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blk-throttle: Free up a group only after one rcu grace period
Soon we will allow accessing a throtl_grp under rcu_read_lock(). Hence start freeing up throtl_grp after one rcu grace period. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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@ -78,6 +78,8 @@ struct throtl_grp {
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/* Some throttle limits got updated for the group */
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int limits_changed;
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struct rcu_head rcu_head;
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};
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struct throtl_data
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@ -151,12 +153,30 @@ static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg)
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return tg;
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}
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static void throtl_free_tg(struct rcu_head *head)
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{
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struct throtl_grp *tg;
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tg = container_of(head, struct throtl_grp, rcu_head);
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kfree(tg);
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}
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static void throtl_put_tg(struct throtl_grp *tg)
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{
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BUG_ON(atomic_read(&tg->ref) <= 0);
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if (!atomic_dec_and_test(&tg->ref))
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return;
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kfree(tg);
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/*
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* A group is freed in rcu manner. But having an rcu lock does not
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* mean that one can access all the fields of blkg and assume these
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* are valid. For example, don't try to follow throtl_data and
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* request queue links.
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*
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* Having a reference to blkg under an rcu allows acess to only
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* values local to groups like group stats and group rate limits
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*/
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call_rcu(&tg->rcu_head, throtl_free_tg);
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}
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static void throtl_init_group(struct throtl_grp *tg)
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