From: Jan Kara <jack@suse.cz>
To: Yu Kuai <yukuai3@huawei.com>
Cc: tj@kernel.org, axboe@kernel.dk, paolo.valente@linaro.org,
jack@suse.cz, cgroups@vger.kernel.org,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
yi.zhang@huawei.com
Subject: Re: [PATCH -next 02/11] block, bfq: apply news apis where root group is not expected
Date: Wed, 13 Apr 2022 11:50:44 +0200 [thread overview]
Message-ID: <20220413095044.uwxeqli2ytcdanem@quack3.lan> (raw)
In-Reply-To: <20220305091205.4188398-3-yukuai3@huawei.com>
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@huawei.com>
> ---
> 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@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2022-04-13 9:50 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-05 9:11 [PATCH -next 00/11] support concurrent sync io for bfq on a specail occasion Yu Kuai
2022-03-05 9:11 ` [PATCH -next 01/11] block, bfq: add new apis to iterate bfq entities Yu Kuai
2022-03-05 9:11 ` [PATCH -next 02/11] block, bfq: apply news apis where root group is not expected Yu Kuai
2022-04-13 9:50 ` Jan Kara [this message]
2022-04-13 10:59 ` Jan Kara
2022-04-13 11:11 ` yukuai (C)
2022-03-05 9:11 ` [PATCH -next 03/11] block, bfq: cleanup for __bfq_activate_requeue_entity() Yu Kuai
2022-03-05 9:11 ` [PATCH -next 04/11] block, bfq: move the increasement of 'num_groups_with_pending_reqs' to it's caller Yu Kuai
2022-03-05 9:11 ` [PATCH -next 05/11] block, bfq: count root group into 'num_groups_with_pending_reqs' Yu Kuai
2022-04-13 11:05 ` Jan Kara
2022-03-05 9:12 ` [PATCH -next 06/11] block, bfq: do not idle if only one cgroup is activated Yu Kuai
2022-03-05 9:12 ` [PATCH -next 07/11] block, bfq: only count parent bfqg when bfqq " Yu Kuai
2022-03-05 9:12 ` [PATCH -next 08/11] block, bfq: record how many queues have pending requests in bfq_group Yu Kuai
2022-03-05 9:12 ` [PATCH -next 09/11] block, bfq: move forward __bfq_weights_tree_remove() Yu Kuai
2022-03-05 9:12 ` [PATCH -next 10/11] block, bfq: decrease 'num_groups_with_pending_reqs' earlier Yu Kuai
2022-04-13 11:28 ` Jan Kara
2022-04-13 11:40 ` yukuai (C)
2022-04-15 1:10 ` yukuai (C)
2022-04-19 9:49 ` Jan Kara
2022-04-19 11:37 ` yukuai (C)
2022-04-21 8:17 ` Jan Kara
2022-03-05 9:12 ` [PATCH -next 11/11] block, bfq: cleanup bfqq_group() Yu Kuai
2022-03-11 6:31 ` [PATCH -next 00/11] support concurrent sync io for bfq on a specail occasion yukuai (C)
2022-03-17 1:49 ` yukuai (C)
2022-03-18 12:38 ` Paolo Valente
2022-03-19 2:34 ` yukuai (C)
2022-03-25 7:30 ` yukuai (C)
2022-04-01 3:43 ` yukuai (C)
2022-04-08 6:50 ` yukuai (C)
2022-04-13 11:12 ` Jan Kara
2022-04-13 11:33 ` yukuai (C)
2022-04-26 14:24 ` Paolo Valente
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