1 files changed, 511 insertions, 118 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ec52807cdd09..4f0ade74cfd0 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -85,7 +85,6 @@ struct cfq_rb_root {
         struct rb_root rb;
         struct rb_node *left;
         unsigned count;
-        unsigned total_weight;
         u64 min_vdisktime;
         struct cfq_ttime ttime;
 };
@@ -155,7 +154,7 @@ struct cfq_queue {
  * First index in the service_trees.
  * IDLE is handled separately, so it has negative index
  */
-enum wl_prio_t {
+enum wl_class_t {
         BE_WORKLOAD = 0,
         RT_WORKLOAD = 1,
         IDLE_WORKLOAD = 2,
@@ -223,10 +222,45 @@ struct cfq_group {
 
         /* group service_tree key */
         u64 vdisktime;
+
+        /*
+         * The number of active cfqgs and sum of their weights under this
+         * cfqg.  This covers this cfqg's leaf_weight and all children's
+         * weights, but does not cover weights of further descendants.
+         *
+         * If a cfqg is on the service tree, it's active.  An active cfqg
+         * also activates its parent and contributes to the children_weight
+         * of the parent.
+         */
+        int nr_active;
+        unsigned int children_weight;
+
+        /*
+         * vfraction is the fraction of vdisktime that the tasks in this
+         * cfqg are entitled to.  This is determined by compounding the
+         * ratios walking up from this cfqg to the root.
+         *
+         * It is in fixed point w/ CFQ_SERVICE_SHIFT and the sum of all
+         * vfractions on a service tree is approximately 1.  The sum may
+         * deviate a bit due to rounding errors and fluctuations caused by
+         * cfqgs entering and leaving the service tree.
+         */
+        unsigned int vfraction;
+
+        /*
+         * There are two weights - (internal) weight is the weight of this
+         * cfqg against the sibling cfqgs.  leaf_weight is the wight of
+         * this cfqg against the child cfqgs.  For the root cfqg, both
+         * weights are kept in sync for backward compatibility.
+         */
         unsigned int weight;
         unsigned int new_weight;
         unsigned int dev_weight;
 
+        unsigned int leaf_weight;
+        unsigned int new_leaf_weight;
+        unsigned int dev_leaf_weight;
+
         /* number of cfqq currently on this group */
         int nr_cfqq;
 
@@ -248,14 +282,15 @@ struct cfq_group {
         struct cfq_rb_root service_trees[2][3];
         struct cfq_rb_root service_tree_idle;
 
-        unsigned long saved_workload_slice;
-        enum wl_type_t saved_workload;
-        enum wl_prio_t saved_serving_prio;
+        unsigned long saved_wl_slice;
+        enum wl_type_t saved_wl_type;
+        enum wl_class_t saved_wl_class;
 
         /* number of requests that are on the dispatch list or inside driver */
         int dispatched;
         struct cfq_ttime ttime;
-        struct cfqg_stats stats;
+        struct cfqg_stats stats;        /* stats for this cfqg */
+        struct cfqg_stats dead_stats;   /* stats pushed from dead children */
 };
 
 struct cfq_io_cq {
@@ -280,8 +315,8 @@ struct cfq_data {
         /*
          * The priority currently being served
          */
-        enum wl_prio_t serving_prio;
-        enum wl_type_t serving_type;
+        enum wl_class_t serving_wl_class;
+        enum wl_type_t serving_wl_type;
         unsigned long workload_expires;
         struct cfq_group *serving_group;
 
@@ -353,17 +388,17 @@ struct cfq_data {
 
 static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
 
-static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
-                                            enum wl_prio_t prio,
+static struct cfq_rb_root *st_for(struct cfq_group *cfqg,
+                                            enum wl_class_t class,
                                             enum wl_type_t type)
 {
         if (!cfqg)
                 return NULL;
 
-        if (prio == IDLE_WORKLOAD)
+        if (class == IDLE_WORKLOAD)
                 return &cfqg->service_tree_idle;
 
-        return &cfqg->service_trees[prio][type];
+        return &cfqg->service_trees[class][type];
 }
 
 enum cfqq_state_flags {
@@ -502,7 +537,7 @@ static void cfqg_stats_set_start_empty_time(struct cfq_group *cfqg)
 {
         struct cfqg_stats *stats = &cfqg->stats;
 
-        if (blkg_rwstat_sum(&stats->queued))
+        if (blkg_rwstat_total(&stats->queued))
                 return;
 
         /*
@@ -546,7 +581,7 @@ static void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg)
         struct cfqg_stats *stats = &cfqg->stats;
 
         blkg_stat_add(&stats->avg_queue_size_sum,
-                      blkg_rwstat_sum(&stats->queued));
+                      blkg_rwstat_total(&stats->queued));
         blkg_stat_add(&stats->avg_queue_size_samples, 1);
         cfqg_stats_update_group_wait_time(stats);
 }
@@ -572,6 +607,13 @@ static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)
         return pd_to_cfqg(blkg_to_pd(blkg, &blkcg_policy_cfq));
 }
 
