blkcg: restructure statistics printing

blkcg stats handling is a mess.  None of the stats has much to do with
blkcg core but they are all implemented in blkcg core.  Code sharing
is achieved by mixing common code with hard-coded cases for each stat
counter.

This patch restructures statistics printing such that

* Common logic exists as helper functions and specific print functions
  use the helpers to implement specific cases.

* Printing functions serving multiple counters don't require hardcoded
  switching on specific counters.

* Printing uses read_seq_string callback (other methods will be phased
  out).

This change enables further cleanups and relocating stats code to the
policy implementation it belongs to.

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

2 files changed, 243 insertions, 374 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 09ac462ba89..951e7f3a8c8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -753,186 +753,227 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         return 0;
 }
 
-static void blkio_get_key_name(enum blkg_rwstat_type type, const char *dname,
-                               char *str, int chars_left, bool diskname_only)
-{
-        snprintf(str, chars_left, "%s", dname);
-        chars_left -= strlen(str);
-        if (chars_left <= 0) {
-                printk(KERN_WARNING
-                        "Possibly incorrect cgroup stat display format");
-                return;
-        }
-        if (diskname_only)
-                return;
-        switch (type) {
-        case BLKG_RWSTAT_READ:
-                strlcat(str, " Read", chars_left);
-                break;
-        case BLKG_RWSTAT_WRITE:
-                strlcat(str, " Write", chars_left);
-                break;
-        case BLKG_RWSTAT_SYNC:
-                strlcat(str, " Sync", chars_left);
-                break;
-        case BLKG_RWSTAT_ASYNC:
-                strlcat(str, " Async", chars_left);
-                break;
-        case BLKG_RWSTAT_TOTAL:
-                strlcat(str, " Total", chars_left);
-                break;
-        default:
-                strlcat(str, " Invalid", chars_left);
-        }
+static const char *blkg_dev_name(struct blkio_group *blkg)
+{
+        /* some drivers (floppy) instantiate a queue w/o disk registered */
+        if (blkg->q->backing_dev_info.dev)
+                return dev_name(blkg->q->backing_dev_info.dev);
+        return NULL;
 }
 
-static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg, int plid,
-                                    enum stat_type_cpu type,
-                                    enum blkg_rwstat_type sub_type)
+/**
+ * blkcg_print_blkgs - helper for printing per-blkg data
+ * @sf: seq_file to print to
+ * @blkcg: blkcg of interest
+ * @prfill: fill function to print out a blkg
+ * @pol: policy in question
+ * @data: data to be passed to @prfill
+ * @show_total: to print out sum of prfill return values or not
+ *
+ * This function invokes @prfill on each blkg of @blkcg if pd for the
+ * policy specified by @pol exists.  @prfill is invoked with @sf, the
+ * policy data and @data.  If @show_total is %true, the sum of the return
+ * values from @prfill is printed with "Total" label at the end.
+ *
+ * This is to be used to construct print functions for
+ * cftype->read_seq_string method.
+ */
+static void blkcg_print_blkgs(struct seq_file *sf, struct blkio_cgroup *blkcg,
+                              u64 (*prfill)(struct seq_file *,
+                                            struct blkg_policy_data *, int),
+                              int pol, int data, bool show_total)
 {
-        struct blkg_policy_data *pd = blkg->pd[plid];
-        u64 val = 0;
-        int cpu;
+        struct blkio_group *blkg;
+        struct hlist_node *n;
+        u64 total = 0;
 
