From: Paolo Valente <paolo.valente@linaro.org>
Date: Thu, 22 Aug 2019 17:20:35 +0200
Subject: [PATCH] block, bfq: reduce upper bound for inject limit to
 max_rq_in_driver+1
Git-commit: c1e0a18228822258cbeb49a923d93f8f01c74a76
Patch-Mainline: v5.4-rc1
References: bsc#1156419,jsc#SLE-8281

Upon an increment attempt of the injection limit, the latter is
constrained not to become higher than twice the maximum number
max_rq_in_driver of I/O requests that have happened to be in service
in the drive. This high bound allows the injection limit to grow
beyond max_rq_in_driver, which may then cause max_rq_in_driver itself
to grow.

However, since the limit is incremented by only one unit at a time,
there is no need for such a high bound, and just max_rq_in_driver+1 is
enough.

Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.de>
---
 block/bfq-iosched.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 5a2bbd8613a8..e114282204f6 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5805,7 +5805,7 @@ static void bfq_update_inject_limit(struct bfq_data *bfqd,
 			bfqq->inject_limit--;
 			bfqq->decrease_time_jif = jiffies;
 		} else if (tot_time_ns < threshold &&
-			   old_limit < bfqd->max_rq_in_driver<<1)
+			   old_limit <= bfqd->max_rq_in_driver)
 			bfqq->inject_limit++;
 	}
 
-- 
2.16.4