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SubjectRe: [PATCH 1/7] blkcg: relocate __blkg_release_rcu()
On Sun, Nov 12, 2017 at 02:26:07PM -0800, Tejun Heo wrote:
> Move __blkg_release_rcu() above blkg_alloc(). This is a pure code
> reorganization to prepare for the switch to percpu_ref.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

Reviewed-by: Shaohua Li <shli@kernel.org>
> ---
> block/blk-cgroup.c | 46 +++++++++++++++++++++++-----------------------
> 1 file changed, 23 insertions(+), 23 deletions(-)
>
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index d3f56ba..6482be5 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -81,6 +81,29 @@ static void blkg_free(struct blkcg_gq *blkg)
> kfree(blkg);
> }
>
> +/*
> + * A group is RCU protected, but having an rcu lock does not mean that one
> + * can access all the fields of blkg and assume these are valid. For
> + * example, don't try to follow throtl_data and request queue links.
> + *
> + * Having a reference to blkg under an rcu allows accesses to only values
> + * local to groups like group stats and group rate limits.
> + */
> +void __blkg_release_rcu(struct rcu_head *rcu_head)
> +{
> + struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
> +
> + /* release the blkcg and parent blkg refs this blkg has been holding */
> + css_put(&blkg->blkcg->css);
> + if (blkg->parent)
> + blkg_put(blkg->parent);
> +
> + wb_congested_put(blkg->wb_congested);
> +
> + blkg_free(blkg);
> +}
> +EXPORT_SYMBOL_GPL(__blkg_release_rcu);
> +
> /**
> * blkg_alloc - allocate a blkg
> * @blkcg: block cgroup the new blkg is associated with
> @@ -378,29 +401,6 @@ static void blkg_destroy_all(struct request_queue *q)
> }
>
> /*
> - * A group is RCU protected, but having an rcu lock does not mean that one
> - * can access all the fields of blkg and assume these are valid. For
> - * example, don't try to follow throtl_data and request queue links.
> - *
> - * Having a reference to blkg under an rcu allows accesses to only values
> - * local to groups like group stats and group rate limits.
> - */
> -void __blkg_release_rcu(struct rcu_head *rcu_head)
> -{
> - struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
> -
> - /* release the blkcg and parent blkg refs this blkg has been holding */
> - css_put(&blkg->blkcg->css);
> - if (blkg->parent)
> - blkg_put(blkg->parent);
> -
> - wb_congested_put(blkg->wb_congested);
> -
> - blkg_free(blkg);
> -}
> -EXPORT_SYMBOL_GPL(__blkg_release_rcu);
> -
> -/*
> * The next function used by blk_queue_for_each_rl(). It's a bit tricky
> * because the root blkg uses @q->root_rl instead of its own rl.
> */
> --
> 2.9.5
>

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