-        if (pd->stats_cpu == NULL)
-                return val;
+        spin_lock_irq(&blkcg->lock);
+        hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node)
+                if (blkg->pd[pol])
+                        total += prfill(sf, blkg->pd[pol], data);
+        spin_unlock_irq(&blkcg->lock);
+
+        if (show_total)
+                seq_printf(sf, "Total %llu\n", (unsigned long long)total);
+}
+
+/**
+ * __blkg_prfill_u64 - prfill helper for a single u64 value
+ * @sf: seq_file to print to
+ * @pd: policy data of interest
+ * @v: value to print
+ *
+ * Print @v to @sf for the device assocaited with @pd.
+ */
+static u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd,
+                             u64 v)
+{
+        const char *dname = blkg_dev_name(pd->blkg);
+
+        if (!dname)
+                return 0;
+
+        seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
+        return v;
+}
+
+/**
+ * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
+ * @sf: seq_file to print to
+ * @pd: policy data of interest
+ * @rwstat: rwstat to print
+ *
+ * Print @rwstat to @sf for the device assocaited with @pd.
+ */
+static u64 __blkg_prfill_rwstat(struct seq_file *sf,
+                                struct blkg_policy_data *pd,
+                                const struct blkg_rwstat *rwstat)
+{
+        static const char *rwstr[] = {
+                [BLKG_RWSTAT_READ]      = "Read",
+                [BLKG_RWSTAT_WRITE]     = "Write",
+                [BLKG_RWSTAT_SYNC]      = "Sync",
+                [BLKG_RWSTAT_ASYNC]     = "Async",
+        };
+        const char *dname = blkg_dev_name(pd->blkg);
+        u64 v;
+        int i;
+
+        if (!dname)
+                return 0;
+
+        for (i = 0; i < BLKG_RWSTAT_NR; i++)
+                seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
+                           (unsigned long long)rwstat->cnt[i]);
+
+        v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
+        seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
+        return v;
+}
+
+static u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd,
+                            int off)
+{
+        return __blkg_prfill_u64(sf, pd,
+                                 blkg_stat_read((void *)&pd->stats + off));
+}
+
+static u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
+                              int off)
+{
+        struct blkg_rwstat rwstat = blkg_rwstat_read((void *)&pd->stats + off);
+
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
+}
+
+/* print blkg_stat specified by BLKCG_STAT_PRIV() */
+static int blkcg_print_stat(struct cgroup *cgrp, struct cftype *cft,
+                            struct seq_file *sf)
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+        blkcg_print_blkgs(sf, blkcg, blkg_prfill_stat,
+                          BLKCG_STAT_POL(cft->private),
+                          BLKCG_STAT_OFF(cft->private), false);
+        return 0;
+}
+
+/* print blkg_rwstat specified by BLKCG_STAT_PRIV() */
+static int blkcg_print_rwstat(struct cgroup *cgrp, struct cftype *cft,
+                              struct seq_file *sf)
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
+
+        blkcg_print_blkgs(sf, blkcg, blkg_prfill_rwstat,
+                          BLKCG_STAT_POL(cft->private),
+                          BLKCG_STAT_OFF(cft->private), true);
+        return 0;
+}
+
+static u64 blkg_prfill_cpu_stat(struct seq_file *sf,
+                                struct blkg_policy_data *pd, int off)
+{
+        u64 v = 0;
+        int cpu;
 
         for_each_possible_cpu(cpu) {
-                struct blkio_group_stats_cpu *stats_cpu =
+                struct blkio_group_stats_cpu *sc =
                         per_cpu_ptr(pd->stats_cpu, cpu);
-                struct blkg_rwstat rws;
 
-                switch (type) {
-                case BLKIO_STAT_CPU_SECTORS:
-                        val += blkg_stat_read(&stats_cpu->sectors);
-                        break;
-                case BLKIO_STAT_CPU_SERVICE_BYTES:
-                        rws = blkg_rwstat_read(&stats_cpu->service_bytes);
-                        val += rws.cnt[sub_type];
-                        break;
-                case BLKIO_STAT_CPU_SERVICED:
-                        rws = blkg_rwstat_read(&stats_cpu->serviced);
-                        val += rws.cnt[sub_type];
-                        break;
-                }
+                v += blkg_stat_read((void *)sc + off);
         }
 
-        return val;
+        return __blkg_prfill_u64(sf, pd, v);
 }
 
-static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
-                                   struct cgroup_map_cb *cb, const char *dname,
-                                   enum stat_type_cpu type)
+static u64 blkg_prfill_cpu_rwstat(struct seq_file *sf,
+                                  struct blkg_policy_data *pd, int off)
 {
-        uint64_t disk_total, val;
-        char key_str[MAX_KEY_LEN];
-        enum blkg_rwstat_type sub_type;
+        struct blkg_rwstat rwstat = { }, tmp;
+        int i, cpu;
 
-        if (type == BLKIO_STAT_CPU_SECTORS) {
-                val = blkio_read_stat_cpu(blkg, plid, type, 0);
-                blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
-                cb->fill(cb, key_str, val);
-                return val;
-        }
+        for_each_possible_cpu(cpu) {
+                struct blkio_group_stats_cpu *sc =
+                        per_cpu_ptr(pd->stats_cpu, cpu);
 
