block: move the poll flag to queue_limits

Move the poll flag into the queue_limits feature field so that it can
be set atomically with the queue frozen.

Stacking drivers are simplified in that they now can simply set the
flag, and blk_stack_limits will clear it when the features is not
supported by any of the underlying devices.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20240617060532.127975-22-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 13 insertions, 41 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index e44697037e86..ca1f136575cf 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -582,7 +582,7 @@ int dm_split_args(int *argc, char ***argvp, char *input)
 static void dm_set_stacking_limits(struct queue_limits *limits)
 {
 	blk_set_stacking_limits(limits);
-	limits->features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT;
+	limits->features |= BLK_FEAT_IO_STAT | BLK_FEAT_NOWAIT | BLK_FEAT_POLL;
 }
 
 /*
@@ -1024,14 +1024,13 @@ bool dm_table_request_based(struct dm_table *t)
 	return __table_type_request_based(dm_table_get_type(t));
 }
 
-static bool dm_table_supports_poll(struct dm_table *t);
-
 static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *md)
 {
 	enum dm_queue_mode type = dm_table_get_type(t);
 	unsigned int per_io_data_size = 0, front_pad, io_front_pad;
 	unsigned int min_pool_size = 0, pool_size;
 	struct dm_md_mempools *pools;
+	unsigned int bioset_flags = 0;
 
 	if (unlikely(type == DM_TYPE_NONE)) {
 		DMERR("no table type is set, can't allocate mempools");
@@ -1048,6 +1047,9 @@ static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *
 		goto init_bs;
 	}
 
+	if (md->queue->limits.features & BLK_FEAT_POLL)
+		bioset_flags |= BIOSET_PERCPU_CACHE;
+
 	for (unsigned int i = 0; i < t->num_targets; i++) {
 		struct dm_target *ti = dm_table_get_target(t, i);
 
@@ -1060,8 +1062,7 @@ static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *
 
 	io_front_pad = roundup(per_io_data_size,
 		__alignof__(struct dm_io)) + DM_IO_BIO_OFFSET;
-	if (bioset_init(&pools->io_bs, pool_size, io_front_pad,
-			dm_table_supports_poll(t) ? BIOSET_PERCPU_CACHE : 0))
+	if (bioset_init(&pools->io_bs, pool_size, io_front_pad, bioset_flags))
 		goto out_free_pools;
 	if (t->integrity_supported &&
 	    bioset_integrity_create(&pools->io_bs, pool_size))
@@ -1404,14 +1405,6 @@ 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)
-{
-	struct request_queue *q = bdev_get_queue(dev->bdev);
-
-	return !test_bit(QUEUE_FLAG_POLL, &q->queue_flags);
-}
-
 /*
  * type->iterate_devices() should be called when the sanity check needs to
  * iterate and check all underlying data devices. iterate_devices() will
@@ -1459,19 +1452,6 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev,
 	return 0;
 }
 
-static bool dm_table_supports_poll(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->type->iterate_devices ||
-		    ti->type->iterate_devices(ti, device_not_poll_capable, NULL))
-			return false;
-	}
-
-	return true;
-}
-
 /*
  * Check whether a table has no data devices attached using each
  * target's iterate_devices method.
@@ -1817,6 +1797,13 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	if (!dm_table_supports_nowait(t))
 		limits->features &= ~BLK_FEAT_NOWAIT;
 
+	/*
+	 * The current polling impementation does not support request based
+	 * stacking.
+	 */
+	if (!__table_type_bio_based(t->type))
+		limits->features &= ~BLK_FEAT_POLL;
+
 	if (!dm_table_supports_discards(t)) {
 		limits->max_hw_discard_sectors = 0;
 		limits->discard_granularity = 0;
@@ -1858,21 +1845,6 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 		return r;
 
 	dm_update_crypto_profile(q, t);
-
-	/*
-	 * Check for request-based device is left 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);
-	}
-
 	return 0;
 }