diff --git a/[refs] b/[refs]
index 2cd35d874a1f..1d55e8b40483 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 34d0f179d6dd711d3fc13c0820a456c59aae8048
+refs/heads/master: da69da184c06f365b335a0e013dc6360a82abe85
diff --git a/trunk/Documentation/cgroups/blkio-controller.txt b/trunk/Documentation/cgroups/blkio-controller.txt
index db054ea3e7fb..d422b410a995 100644
--- a/trunk/Documentation/cgroups/blkio-controller.txt
+++ b/trunk/Documentation/cgroups/blkio-controller.txt
@@ -76,9 +76,38 @@ CONFIG_DEBUG_BLK_CGROUP
 Details of cgroup files
 =======================
 - blkio.weight
-	- Specifies per cgroup weight.
+	- Specifies per cgroup weight. This is default weight of the group
+	  on all the devices until and unless overridden by per device rule.
+	  (See blkio.weight_device).
 	  Currently allowed range of weights is from 100 to 1000.
 
+- blkio.weight_device
+	- One can specify per cgroup per device rules using this interface.
+	  These rules override the default value of group weight as specified
+	  by blkio.weight.
+
+	  Following is the format.
+
+	  #echo dev_maj:dev_minor weight > /path/to/cgroup/blkio.weight_device
+	  Configure weight=300 on /dev/sdb (8:16) in this cgroup
+	  # echo 8:16 300 > blkio.weight_device
+	  # cat blkio.weight_device
+	  dev     weight
+	  8:16    300
+
+	  Configure weight=500 on /dev/sda (8:0) in this cgroup
+	  # echo 8:0 500 > blkio.weight_device
+	  # cat blkio.weight_device
+	  dev     weight
+	  8:0     500
+	  8:16    300
+
+	  Remove specific weight for /dev/sda in this cgroup
+	  # echo 8:0 0 > blkio.weight_device
+	  # cat blkio.weight_device
+	  dev     weight
+	  8:16    300
+
 - blkio.time
 	- disk time allocated to cgroup per device in milliseconds. First
 	  two fields specify the major and minor number of the device and