blkcg: move blkio_group_stats_cpu and friends to blk-throttle.c

blkio_group_stats_cpu is used only by blk-throtl and has no reason to
be defined in blkcg core.

* Move blkio_group_stats_cpu to blk-throttle.c and rename it to
  tg_stats_cpu.

* blkg_policy_data->stats_cpu is replaced with throtl_grp->stats_cpu.
  prfill functions updated accordingly.

* All related macros / functions are renamed so that they have tg_
  prefix and the unnecessary @pol arguments are dropped.

* Per-cpu stats allocation code is also moved from blk-cgroup.c to
  blk-throttle.c and gets simplified to only deal with
  BLKIO_POLICY_THROTL.  percpu stat free is performed by the exit
  method throtl_exit_blkio_group().

* throtl_reset_group_stats() implemented for
  blkio_reset_group_stats_fn method so that tg->stats_cpu can be
  reset.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 1 insertions, 97 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index cfdda44f4a0b..16f6ee65a593 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,13 +30,6 @@ static LIST_HEAD(blkio_list);
 static DEFINE_MUTEX(all_q_mutex);
 static LIST_HEAD(all_q_list);
 
-/* List of groups pending per cpu stats allocation */
-static DEFINE_SPINLOCK(alloc_list_lock);
-static LIST_HEAD(alloc_list);
-
-static void blkio_stat_alloc_fn(struct work_struct *);
-static DECLARE_DELAYED_WORK(blkio_stat_alloc_work, blkio_stat_alloc_fn);
-
 struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
 EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
@@ -63,60 +56,6 @@ struct blkio_cgroup *bio_blkio_cgroup(struct bio *bio)
 }
 EXPORT_SYMBOL_GPL(bio_blkio_cgroup);
 
-/*
- * Worker for allocating per cpu stat for blk groups. This is scheduled on
- * the system_nrt_wq once there are some groups on the alloc_list waiting
- * for allocation.
- */
-static void blkio_stat_alloc_fn(struct work_struct *work)
-{
-        static void *pcpu_stats[BLKIO_NR_POLICIES];
-        struct delayed_work *dwork = to_delayed_work(work);
-        struct blkio_group *blkg;
-        int i;
-        bool empty = false;
-
-alloc_stats:
-        for (i = 0; i < BLKIO_NR_POLICIES; i++) {
-                if (pcpu_stats[i] != NULL)
-                        continue;
-
-                pcpu_stats[i] = alloc_percpu(struct blkio_group_stats_cpu);
-
-                /* Allocation failed. Try again after some time. */
-                if (pcpu_stats[i] == NULL) {
-                        queue_delayed_work(system_nrt_wq, dwork,
-                                                msecs_to_jiffies(10));
-                        return;
-                }
-        }
-
-        spin_lock_irq(&blkio_list_lock);
-        spin_lock(&alloc_list_lock);
-
-        /* cgroup got deleted or queue exited. */
-        if (!list_empty(&alloc_list)) {
-                blkg = list_first_entry(&alloc_list, struct blkio_group,
-                                                alloc_node);
-                for (i = 0; i < BLKIO_NR_POLICIES; i++) {
-                        struct blkg_policy_data *pd = blkg->pd[i];
-
-                        if (blkio_policy[i] && pd && !pd->stats_cpu)
-                                swap(pd->stats_cpu, pcpu_stats[i]);
-                }
-
-                list_del_init(&blkg->alloc_node);
-        }
-
-        empty = list_empty(&alloc_list);
-
-        spin_unlock(&alloc_list_lock);
-        spin_unlock_irq(&blkio_list_lock);
-
-        if (!empty)
-                goto alloc_stats;
-}
-
 /**
  * blkg_free - free a blkg
  * @blkg: blkg to free
@@ -140,7 +79,6 @@ static void blkg_free(struct blkio_group *blkg)
                 if (pol && pol->ops.blkio_exit_group_fn)
                         pol->ops.blkio_exit_group_fn(blkg);
 
-                free_percpu(pd->stats_cpu);
                 kfree(pd);
         }
 
@@ -167,7 +105,6 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
 
         blkg->q = q;
         INIT_LIST_HEAD(&blkg->q_node);
-        INIT_LIST_HEAD(&blkg->alloc_node);
         blkg->blkcg = blkcg;
         blkg->refcnt = 1;
         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
@@ -245,12 +182,6 @@ struct blkio_group *blkg_lookup_create(struct blkio_cgroup *blkcg,
         hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
         list_add(&blkg->q_node, &q->blkg_list);
         spin_unlock(&blkcg->lock);
-
-        spin_lock(&alloc_list_lock);
-        list_add(&blkg->alloc_node, &alloc_list);
-        /* Queue per cpu stat allocation from worker thread. */
-        queue_delayed_work(system_nrt_wq, &blkio_stat_alloc_work, 0);
-        spin_unlock(&alloc_list_lock);
 out:
         return blkg;
 }
@@ -284,10 +215,6 @@ static void blkg_destroy(struct blkio_group *blkg)
         list_del_init(&blkg->q_node);
         hlist_del_init_rcu(&blkg->blkcg_node);
 
-        spin_lock(&alloc_list_lock);
-        list_del_init(&blkg->alloc_node);
-        spin_unlock(&alloc_list_lock);
-
         /*
          * Put the reference taken at the time of creation so that when all
          * queues are gone, group can be destroyed.
@@ -319,9 +246,6 @@ void update_root_blkg_pd(struct request_queue *q, enum blkio_policy_id plid)
         pd = kzalloc(sizeof(*pd) + pol->pdata_size, GFP_KERNEL);
         WARN_ON_ONCE(!pd);
 
-        pd->stats_cpu = alloc_percpu(struct blkio_group_stats_cpu);
-        WARN_ON_ONCE(!pd->stats_cpu);
-
         blkg->pd[plid] = pd;
         pd->blkg = blkg;
         pol->ops.blkio_init_group_fn(blkg);
@@ -381,23 +305,6 @@ void __blkg_release(struct blkio_group *blkg)
 }
 EXPORT_SYMBOL_GPL(__blkg_release);
 
-static void blkio_reset_stats_cpu(struct blkio_group *blkg, int plid)
-{
-        struct blkg_policy_data *pd = blkg->pd[plid];
-        int cpu;
-
-        if (pd->stats_cpu == NULL)
-                return;
-
-        for_each_possible_cpu(cpu) {
-                struct blkio_group_stats_cpu *sc =
-                        per_cpu_ptr(pd->stats_cpu, cpu);
-
-                blkg_rwstat_reset(&sc->service_bytes);
-                blkg_rwstat_reset(&sc->serviced);
-        }
-}
-
 static int
 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 {
@@ -416,12 +323,9 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
                 struct blkio_policy_type *pol;
 
-                list_for_each_entry(pol, &blkio_list, list) {
-                        blkio_reset_stats_cpu(blkg, pol->plid);
-
+                list_for_each_entry(pol, &blkio_list, list)
                         if (pol->ops.blkio_reset_group_stats_fn)
                                 pol->ops.blkio_reset_group_stats_fn(blkg);
-                }
         }
 
         spin_unlock_irq(&blkcg->lock);