blkio: Take care of cgroup deletion and cfq group reference counting

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / block / cfq-iosched.c

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index a877eeee80af7e82a09e3c3d0c1d75220b2b0f44..8bc31a50a57f77ec274d4ff78fc443f0977ba225 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -192,6 +192,7 @@ struct cfq_group {
        struct blkio_group blkg;
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
        struct hlist_node cfqd_node;
+       atomic_t ref;
 #endif
 };
 
@@ -924,6 +925,14 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
                *st = CFQ_RB_ROOT;
        RB_CLEAR_NODE(&cfqg->rb_node);
 
+       /*
+        * Take the initial reference that will be released on destroy
+        * This can be thought of a joint reference by cgroup and
+        * elevator which will be dropped by either elevator exit
+        * or cgroup deletion path depending on who is exiting first.
+        */
+       atomic_set(&cfqg->ref, 1);
+
        /* Add group onto cgroup list */
        blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd);
 
@@ -960,7 +969,77 @@ static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
                cfqg = &cfqq->cfqd->root_group;
 
        cfqq->cfqg = cfqg;
+       /* cfqq reference on cfqg */
+       atomic_inc(&cfqq->cfqg->ref);
+}
+
+static void cfq_put_cfqg(struct cfq_group *cfqg)
+{
+       struct cfq_rb_root *st;
+       int i, j;
+
+       BUG_ON(atomic_read(&cfqg->ref) <= 0);
+       if (!atomic_dec_and_test(&cfqg->ref))
+               return;
+       for_each_cfqg_st(cfqg, i, j, st)
+               BUG_ON(!RB_EMPTY_ROOT(&st->rb) || st->active != NULL);
+       kfree(cfqg);
+}
+
+static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
+{
+       /* Something wrong if we are trying to remove same group twice */
+       BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
+
+       hlist_del_init(&cfqg->cfqd_node);
+
+       /*
+        * Put the reference taken at the time of creation so that when all
+        * queues are gone, group can be destroyed.
+        */
+       cfq_put_cfqg(cfqg);
+}
+
+static void cfq_release_cfq_groups(struct cfq_data *cfqd)
+{
+       struct hlist_node *pos, *n;
+       struct cfq_group *cfqg;
+
+       hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
+               /*
+                * 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(&cfqg->blkg))
+                       cfq_destroy_cfqg(cfqd, cfqg);
+       }
 }
+
+/*
+ * 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 "key" is a valid cfq_data pointer as long as we are rcu
+ * read lock.
+ *
+ * "key" 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.
+ */
+void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
+{
+       unsigned long  flags;
+       struct cfq_data *cfqd = key;
+
+       spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+       cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
+       spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+}
+
 #else /* GROUP_IOSCHED */
 static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
 {
@@ -971,6 +1050,9 @@ 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) {}
+static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
+
 #endif /* GROUP_IOSCHED */
 
 /*
@@ -2172,11 +2254,13 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
  * task holds one reference to the queue, dropped when task exits. each rq
  * in-flight on this queue also holds a reference, dropped when rq is freed.
  *
+ * Each cfq queue took a reference on the parent group. Drop it now.
  * queue lock must be held here.
  */
 static void cfq_put_queue(struct cfq_queue *cfqq)
 {
        struct cfq_data *cfqd = cfqq->cfqd;
+       struct cfq_group *cfqg;
 
        BUG_ON(atomic_read(&cfqq->ref) <= 0);
 
@@ -2186,6 +2270,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
        cfq_log_cfqq(cfqd, cfqq, "put_queue");
        BUG_ON(rb_first(&cfqq->sort_list));
        BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
+       cfqg = cfqq->cfqg;
 
        if (unlikely(cfqd->active_queue == cfqq)) {
                __cfq_slice_expired(cfqd, cfqq, 0);
@@ -2194,6 +2279,7 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
 
        BUG_ON(cfq_cfqq_on_rr(cfqq));
        kmem_cache_free(cfq_pool, cfqq);
+       cfq_put_cfqg(cfqg);
 }
 
 /*
@@ -3369,11 +3455,15 @@ static void cfq_exit_queue(struct elevator_queue *e)
        }
 
        cfq_put_async_queues(cfqd);
+       cfq_release_cfq_groups(cfqd);
+       blkiocg_del_blkio_group(&cfqd->root_group.blkg);
 
        spin_unlock_irq(q->queue_lock);
 
        cfq_shutdown_timer_wq(cfqd);
 
+       /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
+       synchronize_rcu();
        kfree(cfqd);
 }
 
@@ -3401,6 +3491,11 @@ static void *cfq_init_queue(struct request_queue *q)
        cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
+       /*
+        * Take a reference to root group which we never drop. This is just
+        * to make sure that cfq_put_cfqg() does not try to kfree root group
+        */
+       atomic_set(&cfqg->ref, 1);
        blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd);
 #endif
        /*