From a588261dc7274092fa88f314ab25948a5dbc0271 Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Thu, 19 May 2011 15:38:30 -0400
Subject: [PATCH] --- yaml --- r: 251160 b: refs/heads/master c:
 f0bdc8cdd9a2bcc2c84ae2a1fdbff4188b354d8d h: refs/heads/master v: v3

---
 [refs]                   |  2 +-
 trunk/block/blk-cgroup.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index f5a3a4fb02ec..435b0c5c6ba6 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 575969a0dd3fe65c6556bcb8f87c42303326ea55
+refs/heads/master: f0bdc8cdd9a2bcc2c84ae2a1fdbff4188b354d8d
diff --git a/trunk/block/blk-cgroup.c b/trunk/block/blk-cgroup.c
index 3622518e1c23..e41cc6f2ccc1 100644
--- a/trunk/block/blk-cgroup.c
+++ b/trunk/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;
 }