From 03aa264ac15637b6f98374270bcdf31400965505 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 5 Mar 2012 13:15:19 -0800 Subject: blkcg: let blkcg core manage per-queue blkg list and counter With the previous patch to move blkg list heads and counters to request_queue and blkg, logic to manage them in both policies are almost identical and can be moved to blkcg core. This patch moves blkg link logic into blkg_lookup_create(), implements common blkg unlink code in blkg_destroy(), and updates blkg_destory_all() so that it's policy specific and can skip root group. The updated blkg_destroy_all() is now used to both clear queue for bypassing and elv switching, and release all blkgs on q exit. This patch introduces a race window where policy [de]registration may race against queue blkg clearing. This can only be a problem on cfq unload and shouldn't be a real problem in practice (and we have many other places where this race already exists). Future patches will remove these unlikely races. Signed-off-by: Tejun Heo Cc: Vivek Goyal Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 100 ++++------------------------------------------------ 1 file changed, 6 insertions(+), 94 deletions(-) (limited to 'block/cfq-iosched.c') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index e846803280a..dc73690dec4 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1045,14 +1045,6 @@ static void cfq_update_blkio_group_weight(struct request_queue *q, cfqg->needs_update = true; } -static void cfq_link_blkio_group(struct request_queue *q, - struct blkio_group *blkg) -{ - list_add(&blkg->q_node[BLKIO_POLICY_PROP], - &q->blkg_list[BLKIO_POLICY_PROP]); - q->nr_blkgs[BLKIO_POLICY_PROP]++; -} - static void cfq_init_blkio_group(struct blkio_group *blkg) { struct cfq_group *cfqg = blkg_to_cfqg(blkg); @@ -1096,84 +1088,6 @@ static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) blkg_get(cfqg_to_blkg(cfqg)); } -static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg) -{ - struct blkio_group *blkg = cfqg_to_blkg(cfqg); - - /* Something wrong if we are trying to remove same group twice */ - BUG_ON(list_empty(&blkg->q_node[BLKIO_POLICY_PROP])); - - list_del_init(&blkg->q_node[BLKIO_POLICY_PROP]); - - BUG_ON(cfqd->queue->nr_blkgs[BLKIO_POLICY_PROP] <= 0); - cfqd->queue->nr_blkgs[BLKIO_POLICY_PROP]--; - - /* - * Put the reference taken at the time of creation so that when all - * queues are gone, group can be destroyed. - */ - blkg_put(cfqg_to_blkg(cfqg)); -} - -static bool cfq_release_cfq_groups(struct cfq_data *cfqd) -{ - struct request_queue *q = cfqd->queue; - struct blkio_group *blkg, *n; - bool empty = true; - - list_for_each_entry_safe(blkg, n, &q->blkg_list[BLKIO_POLICY_PROP], - q_node[BLKIO_POLICY_PROP]) { - /* - * If cgroup removal path got to blk_group first and removed - * it from cgroup list, then it will take care of destroying - * cfqg also. - */ - if (!cfq_blkiocg_del_blkio_group(blkg)) - cfq_destroy_cfqg(cfqd, blkg_to_cfqg(blkg)); - else - empty = false; - } - return empty; -} - -/* - * Blk cgroup controller notification saying that blkio_group object is being - * delinked as associated cgroup object is going away. That also means that - * no new IO will come in this group. So get rid of this group as soon as - * any pending IO in the group is finished. - * - * This function is called under rcu_read_lock(). key is the rcu protected - * pointer. That means @q is a valid request_queue pointer as long as we - * are rcu read lock. - * - * @q was fetched from blkio_group under blkio_cgroup->lock. That means - * it should not be NULL as even if elevator was exiting, cgroup deltion - * path got to it first. - */ -static void cfq_unlink_blkio_group(struct request_queue *q, - struct blkio_group *blkg) -{ - struct cfq_data *cfqd = q->elevator->elevator_data; - unsigned long flags; - - spin_lock_irqsave(q->queue_lock, flags); - cfq_destroy_cfqg(cfqd, blkg_to_cfqg(blkg)); - spin_unlock_irqrestore(q->queue_lock, flags); -} - -static struct elevator_type iosched_cfq; - -static bool cfq_clear_queue(struct request_queue *q) -{ - lockdep_assert_held(q->queue_lock); - - /* shoot down blkgs iff the current elevator is cfq */ - if (!q->elevator || q->elevator->type != &iosched_cfq) - return true; - - return cfq_release_cfq_groups(q->elevator->elevator_data); -} - #else /* GROUP_IOSCHED */ static struct cfq_group *cfq_lookup_create_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg) @@ -1186,8 +1100,6 @@ cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) { cfqq->cfqg = cfqg; } -static void cfq_release_cfq_groups(struct cfq_data *cfqd) {} - #endif /* GROUP_IOSCHED */ /* @@ -3547,17 +3459,20 @@ static void cfq_exit_queue(struct elevator_queue *e) __cfq_slice_expired(cfqd, cfqd->active_queue, 0); cfq_put_async_queues(cfqd); - cfq_release_cfq_groups(cfqd); + + spin_unlock_irq(q->queue_lock); + + blkg_destroy_all(q, BLKIO_POLICY_PROP, true); #ifdef CONFIG_BLK_CGROUP /* * If there are groups which we could not unlink from blkcg list, * wait for a rcu period for them to be freed. */ + spin_lock_irq(q->queue_lock); wait = q->nr_blkgs[BLKIO_POLICY_PROP]; -#endif spin_unlock_irq(q->queue_lock); - +#endif cfq_shutdown_timer_wq(cfqd); /* @@ -3794,9 +3709,6 @@ static struct elevator_type iosched_cfq = { static struct blkio_policy_type blkio_policy_cfq = { .ops = { .blkio_init_group_fn = cfq_init_blkio_group, - .blkio_link_group_fn = cfq_link_blkio_group, - .blkio_unlink_group_fn = cfq_unlink_blkio_group, - .blkio_clear_queue_fn = cfq_clear_queue, .blkio_update_group_weight_fn = cfq_update_blkio_group_weight, }, .plid = BLKIO_POLICY_PROP, -- cgit v1.2.3