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg)
+{
+        struct blkcg_gq *pblkg = cfqg_to_blkg(cfqg)->parent;
+
+        return pblkg ? blkg_to_cfqg(pblkg) : NULL;
+}
+
 static inline void cfqg_get(struct cfq_group *cfqg)
 {
         return blkg_get(cfqg_to_blkg(cfqg));
@@ -586,8 +628,9 @@ static inline void cfqg_put(struct cfq_group *cfqg)
         char __pbuf[128];                                               \
                                                                         \
         blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));  \
-        blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
-                          cfq_cfqq_sync((cfqq)) ? 'S' : 'A',            \
+        blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
+                        cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
+                        cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
                           __pbuf, ##args);                              \
 } while (0)
 
@@ -646,11 +689,9 @@ static inline void cfqg_stats_update_completion(struct cfq_group *cfqg,
                                 io_start_time - start_time);
 }
 
-static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
+/* @stats = 0 */
+static void cfqg_stats_reset(struct cfqg_stats *stats)
 {
-        struct cfq_group *cfqg = blkg_to_cfqg(blkg);
-        struct cfqg_stats *stats = &cfqg->stats;
-
         /* queued stats shouldn't be cleared */
         blkg_rwstat_reset(&stats->service_bytes);
         blkg_rwstat_reset(&stats->serviced);
@@ -669,13 +710,58 @@ static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
 #endif
 }
 
+/* @to += @from */
+static void cfqg_stats_merge(struct cfqg_stats *to, struct cfqg_stats *from)
+{
+        /* queued stats shouldn't be cleared */
+        blkg_rwstat_merge(&to->service_bytes, &from->service_bytes);
+        blkg_rwstat_merge(&to->serviced, &from->serviced);
+        blkg_rwstat_merge(&to->merged, &from->merged);
+        blkg_rwstat_merge(&to->service_time, &from->service_time);
+        blkg_rwstat_merge(&to->wait_time, &from->wait_time);
+        blkg_stat_merge(&from->time, &from->time);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+        blkg_stat_merge(&to->unaccounted_time, &from->unaccounted_time);
+        blkg_stat_merge(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
+        blkg_stat_merge(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
+        blkg_stat_merge(&to->dequeue, &from->dequeue);
+        blkg_stat_merge(&to->group_wait_time, &from->group_wait_time);
+        blkg_stat_merge(&to->idle_time, &from->idle_time);
+        blkg_stat_merge(&to->empty_time, &from->empty_time);
+#endif
+}
+
+/*
+ * Transfer @cfqg's stats to its parent's dead_stats so that the ancestors'
+ * recursive stats can still account for the amount used by this cfqg after
+ * it's gone.
+ */
+static void cfqg_stats_xfer_dead(struct cfq_group *cfqg)
+{
+        struct cfq_group *parent = cfqg_parent(cfqg);
+
+        lockdep_assert_held(cfqg_to_blkg(cfqg)->q->queue_lock);
+
+        if (unlikely(!parent))
+                return;
+
+        cfqg_stats_merge(&parent->dead_stats, &cfqg->stats);
+        cfqg_stats_merge(&parent->dead_stats, &cfqg->dead_stats);
+        cfqg_stats_reset(&cfqg->stats);
+        cfqg_stats_reset(&cfqg->dead_stats);
+}
+
 #else   /* CONFIG_CFQ_GROUP_IOSCHED */
 
+static inline struct cfq_group *cfqg_parent(struct cfq_group *cfqg) { return NULL; }
 static inline void cfqg_get(struct cfq_group *cfqg) { }
 static inline void cfqg_put(struct cfq_group *cfqg) { }
 
 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)  \
-        blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
+        blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
+                        cfq_cfqq_sync((cfqq)) ? 'S' : 'A',              \
+                        cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
+                                ##args)
 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)          do {} while (0)
 
 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,
@@ -732,7 +818,7 @@ static inline bool iops_mode(struct cfq_data *cfqd)
                 return false;
 }
 
-static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
+static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
 {
         if (cfq_class_idle(cfqq))
                 return IDLE_WORKLOAD;
@@ -751,23 +837,23 @@ static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
         return SYNC_WORKLOAD;
 }
 
-static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
+static inline int cfq_group_busy_queues_wl(enum wl_class_t wl_class,
                                         struct cfq_data *cfqd,
                                         struct cfq_group *cfqg)
 {
-        if (wl == IDLE_WORKLOAD)
+        if (wl_class == IDLE_WORKLOAD)
                 return cfqg->service_tree_idle.count;
 
-        return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
-                + cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
-                + cfqg->service_trees[wl][SYNC_WORKLOAD].count;
+        return cfqg->service_trees[wl_class][ASYNC_WORKLOAD].count +
+                cfqg->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
+                cfqg->service_trees[wl_class][SYNC_WORKLOAD].count;
 }
 
 static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
                                         struct cfq_group *cfqg)
 {
-        return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
-                + cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
+        return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
+                cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
 }
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
@@ -847,13 +933,27 @@ cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
 }
 
