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    Subject[PATCH 1/7] blkcg: relocate __blkg_release_rcu()
    Date
    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>
    ---
    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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