block: Introduce IOPRIO_NR_LEVELS

The BFQ scheduler and ioprio_check_cap() both assume that the RT
priority class (IOPRIO_CLASS_RT) can have up to 8 different priority
levels, similarly to the BE class (IOPRIO_CLASS_iBE). This is
controlled using the IOPRIO_BE_NR macro , which is badly named as the
number of levels also applies to the RT class.

Introduce the class independent IOPRIO_NR_LEVELS macro, defined to 8,
to make things clear. Keep the old IOPRIO_BE_NR macro definition as an
alias for IOPRIO_NR_LEVELS.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210811033702.368488-6-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

@@ -2508,7 +2508,7 @@ void bfq_end_wr_async_queues(struct bfq_data *bfqd,
 	int i, j;
 
 	for (i = 0; i < 2; i++)
-		for (j = 0; j < IOPRIO_BE_NR; j++)
+		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
 			if (bfqg->async_bfqq[i][j])
 				bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
 	if (bfqg->async_idle_bfqq)
@@ -5293,10 +5293,10 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
 		break;
 	}
 
-	if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
+	if (bfqq->new_ioprio >= IOPRIO_NR_LEVELS) {
 		pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
 			bfqq->new_ioprio);
-		bfqq->new_ioprio = IOPRIO_BE_NR - 1;
+		bfqq->new_ioprio = IOPRIO_NR_LEVELS - 1;
 	}
 
 	bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
@@ -6825,7 +6825,7 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
 	int i, j;
 
 	for (i = 0; i < 2; i++)
-		for (j = 0; j < IOPRIO_BE_NR; j++)
+		for (j = 0; j < IOPRIO_NR_LEVELS; j++)
 			__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
 
 	__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);

block/bfq-iosched.h

@@ -931,7 +931,7 @@ struct bfq_group {
 
 	void *bfqd;
 
-	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
 	struct bfq_queue *async_idle_bfqq;
 
 	struct bfq_entity *my_entity;
@@ -948,7 +948,7 @@ struct bfq_group {
 	struct bfq_entity entity;
 	struct bfq_sched_data sched_data;
 
-	struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
+	struct bfq_queue *async_bfqq[2][IOPRIO_NR_LEVELS];
 	struct bfq_queue *async_idle_bfqq;
 
 	struct rb_root rq_pos_tree;

block/bfq-wf2q.c

@@ -505,7 +505,7 @@ static void bfq_active_insert(struct bfq_service_tree *st,
  */
 unsigned short bfq_ioprio_to_weight(int ioprio)
 {
-	return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
+	return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
 }
 
 /**
@@ -514,12 +514,12 @@ unsigned short bfq_ioprio_to_weight(int ioprio)
  *
  * To preserve as much as possible the old only-ioprio user interface,
  * 0 is used as an escape ioprio value for weights (numerically) equal or
- * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
+ * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
  */
 static unsigned short bfq_weight_to_ioprio(int weight)
 {
 	return max_t(int, 0,
-		     IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
+		     IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF - weight);
 }
 
 static void bfq_get_entity(struct bfq_entity *entity)

block/ioprio.c

@@ -74,9 +74,8 @@ int ioprio_check_cap(int ioprio)
 			fallthrough;
 			/* rt has prio field too */
 		case IOPRIO_CLASS_BE:
-			if (data >= IOPRIO_BE_NR || data < 0)
+			if (data >= IOPRIO_NR_LEVELS || data < 0)
 				return -EINVAL;
-
 			break;
 		case IOPRIO_CLASS_IDLE:
 			break;

fs/f2fs/sysfs.c

@@ -378,7 +378,7 @@ out:
 		ret = kstrtol(name, 10, &data);
 		if (ret)
 			return ret;
-		if (data >= IOPRIO_BE_NR || data < 0)
+		if (data >= IOPRIO_NR_LEVELS || data < 0)
 			return -EINVAL;
 
 		cprc->ckpt_thread_ioprio = IOPRIO_PRIO_VALUE(class, data);

include/uapi/linux/ioprio.h

@@ -32,9 +32,10 @@ enum {
 };
 
 /*
- * 8 best effort priority levels are supported
+ * The RT and BE priority classes both support up to 8 priority levels.
  */
-#define IOPRIO_BE_NR	(8)
+#define IOPRIO_NR_LEVELS	8
+#define IOPRIO_BE_NR		IOPRIO_NR_LEVELS
 
 enum {
 	IOPRIO_WHO_PROCESS = 1,