7975483816e4..44969a20295e 100644
> > --- a/include/linux/device-mapper.h
> > +++ b/include/linux/device-mapper.h
> > @@ -380,6 +380,11 @@ struct dm_target {
> >  	 * bio_set_dev(). NOTE: ideally a target should _not_ need this.
> >  	 */
> >  	bool needs_bio_set_dev:1;
> > +
> > +	/*
> > +	 * copy offload is supported
> > +	 */
> > +	bool copy_offload_supported:1;
> >  };
> >  
> >  void *dm_per_bio_data(struct bio *bio, size_t data_size);
> 
> -- 
> Damien Le Moal
> Western Digital Research
> 
> 
Thank you,
Nitesh Shetty