[PATCH BUGFIX/IMPROVEMENT 4/6] block, bfq: fix weight-raising resume with !low_latency

Paolo Valente
2021-01-26T10:53:07Z

When the io_latency heuristic is off, bfq_queues must not start to be
weight-raised. Unfortunately, by mistake, this may happen when the
state of a previously weight-raised bfq_queue is resumed after a queue
split. This commit fixes this error.

Tested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
---
block/bfq-iosched.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index c5bda33c0923..0c7e203085f1 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -1010,7 +1010,7 @@ static void
bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
struct bfq_io_cq *bic, bool bfq_already_existing)
{
- unsigned int old_wr_coeff = bfqq->wr_coeff;
+ unsigned int old_wr_coeff = 1;
bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq);

if (bic->saved_has_short_ttime)
@@ -1031,7 +1031,13 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
bfqq->ttime = bic->saved_ttime;
bfqq->io_start_time = bic->saved_io_start_time;
bfqq->tot_idle_time = bic->saved_tot_idle_time;
- bfqq->wr_coeff = bic->saved_wr_coeff;
+ /*
+ * Restore weight coefficient only if low_latency is on
+ */
+ if (bfqd->low_latency) {
+ old_wr_coeff = bfqq->wr_coeff;
+ bfqq->wr_coeff = bic->saved_wr_coeff;
+ }
bfqq->service_from_wr = bic->saved_service_from_wr;
bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt;
bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish;
--
2.20.1