-static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
+/**
+ * cfqg_scale_charge - scale disk time charge according to cfqg weight
+ * @charge: disk time being charged
+ * @vfraction: vfraction of the cfqg, fixed point w/ CFQ_SERVICE_SHIFT
+ *
+ * Scale @charge according to @vfraction, which is in range (0, 1].  The
+ * scaling is inversely proportional.
+ *
+ * scaled = charge / vfraction
+ *
+ * The result is also in fixed point w/ CFQ_SERVICE_SHIFT.
+ */
+static inline u64 cfqg_scale_charge(unsigned long charge,
+                                    unsigned int vfraction)
 {
-        u64 d = delta << CFQ_SERVICE_SHIFT;
+        u64 c = charge << CFQ_SERVICE_SHIFT;    /* make it fixed point */
 
-        d = d * CFQ_WEIGHT_DEFAULT;
-        do_div(d, cfqg->weight);
-        return d;
+        /* charge / vfraction */
+        c <<= CFQ_SERVICE_SHIFT;
+        do_div(c, vfraction);
+        return c;
 }
 
 static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
@@ -909,9 +1009,7 @@ static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
 static inline unsigned
 cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
-        struct cfq_rb_root *st = &cfqd->grp_service_tree;
-
-        return cfqd->cfq_target_latency * cfqg->weight / st->total_weight;
+        return cfqd->cfq_target_latency * cfqg->vfraction >> CFQ_SERVICE_SHIFT;
 }
 
 static inline unsigned
@@ -1178,20 +1276,61 @@ static void
 cfq_update_group_weight(struct cfq_group *cfqg)
 {
         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+
         if (cfqg->new_weight) {
                 cfqg->weight = cfqg->new_weight;
                 cfqg->new_weight = 0;
         }
+
+        if (cfqg->new_leaf_weight) {
+                cfqg->leaf_weight = cfqg->new_leaf_weight;
+                cfqg->new_leaf_weight = 0;
+        }
 }
 
 static void
 cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
 {
+        unsigned int vfr = 1 << CFQ_SERVICE_SHIFT;      /* start with 1 */
+        struct cfq_group *pos = cfqg;
+        struct cfq_group *parent;
+        bool propagate;
+
+        /* add to the service tree */
         BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
 
         cfq_update_group_weight(cfqg);
         __cfq_group_service_tree_add(st, cfqg);
-        st->total_weight += cfqg->weight;
+
+        /*
+         * Activate @cfqg and calculate the portion of vfraction @cfqg is
+         * entitled to.  vfraction is calculated by walking the tree
+         * towards the root calculating the fraction it has at each level.
+         * The compounded ratio is how much vfraction @cfqg owns.
+         *
+         * Start with the proportion tasks in this cfqg has against active
+         * children cfqgs - its leaf_weight against children_weight.
+         */
+        propagate = !pos->nr_active++;
+        pos->children_weight += pos->leaf_weight;
+        vfr = vfr * pos->leaf_weight / pos->children_weight;
+
+        /*
+         * Compound ->weight walking up the tree.  Both activation and
+         * vfraction calculation are done in the same loop.  Propagation
+         * stops once an already activated node is met.  vfraction
+         * calculation should always continue to the root.
+         */
+        while ((parent = cfqg_parent(pos))) {
+                if (propagate) {
+                        propagate = !parent->nr_active++;
+                        parent->children_weight += pos->weight;
+                }
+                vfr = vfr * pos->weight / parent->children_weight;
+                pos = parent;
+        }
+
+        cfqg->vfraction = max_t(unsigned, vfr, 1);
 }
 
 static void
@@ -1222,7 +1361,32 @@ cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
 static void
 cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
 {
-        st->total_weight -= cfqg->weight;
+        struct cfq_group *pos = cfqg;
+        bool propagate;
+
+        /*
+         * Undo activation from cfq_group_service_tree_add().  Deactivate
+         * @cfqg and propagate deactivation upwards.
+         */
+        propagate = !--pos->nr_active;
+        pos->children_weight -= pos->leaf_weight;
+
+        while (propagate) {
+                struct cfq_group *parent = cfqg_parent(pos);
+
+                /* @pos has 0 nr_active at this point */
+                WARN_ON_ONCE(pos->children_weight);
+                pos->vfraction = 0;
+
+                if (!parent)
+                        break;
+
+                propagate = !--parent->nr_active;
+                parent->children_weight -= pos->weight;
+                pos = parent;
+        }
+
+        /* remove from the service tree */
         if (!RB_EMPTY_NODE(&cfqg->rb_node))
                 cfq_rb_erase(&cfqg->rb_node, st);
 }
@@ -1241,7 +1405,7 @@ cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
 
         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
         cfq_group_service_tree_del(st, cfqg);
-        cfqg->saved_workload_slice = 0;
+        cfqg->saved_wl_slice = 0;
         cfqg_stats_update_dequeue(cfqg);
 }
 