-        for (sub_type = BLKG_RWSTAT_READ; sub_type < BLKG_RWSTAT_NR;
-                        sub_type++) {
-                blkio_get_key_name(sub_type, dname, key_str, MAX_KEY_LEN,
-                                   false);
-                val = blkio_read_stat_cpu(blkg, plid, type, sub_type);
-                cb->fill(cb, key_str, val);
+                tmp = blkg_rwstat_read((void *)sc + off);
+                for (i = 0; i < BLKG_RWSTAT_NR; i++)
+                        rwstat.cnt[i] += tmp.cnt[i];
         }
 
-        disk_total = blkio_read_stat_cpu(blkg, plid, type, BLKG_RWSTAT_READ) +
-                blkio_read_stat_cpu(blkg, plid, type, BLKG_RWSTAT_WRITE);
-
-        blkio_get_key_name(BLKG_RWSTAT_TOTAL, dname, key_str, MAX_KEY_LEN,
-                           false);
-        cb->fill(cb, key_str, disk_total);
-        return disk_total;
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 
-static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
-                               struct cgroup_map_cb *cb, const char *dname,
-                               enum stat_type type)
+/* print per-cpu blkg_stat specified by BLKCG_STAT_PRIV() */
+static int blkcg_print_cpu_stat(struct cgroup *cgrp, struct cftype *cft,
+                                struct seq_file *sf)
 {
-        struct blkio_group_stats *stats = &blkg->pd[plid]->stats;
-        uint64_t v = 0, disk_total = 0;
-        char key_str[MAX_KEY_LEN];
-        struct blkg_rwstat rws = { };
-        int st;
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
 
-        if (type >= BLKIO_STAT_ARR_NR) {
-                switch (type) {
-                case BLKIO_STAT_TIME:
-                        v = blkg_stat_read(&stats->time);
-                        break;
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-                case BLKIO_STAT_UNACCOUNTED_TIME:
-                        v = blkg_stat_read(&stats->unaccounted_time);
-                        break;
-                case BLKIO_STAT_AVG_QUEUE_SIZE: {
-                        uint64_t samples;
+        blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_stat,
+                          BLKCG_STAT_POL(cft->private),
+                          BLKCG_STAT_OFF(cft->private), false);
+        return 0;
+}
 
-                        samples = blkg_stat_read(&stats->avg_queue_size_samples);
-                        if (samples) {
-                                v = blkg_stat_read(&stats->avg_queue_size_sum);
-                                do_div(v, samples);
-                        }
-                        break;
-                }
-                case BLKIO_STAT_IDLE_TIME:
-                        v = blkg_stat_read(&stats->idle_time);
-                        break;
-                case BLKIO_STAT_EMPTY_TIME:
-                        v = blkg_stat_read(&stats->empty_time);
-                        break;
-                case BLKIO_STAT_DEQUEUE:
-                        v = blkg_stat_read(&stats->dequeue);
-                        break;
-                case BLKIO_STAT_GROUP_WAIT_TIME:
-                        v = blkg_stat_read(&stats->group_wait_time);
-                        break;
-#endif
-                default:
-                        WARN_ON_ONCE(1);
-                }
+/* print per-cpu blkg_rwstat specified by BLKCG_STAT_PRIV() */
+static int blkcg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft,
+                                  struct seq_file *sf)
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
 
-                blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
-                cb->fill(cb, key_str, v);
-                return v;
-        }
+        blkcg_print_blkgs(sf, blkcg, blkg_prfill_cpu_rwstat,
+                          BLKCG_STAT_POL(cft->private),
+                          BLKCG_STAT_OFF(cft->private), true);
+        return 0;
+}
 
-        switch (type) {
-        case BLKIO_STAT_MERGED:
-                rws = blkg_rwstat_read(&stats->merged);
-                break;
-        case BLKIO_STAT_SERVICE_TIME:
-                rws = blkg_rwstat_read(&stats->service_time);
-                break;
-        case BLKIO_STAT_WAIT_TIME:
-                rws = blkg_rwstat_read(&stats->wait_time);
-                break;
-        case BLKIO_STAT_QUEUED:
-                rws = blkg_rwstat_read(&stats->queued);
-                break;
-        default:
-                WARN_ON_ONCE(true);
-                break;
-        }
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+static u64 blkg_prfill_avg_queue_size(struct seq_file *sf,
+                                      struct blkg_policy_data *pd, int off)
+{
+        u64 samples = blkg_stat_read(&pd->stats.avg_queue_size_samples);
+        u64 v = 0;
 
