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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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