blkcg: restructure blkio_get_stat()

Restructure blkio_get_stat() to prepare for removal of stats_lock.

* Define BLKIO_STAT_ARR_NR explicitly to denote which stats have
  subtypes instead of using BLKIO_STAT_QUEUED.

* Separate out stat acquisition and printing.  After this, there are
  only two users of blkio_fill_stat().  Just open code it.

* The code was mixing MAX_KEY_LEN and MAX_KEY_LEN - 1.  There's no
  need to subtract one.  Use MAX_KEY_LEN consistently.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 51 insertions, 49 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 759bc58154c2..80887bc3a049 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -868,15 +868,6 @@ static void blkio_get_key_name(enum stat_sub_type type, const char *dname,
         }
 }
 
-static uint64_t blkio_fill_stat(char *str, int chars_left, uint64_t val,
-                                struct cgroup_map_cb *cb, const char *dname)
-{
-        blkio_get_key_name(0, dname, str, chars_left, true);
-        cb->fill(cb, str, val);
-        return val;
-}
-
-
 static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg, int plid,
                         enum stat_type_cpu type, enum stat_sub_type sub_type)
 {
@@ -916,8 +907,9 @@ static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
 
         if (type == BLKIO_STAT_CPU_SECTORS) {
                 val = blkio_read_stat_cpu(blkg, plid, type, 0);
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1, val, cb,
-                                       dname);
+                blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
+                cb->fill(cb, key_str, val);
+                return val;
         }
 
         for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
@@ -942,50 +934,60 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
                                struct cgroup_map_cb *cb, const char *dname,
                                enum stat_type type)
 {
-        struct blkg_policy_data *pd = blkg->pd[plid];
-        uint64_t disk_total;
+        struct blkio_group_stats *stats = &blkg->pd[plid]->stats;
+        uint64_t v = 0, disk_total = 0;
         char key_str[MAX_KEY_LEN];
-        enum stat_sub_type sub_type;
+        int st;
 
-        if (type == BLKIO_STAT_TIME)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                        pd->stats.time, cb, dname);
+        if (type >= BLKIO_STAT_ARR_NR) {
+                switch (type) {
+                case BLKIO_STAT_TIME:
+                        v = stats->time;
+                        break;
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-        if (type == BLKIO_STAT_UNACCOUNTED_TIME)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       pd->stats.unaccounted_time, cb, dname);
-        if (type == BLKIO_STAT_AVG_QUEUE_SIZE) {
-                uint64_t sum = pd->stats.avg_queue_size_sum;
-                uint64_t samples = pd->stats.avg_queue_size_samples;
-                if (samples)
-                        do_div(sum, samples);
-                else
-                        sum = 0;
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       sum, cb, dname);
-        }
-        if (type == BLKIO_STAT_GROUP_WAIT_TIME)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       pd->stats.group_wait_time, cb, dname);
-        if (type == BLKIO_STAT_IDLE_TIME)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       pd->stats.idle_time, cb, dname);
-        if (type == BLKIO_STAT_EMPTY_TIME)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       pd->stats.empty_time, cb, dname);
-        if (type == BLKIO_STAT_DEQUEUE)
-                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
-                                       pd->stats.dequeue, cb, dname);
+                case BLKIO_STAT_UNACCOUNTED_TIME:
+                        v = stats->unaccounted_time;
+                        break;
+                case BLKIO_STAT_AVG_QUEUE_SIZE: {
+                        uint64_t samples = stats->avg_queue_size_samples;
+
+                        if (samples) {
+                                v = stats->avg_queue_size_sum;
+                                do_div(v, samples);
+                        }
+                        break;
+                }
+                case BLKIO_STAT_IDLE_TIME:
+                        v = stats->idle_time;
+                        break;
+                case BLKIO_STAT_EMPTY_TIME:
+                        v = stats->empty_time;
+                        break;
+                case BLKIO_STAT_DEQUEUE:
+                        v = stats->dequeue;
+                        break;
+                case BLKIO_STAT_GROUP_WAIT_TIME:
+                        v = stats->group_wait_time;
+                        break;
 #endif
+                default:
+                        WARN_ON_ONCE(1);
+                }
 
-        for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
-                        sub_type++) {
-                blkio_get_key_name(sub_type, dname, key_str, MAX_KEY_LEN,
-                                   false);
-                cb->fill(cb, key_str, pd->stats.stat_arr[type][sub_type]);
+                blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
+                cb->fill(cb, key_str, v);
+                return v;
         }
-        disk_total = pd->stats.stat_arr[type][BLKIO_STAT_READ] +
-                        pd->stats.stat_arr[type][BLKIO_STAT_WRITE];
+
+        for (st = BLKIO_STAT_READ; st < BLKIO_STAT_TOTAL; st++) {
+                v = stats->stat_arr[type][st];
+
+                blkio_get_key_name(st, dname, key_str, MAX_KEY_LEN, false);
+                cb->fill(cb, key_str, v);
+                if (st == BLKIO_STAT_READ || st == BLKIO_STAT_WRITE)
+                        disk_total += v;
+        }
+
         blkio_get_key_name(BLKIO_STAT_TOTAL, dname, key_str, MAX_KEY_LEN,
                            false);
         cb->fill(cb, key_str, disk_total);