@@ -1284,6 +1448,7 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
         unsigned int used_sl, charge, unaccounted_sl = 0;
         int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
                         - cfqg->service_tree_idle.count;
+        unsigned int vfr;
 
         BUG_ON(nr_sync < 0);
         used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
@@ -1293,20 +1458,25 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
         else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
                 charge = cfqq->allocated_slice;
 
-        /* Can't update vdisktime while group is on service tree */
+        /*
+         * Can't update vdisktime while on service tree and cfqg->vfraction
+         * is valid only while on it.  Cache vfr, leave the service tree,
+         * update vdisktime and go back on.  The re-addition to the tree
+         * will also update the weights as necessary.
+         */
+        vfr = cfqg->vfraction;
         cfq_group_service_tree_del(st, cfqg);
-        cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
-        /* If a new weight was requested, update now, off tree */
+        cfqg->vdisktime += cfqg_scale_charge(charge, vfr);
         cfq_group_service_tree_add(st, cfqg);
 
         /* This group is being expired. Save the context */
         if (time_after(cfqd->workload_expires, jiffies)) {
-                cfqg->saved_workload_slice = cfqd->workload_expires
+                cfqg->saved_wl_slice = cfqd->workload_expires
                                                 - jiffies;
-                cfqg->saved_workload = cfqd->serving_type;
-                cfqg->saved_serving_prio = cfqd->serving_prio;
+                cfqg->saved_wl_type = cfqd->serving_wl_type;
+                cfqg->saved_wl_class = cfqd->serving_wl_class;
         } else
-                cfqg->saved_workload_slice = 0;
+                cfqg->saved_wl_slice = 0;
 
         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
                                         st->min_vdisktime);
@@ -1344,6 +1514,52 @@ static void cfq_pd_init(struct blkcg_gq *blkg)
 
         cfq_init_cfqg_base(cfqg);
         cfqg->weight = blkg->blkcg->cfq_weight;
+        cfqg->leaf_weight = blkg->blkcg->cfq_leaf_weight;
+}
+
+static void cfq_pd_offline(struct blkcg_gq *blkg)
+{
+        /*
+         * @blkg is going offline and will be ignored by
+         * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
+         * that they don't get lost.  If IOs complete after this point, the
+         * stats for them will be lost.  Oh well...
+         */
+        cfqg_stats_xfer_dead(blkg_to_cfqg(blkg));
+}
+
+/* offset delta from cfqg->stats to cfqg->dead_stats */
+static const int dead_stats_off_delta = offsetof(struct cfq_group, dead_stats) -
+                                        offsetof(struct cfq_group, stats);
+
+/* to be used by recursive prfill, sums live and dead stats recursively */
+static u64 cfqg_stat_pd_recursive_sum(struct blkg_policy_data *pd, int off)
+{
+        u64 sum = 0;
+
+        sum += blkg_stat_recursive_sum(pd, off);
+        sum += blkg_stat_recursive_sum(pd, off + dead_stats_off_delta);
+        return sum;
+}
+
+/* to be used by recursive prfill, sums live and dead rwstats recursively */
+static struct blkg_rwstat cfqg_rwstat_pd_recursive_sum(struct blkg_policy_data *pd,
+                                                       int off)
+{
+        struct blkg_rwstat a, b;
+
+        a = blkg_rwstat_recursive_sum(pd, off);
+        b = blkg_rwstat_recursive_sum(pd, off + dead_stats_off_delta);
+        blkg_rwstat_merge(&a, &b);
+        return a;
+}
+
+static void cfq_pd_reset_stats(struct blkcg_gq *blkg)
+{
+        struct cfq_group *cfqg = blkg_to_cfqg(blkg);
+
+        cfqg_stats_reset(&cfqg->stats);
+        cfqg_stats_reset(&cfqg->dead_stats);
 }
 