-        for (st = BLKG_RWSTAT_READ; st < BLKG_RWSTAT_NR; st++) {
-                blkio_get_key_name(st, dname, key_str, MAX_KEY_LEN, false);
-                cb->fill(cb, key_str, rws.cnt[st]);
-                if (st == BLKG_RWSTAT_READ || st == BLKG_RWSTAT_WRITE)
-                        disk_total += rws.cnt[st];
+        if (samples) {
+                v = blkg_stat_read(&pd->stats.avg_queue_size_sum);
+                do_div(v, samples);
         }
+        __blkg_prfill_u64(sf, pd, v);
+        return 0;
+}
+
+/* print avg_queue_size */
+static int blkcg_print_avg_queue_size(struct cgroup *cgrp, struct cftype *cft,
+                                      struct seq_file *sf)
+{
+        struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgrp);
 
-        blkio_get_key_name(BLKG_RWSTAT_TOTAL, dname, key_str, MAX_KEY_LEN,
-                           false);
-        cb->fill(cb, key_str, disk_total);
-        return disk_total;
+        blkcg_print_blkgs(sf, blkcg, blkg_prfill_avg_queue_size,
+                          BLKIO_POLICY_PROP, 0, false);
+        return 0;
 }
+#endif  /* CONFIG_DEBUG_BLK_CGROUP */
 
 static int blkio_policy_parse_and_set(char *buf, enum blkio_policy_id plid,
                                       int fileid, struct blkio_cgroup *blkcg)
@@ -1074,14 +1115,6 @@ static int blkiocg_file_write(struct cgroup *cgrp, struct cftype *cft,
         return ret;
 }
 
-static const char *blkg_dev_name(struct blkio_group *blkg)
-{
-        /* some drivers (floppy) instantiate a queue w/o disk registered */
-        if (blkg->q->backing_dev_info.dev)
-                return dev_name(blkg->q->backing_dev_info.dev);
-        return NULL;
-}
-
 static void blkio_print_group_conf(struct cftype *cft, struct blkio_group *blkg,
                                    struct seq_file *m)
 {
@@ -1174,116 +1207,6 @@ static int blkiocg_file_read(struct cgroup *cgrp, struct cftype *cft,
         return 0;
 }
 
