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Subject[PATCH 4/5] blkcg: restructure blkio_get_stat()
Date
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>
---
block/blk-cgroup.c | 100 ++++++++++++++++++++++++++-------------------------
block/blk-cgroup.h | 6 +++-
2 files changed, 56 insertions(+), 50 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 759bc58..80887bc 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);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1fa3c5e..8bdcf50 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -39,6 +39,7 @@ enum stat_type {
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
@@ -52,6 +53,9 @@ enum stat_type {
#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 {
BLKIO_STAT_CPU_SECTORS,
@@ -117,7 +121,7 @@ struct blkio_cgroup {
struct blkio_group_stats {
/* total disk time and nr sectors dispatched by this group */
uint64_t time;
- uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
+ uint64_t stat_arr[BLKIO_STAT_ARR_NR][BLKIO_STAT_TOTAL];
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* Time not charged to this cgroup */
uint64_t unaccounted_time;
--
1.7.7.3


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