 /*
@@ -1400,6 +1616,26 @@ static int cfqg_print_weight_device(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
+static u64 cfqg_prfill_leaf_weight_device(struct seq_file *sf,
+                                          struct blkg_policy_data *pd, int off)
+{
+        struct cfq_group *cfqg = pd_to_cfqg(pd);
+
+        if (!cfqg->dev_leaf_weight)
+                return 0;
+        return __blkg_prfill_u64(sf, pd, cfqg->dev_leaf_weight);
+}
+
+static int cfqg_print_leaf_weight_device(struct cgroup *cgrp,
+                                         struct cftype *cft,
+                                         struct seq_file *sf)
+{
+        blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp),
+                          cfqg_prfill_leaf_weight_device, &blkcg_policy_cfq, 0,
+                          false);
+        return 0;
+}
+
 static int cfq_print_weight(struct cgroup *cgrp, struct cftype *cft,
                             struct seq_file *sf)
 {
@@ -1407,8 +1643,16 @@ static int cfq_print_weight(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
-static int cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
-                                  const char *buf)
+static int cfq_print_leaf_weight(struct cgroup *cgrp, struct cftype *cft,
+                                 struct seq_file *sf)
+{
+        seq_printf(sf, "%u\n",
+                   cgroup_to_blkcg(cgrp)->cfq_leaf_weight);
+        return 0;
+}
+
+static int __cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
+                                    const char *buf, bool is_leaf_weight)
 {
         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
         struct blkg_conf_ctx ctx;
@@ -1422,8 +1666,13 @@ static int cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
         ret = -EINVAL;
         cfqg = blkg_to_cfqg(ctx.blkg);
         if (!ctx.v || (ctx.v >= CFQ_WEIGHT_MIN && ctx.v <= CFQ_WEIGHT_MAX)) {
-                cfqg->dev_weight = ctx.v;
-                cfqg->new_weight = cfqg->dev_weight ?: blkcg->cfq_weight;
+                if (!is_leaf_weight) {
+                        cfqg->dev_weight = ctx.v;
+                        cfqg->new_weight = ctx.v ?: blkcg->cfq_weight;
+                } else {
+                        cfqg->dev_leaf_weight = ctx.v;
+                        cfqg->new_leaf_weight = ctx.v ?: blkcg->cfq_leaf_weight;
+                }
                 ret = 0;
         }
 
@@ -1431,7 +1680,20 @@ static int cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
         return ret;
 }
 
-static int cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
+static int cfqg_set_weight_device(struct cgroup *cgrp, struct cftype *cft,
+                                  const char *buf)
+{
+        return __cfqg_set_weight_device(cgrp, cft, buf, false);
+}
+
+static int cfqg_set_leaf_weight_device(struct cgroup *cgrp, struct cftype *cft,
+                                       const char *buf)
+{
+        return __cfqg_set_weight_device(cgrp, cft, buf, true);
+}
+
+static int __cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val,
+                            bool is_leaf_weight)
 {
         struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
         struct blkcg_gq *blkg;
@@ -1440,19 +1702,41 @@ static int cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
                 return -EINVAL;
 
         spin_lock_irq(&blkcg->lock);
-        blkcg->cfq_weight = (unsigned int)val;
+
+        if (!is_leaf_weight)
+                blkcg->cfq_weight = val;
+        else
+                blkcg->cfq_leaf_weight = val;
 
         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
                 struct cfq_group *cfqg = blkg_to_cfqg(blkg);
 
-                if (cfqg && !cfqg->dev_weight)
-                        cfqg->new_weight = blkcg->cfq_weight;
+                if (!cfqg)
+                        continue;
+
+                if (!is_leaf_weight) {
+                        if (!cfqg->dev_weight)
+                                cfqg->new_weight = blkcg->cfq_weight;
+                } else {
+                        if (!cfqg->dev_leaf_weight)
+                                cfqg->new_leaf_weight = blkcg->cfq_leaf_weight;
+                }
         }
 
         spin_unlock_irq(&blkcg->lock);
         return 0;
 }
 
+static int cfq_set_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+        return __cfq_set_weight(cgrp, cft, val, false);
+}
+
+static int cfq_set_leaf_weight(struct cgroup *cgrp, struct cftype *cft, u64 val)
+{
+        return __cfq_set_weight(cgrp, cft, val, true);
+}
+
 static int cfqg_print_stat(struct cgroup *cgrp, struct cftype *cft,
                            struct seq_file *sf)
 {
@@ -1473,6 +1757,42 @@ static int cfqg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
+static u64 cfqg_prfill_stat_recursive(struct seq_file *sf,
+                                      struct blkg_policy_data *pd, int off)
+{
+        u64 sum = cfqg_stat_pd_recursive_sum(pd, off);
+
+        return __blkg_prfill_u64(sf, pd, sum);
+}
+
+static u64 cfqg_prfill_rwstat_recursive(struct seq_file *sf,
+                                        struct blkg_policy_data *pd, int off)
+{
+        struct blkg_rwstat sum = cfqg_rwstat_pd_recursive_sum(pd, off);
+
+        return __blkg_prfill_rwstat(sf, pd, &sum);
+}
+
+static int cfqg_print_stat_recursive(struct cgroup *cgrp, struct cftype *cft,
+                                     struct seq_file *sf)
+{
+        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+        blkcg_print_blkgs(sf, blkcg, cfqg_prfill_stat_recursive,
+                          &blkcg_policy_cfq, cft->private, false);
+        return 0;
+}
+
+static int cfqg_print_rwstat_recursive(struct cgroup *cgrp, struct cftype *cft,
+                                       struct seq_file *sf)
+{
+        struct blkcg *blkcg = cgroup_to_blkcg(cgrp);
+
+        blkcg_print_blkgs(sf, blkcg, cfqg_prfill_rwstat_recursive,
+                          &blkcg_policy_cfq, cft->private, true);
+        return 0;
+}
+
 #ifdef CONFIG_DEBUG_BLK_CGROUP
 static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,
                                       struct blkg_policy_data *pd, int off)
@@ -1502,17 +1822,49 @@ static int cfqg_print_avg_queue_size(struct cgroup *cgrp, struct cftype *cft,
 #endif  /* CONFIG_DEBUG_BLK_CGROUP */
 
