+#ifdef CONFIG_BFQ_CGROUP_DEBUG
+static int bfq_stat_init(struct bfq_stat *stat, gfp_t gfp)
+{
+ int ret;
+
+ ret = percpu_counter_init(&stat->cpu_cnt, 0, gfp);
+ if (ret)
+ return ret;
+
+ atomic64_set(&stat->aux_cnt, 0);
+ return 0;
+}
+
+static void bfq_stat_exit(struct bfq_stat *stat)
+{
+ percpu_counter_destroy(&stat->cpu_cnt);
+}
+
+/**
+ * bfq_stat_add - add a value to a bfq_stat
+ * @stat: target bfq_stat
+ * @val: value to add
+ *
+ * Add @val to @stat. The caller must ensure that IRQ on the same CPU
+ * don't re-enter this function for the same counter.
+ */
+static inline void bfq_stat_add(struct bfq_stat *stat, uint64_t val)
+{
+ percpu_counter_add_batch(&stat->cpu_cnt, val, BLKG_STAT_CPU_BATCH);
+}
+
+/**
+ * bfq_stat_read - read the current value of a bfq_stat
+ * @stat: bfq_stat to read
+ */
+static inline uint64_t bfq_stat_read(struct bfq_stat *stat)
+{
+ return percpu_counter_sum_positive(&stat->cpu_cnt);
+}
+
+/**
+ * bfq_stat_reset - reset a bfq_stat
+ * @stat: bfq_stat to reset
+ */
+static inline void bfq_stat_reset(struct bfq_stat *stat)
+{
+ percpu_counter_set(&stat->cpu_cnt, 0);
+ atomic64_set(&stat->aux_cnt, 0);
+}
+
+/**
+ * bfq_stat_add_aux - add a bfq_stat into another's aux count
+ * @to: the destination bfq_stat
+ * @from: the source
+ *
+ * Add @from's count including the aux one to @to's aux count.
+ */
+static inline void bfq_stat_add_aux(struct bfq_stat *to,
+ struct bfq_stat *from)
+{
+ atomic64_add(bfq_stat_read(from) + atomic64_read(&from->aux_cnt),
+ &to->aux_cnt);
+}
+
+/**
+ * blkg_prfill_stat - prfill callback for bfq_stat
+ * @sf: seq_file to print to
+ * @pd: policy private data of interest
+ * @off: offset to the bfq_stat in @pd
+ *
+ * prfill callback for printing a bfq_stat.
+ */
+static u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ return __blkg_prfill_u64(sf, pd, bfq_stat_read((void *)pd + off));
+}