4.19-stable review patch. If anyone has any objections, please let me know.
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From: Paolo Valente paolo.valente@linaro.org
[ Upstream commit cbeb869a3d1110450186b738199963c5e68c2a71 ]
BFQ schedules entities (which represent either per-process queues or groups of queues) as a function of their timestamps. In particular, as a function of their (virtual) finish times. The finish time of an entity is computed as a function of the budget assigned to the entity, assuming, tentatively, that the entity, once in service, will receive an amount of service equal to its budget. Then, when the entity is expired because it finishes to be served, this finish time is updated as a function of the actual service received by the entity. This allows the entity to be correctly charged with only the service received, and then to be correctly re-scheduled.
Yet an entity may receive service also while not being the entity in service (in the scheduling environment of its parent entity), for several reasons. If the entity remains with no backlog while receiving this 'unofficial' service, then it is expired. Also on such an expiration, the finish time of the entity should be updated to account for only the service actually received by the entity. Unfortunately, such an update is not performed for an entity expiring without being the entity in service.
In a similar vein, the service counter of the entity in service is reset when the entity is expired, to be ready to be used for next service cycle. This reset too should be performed also in case an entity is expired because it remains empty after receiving service while not being the entity in service. But in this case the reset is not performed.
This commit performs the above update of the finish time and reset of the service received, also for an entity expiring while not being the entity in service.
Signed-off-by: Paolo Valente paolo.valente@linaro.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/bfq-wf2q.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
--- a/block/bfq-wf2q.c +++ b/block/bfq-wf2q.c @@ -1181,10 +1181,17 @@ bool __bfq_deactivate_entity(struct bfq_ st = bfq_entity_service_tree(entity); is_in_service = entity == sd->in_service_entity;
- if (is_in_service) { - bfq_calc_finish(entity, entity->service); + bfq_calc_finish(entity, entity->service); + + if (is_in_service) sd->in_service_entity = NULL; - } + else + /* + * Non in-service entity: nobody will take care of + * resetting its service counter on expiration. Do it + * now. + */ + entity->service = 0;
if (entity->tree == &st->active) bfq_active_extract(st, entity);