 static struct cftype cfq_blkcg_files[] = {
+        /* on root, weight is mapped to leaf_weight */
+        {
+                .name = "weight_device",
+                .flags = CFTYPE_ONLY_ON_ROOT,
+                .read_seq_string = cfqg_print_leaf_weight_device,
+                .write_string = cfqg_set_leaf_weight_device,
+                .max_write_len = 256,
+        },
+        {
+                .name = "weight",
+                .flags = CFTYPE_ONLY_ON_ROOT,
+                .read_seq_string = cfq_print_leaf_weight,
+                .write_u64 = cfq_set_leaf_weight,
+        },
+
+        /* no such mapping necessary for !roots */
         {
                 .name = "weight_device",
+                .flags = CFTYPE_NOT_ON_ROOT,
                 .read_seq_string = cfqg_print_weight_device,
                 .write_string = cfqg_set_weight_device,
                 .max_write_len = 256,
         },
         {
                 .name = "weight",
+                .flags = CFTYPE_NOT_ON_ROOT,
                 .read_seq_string = cfq_print_weight,
                 .write_u64 = cfq_set_weight,
         },
+
+        {
+                .name = "leaf_weight_device",
+                .read_seq_string = cfqg_print_leaf_weight_device,
+                .write_string = cfqg_set_leaf_weight_device,
+                .max_write_len = 256,
+        },
+        {
+                .name = "leaf_weight",
+                .read_seq_string = cfq_print_leaf_weight,
+                .write_u64 = cfq_set_leaf_weight,
+        },
+
+        /* statistics, covers only the tasks in the cfqg */
         {
                 .name = "time",
                 .private = offsetof(struct cfq_group, stats.time),
@@ -1553,6 +1905,48 @@ static struct cftype cfq_blkcg_files[] = {
                 .private = offsetof(struct cfq_group, stats.queued),
                 .read_seq_string = cfqg_print_rwstat,
         },
+
+        /* the same statictics which cover the cfqg and its descendants */
+        {
+                .name = "time_recursive",
+                .private = offsetof(struct cfq_group, stats.time),
+                .read_seq_string = cfqg_print_stat_recursive,
+        },
+        {
+                .name = "sectors_recursive",
+                .private = offsetof(struct cfq_group, stats.sectors),
+                .read_seq_string = cfqg_print_stat_recursive,
+        },
+        {
+                .name = "io_service_bytes_recursive",
+                .private = offsetof(struct cfq_group, stats.service_bytes),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
+        {
+                .name = "io_serviced_recursive",
+                .private = offsetof(struct cfq_group, stats.serviced),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
+        {
+                .name = "io_service_time_recursive",
+                .private = offsetof(struct cfq_group, stats.service_time),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
+        {
+                .name = "io_wait_time_recursive",
+                .private = offsetof(struct cfq_group, stats.wait_time),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
+        {
+                .name = "io_merged_recursive",
+                .private = offsetof(struct cfq_group, stats.merged),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
+        {
+                .name = "io_queued_recursive",
+                .private = offsetof(struct cfq_group, stats.queued),
+                .read_seq_string = cfqg_print_rwstat_recursive,
+        },
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         {
                 .name = "avg_queue_size",
@@ -1611,15 +2005,14 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         struct rb_node **p, *parent;
         struct cfq_queue *__cfqq;
         unsigned long rb_key;
-        struct cfq_rb_root *service_tree;
+        struct cfq_rb_root *st;
         int left;
         int new_cfqq = 1;
 
-        service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
-                                                cfqq_type(cfqq));
+        st = st_for(cfqq->cfqg, cfqq_class(cfqq), cfqq_type(cfqq));
         if (cfq_class_idle(cfqq)) {
                 rb_key = CFQ_IDLE_DELAY;
-                parent = rb_last(&service_tree->rb);
+                parent = rb_last(&st->rb);
                 if (parent && parent != &cfqq->rb_node) {
                         __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
                         rb_key += __cfqq->rb_key;
@@ -1637,7 +2030,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 cfqq->slice_resid = 0;
         } else {
                 rb_key = -HZ;
-                __cfqq = cfq_rb_first(service_tree);
+                __cfqq = cfq_rb_first(st);
                 rb_key += __cfqq ? __cfqq->rb_key : jiffies;
         }
 
@@ -1646,8 +2039,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 /*
                  * same position, nothing more to do
                  */
-                if (rb_key == cfqq->rb_key &&
-                    cfqq->service_tree == service_tree)
+                if (rb_key == cfqq->rb_key && cfqq->service_tree == st)
                         return;
 
                 cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
@@ -1656,11 +2048,9 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 
         left = 1;
         parent = NULL;
-        cfqq->service_tree = service_tree;
-        p = &service_tree->rb.rb_node;
+        cfqq->service_tree = st;
+        p = &st->rb.rb_node;
         while (*p) {
-                struct rb_node **n;
-
                 parent = *p;
                 __cfqq = rb_entry(parent, struct cfq_queue, rb_node);
 
