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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/blk-throttle.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/blk-throttle.c')
-rw-r--r--block/blk-throttle.c99
1 files changed, 2 insertions, 97 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index c15d38307e1d..132941260e58 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -157,14 +157,6 @@ static void throtl_init_blkio_group(struct blkio_group *blkg)
tg->iops[WRITE] = -1;
}
-static void throtl_link_blkio_group(struct request_queue *q,
- struct blkio_group *blkg)
-{
- list_add(&blkg->q_node[BLKIO_POLICY_THROTL],
- &q->blkg_list[BLKIO_POLICY_THROTL]);
- q->nr_blkgs[BLKIO_POLICY_THROTL]++;
-}
-
static struct
throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkio_cgroup *blkcg)
{
@@ -813,89 +805,6 @@ throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay)
}
}
-static void
-throtl_destroy_tg(struct throtl_data *td, struct throtl_grp *tg)
-{
- struct blkio_group *blkg = tg_to_blkg(tg);
-
- /* Something wrong if we are trying to remove same group twice */
- WARN_ON_ONCE(list_empty(&blkg->q_node[BLKIO_POLICY_THROTL]));
-
- list_del_init(&blkg->q_node[BLKIO_POLICY_THROTL]);
-
- /*
- * Put the reference taken at the time of creation so that when all
- * queues are gone, group can be destroyed.
- */
- blkg_put(tg_to_blkg(tg));
- td->queue->nr_blkgs[BLKIO_POLICY_THROTL]--;
-}
-
-static bool throtl_release_tgs(struct throtl_data *td, bool release_root)
-{
- struct request_queue *q = td->queue;
- struct blkio_group *blkg, *n;
- bool empty = true;
-
- list_for_each_entry_safe(blkg, n, &q->blkg_list[BLKIO_POLICY_THROTL],
- q_node[BLKIO_POLICY_THROTL]) {
- struct throtl_grp *tg = blkg_to_tg(blkg);
-
- /* skip root? */
- if (!release_root && tg == td->root_tg)
- continue;
-
- /*
- * 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 (!blkiocg_del_blkio_group(blkg))
- throtl_destroy_tg(td, tg);
- 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(). @q 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 queue was going away, cgroup deltion
- * path got to it first.
- */
-void throtl_unlink_blkio_group(struct request_queue *q,
- struct blkio_group *blkg)
-{
- unsigned long flags;
-
- spin_lock_irqsave(q->queue_lock, flags);
- throtl_destroy_tg(q->td, blkg_to_tg(blkg));
- spin_unlock_irqrestore(q->queue_lock, flags);
-}
-
-static bool throtl_clear_queue(struct request_queue *q)
-{
- lockdep_assert_held(q->queue_lock);
-
- /*
- * Clear tgs but leave the root one alone. This is necessary
- * because root_tg is expected to be persistent and safe because
- * blk-throtl can never be disabled while @q is alive. This is a
- * kludge to prepare for unified blkg. This whole function will be
- * removed soon.
- */
- return throtl_release_tgs(q->td, false);
-}
-
static void throtl_update_blkio_group_common(struct throtl_data *td,
struct throtl_grp *tg)
{
@@ -960,9 +869,6 @@ static void throtl_shutdown_wq(struct request_queue *q)
static struct blkio_policy_type blkio_policy_throtl = {
.ops = {
.blkio_init_group_fn = throtl_init_blkio_group,
- .blkio_link_group_fn = throtl_link_blkio_group,
- .blkio_unlink_group_fn = throtl_unlink_blkio_group,
- .blkio_clear_queue_fn = throtl_clear_queue,
.blkio_update_group_read_bps_fn =
throtl_update_blkio_group_read_bps,
.blkio_update_group_write_bps_fn =
@@ -1148,12 +1054,11 @@ void blk_throtl_exit(struct request_queue *q)
throtl_shutdown_wq(q);
- spin_lock_irq(q->queue_lock);
- throtl_release_tgs(td, true);
+ blkg_destroy_all(q, BLKIO_POLICY_THROTL, true);
/* If there are other groups */
+ spin_lock_irq(q->queue_lock);
wait = q->nr_blkgs[BLKIO_POLICY_THROTL];
-
spin_unlock_irq(q->queue_lock);
/*