block, bfq: reduce upper bound for inject limit to max_rq_in_driver+1

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>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 5a2bbd8..e114282 100644 (file)
--- 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++;
        }