@@ -1668,22 +2058,20 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                  * sort by key, that represents service time.
                  */
                 if (time_before(rb_key, __cfqq->rb_key))
-                        n = &(*p)->rb_left;
+                        p = &parent->rb_left;
                 else {
-                        n = &(*p)->rb_right;
+                        p = &parent->rb_right;
                         left = 0;
                 }
-
-                p = n;
         }
 
         if (left)
-                service_tree->left = &cfqq->rb_node;
+                st->left = &cfqq->rb_node;
 
         cfqq->rb_key = rb_key;
         rb_link_node(&cfqq->rb_node, parent, p);
-        rb_insert_color(&cfqq->rb_node, &service_tree->rb);
-        service_tree->count++;
+        rb_insert_color(&cfqq->rb_node, &st->rb);
+        st->count++;
         if (add_front || !new_cfqq)
                 return;
         cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
@@ -2029,8 +2417,8 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
                                    struct cfq_queue *cfqq)
 {
         if (cfqq) {
-                cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
-                                cfqd->serving_prio, cfqd->serving_type);
+                cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
+                                cfqd->serving_wl_class, cfqd->serving_wl_type);
                 cfqg_stats_update_avg_queue_size(cfqq->cfqg);
                 cfqq->slice_start = 0;
                 cfqq->dispatch_start = jiffies;
@@ -2116,19 +2504,18 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
  */
 static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
 {
-        struct cfq_rb_root *service_tree =
-                service_tree_for(cfqd->serving_group, cfqd->serving_prio,
-                                        cfqd->serving_type);
+        struct cfq_rb_root *st = st_for(cfqd->serving_group,
+                        cfqd->serving_wl_class, cfqd->serving_wl_type);
 
         if (!cfqd->rq_queued)
                 return NULL;
 
         /* There is nothing to dispatch */
-        if (!service_tree)
+        if (!st)
                 return NULL;
-        if (RB_EMPTY_ROOT(&service_tree->rb))
+        if (RB_EMPTY_ROOT(&st->rb))
                 return NULL;
-        return cfq_rb_first(service_tree);
+        return cfq_rb_first(st);
 }
 
 static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
@@ -2284,17 +2671,17 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
 
 static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
-        enum wl_prio_t prio = cfqq_prio(cfqq);
-        struct cfq_rb_root *service_tree = cfqq->service_tree;
+        enum wl_class_t wl_class = cfqq_class(cfqq);
+        struct cfq_rb_root *st = cfqq->service_tree;
 
-        BUG_ON(!service_tree);
-        BUG_ON(!service_tree->count);
+        BUG_ON(!st);
+        BUG_ON(!st->count);
 
         if (!cfqd->cfq_slice_idle)
                 return false;
 
         /* We never do for idle class queues. */
-        if (prio == IDLE_WORKLOAD)
+        if (wl_class == IDLE_WORKLOAD)
                 return false;
 
         /* We do for queues that were marked with idle window flag. */
@@ -2306,11 +2693,10 @@ static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
          * Otherwise, we do only if they are the last ones
          * in their service tree.
          */
-        if (service_tree->count == 1 && cfq_cfqq_sync(cfqq) &&
-           !cfq_io_thinktime_big(cfqd, &service_tree->ttime, false))
+        if (st->count == 1 && cfq_cfqq_sync(cfqq) &&
+           !cfq_io_thinktime_big(cfqd, &st->ttime, false))
                 return true;
-        cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
-                        service_tree->count);
+        cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d", st->count);
         return false;
 }
 
@@ -2493,8 +2879,8 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
         }
 }
 
-static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
-                                struct cfq_group *cfqg, enum wl_prio_t prio)
+static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
+                        struct cfq_group *cfqg, enum wl_class_t wl_class)
 {
         struct cfq_queue *queue;
         int i;
@@ -2504,7 +2890,7 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
 
         for (i = 0; i <= SYNC_WORKLOAD; ++i) {
                 /* select the one with lowest rb_key */
-                queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
+                queue = cfq_rb_first(st_for(cfqg, wl_class, i));
                 if (queue &&
                     (!key_valid || time_before(queue->rb_key, lowest_key))) {
                         lowest_key = queue->rb_key;
@@ -2516,26 +2902,27 @@ static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
         return cur_best;
 }
 
-static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
+static void
+choose_wl_class_and_type(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
         unsigned slice;
         unsigned count;
         struct cfq_rb_root *st;
         unsigned group_slice;
-        enum wl_prio_t original_prio = cfqd->serving_prio;
+        enum wl_class_t original_class = cfqd->serving_wl_class;
 
