1 files changed, 169 insertions, 63 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ab7a9e6a9b1c..7c52d6888924 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -300,7 +300,9 @@ struct cfq_data {
 
         /* List of cfq groups being managed on this device*/
         struct hlist_head cfqg_list;
-        struct rcu_head rcu;
+
+        /* Number of groups which are on blkcg->blkg_list */
+        unsigned int nr_blkcg_linked_grps;
 };
 
 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
@@ -665,15 +667,11 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2,
         if (rq2 == NULL)
                 return rq1;
 
-        if (rq_is_sync(rq1) && !rq_is_sync(rq2))
-                return rq1;
-        else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
-                return rq2;
-        if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
-                return rq1;
-        else if ((rq2->cmd_flags & REQ_META) &&
-                 !(rq1->cmd_flags & REQ_META))
-                return rq2;
+        if (rq_is_sync(rq1) != rq_is_sync(rq2))
+                return rq_is_sync(rq1) ? rq1 : rq2;
+
+        if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_META)
+                return rq1->cmd_flags & REQ_META ? rq1 : rq2;
 
         s1 = blk_rq_pos(rq1);
         s2 = blk_rq_pos(rq2);
@@ -1014,28 +1012,47 @@ void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
         cfqg->needs_update = true;
 }
 
-static struct cfq_group * cfq_find_alloc_cfqg(struct cfq_data *cfqd,
-                struct blkio_cgroup *blkcg, int create)
+static void cfq_init_add_cfqg_lists(struct cfq_data *cfqd,
+                        struct cfq_group *cfqg, struct blkio_cgroup *blkcg)
 {
-        struct cfq_group *cfqg = NULL;
-        void *key = cfqd;
-        int i, j;
-        struct cfq_rb_root *st;
         struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
         unsigned int major, minor;
 
-        cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
-        if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
+        /*
+         * Add group onto cgroup list. It might happen that bdi->dev is
+         * not initialized yet. Initialize this new group without major
+         * and minor info and this info will be filled in once a new thread
+         * comes for IO.
+         */
+        if (bdi->dev) {
                 sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-                cfqg->blkg.dev = MKDEV(major, minor);
-                goto done;
-        }
-        if (cfqg || !create)
-                goto done;
+                cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
+                                        (void *)cfqd, MKDEV(major, minor));
+        } else
+                cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg,
+                                        (void *)cfqd, 0);
+
+        cfqd->nr_blkcg_linked_grps++;
+        cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
+
+        /* Add group on cfqd list */
+        hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
+}
+
+/*
+ * Should be called from sleepable context. No request queue lock as per
+ * cpu stats are allocated dynamically and alloc_percpu needs to be called
+ * from sleepable context.
+ */
+static struct cfq_group * cfq_alloc_cfqg(struct cfq_data *cfqd)
+{
+        struct cfq_group *cfqg = NULL;
+        int i, j, ret;
+        struct cfq_rb_root *st;
 
         cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
         if (!cfqg)
-                goto done;
+                return NULL;
 
         for_each_cfqg_st(cfqg, i, j, st)
                 *st = CFQ_RB_ROOT;
@@ -1049,43 +1066,94 @@ static struct cfq_group * cfq_find_alloc_cfqg(struct cfq_data *cfqd,
          */
         cfqg->ref = 1;
 
+        ret = blkio_alloc_blkg_stats(&cfqg->blkg);
+        if (ret) {
+                kfree(cfqg);
+                return NULL;
+        }
+
+        return cfqg;
+}
+
+static struct cfq_group *
+cfq_find_cfqg(struct cfq_data *cfqd, struct blkio_cgroup *blkcg)
+{
+        struct cfq_group *cfqg = NULL;
+        void *key = cfqd;
+        struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
+        unsigned int major, minor;
+
         /*
-         * Add group onto cgroup list. It might happen that bdi->dev is
-         * not initialized yet. Initialize this new group without major
-         * and minor info and this info will be filled in once a new thread
-         * comes for IO. See code above.
+         * This is the common case when there are no blkio cgroups.
+         * Avoid lookup in this case
          */
-        if (bdi->dev) {
-                sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
-                cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
-                                        MKDEV(major, minor));
-        } else
-                cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
-                                        0);
-
-        cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
+        if (blkcg == &blkio_root_cgroup)
+                cfqg = &cfqd->root_group;
+        else
+                cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
 
