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block: return just one value from part_in_flight

PATCH In review Mikulas Patocka 2 participants 2 messages Nov 28, 2018 – Nov 30, 2018

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Block layer Device mapper
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Mikulas Patocka

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#0 lore raw

PATCH 3/3 block: return just one value from part_in_flight

The previous patches deleted all the code that needed the second value returned from part_in_flight - now the kernel only uses the first value.

Consequently, part_in_flight (and blk_mq_in_flight) may be changed so that it only returns one value.

This patch just refactors the code, there's no functional change.

Signed-off-by Mikulas Patocka <[email protected]>
---
 block/blk-mq.c            |    6 ++++--
 block/blk-mq.h            |    3 +--
 block/genhd.c             |   32 +++++++++++---------------------
 block/partition-generic.c |    6 +++---
 include/linux/genhd.h     |    3 +--
 5 files changed, 20 insertions(+), 30 deletions(-)
block/blk-mq.c +4 -2
Index: linux-block/block/blk-mq.c
===================================================================
@@ -113,13 +113,15 @@ static bool blk_mq_check_inflight(struct
 	return true;
 }
 
-void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
-		      unsigned int inflight[2])
+unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
 {
+	unsigned inflight[2];
 	struct mq_inflight mi = { .part = part, .inflight = inflight, };
 
 	inflight[0] = inflight[1] = 0;
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
+
+	return inflight[0];
 }
 
 static bool blk_mq_check_inflight_rw(struct blk_mq_hw_ctx *hctx,
block/blk-mq.h +1 -2
Index: linux-block/block/blk-mq.h
===================================================================
@@ -184,8 +184,7 @@ static inline bool blk_mq_hw_queue_mappe
 	return hctx->nr_ctx && hctx->tags;
 }
 
-void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
-		      unsigned int inflight[2]);
+unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part);
 void blk_mq_in_flight_rw(struct request_queue *q, struct hd_struct *part,
 			 unsigned int inflight[2]);
block/genhd.c +11 -21
Index: linux-block/block/genhd.c
===================================================================
@@ -65,34 +65,24 @@ void part_dec_in_flight(struct request_q
 		local_dec(per_cpu_ptr(part_to_disk(part)->part0.dkstats, cpu)->in_flight);
 }
 
-void part_in_flight(struct request_queue *q, struct hd_struct *part,
-		    unsigned int inflight[2])
+unsigned int part_in_flight(struct request_queue *q, struct hd_struct *part)
 {
 	int cpu;
+	int inflight;
 
 	if (queue_is_mq(q)) {
-		blk_mq_in_flight(q, part, inflight);
-		return;
+		return blk_mq_in_flight(q, part);
 	}
 
-	inflight[0] = 0;
+	inflight = 0;
 	for_each_possible_cpu(cpu) {
-		inflight[0] +=	local_read(&per_cpu_ptr(part->dkstats, cpu)->in_flight[0]) +
+		inflight +=	local_read(&per_cpu_ptr(part->dkstats, cpu)->in_flight[0]) +
 				local_read(&per_cpu_ptr(part->dkstats, cpu)->in_flight[1]);
 	}
-	if ((int)inflight[0] < 0)
-		inflight[0] = 0;
+	if (inflight < 0)
+		inflight = 0;
 
-	if (part->partno) {
-		part = &part_to_disk(part)->part0;
-		inflight[1] = 0;
-		for_each_possible_cpu(cpu) {
-			inflight[1] +=	local_read(&per_cpu_ptr(part->dkstats, cpu)->in_flight[0]) +
-					local_read(&per_cpu_ptr(part->dkstats, cpu)->in_flight[1]);
-		}
-		if ((int)inflight[1] < 0)
-			inflight[1] = 0;
-	}
+	return (unsigned int)inflight;
 }
 
 void part_in_flight_rw(struct request_queue *q, struct hd_struct *part,

@@ -1348,7 +1338,7 @@ static int diskstats_show(struct seq_fil
 	struct disk_part_iter piter;
 	struct hd_struct *hd;
 	char buf[BDEVNAME_SIZE];
-	unsigned int inflight[2];
+	unsigned int inflight;
 
 	/*
 	if (&disk_to_dev(gp)->kobj.entry == block_class.devices.next)

