Re: [PATCH RFC 8/9] block, bfq: move forward __bfq_weights_tree_remove()

[yukuai (C)]

在 2021/12/10 18:00, Paolo Valente 写道:
> > Il giorno 27 nov 2021, alle ore 11:11, Yu Kuai <yukuai3@xxxxxxxxxx> ha scritto:
> >
> > Prepare to decrease 'num_groups_with_pending_reqs' earlier.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> > block/bfq-iosched.c | 13 +++++--------
> > 1 file changed, 5 insertions(+), 8 deletions(-)
> >
> > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> > index e3c31db4bffb..4239b3996e23 100644
> > --- a/block/bfq-iosched.c
> > +++ b/block/bfq-iosched.c
> > @@ -882,6 +882,10 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
> > {
> > 	struct bfq_entity *entity = bfqq->entity.parent;
> >
> > +	bfqq->ref++;
> > +	__bfq_weights_tree_remove(bfqd, bfqq,
> > +				  &bfqd->queue_weights_tree);
> > +
> > 	for_each_entity(entity) {
> > 		struct bfq_sched_data *sd = entity->my_sched_data;
> >
> > @@ -916,14 +920,7 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
> > 		}
> > 	}
> >
> > -	/*
> > -	 * Next function is invoked last, because it causes bfqq to be
> > -	 * freed if the following holds: bfqq is not in service and
> > -	 * has no dispatched request. DO NOT use bfqq after the next
> > -	 * function invocation.
> > -	 */
> > -	__bfq_weights_tree_remove(bfqd, bfqq,
> > -				  &bfqd->queue_weights_tree);
> > +	bfq_put_queue(bfqq);
> > }
>
> why it is not dangerous any longer to invoke __bfq_weights_tree_remove earlier, and the comment can be removed?

Hi, Paolo

Here I grab an additional ref to the bfqq, thus the bfqq is ensured not
to be free before bfq_put_queue() at the end of the function.

Maybe some comments is more appropriate.

Thanks,
Kuai
> Paolo
>
> > /*
> > --
> > 2.31.1
>
> .