diff options
| -rw-r--r-- | block/blk-throttle.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index b9412d1..90ad407 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -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) |