         /* Choose next priority. RT > BE > IDLE */
         if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
-                cfqd->serving_prio = RT_WORKLOAD;
+                cfqd->serving_wl_class = RT_WORKLOAD;
         else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
-                cfqd->serving_prio = BE_WORKLOAD;
+                cfqd->serving_wl_class = BE_WORKLOAD;
         else {
-                cfqd->serving_prio = IDLE_WORKLOAD;
+                cfqd->serving_wl_class = IDLE_WORKLOAD;
                 cfqd->workload_expires = jiffies + 1;
                 return;
         }
 
-        if (original_prio != cfqd->serving_prio)
+        if (original_class != cfqd->serving_wl_class)
                 goto new_workload;
 
         /*
@@ -2543,7 +2930,7 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
          * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
          * expiration time
          */
-        st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
+        st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
         count = st->count;
 
         /*
@@ -2554,9 +2941,9 @@ static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
 
 new_workload:
         /* otherwise select new workload type */
-        cfqd->serving_type =
-                cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
-        st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
+        cfqd->serving_wl_type = cfq_choose_wl_type(cfqd, cfqg,
+                                        cfqd->serving_wl_class);
+        st = st_for(cfqg, cfqd->serving_wl_class, cfqd->serving_wl_type);
         count = st->count;
 
         /*
@@ -2567,10 +2954,11 @@ new_workload:
         group_slice = cfq_group_slice(cfqd, cfqg);
 
         slice = group_slice * count /
-                max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
-                      cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
+                max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_wl_class],
+                      cfq_group_busy_queues_wl(cfqd->serving_wl_class, cfqd,
+                                        cfqg));
 
-        if (cfqd->serving_type == ASYNC_WORKLOAD) {
+        if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
                 unsigned int tmp;
 
                 /*
@@ -2616,14 +3004,14 @@ static void cfq_choose_cfqg(struct cfq_data *cfqd)
         cfqd->serving_group = cfqg;
 
         /* Restore the workload type data */
-        if (cfqg->saved_workload_slice) {
-                cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
-                cfqd->serving_type = cfqg->saved_workload;
-                cfqd->serving_prio = cfqg->saved_serving_prio;
+        if (cfqg->saved_wl_slice) {
+                cfqd->workload_expires = jiffies + cfqg->saved_wl_slice;
+                cfqd->serving_wl_type = cfqg->saved_wl_type;
+                cfqd->serving_wl_class = cfqg->saved_wl_class;
         } else
                 cfqd->workload_expires = jiffies - 1;
 
-        choose_service_tree(cfqd, cfqg);
+        choose_wl_class_and_type(cfqd, cfqg);
 }
 
 /*
@@ -3205,6 +3593,8 @@ retry:
                         spin_lock_irq(cfqd->queue->queue_lock);
                         if (new_cfqq)
                                 goto retry;
+                        else
+                                return &cfqd->oom_cfqq;
                 } else {
                         cfqq = kmem_cache_alloc_node(cfq_pool,
                                         gfp_mask | __GFP_ZERO,
@@ -3402,7 +3792,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
                 return true;
 
         /* Allow preemption only if we are idling on sync-noidle tree */
-        if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
+        if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
             cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
             new_cfqq->service_tree->count == 2 &&
             RB_EMPTY_ROOT(&cfqq->sort_list))
@@ -3454,7 +3844,7 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
          * doesn't happen
          */
         if (old_type != cfqq_type(cfqq))
-                cfqq->cfqg->saved_workload_slice = 0;
+                cfqq->cfqg->saved_wl_slice = 0;
 
         /*
          * Put the new queue at the front of the of the current list,
@@ -3636,16 +4026,17 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
 
         if (sync) {
-                struct cfq_rb_root *service_tree;
+                struct cfq_rb_root *st;
 
                 RQ_CIC(rq)->ttime.last_end_request = now;
 
                 if (cfq_cfqq_on_rr(cfqq))
-                        service_tree = cfqq->service_tree;
+                        st = cfqq->service_tree;
                 else
-                        service_tree = service_tree_for(cfqq->cfqg,
-                                cfqq_prio(cfqq), cfqq_type(cfqq));
-                service_tree->ttime.last_end_request = now;
+                        st = st_for(cfqq->cfqg, cfqq_class(cfqq),
+                                        cfqq_type(cfqq));
+
+                st->ttime.last_end_request = now;
                 if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
                         cfqd->last_delayed_sync = now;
         }
@@ -3992,6 +4383,7 @@ static int cfq_init_queue(struct request_queue *q)
         cfq_init_cfqg_base(cfqd->root_group);
 #endif
         cfqd->root_group->weight = 2 * CFQ_WEIGHT_DEFAULT;
+        cfqd->root_group->leaf_weight = 2 * CFQ_WEIGHT_DEFAULT;
 
         /*
          * Not strictly needed (since RB_ROOT just clears the node and we
@@ -4176,6 +4568,7 @@ static struct blkcg_policy blkcg_policy_cfq = {
         .cftypes                = cfq_blkcg_files,
 
         .pd_init_fn             = cfq_pd_init,
+        .pd_offline_fn          = cfq_pd_offline,
         .pd_reset_stats_fn      = cfq_pd_reset_stats,
 };
 #endif