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authorDamien Le Moal <damien.lemoal@wdc.com>2019-09-05 18:51:32 +0900
committerJens Axboe <axboe@kernel.dk>2019-09-05 19:52:34 -0600
commita0958ba7fcdc316e3900f8d2afda519850d60985 (patch)
tree6a8167c62b6a585670ffaf11a37e10cf06e2f953 /block
parent68c43f133a754c7bf5cb1018bb16dc0821cc43a1 (diff)
block: Improve default elevator selection
For block devices that do not specify required features, preserve the current default elevator selection (mq-deadline for single queue devices, none for multi-queue devices). However, for devices specifying required features (e.g. zoned block devices ELEVATOR_F_ZBD_SEQ_WRITE feature), select the first available elevator providing the required features. In all cases, default to "none" if no elevator is available or if the initialization of the default elevator fails. Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/elevator.c51
1 files changed, 44 insertions, 7 deletions
diff --git a/block/elevator.c b/block/elevator.c
index ac7c8ad580ba..520d6b224b74 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -651,9 +651,46 @@ static inline bool elv_support_iosched(struct request_queue *q)
}
/*
- * For blk-mq devices supporting IO scheduling, we default to using mq-deadline,
- * if available, for single queue devices. If deadline isn't available OR
- * deadline initialization fails OR we have multiple queues, default to "none".
+ * For single queue devices, default to using mq-deadline. If we have multiple
+ * queues or mq-deadline is not available, default to "none".
+ */
+static struct elevator_type *elevator_get_default(struct request_queue *q)
+{
+ if (q->nr_hw_queues != 1)
+ return NULL;
+
+ return elevator_get(q, "mq-deadline", false);
+}
+
+/*
+ * 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;
+
+ spin_lock(&elv_list_lock);
+
+ list_for_each_entry(e, &elv_list, list) {
+ if (elv_support_features(e->elevator_features,
+ q->required_elevator_features))
+ break;
+ }
+
+ if (e && !try_module_get(e->elevator_owner))
+ e = NULL;
+
+ spin_unlock(&elv_list_lock);
+
+ return e;
+}
+
+/*
+ * 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).
*/
void elevator_init_mq(struct request_queue *q)
{
@@ -663,15 +700,15 @@ void elevator_init_mq(struct request_queue *q)
if (!elv_support_iosched(q))
return;
- if (q->nr_hw_queues != 1)
- return;
-
WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags));
if (unlikely(q->elevator))
return;
- e = elevator_get(q, "mq-deadline", false);
+ if (!q->required_elevator_features)
+ e = elevator_get_default(q);
+ else
+ e = elevator_get_by_features(q);
if (!e)
return;

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