[PATCH v3 2/3] dm: Add support for block provisioning

Sarthak Kukreti
2023-04-14T00:03:01Z

Add support to dm devices for REQ_OP_PROVISION. The default mode
is to passthrough the request to the underlying device, if it
supports it. 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.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.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 | 110 +++++++++++++++++++++++++++++++---
drivers/md/dm.c | 4 ++
include/linux/device-mapper.h | 11 ++++
7 files changed, 153 insertions(+), 9 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 3ba53dc3cc3f..5c655bfd4686 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -3087,6 +3087,8 @@ static int crypt_ctr_optional(struct dm_target *ti, unsigned int argc, char **ar
if (ret)
return ret;

+ ti->num_provision_bios = 1;
+
while (opt_params--) {
opt_string = dm_shift_arg(&as);
if (!opt_string) {
@@ -3390,7 +3392,7 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
* - for REQ_OP_DISCARD caller must use flush if IO ordering matters
*/
if (unlikely(bio->bi_opf & REQ_PREFLUSH ||
- bio_op(bio) == REQ_OP_DISCARD)) {
+ bio_op(bio) == REQ_OP_DISCARD || bio_op(bio) == REQ_OP_PROVISION)) {
bio_set_dev(bio, cc->dev->bdev);
if (bio_sectors(bio))
bio->bi_iter.bi_sector = cc->start +
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 3e622dcc9dbd..7843e548e850 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -62,6 +62,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->num_discard_bios = 1;
ti->num_secure_erase_bios = 1;
ti->num_write_zeroes_bios = 1;
+ ti->num_provision_bios = 1;
ti->private = lc;
return 0;

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index f766c21408f1..f6b224a12000 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1358,6 +1358,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
if (s->discard_zeroes_cow)
ti->num_discard_bios = (s->discard_passdown_origin ? 2 : 1);
ti->per_io_data_size = sizeof(struct dm_snap_tracked_chunk);
+ ti->num_provision_bios = 1;

/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
@@ -2003,6 +2004,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
/* If the block is already remapped - use that, else remap it */
e = dm_lookup_exception(&s->complete, chunk);
if (e) {
+ if (unlikely(bio_op(bio) == REQ_OP_PROVISION)) {
+ bio_endio(bio);
+ r = DM_MAPIO_SUBMITTED;
+ goto out_unlock;
+ }
remap_exception(s, e, bio, chunk);
if (unlikely(bio_op(bio) == REQ_OP_DISCARD) &&
io_overlaps_chunk(s, bio)) {
@@ -2413,6 +2419,7 @@ static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits)
/* All discards are split on chunk_size boundary */
limits->discard_granularity = snap->store->chunk_size;
limits->max_discard_sectors = snap->store->chunk_size;
+ limits->max_provision_sectors = snap->store->chunk_size;

up_read(&_origins_lock);
}
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 2055a758541d..5985343384a7 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1850,6 +1850,26 @@ static bool dm_table_supports_write_zeroes(struct dm_table *t)
return true;
}

+static int device_provision_capable(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ return !bdev_max_provision_sectors(dev->bdev);
+}
+
+static bool dm_table_supports_provision(struct dm_table *t)
+{
+ for (unsigned int i = 0; i < t->num_targets; i++) {
+ struct dm_target *ti = dm_table_get_target(t, i);
+
+ if (ti->provision_supported ||
+ (ti->type->iterate_devices &&
+ ti->type->iterate_devices(ti, device_provision_capable, NULL)))
+ return true;
+ }
+
+ return false;
+}
+
static int device_not_nowait_capable(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
@@ -1983,6 +2003,11 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
if (!dm_table_supports_write_zeroes(t))
q->limits.max_write_zeroes_sectors = 0;

+ if (dm_table_supports_provision(t))
+ blk_queue_max_provision_sectors(q, UINT_MAX >> 9);
+ else
+ q->limits.max_provision_sectors = 0;
+
dm_table_verify_integrity(t);