-        /* Add group on cfqd list */
-        hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
+        if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
+                sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+                cfqg->blkg.dev = MKDEV(major, minor);
+        }
 
-done:
         return cfqg;
 }
 
 /*
- * Search for the cfq group current task belongs to. If create = 1, then also
- * create the cfq group if it does not exist. request_queue lock must be held.
+ * Search for the cfq group current task belongs to. request_queue lock must
+ * be held.
  */
-static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
 {
         struct blkio_cgroup *blkcg;
-        struct cfq_group *cfqg = NULL;
+        struct cfq_group *cfqg = NULL, *__cfqg = NULL;
+        struct request_queue *q = cfqd->queue;
 
         rcu_read_lock();
         blkcg = task_blkio_cgroup(current);
-        cfqg = cfq_find_alloc_cfqg(cfqd, blkcg, create);
-        if (!cfqg && create)
+        cfqg = cfq_find_cfqg(cfqd, blkcg);
+        if (cfqg) {
+                rcu_read_unlock();
+                return cfqg;
+        }
+
+        /*
+         * Need to allocate a group. Allocation of group also needs allocation
+         * of per cpu stats which in-turn takes a mutex() and can block. Hence
+         * we need to drop rcu lock and queue_lock before we call alloc.
+         *
+         * Not taking any queue reference here and assuming that queue is
+         * around by the time we return. CFQ queue allocation code does
+         * the same. It might be racy though.
+         */
+
+        rcu_read_unlock();
+        spin_unlock_irq(q->queue_lock);
+
+        cfqg = cfq_alloc_cfqg(cfqd);
+
+        spin_lock_irq(q->queue_lock);
+
+        rcu_read_lock();
+        blkcg = task_blkio_cgroup(current);
+
+        /*
+         * If some other thread already allocated the group while we were
+         * not holding queue lock, free up the group
+         */
+        __cfqg = cfq_find_cfqg(cfqd, blkcg);
+
+        if (__cfqg) {
+                kfree(cfqg);
+                rcu_read_unlock();
+                return __cfqg;
+        }
+
+        if (!cfqg)
                 cfqg = &cfqd->root_group;
+
+        cfq_init_add_cfqg_lists(cfqd, cfqg, blkcg);
         rcu_read_unlock();
         return cfqg;
 }
@@ -1118,6 +1186,7 @@ static void cfq_put_cfqg(struct cfq_group *cfqg)
                 return;
         for_each_cfqg_st(cfqg, i, j, st)
                 BUG_ON(!RB_EMPTY_ROOT(&st->rb));
+        free_percpu(cfqg->blkg.stats_cpu);
         kfree(cfqg);
 }
 
@@ -1176,7 +1245,7 @@ void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
 }
 
 #else /* GROUP_IOSCHED */
-static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
+static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd)
 {
         return &cfqd->root_group;
 }
@@ -1210,7 +1279,6 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         struct cfq_rb_root *service_tree;
         int left;
         int new_cfqq = 1;
-        int group_changed = 0;
 
         service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
                                                 cfqq_type(cfqq));
@@ -1281,7 +1349,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         rb_link_node(&cfqq->rb_node, parent, p);
         rb_insert_color(&cfqq->rb_node, &service_tree->rb);
         service_tree->count++;
-        if ((add_front || !new_cfqq) && !group_changed)
+        if (add_front || !new_cfqq)
                 return;
         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
 }
@@ -2029,7 +2097,7 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 
         WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
 
-        return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
+        return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
 }
 
