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Message-ID: <Y7biAQyLKJDjsAlz@bfoster>
Date: Thu, 5 Jan 2023 09:43:13 -0500
From: Brian Foster <bfoster@...hat.com>
To: Sarthak Kukreti <sarthakkukreti@...omium.org>
Cc: sarthakkukreti@...gle.com, dm-devel@...hat.com,
linux-block@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Jens Axboe <axboe@...nel.dk>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Stefan Hajnoczi <stefanha@...hat.com>,
Alasdair Kergon <agk@...hat.com>,
Mike Snitzer <snitzer@...nel.org>,
Christoph Hellwig <hch@...radead.org>,
Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
Bart Van Assche <bvanassche@...gle.com>,
Daniil Lunev <dlunev@...gle.com>,
"Darrick J. Wong" <djwong@...nel.org>
Subject: Re: [PATCH v2 2/7] dm: Add support for block provisioning
On Thu, Dec 29, 2022 at 12:12:47AM -0800, Sarthak Kukreti wrote:
> Add support to dm devices for REQ_OP_PROVISION. The default mode
> is to pass through the request and dm-thin will utilize it to provision
> blocks.
>
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@...omium.org>
> ---
> drivers/md/dm-crypt.c | 4 +-
> drivers/md/dm-linear.c | 1 +
> drivers/md/dm-snap.c | 7 +++
> drivers/md/dm-table.c | 25 ++++++++++
> drivers/md/dm-thin.c | 90 ++++++++++++++++++++++++++++++++++-
> drivers/md/dm.c | 4 ++
> include/linux/device-mapper.h | 11 +++++
> 7 files changed, 139 insertions(+), 3 deletions(-)
>
...
> diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> index 64cfcf46881d..ab3f1abfabaf 100644
> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
...
> @@ -1980,6 +1992,70 @@ static void process_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell)
> }
> }
>
> +static void process_provision_cell(struct thin_c *tc, struct dm_bio_prison_cell *cell)
> +{
> + int r;
> + struct pool *pool = tc->pool;
> + struct bio *bio = cell->holder;
> + dm_block_t begin, end;
> + struct dm_thin_lookup_result lookup_result;
> +
> + if (tc->requeue_mode) {
> + cell_requeue(pool, cell);
> + return;
> + }
> +
> + get_bio_block_range(tc, bio, &begin, &end);
> +
> + while (begin != end) {
> + r = ensure_next_mapping(pool);
> + if (r)
> + /* we did our best */
> + return;
> +
> + r = dm_thin_find_block(tc->td, begin, 1, &lookup_result);
Hi Sarthak,
I think we discussed this before.. but remind me if/how we wanted to
handle the case if the thin blocks are shared..? Would a provision op
carry enough information to distinguish an FALLOC_FL_UNSHARE_RANGE
request from upper layers to conditionally provision in that case?
Brian
> + switch (r) {
> + case 0:
> + begin++;
> + break;
> + case -ENODATA:
> + bio_inc_remaining(bio);
> + provision_block(tc, bio, begin, cell);
> + begin++;
> + break;
> + default:
> + DMERR_LIMIT(
> + "%s: dm_thin_find_block() failed: error = %d",
> + __func__, r);
> + cell_defer_no_holder(tc, cell);
> + bio_io_error(bio);
> + begin++;
> + break;
> + }
> + }
> + bio_endio(bio);
> + cell_defer_no_holder(tc, cell);
> +}
> +
> +static void process_provision_bio(struct thin_c *tc, struct bio *bio)
> +{
> + dm_block_t begin, end;
> + struct dm_cell_key virt_key;
> + struct dm_bio_prison_cell *virt_cell;
> +
> + get_bio_block_range(tc, bio, &begin, &end);
> + if (begin == end) {
> + bio_endio(bio);
> + return;
> + }
> +
> + build_key(tc->td, VIRTUAL, begin, end, &virt_key);
> + if (bio_detain(tc->pool, &virt_key, bio, &virt_cell))
> + return;
> +
> + process_provision_cell(tc, virt_cell);
> +}
> +
> static void process_bio(struct thin_c *tc, struct bio *bio)
> {
> struct pool *pool = tc->pool;
> @@ -2200,6 +2276,8 @@ 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)
> + process_provision_bio(tc, bio);
> else
> pool->process_bio(tc, bio);
>
> @@ -2716,7 +2794,8 @@ 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;
> }
> @@ -3355,6 +3434,8 @@ static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
> pt->low_water_blocks = low_water_blocks;
> pt->adjusted_pf = pt->requested_pf = pf;
> ti->num_flush_bios = 1;
> + ti->num_provision_bios = 1;
> + ti->provision_supported = true;
>
> /*
> * Only need to enable discards if the pool should pass
> @@ -4053,6 +4134,7 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
> blk_limits_io_opt(limits, pool->sectors_per_block << SECTOR_SHIFT);
> }
>
> +
> /*
> * pt->adjusted_pf is a staging area for the actual features to use.
> * They get transferred to the live pool in bind_control_target()
> @@ -4243,6 +4325,9 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
> ti->num_discard_bios = 1;
> }
>
> + ti->num_provision_bios = 1;
> + ti->provision_supported = true;
> +
> mutex_unlock(&dm_thin_pool_table.mutex);
>
> spin_lock_irq(&tc->pool->lock);
> @@ -4457,6 +4542,7 @@ static void thin_io_hints(struct dm_target *ti, struct queue_limits *limits)
>
> limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
> limits->max_discard_sectors = 2048 * 1024 * 16; /* 16G */
> + limits->max_provision_sectors = 2048 * 1024 * 16; /* 16G */
> }
>
> static struct target_type thin_target = {
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index e1ea3a7bd9d9..4d19bae9da4a 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1587,6 +1587,7 @@ static bool is_abnormal_io(struct bio *bio)
> case REQ_OP_DISCARD:
> case REQ_OP_SECURE_ERASE:
> case REQ_OP_WRITE_ZEROES:
> + case REQ_OP_PROVISION:
> return true;
> default:
> break;
> @@ -1611,6 +1612,9 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci,
> case REQ_OP_WRITE_ZEROES:
> num_bios = ti->num_write_zeroes_bios;
> break;
> + case REQ_OP_PROVISION:
> + num_bios = ti->num_provision_bios;
> + break;
> default:
> break;
> }
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 04c6acf7faaa..b4d97d5d75b8 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -333,6 +333,12 @@ struct dm_target {
> */
> unsigned num_write_zeroes_bios;
>
> + /*
> + * The number of PROVISION bios that will be submitted to the target.
> + * The bio number can be accessed with dm_bio_get_target_bio_nr.
> + */
> + unsigned num_provision_bios;
> +
> /*
> * The minimum number of extra bytes allocated in each io for the
> * target to use.
> @@ -357,6 +363,11 @@ struct dm_target {
> */
> bool discards_supported:1;
>
> + /* Set if this target needs to receive provision requests regardless of
> + * whether or not its underlying devices have support.
> + */
> + bool provision_supported:1;
> +
> /*
> * Set if we need to limit the number of in-flight bios when swapping.
> */
> --
> 2.37.3
>
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