[PATCH] Block: initialize bio_cnt_ret_time for the first time

[Liu Bo <bo.liu@linux.alibaba.com>]

When a new tg is created, tg->bio_cnt_ret_time is 0, so if the first
IO going thru this tg turns out to be a bad one, we fail to record it
in tg->bad_bio_cnt as

if (jiffies > bio_cnt_ret_time) {
	tg->bad_bio_cnt /= 2;
}

Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
---
 block/blk-throttle.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 82282e6fdcf8..8bd54118dc0a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2329,6 +2329,8 @@ void blk_throtl_bio_endio(struct bio *bio)
 		tg->bio_cnt++;
 	}
 
+	if (unlikely(!tg->bio_cnt_reset_time))
+		tg->bio_cnt_reset_time = jiffies;
 	if (time_after(jiffies, tg->bio_cnt_reset_time) || tg->bio_cnt > 1024) {
 		tg->bio_cnt_reset_time = tg->td->throtl_slice + jiffies;
 		tg->bio_cnt /= 2;
-- 
1.8.3.1