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

Damien Le Moal
2023-03-29T09:00:22Z

On 3/27/23 17:40, Anuj Gupta wrote:
> From: Nitesh Shetty <nj.shetty@samsung.com>
>

Drop the period at the end of the patch title.

> 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 | 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.

> + 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