-static int blkio_read_blkg_stats(struct blkio_cgroup *blkcg,
-                struct cftype *cft, struct cgroup_map_cb *cb,
-                enum stat_type type, bool show_total, bool pcpu)
-{
-        struct blkio_group *blkg;
-        struct hlist_node *n;
-        uint64_t cgroup_total = 0;
-
-        spin_lock_irq(&blkcg->lock);
-
-        hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
-                const char *dname = blkg_dev_name(blkg);
-                int plid = BLKIOFILE_POLICY(cft->private);
-
-                if (!dname)
-                        continue;
-                if (pcpu)
-                        cgroup_total += blkio_get_stat_cpu(blkg, plid,
-                                                           cb, dname, type);
-                else
-                        cgroup_total += blkio_get_stat(blkg, plid,
-                                                       cb, dname, type);
-        }
-        if (show_total)
-                cb->fill(cb, "Total", cgroup_total);
-
-        spin_unlock_irq(&blkcg->lock);
-        return 0;
-}
-
-/* All map kind of cgroup file get serviced by this function */
-static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
-                                struct cgroup_map_cb *cb)
-{
-        struct blkio_cgroup *blkcg;
-        enum blkio_policy_id plid = BLKIOFILE_POLICY(cft->private);
-        int name = BLKIOFILE_ATTR(cft->private);
-
-        blkcg = cgroup_to_blkio_cgroup(cgrp);
-
-        switch(plid) {
-        case BLKIO_POLICY_PROP:
-                switch(name) {
-                case BLKIO_PROP_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_TIME, 0, 0);
-                case BLKIO_PROP_sectors:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_CPU_SECTORS, 0, 1);
-                case BLKIO_PROP_io_service_bytes:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                        BLKIO_STAT_CPU_SERVICE_BYTES, 1, 1);
-                case BLKIO_PROP_io_serviced:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_CPU_SERVICED, 1, 1);
-                case BLKIO_PROP_io_service_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_SERVICE_TIME, 1, 0);
-                case BLKIO_PROP_io_wait_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_WAIT_TIME, 1, 0);
-                case BLKIO_PROP_io_merged:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_MERGED, 1, 0);
-                case BLKIO_PROP_io_queued:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_QUEUED, 1, 0);
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-                case BLKIO_PROP_unaccounted_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                        BLKIO_STAT_UNACCOUNTED_TIME, 0, 0);
-                case BLKIO_PROP_dequeue:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_DEQUEUE, 0, 0);
-                case BLKIO_PROP_avg_queue_size:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                        BLKIO_STAT_AVG_QUEUE_SIZE, 0, 0);
-                case BLKIO_PROP_group_wait_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                        BLKIO_STAT_GROUP_WAIT_TIME, 0, 0);
-                case BLKIO_PROP_idle_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_IDLE_TIME, 0, 0);
-                case BLKIO_PROP_empty_time:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_EMPTY_TIME, 0, 0);
-#endif
-                default:
-                        BUG();
-                }
-                break;
-        case BLKIO_POLICY_THROTL:
-                switch(name){
-                case BLKIO_THROTL_io_service_bytes:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_CPU_SERVICE_BYTES, 1, 1);
-                case BLKIO_THROTL_io_serviced:
-                        return blkio_read_blkg_stats(blkcg, cft, cb,
-                                                BLKIO_STAT_CPU_SERVICED, 1, 1);
-                default:
-                        BUG();
-                }
-                break;
-        default:
-                BUG();
-        }
-
-        return 0;
-}
-
 static int blkio_weight_write(struct blkio_cgroup *blkcg, int plid, u64 val)
 {
         struct blkio_group *blkg;
@@ -1369,51 +1292,51 @@ struct cftype blkio_files[] = {
         },
         {
                 .name = "time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, time)),
+                .read_seq_string = blkcg_print_stat,
         },
         {
                 .name = "sectors",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_sectors),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats_cpu, sectors)),
+                .read_seq_string = blkcg_print_cpu_stat,
         },
         {
                 .name = "io_service_bytes",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_service_bytes),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats_cpu, service_bytes)),
+                .read_seq_string = blkcg_print_cpu_rwstat,
         },
         {
                 .name = "io_serviced",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_serviced),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats_cpu, serviced)),
+                .read_seq_string = blkcg_print_cpu_rwstat,
         },
         {
                 .name = "io_service_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_service_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, service_time)),
+                .read_seq_string = blkcg_print_rwstat,
         },
         {
                 .name = "io_wait_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_wait_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, wait_time)),
+                .read_seq_string = blkcg_print_rwstat,
         },
         {
                 .name = "io_merged",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_merged),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, merged)),
+                .read_seq_string = blkcg_print_rwstat,
         },
         {
                 .name = "io_queued",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_io_queued),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, queued)),
+                .read_seq_string = blkcg_print_rwstat,
         },
         {
                 .name = "reset_stats",
@@ -1457,54 +1380,52 @@ struct cftype blkio_files[] = {
         },
         {
                 .name = "throttle.io_service_bytes",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_io_service_bytes),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_THROTL,
+                                offsetof(struct blkio_group_stats_cpu, service_bytes)),
+                .read_seq_string = blkcg_print_cpu_rwstat,
         },
         {
                 .name = "throttle.io_serviced",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_THROTL,
-                                BLKIO_THROTL_io_serviced),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_THROTL,
+                                offsetof(struct blkio_group_stats_cpu, serviced)),
+                .read_seq_string = blkcg_print_cpu_rwstat,
         },
 #endif /* CONFIG_BLK_DEV_THROTTLING */
 
