[PATCHv3 3/7] zram: use generic start/end io accounting

[Sergey Senozhatsky <sergey.senozhatsky@gmail.com>]

Use bio generic_start_io_acct() and generic_end_io_acct() to account
device's block layer statistics. This will let users to monitor zram
activities using sysstat and similar packages/tools.

Apart from the usual per-stat sysfs attr, zram IO stats are now also
available in '/sys/block/zram<id>/stat' and '/proc/diskstats' files.

We will slowly get rid of per-stat sysfs files.

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2d5848a..6adccdf 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -743,8 +743,12 @@ static void zram_bio_discard(struct zram *zram, u32 index,
 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 			int offset, int rw)
 {
+	unsigned long start_time = jiffies;
 	int ret;
 
+	generic_start_io_acct(rw, bvec->bv_len >> SECTOR_SHIFT,
+			&zram->disk->part0);
+
 	if (rw == READ) {
 		atomic64_inc(&zram->stats.num_reads);
 		ret = zram_bvec_read(zram, bvec, index, offset);
@@ -753,6 +757,8 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 		ret = zram_bvec_write(zram, bvec, index, offset);
 	}
 
+	generic_end_io_acct(rw, &zram->disk->part0, start_time);
+
 	if (unlikely(ret)) {
 		if (rw == READ)
 			atomic64_inc(&zram->stats.failed_reads);
-- 
2.3.2.223.g7a9409c