1 files changed, 28 insertions, 0 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3622518e1c23..e41cc6f2ccc1 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -537,6 +537,30 @@ struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
 }
 EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
 
+static void blkio_reset_stats_cpu(struct blkio_group *blkg)
+{
+        struct blkio_group_stats_cpu *stats_cpu;
+        int i, j, k;
+        /*
+         * Note: On 64 bit arch this should not be an issue. This has the
+         * possibility of returning some inconsistent value on 32bit arch
+         * as 64bit update on 32bit is non atomic. Taking care of this
+         * corner case makes code very complicated, like sending IPIs to
+         * cpus, taking care of stats of offline cpus etc.
+         *
+         * reset stats is anyway more of a debug feature and this sounds a
+         * corner case. So I am not complicating the code yet until and
+         * unless this becomes a real issue.
+         */
+        for_each_possible_cpu(i) {
+                stats_cpu = per_cpu_ptr(blkg->stats_cpu, i);
+                stats_cpu->sectors = 0;
+                for(j = 0; j < BLKIO_STAT_CPU_NR; j++)
+                        for (k = 0; k < BLKIO_STAT_TOTAL; k++)
+                                stats_cpu->stat_arr_cpu[j][k] = 0;
+        }
+}
+
 static int
 blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 {
@@ -581,7 +605,11 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
                 }
 #endif
                 spin_unlock(&blkg->stats_lock);
+
+                /* Reset Per cpu stats which don't take blkg->stats_lock */
+                blkio_reset_stats_cpu(blkg);
         }
+
         spin_unlock_irq(&blkcg->lock);
         return 0;
 }