Commit f3218ad8 authored by Paolo Valente's avatar Paolo Valente Committed by Jens Axboe

block, bfq: make sure queue budgets are not below service received

With some unlucky sequences of events, the function bfq_updated_next_req
updates the current budget of a bfq_queue to a lower value than the
service received by the queue using such a budget. Unfortunately, if
this happens, then the return value of the function bfq_bfqq_budget_left
becomes inconsistent. This commit solves this problem by lower-bounding
the budget computed in bfq_updated_next_req to the service currently
charged to the queue.
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 218cb897
...@@ -907,8 +907,10 @@ static void bfq_updated_next_req(struct bfq_data *bfqd, ...@@ -907,8 +907,10 @@ static void bfq_updated_next_req(struct bfq_data *bfqd,
*/ */
return; return;
new_budget = max_t(unsigned long, bfqq->max_budget, new_budget = max_t(unsigned long,
bfq_serv_to_charge(next_rq, bfqq)); max_t(unsigned long, bfqq->max_budget,
bfq_serv_to_charge(next_rq, bfqq)),
entity->service);
if (entity->budget != new_budget) { if (entity->budget != new_budget) {
entity->budget = new_budget; entity->budget = new_budget;
bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment