From 161f10881920265f4e6d0a71796c2da175ed5873 Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Mon, 23 May 2011 10:02:19 +0200
Subject: [PATCH] --- yaml --- r: 251167 b: refs/heads/master c:
 317389a7739675aa990b7e0d750a7c435f1d25d7 h: refs/heads/master i:   251165:
 3775e6ecc5eceb28c054a12ad94554d05aeafe35   251163:
 37f034e66af22db6f5538cc43895e26554f07f51   251159:
 6ea221519e0c726e28935a2e8d16d555027878ee   251151:
 4a8cdebc14f356a5aac13699f5cebe9e2794662e   251135:
 c23549023346d5430b1dbfe80007dcc07d9261c2 v: v3

---
 [refs]                   |  2 +-
 trunk/block/blk-cgroup.c | 22 +++++++++++++++++-----
 trunk/block/blk-cgroup.h |  4 ++--
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 5323294be157..28e5b80d94c9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 2abae55f5a41d29f21b5b259c33d218c950d5c90
+refs/heads/master: 317389a7739675aa990b7e0d750a7c435f1d25d7
diff --git a/trunk/block/blk-cgroup.c b/trunk/block/blk-cgroup.c
index e41cc6f2ccc1..07371cfdfae6 100644
--- a/trunk/block/blk-cgroup.c
+++ b/trunk/block/blk-cgroup.c
@@ -441,15 +441,27 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
 
+/*  Merged stats are per cpu.  */
 void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
 					bool sync)
 {
+	struct blkio_group_stats_cpu *stats_cpu;
 	unsigned long flags;
 
-	spin_lock_irqsave(&blkg->stats_lock, flags);
-	blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_MERGED], 1, direction,
-			sync);
-	spin_unlock_irqrestore(&blkg->stats_lock, flags);
+	/*
+	 * Disabling interrupts to provide mutual exclusion between two
+	 * writes on same cpu. It probably is not needed for 64bit. Not
+	 * optimizing that case yet.
+	 */
+	local_irq_save(flags);
+
+	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
+
+	u64_stats_update_begin(&stats_cpu->syncp);
+	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_MERGED], 1,
+				direction, sync);
+	u64_stats_update_end(&stats_cpu->syncp);
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
 
@@ -1244,7 +1256,7 @@ static int blkiocg_file_read_map(struct cgroup *cgrp, struct cftype *cft,
 						BLKIO_STAT_WAIT_TIME, 1, 0);
 		case BLKIO_PROP_io_merged:
 			return blkio_read_blkg_stats(blkcg, cft, cb,
-						BLKIO_STAT_MERGED, 1, 0);
+						BLKIO_STAT_CPU_MERGED, 1, 1);
 		case BLKIO_PROP_io_queued:
 			return blkio_read_blkg_stats(blkcg, cft, cb,
 						BLKIO_STAT_QUEUED, 1, 0);
diff --git a/trunk/block/blk-cgroup.h b/trunk/block/blk-cgroup.h
index 262226798093..a71d2904ffb9 100644
--- a/trunk/block/blk-cgroup.h
+++ b/trunk/block/blk-cgroup.h
@@ -39,8 +39,6 @@ enum stat_type {
 	BLKIO_STAT_SERVICE_TIME = 0,
 	/* Total time spent waiting in scheduler queue in ns */
 	BLKIO_STAT_WAIT_TIME,
-	/* Number of IOs merged */
-	BLKIO_STAT_MERGED,
 	/* Number of IOs queued up */
 	BLKIO_STAT_QUEUED,
 	/* All the single valued stats go below this */
@@ -63,6 +61,8 @@ enum stat_type_cpu {
 	BLKIO_STAT_CPU_SERVICE_BYTES,
 	/* Total IOs serviced, post merge */
 	BLKIO_STAT_CPU_SERVICED,
+	/* Number of IOs merged */
+	BLKIO_STAT_CPU_MERGED,
 	BLKIO_STAT_CPU_NR
 };