@@ -1360,7 +1350,7 @@ static int diskstats_show(struct seq_fil
 
 	disk_part_iter_init(&piter, gp, DISK_PITER_INCL_EMPTY_PART0);
 	while ((hd = disk_part_iter_next(&piter))) {
-		part_in_flight(gp->queue, hd, inflight);
+		inflight = part_in_flight(gp->queue, hd);
 		seq_printf(seqf, "%4d %7d %s "
 			   "%lu %lu %lu %u "
 			   "%lu %lu %lu %u "

@@ -1376,7 +1366,7 @@ static int diskstats_show(struct seq_fil
 			   part_stat_read(hd, merges[STAT_WRITE]),
 			   part_stat_read(hd, sectors[STAT_WRITE]),
 			   (unsigned int)part_stat_read_msecs(hd, STAT_WRITE),
-			   inflight[0],
+			   inflight,
 			   jiffies_to_msecs(part_stat_read(hd, io_ticks)),
 			   jiffies_to_msecs(part_stat_read(hd, time_in_queue)),
 			   part_stat_read(hd, ios[STAT_DISCARD]),
block/partition-generic.c +3 -3
Index: linux-block/block/partition-generic.c
===================================================================
@@ -120,9 +120,9 @@ ssize_t part_stat_show(struct device *de
 {
 	struct hd_struct *p = dev_to_part(dev);
 	struct request_queue *q = part_to_disk(p)->queue;
-	unsigned int inflight[2];
+	unsigned int inflight;
 
-	part_in_flight(q, p, inflight);
+	inflight = part_in_flight(q, p);
 	return sprintf(buf,
 		"%8lu %8lu %8llu %8u "
 		"%8lu %8lu %8llu %8u "

@@ -137,7 +137,7 @@ ssize_t part_stat_show(struct device *de
 		part_stat_read(p, merges[STAT_WRITE]),
 		(unsigned long long)part_stat_read(p, sectors[STAT_WRITE]),
 		(unsigned int)part_stat_read_msecs(p, STAT_WRITE),
-		inflight[0],
+		inflight,
 		jiffies_to_msecs(part_stat_read(p, io_ticks)),
 		jiffies_to_msecs(part_stat_read(p, time_in_queue)),
 		part_stat_read(p, ios[STAT_DISCARD]),
include/linux/genhd.h +1 -2
Index: linux-block/include/linux/genhd.h
===================================================================
@@ -377,8 +377,7 @@ static inline void free_part_stats(struc
 #define part_stat_sub(cpu, gendiskp, field, subnd)			\
 	part_stat_add(cpu, gendiskp, field, -subnd)
 
-void part_in_flight(struct request_queue *q, struct hd_struct *part,
-		    unsigned int inflight[2]);
+unsigned int part_in_flight(struct request_queue *q, struct hd_struct *part);
 void part_in_flight_rw(struct request_queue *q, struct hd_struct *part,
 		       unsigned int inflight[2]);
 void part_dec_in_flight(struct request_queue *q, int cpu, struct hd_struct *part,
#1 lore raw
Quoted 28 lines · Mikulas Patocka

The previous patches deleted all the code that needed the second value returned from part_in_flight - now the kernel only uses the first value.

Consequently, part_in_flight (and blk_mq_in_flight) may be changed so that it only returns one value.

This patch just refactors the code, there's no functional change.

Signed-off-by Mikulas Patocka <[email protected]>
---
 block/blk-mq.c            |    6 ++++--
 block/blk-mq.h            |    3 +--
 block/genhd.c             |   32 +++++++++++---------------------
 block/partition-generic.c |    6 +++---
 include/linux/genhd.h     |    3 +--
 5 files changed, 20 insertions(+), 30 deletions(-)

Index: linux-block/block/blk-mq.c
===================================================================

block/blk-mq.c +0 -2
@@ -113,13 +113,15 @@ static bool blk_mq_check_inflight(struct
 	return true;
 }
 
-void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part,
-		      unsigned int inflight[2])

block/blk-mq.c static bool blk_mq_check_inflight(struct · line 125

Quoted 10 lines
block/blk-mq.c +4 -0
+unsigned int blk_mq_in_flight(struct request_queue *q, struct hd_struct *part)
 {
+	unsigned inflight[2];
 	struct mq_inflight mi = { .part = part, .inflight = inflight, };
 
 	inflight[0] = inflight[1] = 0;
 	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
+
+	return inflight[0];
 }

I don't think this change goes deep enough. You're leaving unnecessary work (relative to mi->inflight[1]) in blk_mq_check_inflight().

Mike