lkml.org 
[lkml]   [2021]   [Dec]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH RFC] block, bfq: update pos_root for idle bfq_queue in bfq_bfqq_move()
From
Date
在 2021/12/10 16:16, Yu Kuai 写道:
> During code review, we found that if bfqq is not busy in
> bfq_bfqq_move(), bfq_pos_tree_add_move() won't be called for the bfqq,
> thus bfqq->pos_root still points to the old bfqg. However, the ref
> that bfqq hold for the old bfqg will be released, so it's possible
> that the old bfqg can be freed. This is problematic because the freed
> bfqg can still be accessed by bfqq->pos_root.
>
> Fix the problem by calling bfq_pos_tree_add_move() for idle bfqq
> as well.
>
Friendly ping ...
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> ---
> block/bfq-cgroup.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index 24a5c5329bcd..85f34c29b909 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -645,6 +645,7 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> struct bfq_group *bfqg)
> {
> struct bfq_entity *entity = &bfqq->entity;
> + struct bfq_group *old_parent = bfqq_group(bfqq);
>
> /*
> * Get extra reference to prevent bfqq from being freed in
> @@ -666,7 +667,6 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> bfq_deactivate_bfqq(bfqd, bfqq, false, false);
> else if (entity->on_st_or_in_serv)
> bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
> - bfqg_and_blkg_put(bfqq_group(bfqq));
>
> if (entity->parent &&
> entity->parent->last_bfqq_created == bfqq)
> @@ -679,11 +679,16 @@ void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> /* pin down bfqg and its associated blkg */
> bfqg_and_blkg_get(bfqg);
>
> - if (bfq_bfqq_busy(bfqq)) {
> - if (unlikely(!bfqd->nonrot_with_queueing))
> - bfq_pos_tree_add_move(bfqd, bfqq);
> + /*
> + * Don't leave the pos_root to old bfqg, since the ref to old bfqg will
> + * be released and the bfqg might be freed.
> + */
> + if (unlikely(!bfqd->nonrot_with_queueing))
> + bfq_pos_tree_add_move(bfqd, bfqq);
> + bfqg_and_blkg_put(old_parent);
> +
> + if (bfq_bfqq_busy(bfqq))
> bfq_activate_bfqq(bfqd, bfqq);
> - }
>
> if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
> bfq_schedule_dispatch(bfqd);
>

\
 
 \ /
  Last update: 2021-12-18 10:09    [W:0.033 / U:0.520 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site