block: add disk/bio-based accounting helpers

Add two new helpers to simplify I/O accounting for bio based drivers.
Currently these drivers use the generic_start_io_acct and
generic_end_io_acct helpers which have very cumbersome calling
conventions, don't actually return the time they started accounting,
and try to deal with accounting for partitions, which can't happen
for bio based drivers.  The new helpers will be used to subsequently
replace uses of the old helpers.

The main API is the bio based wrappes in blkdev.h, but for zram
which wants to account rw_page based I/O lower level routines are
provided as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 34 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 77e57c2e8d60..8973104f88d9 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1432,6 +1432,40 @@ void blk_account_io_start(struct request *rq, bool new_io)
 	part_stat_unlock();
 }
 
+unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
+		unsigned int op)
+{
+	struct hd_struct *part = &disk->part0;
+	const int sgrp = op_stat_group(op);
+	unsigned long now = READ_ONCE(jiffies);
+
+	part_stat_lock();
+	update_io_ticks(part, now, false);
+	part_stat_inc(part, ios[sgrp]);
+	part_stat_add(part, sectors[sgrp], sectors);
+	part_stat_local_inc(part, in_flight[op_is_write(op)]);
+	part_stat_unlock();
+
+	return now;
+}
+EXPORT_SYMBOL(disk_start_io_acct);
+
+void disk_end_io_acct(struct gendisk *disk, unsigned int op,
+		unsigned long start_time)
+{
+	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;
+
+	part_stat_lock();
+	update_io_ticks(part, now, true);
+	part_stat_add(part, nsecs[sgrp], jiffies_to_nsecs(duration));
+	part_stat_local_dec(part, in_flight[op_is_write(op)]);
+	part_stat_unlock();
+}
+EXPORT_SYMBOL(disk_end_io_acct);
+
 /*
  * Steal bios from a request and add them to a bio list.
  * The request must not have been partially completed before.