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authorTejun Heo <tj@kernel.org>2012-03-05 13:15:19 -0800
committerJens Axboe <axboe@kernel.dk>2012-03-06 21:27:23 +0100
commit03aa264ac15637b6f98374270bcdf31400965505 (patch)
tree6fa9ca54d3f775fba19123790f6655158034a1d8 /block/cfq-iosched.c
parent4eef3049986e8397d5003916aed8cad6567a5e02 (diff)
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 <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/cfq-iosched.c')
-rw-r--r--block/cfq-iosched.c100
1 files changed, 6 insertions, 94 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e846803280a6..dc73690dec44 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,