[PATCH v2 23/28] block: Remove elevator required features

Damien Le Moal
2024-03-25T04:45:38Z

The only elevator feature ever implemented is ELEVATOR_F_ZBD_SEQ_WRITE
for signaling that a scheduler implements zone write locking to tightly
control the dispatching order of write operations to zoned block
devices. With the removal of zone write locking support in mq-deadline
and the reliance of all block device drivers on the block layer zone
write plugging to control ordering of write operations to zones, the
elevator feature ELEVATOR_F_ZBD_SEQ_WRITE is completely unused.
Remove it, and also remove the now unused code for filtering the
possible schedulers for a block device based on required features.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
---
block/blk-settings.c | 16 ---------------
block/elevator.c | 46 +++++-------------------------------------
block/elevator.h | 1 -
include/linux/blkdev.h | 10 ---------
4 files changed, 5 insertions(+), 68 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 82c61d2e4bb8..31d882ac72d4 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -1053,22 +1053,6 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
}
EXPORT_SYMBOL_GPL(blk_queue_write_cache);

-/**
- * blk_queue_required_elevator_features - Set a queue required elevator features
- * @q: the request queue for the target device
- * @features: Required elevator features OR'ed together
- *
- * Tell the block layer that for the device controlled through @q, only the
- * only elevators that can be used are those that implement at least the set of
- * features specified by @features.
- */
-void blk_queue_required_elevator_features(struct request_queue *q,
- unsigned int features)
-{
- q->required_elevator_features = features;
-}
-EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features);
-
/**
* blk_queue_can_use_dma_map_merging - configure queue for merging segments.
* @q: the request queue for the device
diff --git a/block/elevator.c b/block/elevator.c
index 5ff093cb3cf8..f64ebd726e58 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -83,13 +83,6 @@ bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
}
EXPORT_SYMBOL(elv_bio_merge_ok);

-static inline bool elv_support_features(struct request_queue *q,
- const struct elevator_type *e)
-{
- return (q->required_elevator_features & e->elevator_features) ==
- q->required_elevator_features;
-}
-
/**
* elevator_match - Check whether @e's name or alias matches @name
* @e: Scheduler to test
@@ -120,7 +113,7 @@ static struct elevator_type *elevator_find_get(struct request_queue *q,

spin_lock(&elv_list_lock);
e = __elevator_find(name);
- if (e && (!elv_support_features(q, e) || !elevator_tryget(e)))
+ if (e && (!elevator_tryget(e)))
e = NULL;
spin_unlock(&elv_list_lock);
return e;
@@ -580,34 +573,8 @@ static struct elevator_type *elevator_get_default(struct request_queue *q)
}

/*
- * Get the first elevator providing the features required by the request queue.
- * Default to "none" if no matching elevator is found.
- */
-static struct elevator_type *elevator_get_by_features(struct request_queue *q)
-{
- struct elevator_type *e, *found = NULL;
-
- spin_lock(&elv_list_lock);
-
- list_for_each_entry(e, &elv_list, list) {
- if (elv_support_features(q, e)) {
- found = e;
- break;
- }
- }
-
- if (found && !elevator_tryget(found))
- found = NULL;
-
- spin_unlock(&elv_list_lock);
- return found;
-}
-
-/*
- * For a device queue that has no required features, use the default elevator
- * settings. Otherwise, use the first elevator available matching the required
- * features. If no suitable elevator is find or if the chosen elevator
- * initialization fails, fall back to the "none" elevator (no elevator).
+ * Use the default elevator settings. If the chosen elevator initialization
+ * fails, fall back to the "none" elevator (no elevator).
*/
void elevator_init_mq(struct request_queue *q)
{
@@ -622,10 +589,7 @@ void elevator_init_mq(struct request_queue *q)
if (unlikely(q->elevator))
return;

- if (!q->required_elevator_features)
- e = elevator_get_default(q);
- else
- e = elevator_get_by_features(q);
+ e = elevator_get_default(q);
if (!e)
return;

@@ -781,7 +745,7 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
list_for_each_entry(e, &elv_list, list) {
if (e == cur)
len += sprintf(name+len, "[%s] ", e->elevator_name);
- else if (elv_support_features(q, e))
+ else
len += sprintf(name+len, "%s ", e->elevator_name);
}
spin_unlock(&elv_list_lock);
diff --git a/block/elevator.h b/block/elevator.h
index 7ca3d7b6ed82..e9a050a96e53 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -74,7 +74,6 @@ struct elevator_type
struct elv_fs_entry *elevator_attrs;
const char *elevator_name;
const char *elevator_alias;
- const unsigned int elevator_features;
struct module *elevator_owner;
#ifdef CONFIG_BLK_DEBUG_FS
const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2e0087b4c37d..82cda82e9891 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -456,8 +456,6 @@ struct request_queue {

atomic_t nr_active_requests_shared_tags;

- unsigned int required_elevator_features;
-
struct blk_mq_tags *sched_shared_tags;

struct list_head icq_list;
@@ -962,14 +960,6 @@ disk_alloc_independent_access_ranges(struct gendisk *disk, int nr_ia_ranges);
void disk_set_independent_access_ranges(struct gendisk *disk,
struct blk_independent_access_ranges *iars);

-/*
- * Elevator features for blk_queue_required_elevator_features:
- */
-/* Supports zoned block devices sequential write constraint */
-#define ELEVATOR_F_ZBD_SEQ_WRITE (1U << 0)
-
-extern void blk_queue_required_elevator_features(struct request_queue *q,
- unsigned int features);
extern bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
struct device *dev);

--
2.44.0