 /*
@@ -2911,7 +2979,7 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
         struct cfq_group *cfqg;
 
 retry:
-        cfqg = cfq_get_cfqg(cfqd, 1);
+        cfqg = cfq_get_cfqg(cfqd);
         cic = cfq_cic_lookup(cfqd, ioc);
         /* cic always exists here */
         cfqq = cic_to_cfqq(cic, is_sync);
@@ -3815,15 +3883,11 @@ static void cfq_put_async_queues(struct cfq_data *cfqd)
                 cfq_put_queue(cfqd->async_idle_cfqq);
 }
 
-static void cfq_cfqd_free(struct rcu_head *head)
-{
-        kfree(container_of(head, struct cfq_data, rcu));
-}
-
 static void cfq_exit_queue(struct elevator_queue *e)
 {
         struct cfq_data *cfqd = e->elevator_data;
         struct request_queue *q = cfqd->queue;
+        bool wait = false;
 
         cfq_shutdown_timer_wq(cfqd);
 
@@ -3842,7 +3906,13 @@ static void cfq_exit_queue(struct elevator_queue *e)
 
         cfq_put_async_queues(cfqd);
         cfq_release_cfq_groups(cfqd);
-        cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
+
+        /*
+         * If there are groups which we could not unlink from blkcg list,
+         * wait for a rcu period for them to be freed.
+         */
+        if (cfqd->nr_blkcg_linked_grps)
+                wait = true;
 
         spin_unlock_irq(q->queue_lock);
 
@@ -3852,8 +3922,25 @@ static void cfq_exit_queue(struct elevator_queue *e)
         ida_remove(&cic_index_ida, cfqd->cic_index);
         spin_unlock(&cic_index_lock);
 
-        /* Wait for cfqg->blkg->key accessors to exit their grace periods. */
-        call_rcu(&cfqd->rcu, cfq_cfqd_free);
+        /*
+         * Wait for cfqg->blkg->key accessors to exit their grace periods.
+         * Do this wait only if there are other unlinked groups out
+         * there. This can happen if cgroup deletion path claimed the
+         * responsibility of cleaning up a group before queue cleanup code
+         * get to the group.
+         *
+         * Do not call synchronize_rcu() unconditionally as there are drivers
+         * which create/delete request queue hundreds of times during scan/boot
+         * and synchronize_rcu() can take significant time and slow down boot.
+         */
+        if (wait)
+                synchronize_rcu();
+
+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+        /* Free up per cpu stats for root group */
+        free_percpu(cfqd->root_group.blkg.stats_cpu);
+#endif
+        kfree(cfqd);
 }
 
 static int cfq_alloc_cic_index(void)
@@ -3886,8 +3973,12 @@ static void *cfq_init_queue(struct request_queue *q)
                 return NULL;
 
         cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
-        if (!cfqd)
+        if (!cfqd) {
+                spin_lock(&cic_index_lock);
+                ida_remove(&cic_index_ida, i);
+                spin_unlock(&cic_index_lock);
                 return NULL;
+        }
 
         /*
          * Don't need take queue_lock in the routine, since we are
@@ -3909,14 +4000,29 @@ static void *cfq_init_queue(struct request_queue *q)
 
 #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
+         * Set root group reference to 2. One reference will be dropped when
+         * all groups on cfqd->cfqg_list are being deleted during queue exit.
+         * Other reference will remain there as we don't want to delete this
+         * group as it is statically allocated and gets destroyed when
+         * throtl_data goes away.
          */
-        cfqg->ref = 1;
+        cfqg->ref = 2;
+
+        if (blkio_alloc_blkg_stats(&cfqg->blkg)) {
+                kfree(cfqg);
+                kfree(cfqd);
+                return NULL;
+        }
+
         rcu_read_lock();
+
         cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
                                         (void *)cfqd, 0);
         rcu_read_unlock();
+        cfqd->nr_blkcg_linked_grps++;
+
+        /* Add group on cfqd->cfqg_list */
+        hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
 #endif
         /*
          * Not strictly needed (since RB_ROOT just clears the node and we