Re: [PATCH v6 4/5] dm-thin: Add REQ_OP_PROVISION support

Mike Snitzer
2023-05-09T17:07:55Z

On Sat, May 06 2023 at 2:29P -0400,
Sarthak Kukreti <sarthakkukreti@chromium.org> wrote:

> dm-thinpool uses the provision request to provision
> blocks for a dm-thin device. dm-thinpool currently does not
> pass through REQ_OP_PROVISION to underlying devices.
>
> For shared blocks, provision requests will break sharing and copy the
> contents of the entire block. Additionally, if 'skip_block_zeroing'
> is not set, dm-thin will opt to zero out the entire range as a part
> of provisioning.
>
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
> ---
> drivers/md/dm-thin.c | 70 +++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 66 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> index 2b13c949bd72..3f94f53ac956 100644
> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
> @@ -274,6 +274,7 @@ struct pool {
>
> process_bio_fn process_bio;
> process_bio_fn process_discard;
> + process_bio_fn process_provision;
>
> process_cell_fn process_cell;
> process_cell_fn process_discard_cell;
> @@ -913,7 +914,8 @@ static void __inc_remap_and_issue_cell(void *context,
> struct bio *bio;
>
> while ((bio = bio_list_pop(&cell->bios))) {
> - if (op_is_flush(bio->bi_opf) || bio_op(bio) == REQ_OP_DISCARD)
> + if (op_is_flush(bio->bi_opf) || bio_op(bio) == REQ_OP_DISCARD ||
> + bio_op(bio) == REQ_OP_PROVISION)
> bio_list_add(&info->defer_bios, bio);
> else {
> inc_all_io_entry(info->tc->pool, bio);
> @@ -1245,8 +1247,8 @@ static int io_overlaps_block(struct pool *pool, struct bio *bio)
>
> static int io_overwrites_block(struct pool *pool, struct bio *bio)
> {
> - return (bio_data_dir(bio) == WRITE) &&
> - io_overlaps_block(pool, bio);
> + return (bio_data_dir(bio) == WRITE) && io_overlaps_block(pool, bio) &&
> + bio_op(bio) != REQ_OP_PROVISION;
> }
>
> static void save_and_set_endio(struct bio *bio, bio_end_io_t **save,
> @@ -1953,6 +1955,51 @@ static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block
> }
> }
>
> +static void process_provision_bio(struct thin_c *tc, struct bio *bio)
> +{
> + int r;
> + struct pool *pool = tc->pool;
> + dm_block_t block = get_bio_block(tc, bio);
> + struct dm_bio_prison_cell *cell;
> + struct dm_cell_key key;
> + struct dm_thin_lookup_result lookup_result;
> +
> + /*
> + * If cell is already occupied, then the block is already
> + * being provisioned so we have nothing further to do here.
> + */
> + build_virtual_key(tc->td, block, &key);
> + if (bio_detain(pool, &key, bio, &cell))
> + return;
> +
> + if (tc->requeue_mode) {
> + cell_requeue(pool, cell);
> + return;
> + }
> +
> + r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
> + switch (r) {
> + case 0:
> + if (lookup_result.shared) {
> + process_shared_bio(tc, bio, block, &lookup_result, cell);
> + } else {
> + bio_endio(bio);
> + cell_defer_no_holder(tc, cell);
> + }
> + break;
> + case -ENODATA:
> + provision_block(tc, bio, block, cell);
> + break;
> +
> + default:
> + DMERR_LIMIT("%s: dm_thin_find_block() failed: error = %d",
> + __func__, r);
> + cell_defer_no_holder(tc, cell);
> + bio_io_error(bio);
> + break;
> + }
> +}
> +
> static void process_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell)
> {
> int r;
> @@ -2228,6 +2275,8 @@ static void process_thin_deferred_bios(struct thin_c *tc)
>
> if (bio_op(bio) == REQ_OP_DISCARD)
> pool->process_discard(tc, bio);
> + else if (bio_op(bio) == REQ_OP_PROVISION)
> + pool->process_provision(tc, bio);
> else
> pool->process_bio(tc, bio);
>
> @@ -2579,6 +2628,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
> dm_pool_metadata_read_only(pool->pmd);
> pool->process_bio = process_bio_fail;
> pool->process_discard = process_bio_fail;
> + pool->process_provision = process_bio_fail;
> pool->process_cell = process_cell_fail;
> pool->process_discard_cell = process_cell_fail;
> pool->process_prepared_mapping = process_prepared_mapping_fail;
> @@ -2592,6 +2642,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
> dm_pool_metadata_read_only(pool->pmd);
> pool->process_bio = process_bio_read_only;
> pool->process_discard = process_bio_success;
> + pool->process_provision = process_bio_fail;
> pool->process_cell = process_cell_read_only;
> pool->process_discard_cell = process_cell_success;
> pool->process_prepared_mapping = process_prepared_mapping_fail;
> @@ -2612,6 +2663,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
> pool->out_of_data_space = true;
> pool->process_bio = process_bio_read_only;
> pool->process_discard = process_discard_bio;
> + pool->process_provision = process_bio_fail;
> pool->process_cell = process_cell_read_only;
> pool->process_prepared_mapping = process_prepared_mapping;
> set_discard_callbacks(pool);
> @@ -2628,6 +2680,7 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
> dm_pool_metadata_read_write(pool->pmd);
> pool->process_bio = process_bio;
> pool->process_discard = process_discard_bio;
> + pool->process_provision = process_provision_bio;
> pool->process_cell = process_cell;
> pool->process_prepared_mapping = process_prepared_mapping;
> set_discard_callbacks(pool);
> @@ -2749,7 +2802,8 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
> return DM_MAPIO_SUBMITTED;
> }
>
> - if (op_is_flush(bio->bi_opf) || bio_op(bio) == REQ_OP_DISCARD) {
> + if (op_is_flush(bio->bi_opf) || bio_op(bio) == REQ_OP_DISCARD ||
> + bio_op(bio) == REQ_OP_PROVISION) {
> thin_defer_bio_with_throttle(tc, bio);
> return DM_MAPIO_SUBMITTED;
> }
> @@ -3396,6 +3450,9 @@ static int pool_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> pt->adjusted_pf = pt->requested_pf = pf;
> ti->num_flush_bios = 1;
> ti->limit_swap_bios = true;
> + ti->num_provision_bios = 1;
> + ti->provision_supported = true;
> + ti->max_provision_granularity = true;
>
> /*
> * Only need to enable discards if the pool should pass
> @@ -4114,6 +4171,8 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
> * The pool uses the same discard limits as the underlying data
> * device. DM core has already set this up.
> */
> +
> + limits->max_provision_sectors = pool->sectors_per_block;
> }
>
> static struct target_type pool_target = {
> @@ -4288,6 +4347,9 @@ static int thin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> ti->max_discard_granularity = true;
> }
>
> + ti->num_provision_bios = 1;
> + ti->provision_supported = true;
> +

We need this in thin_ctr: ti->max_provision_granularity = true;

More needed in the thin target than thin-pool; otherwise provision bio
issued to thin devices won't be split appropriately. But I do think
its fine to set in both thin_ctr and pool_ctr.

Otherwise, looks good.

Thanks,
Mike