[PATCH V4 6/8] block, bfq: retrieve independent access ranges from request queue

[Paolo Valente]

From: Federico Gavioli <f.gavioli97@xxxxxxxxx>

This patch implements the code to gather the content of the
independent_access_ranges structure from the request_queue and copy
it into the queue's bfq_data. This copy is done at queue initialization.

We copy the access ranges into the bfq_data to avoid taking the queue
lock each time we access the ranges.

This implementation, however, puts a limit to the maximum independent
ranges supported by the scheduler. Such a limit is equal to the constant
BFQ_MAX_ACTUATORS. This limit was placed to avoid the allocation of
dynamic memory.

Co-developed-by: Rory Chen <rory.c.chen@xxxxxxxxxxx>
Signed-off-by: Rory Chen <rory.c.chen@xxxxxxxxxxx>
Signed-off-by: Federico Gavioli <f.gavioli97@xxxxxxxxx>
Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
---
 block/bfq-iosched.c | 54 ++++++++++++++++++++++++++++++++++++++-------
 block/bfq-iosched.h |  5 +++++
 2 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 7c9b5cae05b5..d0109bfc2ed0 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1831,10 +1831,26 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq,
 /* get the index of the actuator that will serve bio */
 static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio)
 {
-	/*
-	 * Multi-actuator support not complete yet, so always return 0
-	 * for the moment.
-	 */
+	struct blk_independent_access_range *iar;
+	unsigned int i;
+	sector_t end;
+
+	/* no search needed if one or zero ranges present */
+	if (bfqd->num_actuators < 2)
+		return 0;
+
+	/* bio_end_sector(bio) gives the sector after the last one */
+	end = bio_end_sector(bio) - 1;
+
+	for (i = 0; i < bfqd->num_actuators; i++) {
+		iar = &(bfqd->ia_ranges[i]);
+		if (end >= iar->sector && end < iar->sector + iar->nr_sectors)
+			return i;
+	}
+
+	WARN_ONCE(true,
+		  "bfq_actuator_index: bio sector out of ranges: end=%llu\n",
+		  end);
 	return 0;
 }
 
@@ -2479,7 +2495,6 @@ static void bfq_remove_request(struct request_queue *q,
 
 	if (rq->cmd_flags & REQ_META)
 		bfqq->meta_pending--;
-
 }
 
 static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
@@ -7137,6 +7152,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
 {
 	struct bfq_data *bfqd;
 	struct elevator_queue *eq;
+	unsigned int i;
+	struct blk_independent_access_ranges *ia_ranges = q->disk->ia_ranges;
 
 	eq = elevator_alloc(q, e);
 	if (!eq)
@@ -7180,10 +7197,31 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
 	bfqd->queue = q;
 
 	/*
-	 * Multi-actuator support not complete yet, default to single
-	 * actuator for the moment.
+	 * If the disk supports multiple actuators, we copy the independent
+	 * access ranges from the request queue structure.
 	 */
-	bfqd->num_actuators = 1;
+	spin_lock_irq(&q->queue_lock);
+	if (ia_ranges) {
+		/*
+		 * Check if the disk ia_ranges size exceeds the current bfq
+		 * actuator limit.
+		 */
+		if (ia_ranges->nr_ia_ranges > BFQ_MAX_ACTUATORS) {
+			pr_crit("nr_ia_ranges higher than act limit: iars=%d, max=%d.\n",
+				ia_ranges->nr_ia_ranges, BFQ_MAX_ACTUATORS);
+			pr_crit("Falling back to single actuator mode.\n");
+			bfqd->num_actuators = 0;
+		} else {
+			bfqd->num_actuators = ia_ranges->nr_ia_ranges;
+
+			for (i = 0; i < bfqd->num_actuators; i++)
+				bfqd->ia_ranges[i] = ia_ranges->ia_range[i];
+		}
+	} else {
+		bfqd->num_actuators = 0;
+	}
+
+	spin_unlock_irq(&q->queue_lock);
 
 	INIT_LIST_HEAD(&bfqd->dispatch);
 
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 5fca86a82411..326d68d65cc9 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -815,6 +815,11 @@ struct bfq_data {
 	 */
 	unsigned int num_actuators;
 
+	/*
+	 * Disk independent access ranges for each actuator
+	 * in this device.
+	 */
+	struct blk_independent_access_range ia_ranges[BFQ_MAX_ACTUATORS];
 };
 
 enum bfqq_state_flags {
-- 
2.20.1