[PATCH RFC 1/5] block: return ns precision from disk_start_io_acct

[Guoqing Jiang <guoqing.jiang@cloud.ionos.com>]

Currently the duration accounting of bio based driver is converted from
jiffies to ns, means it could be less accurate as request based driver.

So let disk_start_io_acct return from ns precision, instead of convert
jiffies to ns in disk_end_io_acct.

Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: drbd-dev@lists.linbit.com
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
---
 block/blk-core.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index d9d632639bd1..0e806a8c62fb 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1466,6 +1466,7 @@ unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
 	struct hd_struct *part = &disk->part0;
 	const int sgrp = op_stat_group(op);
 	unsigned long now = READ_ONCE(jiffies);
+	unsigned long start_ns = ktime_get_ns();
 
 	part_stat_lock();
 	update_io_ticks(part, now, false);
@@ -1474,7 +1475,7 @@ unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
 	part_stat_local_inc(part, in_flight[op_is_write(op)]);
 	part_stat_unlock();
 
-	return now;
+	return start_ns;
 }
 EXPORT_SYMBOL(disk_start_io_acct);
 
@@ -1484,11 +1485,11 @@ void disk_end_io_acct(struct gendisk *disk, unsigned int op,
 	struct hd_struct *part = &disk->part0;
 	const int sgrp = op_stat_group(op);
 	unsigned long now = READ_ONCE(jiffies);
-	unsigned long duration = now - start_time;
+	unsigned long duration = ktime_get_ns() - start_time;
 
 	part_stat_lock();
 	update_io_ticks(part, now, true);
-	part_stat_add(part, nsecs[sgrp], jiffies_to_nsecs(duration));
+	part_stat_add(part, nsecs[sgrp], duration);
 	part_stat_local_dec(part, in_flight[op_is_write(op)]);
 	part_stat_unlock();
 }
-- 
2.17.1