[dm-devel] [RFC PATCH 4/4] dm: support bio polling
Ming Lei
ming.lei at redhat.com
Wed Jun 16 13:05:33 UTC 2021
Support bio(REQ_POLLED) polling in the following approach:
1) setup one list in instance of 'struct dm_io', adds every 'struct
dm_target_io' instance cloned for current dm bio into this list;
store the list in 1) into bio->bi_bio_drv_data
2) hold one refcnt on io->io_count after submitting this dm bio with
REQ_POLLED
4) implement .poll_bio() callback, and iterate over the list in 1) and
polled on each ->clone of 'dm_target_io' instance; call dec_pending()
if all target ios are done in .poll_bio().
4) enable QUEUE_FLAG_POLL if all underlying queues enable QUEUE_FLAG_POLL,
which is based on Jeffle's previous patch.
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
drivers/md/dm-table.c | 24 ++++++++++++++++++
drivers/md/dm.c | 59 ++++++++++++++++++++++++++++++++++++++++---
2 files changed, 79 insertions(+), 4 deletions(-)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index ee47a332b462..b14b379442d2 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1491,6 +1491,12 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
return &t->targets[(KEYS_PER_NODE * n) + k];
}
+static int device_not_poll_capable(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ return !blk_queue_poll(bdev_get_queue(dev->bdev));
+}
+
/*
* type->iterate_devices() should be called when the sanity check needs to
* iterate and check all underlying data devices. iterate_devices() will
@@ -1541,6 +1547,11 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev,
return 0;
}
+static int dm_table_supports_poll(struct dm_table *t)
+{
+ return !dm_table_any_dev_attr(t, device_not_poll_capable, NULL);
+}
+
/*
* Check whether a table has no data devices attached using each
* target's iterate_devices method.
@@ -2078,6 +2089,19 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
dm_update_keyslot_manager(q, t);
blk_queue_update_readahead(q);
+
+ /*
+ * Check for request-based device is remained to
+ * dm_mq_init_request_queue()->blk_mq_init_allocated_queue().
+ * For bio-based device, only set QUEUE_FLAG_POLL when all underlying
+ * devices supporting polling.
+ */
+ if (__table_type_bio_based(t->type)) {
+ if (dm_table_supports_poll(t))
+ blk_queue_flag_set(QUEUE_FLAG_POLL, q);
+ else
+ blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
+ }
}
unsigned int dm_table_get_num_targets(struct dm_table *t)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 363f12a285ce..0a0e4a38f435 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -84,6 +84,7 @@ struct dm_target_io {
struct dm_target *ti;
unsigned target_bio_nr;
unsigned *len_ptr;
+ struct list_head list;
bool inside_dm_io;
struct bio clone;
};
@@ -99,6 +100,7 @@ struct dm_io {
blk_status_t status;
atomic_t io_count;
struct bio *orig_bio;
+ struct list_head poll_head;
unsigned long start_time;
spinlock_t endio_lock;
struct dm_stats_aux stats_aux;
@@ -655,6 +657,11 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io->md = md;
spin_lock_init(&io->endio_lock);
+ if (bio->bi_opf & REQ_POLLED) {
+ bio->bi_bio_drv_data = io;
+ INIT_LIST_HEAD(&io->poll_head);
+ }
+
start_io_acct(io);
return io;
@@ -692,6 +699,8 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci, struct dm_target *t
static void free_tio(struct dm_target_io *tio)
{
+ list_del_init(&tio->list);
+
if (tio->inside_dm_io)
return;
bio_put(&tio->clone);
@@ -936,10 +945,15 @@ static void dec_pending(struct dm_io *io, blk_status_t error)
io_error = io->status;
bio = io->orig_bio;
end_io_acct(io);
+
free_io(md, io);
- if (io_error == BLK_STS_DM_REQUEUE)
+ if (io_error == BLK_STS_DM_REQUEUE) {
+ /* not poll any more in case of requeue */
+ if (bio->bi_opf & REQ_POLLED)
+ bio->bi_opf &= ~REQ_POLLED;
return;
+ }
if ((bio->bi_opf & REQ_PREFLUSH) && bio->bi_iter.bi_size) {
/*
@@ -1043,7 +1057,9 @@ static void clone_endio(struct bio *bio)
up(&md->swap_bios_semaphore);
}
- free_tio(tio);
+ /* Any cloned bio submitted as POLLED, free them all after dm_io is done */
+ if (list_empty(&tio->list))
+ free_tio(tio);
dec_pending(io, error);
}
@@ -1300,6 +1316,11 @@ static void __map_bio(struct dm_target_io *tio)
struct dm_io *io = tio->io;
struct dm_target *ti = tio->ti;
+ if (clone->bi_opf & REQ_POLLED)
+ list_add_tail(&tio->list, &io->poll_head);
+ else
+ INIT_LIST_HEAD(&tio->list);
+
clone->bi_end_io = clone_endio;
/*
@@ -1666,8 +1687,9 @@ static void __split_and_process_bio(struct mapped_device *md,
}
}
- /* drop the extra reference count */
- dec_pending(ci.io, errno_to_blk_status(error));
+ /* drop the extra reference count for non-POLLED bio */
+ if (!(bio->bi_opf & REQ_POLLED))
+ dec_pending(ci.io, errno_to_blk_status(error));
}
static void dm_submit_bio(struct bio *bio)
@@ -1707,6 +1729,34 @@ static void dm_submit_bio(struct bio *bio)
dm_put_live_table(md, srcu_idx);
}
+static int dm_poll_bio(struct bio *bio, unsigned int flags)
+{
+ struct dm_io *io = bio->bi_bio_drv_data;
+ struct dm_target_io *tio;
+
+ if (!(bio->bi_opf & REQ_POLLED) || !io)
+ return 0;
+
+ list_for_each_entry(tio, &io->poll_head, list)
+ bio_poll(&tio->clone, flags);
+
+ /* bio_poll holds the last reference */
+ if (atomic_read(&io->io_count) == 1) {
+ /* free all target IOs submitted as POLLED */
+ while (!list_empty(&io->poll_head)) {
+ struct dm_target_io *tio =
+ list_entry(io->poll_head.next,
+ struct dm_target_io, list);
+ free_tio(tio);
+ }
+ bio->bi_bio_drv_data = NULL;
+ dec_pending(io, 0);
+ return 1;
+ }
+
+ return 0;
+}
+
/*-----------------------------------------------------------------
* An IDR is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
@@ -3121,6 +3171,7 @@ static const struct pr_ops dm_pr_ops = {
static const struct block_device_operations dm_blk_dops = {
.submit_bio = dm_submit_bio,
+ .poll_bio = dm_poll_bio,
.open = dm_blk_open,
.release = dm_blk_close,
.ioctl = dm_blk_ioctl,
--
2.31.1
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