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         {
                 .name = "avg_queue_size",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_avg_queue_size),
-                .read_map = blkiocg_file_read_map,
+                .read_seq_string = blkcg_print_avg_queue_size,
         },
         {
                 .name = "group_wait_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_group_wait_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, group_wait_time)),
+                .read_seq_string = blkcg_print_stat,
         },
         {
                 .name = "idle_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_idle_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, idle_time)),
+                .read_seq_string = blkcg_print_stat,
         },
         {
                 .name = "empty_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_empty_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, empty_time)),
+                .read_seq_string = blkcg_print_stat,
         },
         {
                 .name = "dequeue",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_dequeue),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, dequeue)),
+                .read_seq_string = blkcg_print_stat,
         },
         {
                 .name = "unaccounted_time",
-                .private = BLKIOFILE_PRIVATE(BLKIO_POLICY_PROP,
-                                BLKIO_PROP_unaccounted_time),
-                .read_map = blkiocg_file_read_map,
+                .private = BLKCG_STAT_PRIV(BLKIO_POLICY_PROP,
+                                offsetof(struct blkio_group_stats, unaccounted_time)),
+                .read_seq_string = blkcg_print_stat,
         },
 #endif
         { }     /* terminate */
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 7578df3938b..7331d7965a5 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -28,46 +28,10 @@ enum blkio_policy_id {
 
 #ifdef CONFIG_BLK_CGROUP
 
-enum stat_type {
-        /* Number of IOs merged */
-        BLKIO_STAT_MERGED,
-        /* Total time spent (in ns) between request dispatch to the driver and
-         * request completion for IOs doen by this cgroup. This may not be
-         * accurate when NCQ is turned on. */
-        BLKIO_STAT_SERVICE_TIME,
-        /* Total time spent waiting in scheduler queue in ns */
-        BLKIO_STAT_WAIT_TIME,
-        /* Number of IOs queued up */
-        BLKIO_STAT_QUEUED,
-
-        /* All the single valued stats go below this */
-        BLKIO_STAT_TIME,
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-        /* Time not charged to this cgroup */
-        BLKIO_STAT_UNACCOUNTED_TIME,
-        BLKIO_STAT_AVG_QUEUE_SIZE,
-        BLKIO_STAT_IDLE_TIME,
-        BLKIO_STAT_EMPTY_TIME,
-        BLKIO_STAT_GROUP_WAIT_TIME,
-        BLKIO_STAT_DEQUEUE
-#endif
-};
-
-/* Types lower than this live in stat_arr and have subtypes */
-#define BLKIO_STAT_ARR_NR       (BLKIO_STAT_QUEUED + 1)
-
-/* Per cpu stats */
-enum stat_type_cpu {
-        /* Total bytes transferred */
-        BLKIO_STAT_CPU_SERVICE_BYTES,
-        /* Total IOs serviced, post merge */
-        BLKIO_STAT_CPU_SERVICED,
-
-        /* All the single valued stats go below this */
-        BLKIO_STAT_CPU_SECTORS,
-};
-
-#define BLKIO_STAT_CPU_ARR_NR   (BLKIO_STAT_CPU_SERVICED + 1)
+/* cft->private [un]packing for stat printing */
+#define BLKCG_STAT_PRIV(pol, off)       (((unsigned)(pol) << 16) | (off))
+#define BLKCG_STAT_POL(prv)             ((unsigned)(prv) >> 16)
+#define BLKCG_STAT_OFF(prv)             ((unsigned)(prv) & 0xffff)
 
 enum blkg_rwstat_type {
         BLKG_RWSTAT_READ,
@@ -90,20 +54,6 @@ enum blkg_state_flags {
 enum blkcg_file_name_prop {
         BLKIO_PROP_weight = 1,
         BLKIO_PROP_weight_device,
-        BLKIO_PROP_io_service_bytes,
-        BLKIO_PROP_io_serviced,
-        BLKIO_PROP_time,
-        BLKIO_PROP_sectors,
-        BLKIO_PROP_unaccounted_time,
-        BLKIO_PROP_io_service_time,
-        BLKIO_PROP_io_wait_time,
-        BLKIO_PROP_io_merged,
-        BLKIO_PROP_io_queued,
-        BLKIO_PROP_avg_queue_size,
-        BLKIO_PROP_group_wait_time,
-        BLKIO_PROP_idle_time,
-        BLKIO_PROP_empty_time,
-        BLKIO_PROP_dequeue,
 };
 
 /* cgroup files owned by throttle policy */
@@ -112,8 +62,6 @@ enum blkcg_file_name_throtl {
         BLKIO_THROTL_write_bps_device,
         BLKIO_THROTL_read_iops_device,
         BLKIO_THROTL_write_iops_device,
-        BLKIO_THROTL_io_service_bytes,
-        BLKIO_THROTL_io_serviced,
 };
 
 struct blkio_cgroup {