blkcg: move io_service_bytes and io_serviced stats into blkcg_gq

Currently, both cfq-iosched and blk-throttle keep track of
io_service_bytes and io_serviced stats.  While keeping track of them
separately may be useful during development, it doesn't make much
sense otherwise.  Also, blk-throttle was counting bio's as IOs while
cfq-iosched request's, which is more confusing than informative.

This patch adds ->stat_bytes and ->stat_ios to blkg (blkcg_gq),
removes the counterparts from cfq-iosched and blk-throttle and let
them print from the common blkg counters.  The common counters are
incremented during bio issue in blkcg_bio_issue_check().

The outputs are still filtered by whether the policy has
blkg_policy_data on a given blkg, so cfq's output won't show up if it
has never been used for a given blkg.  The only times when the outputs
would differ significantly are when policies are attached on the fly
or elevators are switched back and forth.  Those are quite exceptional
operations and I don't think they warrant keeping separate counters.

v3: Update blkio-controller.txt accordingly.

v2: Account IOs during bio issues instead of request completions so
    that bio-based drivers can be handled the same way.

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

1 files changed, 98 insertions, 0 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b26320720a3c..a25263ca39ca 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -73,6 +73,9 @@ static void blkg_free(struct blkcg_gq *blkg)
 
         if (blkg->blkcg != &blkcg_root)
                 blk_exit_rl(&blkg->rl);
+
+        blkg_rwstat_exit(&blkg->stat_ios);
+        blkg_rwstat_exit(&blkg->stat_bytes);
         kfree(blkg);
 }
 
@@ -95,6 +98,10 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
         if (!blkg)
                 return NULL;
 
+        if (blkg_rwstat_init(&blkg->stat_bytes, gfp_mask) ||
+            blkg_rwstat_init(&blkg->stat_ios, gfp_mask))
+                goto err_free;
+
         blkg->q = q;
         INIT_LIST_HEAD(&blkg->q_node);
         blkg->blkcg = blkcg;
@@ -300,6 +307,7 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 static void blkg_destroy(struct blkcg_gq *blkg)
 {
         struct blkcg *blkcg = blkg->blkcg;
+        struct blkcg_gq *parent = blkg->parent;
         int i;
 
         lockdep_assert_held(blkg->q->queue_lock);
@@ -315,6 +323,12 @@ static void blkg_destroy(struct blkcg_gq *blkg)
                 if (blkg->pd[i] && pol->pd_offline_fn)
                         pol->pd_offline_fn(blkg->pd[i]);
         }
+
+        if (parent) {
+                blkg_rwstat_add_aux(&parent->stat_bytes, &blkg->stat_bytes);
+                blkg_rwstat_add_aux(&parent->stat_ios, &blkg->stat_ios);
+        }
+
         blkg->online = false;
 
         radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
@@ -431,6 +445,9 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
          * anyway.  If you get hit by a race, retry.
          */
         hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
+                blkg_rwstat_reset(&blkg->stat_bytes);
+                blkg_rwstat_reset(&blkg->stat_ios);
+
                 for (i = 0; i < BLKCG_MAX_POLS; i++) {
                         struct blkcg_policy *pol = blkcg_policy[i];
 
@@ -579,6 +596,87 @@ u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 }
 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
 
+static u64 blkg_prfill_rwstat_field(struct seq_file *sf,
+                                    struct blkg_policy_data *pd, int off)
+{
+        struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd->blkg + off);
+
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
+}
+
+/**
+ * blkg_print_stat_bytes - seq_show callback for blkg->stat_bytes
+ * @sf: seq_file to print to
+ * @v: unused
+ *
+ * To be used as cftype->seq_show to print blkg->stat_bytes.
+ * cftype->private must be set to the blkcg_policy.
+ */
+int blkg_print_stat_bytes(struct seq_file *sf, void *v)
+{
+        blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+                          blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
+                          offsetof(struct blkcg_gq, stat_bytes), true);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(blkg_print_stat_bytes);
+
+/**
+ * blkg_print_stat_bytes - seq_show callback for blkg->stat_ios
+ * @sf: seq_file to print to
+ * @v: unused
+ *
+ * To be used as cftype->seq_show to print blkg->stat_ios.  cftype->private
+ * must be set to the blkcg_policy.
+ */
+int blkg_print_stat_ios(struct seq_file *sf, void *v)
+{
+        blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+                          blkg_prfill_rwstat_field, (void *)seq_cft(sf)->private,
+                          offsetof(struct blkcg_gq, stat_ios), true);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(blkg_print_stat_ios);
+
+static u64 blkg_prfill_rwstat_field_recursive(struct seq_file *sf,
+                                              struct blkg_policy_data *pd,
+                                              int off)
+{
+        struct blkg_rwstat rwstat = blkg_rwstat_recursive_sum(pd->blkg,
+                                                              NULL, off);
+        return __blkg_prfill_rwstat(sf, pd, &rwstat);
+}
+
+/**
+ * blkg_print_stat_bytes_recursive - recursive version of blkg_print_stat_bytes
+ * @sf: seq_file to print to
+ * @v: unused
+ */
+int blkg_print_stat_bytes_recursive(struct seq_file *sf, void *v)
+{
+        blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+                          blkg_prfill_rwstat_field_recursive,
+                          (void *)seq_cft(sf)->private,
+                          offsetof(struct blkcg_gq, stat_bytes), true);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(blkg_print_stat_bytes_recursive);
+
+/**
+ * blkg_print_stat_ios_recursive - recursive version of blkg_print_stat_ios
+ * @sf: seq_file to print to
+ * @v: unused
+ */
+int blkg_print_stat_ios_recursive(struct seq_file *sf, void *v)
+{
+        blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
+                          blkg_prfill_rwstat_field_recursive,
+                          (void *)seq_cft(sf)->private,
+                          offsetof(struct blkcg_gq, stat_ios), true);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(blkg_print_stat_ios_recursive);
+
 /**
  * blkg_stat_recursive_sum - collect hierarchical blkg_stat
  * @blkg: blkg of interest