blk-mq: enable checking two part inflight counts at the same time

Modify blk_mq_in_flight() to count both a partition and root at
the same time. Then we only have to call it once, instead of
potentially looping the tags twice.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -1470,17 +1470,12 @@ static void add_acct_request(struct request_queue *q, struct request *rq,
 }
 
 static void part_round_stats_single(struct request_queue *q, int cpu,
-				    struct hd_struct *part, unsigned long now)
+				    struct hd_struct *part, unsigned long now,
+				    unsigned int inflight)
 {
-	int inflight[2];
-
-	if (now == part->stamp)
-		return;
-
-	part_in_flight(q, part, inflight);
-	if (inflight[0]) {
+	if (inflight) {
 		__part_stat_add(cpu, part, time_in_queue,
-				inflight[0] * (now - part->stamp));
+				inflight * (now - part->stamp));
 		__part_stat_add(cpu, part, io_ticks, (now - part->stamp));
 	}
 	part->stamp = now;
@@ -1505,12 +1500,29 @@ static void part_round_stats_single(struct request_queue *q, int cpu,
  */
 void part_round_stats(struct request_queue *q, int cpu, struct hd_struct *part)
 {
+	struct hd_struct *part2 = NULL;
 	unsigned long now = jiffies;
+	unsigned int inflight[2];
+	int stats = 0;
+
+	if (part->stamp != now)
+		stats |= 1;
+
+	if (part->partno) {
+		part2 = &part_to_disk(part)->part0;
+		if (part2->stamp != now)
+			stats |= 2;
+	}
+
+	if (!stats)
+		return;
+
+	part_in_flight(q, part, inflight);
 
-	if (part->partno)
-		part_round_stats_single(q, cpu, &part_to_disk(part)->part0,
-						now);
-	part_round_stats_single(q, cpu, part, now);
+	if (stats & 2)
+		part_round_stats_single(q, cpu, part2, now, inflight[1]);
+	if (stats & 1)
+		part_round_stats_single(q, cpu, part, now, inflight[0]);
 }
 EXPORT_SYMBOL_GPL(part_round_stats);
 

block/blk-mq.c

@@ -97,11 +97,15 @@ static void blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
 	if (test_bit(REQ_ATOM_STARTED, &rq->atomic_flags) &&
 	    !test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags)) {
 		/*
-		 * Count as inflight if it either matches the partition we
-		 * asked for, or if it's the root
+		 * index[0] counts the specific partition that was asked
+		 * for. index[1] counts the ones that are active on the
+		 * whole device, so increment that if mi->part is indeed
+		 * a partition, and not a whole device.
 		 */
-		if (rq->part == mi->part || mi->part->partno)
+		if (rq->part == mi->part)
 			mi->inflight[0]++;
+		if (mi->part->partno)
+			mi->inflight[1]++;
 	}
 }
 
@@ -110,7 +114,7 @@ void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
 {
 	struct mq_inflight mi = { .part = part, .inflight = inflight, };
 
-	inflight[0] = 0;
+	inflight[0] = inflight[1] = 0;
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
 }