block: clean up blk_mq_in_flight_rw()

Also add comment for part_inflight_show() for the difference between
bio-based and rq-based device.

Link: https://lore.kernel.org/linux-raid/20250506124903.2540268-4-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

3 files changed, 32 insertions, 26 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7d87e893999b..0ceb28989aee 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -89,7 +89,7 @@ struct mq_inflight {
 	unsigned int inflight[2];
 };
 
-static bool blk_mq_check_inflight(struct request *rq, void *priv)
+static bool blk_mq_check_in_driver(struct request *rq, void *priv)
 {
 	struct mq_inflight *mi = priv;
 
@@ -101,14 +101,14 @@ static bool blk_mq_check_inflight(struct request *rq, void *priv)
 	return true;
 }
 
-void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
-		unsigned int inflight[2])
+void blk_mq_in_driver_rw(struct block_device *part, unsigned int inflight[2])
 {
 	struct mq_inflight mi = { .part = part };
 
-	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
-	inflight[0] = mi.inflight[0];
-	inflight[1] = mi.inflight[1];
+	blk_mq_queue_tag_busy_iter(bdev_get_queue(part), blk_mq_check_in_driver,
+				   &mi);
+	inflight[READ] = mi.inflight[READ];
+	inflight[WRITE] = mi.inflight[WRITE];
 }
 
 #ifdef CONFIG_LOCKDEP
diff --git a/block/blk-mq.h b/block/blk-mq.h
index eeac0d47c878..affb2e14b56e 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -246,8 +246,7 @@ static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx)
 	return hctx->nr_ctx && hctx->tags;
 }
 
-void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
-		unsigned int inflight[2]);
+void blk_mq_in_driver_rw(struct block_device *part, unsigned int inflight[2]);
 
 static inline void blk_mq_put_dispatch_budget(struct request_queue *q,
 					      int budget_token)
diff --git a/block/genhd.c b/block/genhd.c
index 6d133061ea3d..1c1a642b321e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -126,27 +126,32 @@ static void part_stat_read_all(struct block_device *part,
 }
 
 static void part_in_flight_rw(struct block_device *part,
-		unsigned int inflight[2])
+		unsigned int inflight[2], bool mq_driver)
 {
 	int cpu;
 
-	inflight[0] = 0;
-	inflight[1] = 0;
-	for_each_possible_cpu(cpu) {
-		inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
-		inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
+	if (mq_driver) {
+		blk_mq_in_driver_rw(part, inflight);
+	} else {
+		for_each_possible_cpu(cpu) {
+			inflight[READ] += part_stat_local_read_cpu(
+						part, in_flight[READ], cpu);
+			inflight[WRITE] += part_stat_local_read_cpu(
+						part, in_flight[WRITE], cpu);
+		}
 	}
-	if (WARN_ON_ONCE((int)inflight[0] < 0))
-		inflight[0] = 0;
-	if (WARN_ON_ONCE((int)inflight[1] < 0))
-		inflight[1] = 0;
+
+	if (WARN_ON_ONCE((int)inflight[READ] < 0))
+		inflight[READ] = 0;
+	if (WARN_ON_ONCE((int)inflight[WRITE] < 0))
+		inflight[WRITE] = 0;
 }
 
 unsigned int part_in_flight(struct block_device *part)
 {
-	unsigned int inflight[2];
+	unsigned int inflight[2] = {0};
 
-	part_in_flight_rw(part, inflight);
+	part_in_flight_rw(part, inflight, false);
 
 	return inflight[READ] + inflight[WRITE];
 }
@@ -1084,19 +1089,21 @@ ssize_t part_stat_show(struct device *dev,
 		(unsigned int)div_u64(stat.nsecs[STAT_FLUSH], NSEC_PER_MSEC));
 }
 
+/*
+ * Show the number of IOs issued to driver.
+ * For bio-based device, started from bdev_start_io_acct();
+ * For rq-based device, started from blk_mq_start_request();
+ */
 ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
 			   char *buf)
 {
 	struct block_device *bdev = dev_to_bdev(dev);
 	struct request_queue *q = bdev_get_queue(bdev);
-	unsigned int inflight[2];
+	unsigned int inflight[2] = {0};
 
-	if (queue_is_mq(q))
-		blk_mq_in_flight_rw(q, bdev, inflight);
-	else
-		part_in_flight_rw(bdev, inflight);
+	part_in_flight_rw(bdev, inflight, queue_is_mq(q));
 
-	return sysfs_emit(buf, "%8u %8u\n", inflight[0], inflight[1]);
+	return sysfs_emit(buf, "%8u %8u\n", inflight[READ], inflight[WRITE]);
 }
 
 static ssize_t disk_capability_show(struct device *dev,