blkcg: implement blkcg_policy->on/offline_pd_fn() and blkcg_gq->online

Add two blkcg_policy methods, ->online_pd_fn() and ->offline_pd_fn(),
which are invoked as the policy_data gets activated and deactivated
while holding both blkcg and q locks.

Also, add blkcg_gq->online bool, which is set and cleared as the
blkcg_gq gets activated and deactivated.  This flag also is toggled
while holding both blkcg and q locks.

These will be used to implement hierarchical stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3a8de32..4d625d2 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -182,7 +182,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
                                    struct blkcg_gq *new_blkg)
 {
        struct blkcg_gq *blkg;
-       int ret;
+       int i, ret;
 
        WARN_ON_ONCE(!rcu_read_lock_held());
        lockdep_assert_held(q->queue_lock);
@@ -218,7 +218,15 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
        if (likely(!ret)) {
                hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
                list_add(&blkg->q_node, &q->blkg_list);
+
+               for (i = 0; i < BLKCG_MAX_POLS; i++) {
+                       struct blkcg_policy *pol = blkcg_policy[i];
+
+                       if (blkg->pd[i] && pol->pd_online_fn)
+                               pol->pd_online_fn(blkg);
+               }
        }
+       blkg->online = true;
        spin_unlock(&blkcg->lock);
 
        if (!ret)
@@ -291,6 +299,7 @@ EXPORT_SYMBOL_GPL(blkg_lookup_create);
 static void blkg_destroy(struct blkcg_gq *blkg)
 {
        struct blkcg *blkcg = blkg->blkcg;
+       int i;
 
        lockdep_assert_held(blkg->q->queue_lock);
        lockdep_assert_held(&blkcg->lock);
@@ -299,6 +308,14 @@ static void blkg_destroy(struct blkcg_gq *blkg)
        WARN_ON_ONCE(list_empty(&blkg->q_node));
        WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
 
+       for (i = 0; i < BLKCG_MAX_POLS; i++) {
+               struct blkcg_policy *pol = blkcg_policy[i];
+
+               if (blkg->pd[i] && pol->pd_offline_fn)
+                       pol->pd_offline_fn(blkg);
+       }
+       blkg->online = false;
+
        radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
        list_del_init(&blkg->q_node);
        hlist_del_init_rcu(&blkg->blkcg_node);
@@ -956,6 +973,8 @@ void blkcg_deactivate_policy(struct request_queue *q,
                /* grab blkcg lock too while removing @pd from @blkg */
                spin_lock(&blkg->blkcg->lock);
 
+               if (pol->pd_offline_fn)
+                       pol->pd_offline_fn(blkg);
                if (pol->pd_exit_fn)
                        pol->pd_exit_fn(blkg);
 

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 40f5b97..678e89e 100644 (file)
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -106,12 +106,17 @@ struct blkcg_gq {
        /* reference count */
        int                             refcnt;
 
+       /* is this blkg online? protected by both blkcg and q locks */
+       bool                            online;
+
        struct blkg_policy_data         *pd[BLKCG_MAX_POLS];
 
        struct rcu_head                 rcu_head;
 };
 
 typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);
 typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
 typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
 
@@ -124,6 +129,8 @@ struct blkcg_policy {
 
        /* operations */
        blkcg_pol_init_pd_fn            *pd_init_fn;
+       blkcg_pol_online_pd_fn          *pd_online_fn;
+       blkcg_pol_offline_pd_fn         *pd_offline_fn;
        blkcg_pol_exit_pd_fn            *pd_exit_fn;
        blkcg_pol_reset_pd_stats_fn     *pd_reset_stats_fn;
 };