On Sat 05-03-22 17:11:56, Yu Kuai wrote:
> 'entity->sched_data' is set to parent group's sched_data, thus it's NULL
> for root group. And for_each_entity() is used widely to access
> 'entity->sched_data', thus aplly news apis if root group is not
^^ apply
> expected. Prepare to count root group into 'num_groups_with_pending_reqs'.
>
> Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
> block/bfq-iosched.c | 2 +-
> block/bfq-iosched.h | 22 ++++++++--------------
> block/bfq-wf2q.c | 10 +++++-----
> 3 files changed, 14 insertions(+), 20 deletions(-)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 69ddf6b0f01d..3bc7a7686aad 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -4393,7 +4393,7 @@ void bfq_bfqq_expire(struct bfq_data *bfqd,
> * service with the same budget.
> */
> entity = entity->parent;
> - for_each_entity(entity)
> + for_each_entity_not_root(entity)
> entity->service = 0;
> }
So why is it a problem to clear the service for root cgroup here?
> diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
> index f8eb340381cf..c4cb935a615a 100644
> --- a/block/bfq-wf2q.c
> +++ b/block/bfq-wf2q.c
> @@ -815,7 +815,7 @@ void bfq_bfqq_served(struct bfq_queue *bfqq, int served)
> bfqq->service_from_wr += served;
>
> bfqq->service_from_backlogged += served;
> - for_each_entity(entity) {
> + for_each_entity_not_root(entity) {
> st = bfq_entity_service_tree(entity);
Hum, right so how come this was not crashing? Because entity->sched_data is
indeed NULL for bfqd->root_group->entity and so bfq_entity_service_tree()
returned some bogus pointer? Similarly for the cases you are changing
below?
Honza
>
> entity->service += served;
> @@ -1201,7 +1201,7 @@ static void bfq_deactivate_entity(struct bfq_entity *entity,
> struct bfq_sched_data *sd;
> struct bfq_entity *parent = NULL;
>
> - for_each_entity_safe(entity, parent) {
> + for_each_entity_not_root_safe(entity, parent) {
> sd = entity->sched_data;
>
> if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) {
> @@ -1270,7 +1270,7 @@ static void bfq_deactivate_entity(struct bfq_entity *entity,
> * is not the case.
> */
> entity = parent;
> - for_each_entity(entity) {
> + for_each_entity_not_root(entity) {
> /*
> * Invoke __bfq_requeue_entity on entity, even if
> * already active, to requeue/reposition it in the
> @@ -1570,7 +1570,7 @@ struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
> * We can finally update all next-to-serve entities along the
> * path from the leaf entity just set in service to the root.
> */
> - for_each_entity(entity) {
> + for_each_entity_not_root(entity) {
> struct bfq_sched_data *sd = entity->sched_data;
>
> if (!bfq_update_next_in_service(sd, NULL, false))
> @@ -1597,7 +1597,7 @@ bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
> * execute the final step: reset in_service_entity along the
> * path from entity to the root.
> */
> - for_each_entity(entity)
> + for_each_entity_not_root(entity)
> entity->sched_data->in_service_entity = NULL;
>
> /*
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