/*
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 13d4677baafd..b08b7ae617be 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -909,7 +909,8 @@ 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);
@@ -1013,6 +1014,15 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m)
goto out;
}

+ /*
+ * For provision requests, once the prepared block has been inserted
+ * into the mapping btree, return.
+ */
+ if (bio && bio_op(bio) == REQ_OP_PROVISION) {
+ bio_endio(bio);
+ return;
+ }
+
/*
* Release any bios held while the block was being provisioned.
* If we are processing a write bio that completely covers the block,
@@ -1241,7 +1251,7 @@ 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) &&
+ return (bio_data_dir(bio) == WRITE) && bio_op(bio) != REQ_OP_PROVISION &&
io_overlaps_block(pool, bio);
}

@@ -1334,10 +1344,11 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
/*
* IO to pool_dev remaps to the pool target's data_dev.
*
- * If the whole block of data is being overwritten, we can issue the
- * bio immediately. Otherwise we use kcopyd to clone the data first.
+ * If the whole block of data is being overwritten and if this is not a
+ * provision request, we can issue the bio immediately.
+ * Otherwise we use kcopyd to clone the data first.
*/
- if (io_overwrites_block(pool, bio))
+ if (io_overwrites_block(pool, bio) && bio_op(bio) != REQ_OP_PROVISION)
remap_and_issue_overwrite(tc, bio, data_dest, m);
else {
struct dm_io_region from, to;
@@ -1356,7 +1367,8 @@ static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
/*
* Do we need to zero a tail region?
*/
- if (len < pool->sectors_per_block && pool->pf.zero_new_blocks) {
+ if (len < pool->sectors_per_block && pool->pf.zero_new_blocks &&
+ bio_op(bio) != REQ_OP_PROVISION) {
atomic_inc(&m->prepare_actions);
ll_zero(tc, m,
data_dest * pool->sectors_per_block + len,
@@ -1390,6 +1402,10 @@ static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
m->data_block = data_block;
m->cell = cell;

+ /* Provision requests are chained on the original bio. */
+ if (bio && bio_op(bio) == REQ_OP_PROVISION)
+ m->bio = bio;
+
/*
* If the whole block of data is being overwritten or we are not
* zeroing pre-existing data, we can issue the bio immediately.
@@ -1865,7 +1881,8 @@ static void process_shared_bio(struct thin_c *tc, struct bio *bio,

if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size) {
break_sharing(tc, bio, block, &key, lookup_result, data_cell);
- cell_defer_no_holder(tc, virt_cell);
+ if (bio_op(bio) != REQ_OP_PROVISION)
+ cell_defer_no_holder(tc, virt_cell);
} else {
struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

@@ -1982,6 +1999,73 @@ 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);
+ switch (r) {
+ case 0:
+ if (lookup_result.shared)
+ process_shared_bio(tc, bio, begin,
+ &lookup_result, cell);
+ 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;
@@ -2202,6 +2286,8 @@ 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);

@@ -2723,7 +2809,8 @@ 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;
}
@@ -3370,6 +3457,8 @@ 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;

/*
* Only need to enable discards if the pool should pass
@@ -4068,6 +4157,7 @@ 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()
@@ -4261,6 +4351,9 @@ static int thin_ctr(struct dm_target *ti, unsigned int 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);
@@ -4475,6 +4568,7 @@ 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 dfde0088147a..d8f1803062b7 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1593,6 +1593,7 @@ 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;
@@ -1617,6 +1618,9 @@ 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 7975483816e4..e9f687521ae6 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -334,6 +334,12 @@ struct dm_target {
*/
unsigned int 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 int num_provision_bios;
+
/*
* The minimum number of extra bytes allocated in each io for the
* target to use.
@@ -358,6 +364,11 @@ 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.
*/
--
2.40.0.634.g4ca3ef3211-goog