Commit 4843c69d authored by Vivek Goyal's avatar Vivek Goyal Committed by Jens Axboe
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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: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 5617cbef

block/blk-throttle.c

+21 −1
Original line number Diff line number Diff line
@@ -78,6 +78,8 @@ struct throtl_grp { 


	/* Some throttle limits got updated for the group */

	int limits_changed;



	struct rcu_head rcu_head;

};



struct throtl_data
@@ -151,12 +153,30 @@ static inline struct throtl_grp *throtl_ref_get_tg(struct throtl_grp *tg) 
	return tg;

}



static void throtl_free_tg(struct rcu_head *head)

{

	struct throtl_grp *tg;



	tg = container_of(head, struct throtl_grp, rcu_head);

	kfree(tg);

}



static void throtl_put_tg(struct throtl_grp *tg)

{

	BUG_ON(atomic_read(&tg->ref) <= 0);

	if (!atomic_dec_and_test(&tg->ref))

		return;

	kfree(tg);



	/*

	 * A group is freed in rcu manner. 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 acess to only

	 * values local to groups like group stats and group rate limits

	 */

	call_rcu(&tg->rcu_head, throtl_free_tg);

}



static void throtl_init_group(struct throtl_grp *tg)