[PATCH 7/7] devcg: Added Documentation of RDMA device cgroup.

[Parav Pandit <pandit.parav-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Modified device cgroup documentation to reflect its dual purpose
without creating new cgroup subsystem for rdma.

Added documentation to describe functionality and usage of device cgroup
extension for RDMA.

Signed-off-by: Parav Pandit <pandit.parav-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 Documentation/cgroups/devices.txt | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/Documentation/cgroups/devices.txt b/Documentation/cgroups/devices.txt
index 3c1095c..eca5b70 100644
--- a/Documentation/cgroups/devices.txt
+++ b/Documentation/cgroups/devices.txt
@@ -1,9 +1,12 @@
-Device Whitelist Controller
+Device Controller
 
 1. Description:
 
-Implement a cgroup to track and enforce open and mknod restrictions
-on device files.  A device cgroup associates a device access
+Device controller implements a cgroup for two purposes.
+
+1.1 Device white list controller
+It implement a cgroup to track and enforce open and mknod
+restrictions on device files.  A device cgroup associates a device access
 whitelist with each cgroup.  A whitelist entry has 4 fields.
 'type' is a (all), c (char), or b (block).  'all' means it applies
 to all types and all major and minor numbers.  Major and minor are
@@ -15,8 +18,15 @@ cgroup gets a copy of the parent.  Administrators can then remove
 devices from the whitelist or add new entries.  A child cgroup can
 never receive a device access which is denied by its parent.
 
+1.2 RDMA device resource controller
+It implements a cgroup to limit various RDMA device resources for
+a controller. Such resource includes RDMA PD, CQ, AH, MR, SRQ, QP, FLOW.
+It limits RDMA resources access to tasks of the cgroup across multiple
+RDMA devices.
+
 2. User Interface
 
+2.1 Device white list controller
 An entry is added using devices.allow, and removed using
 devices.deny.  For instance
 
@@ -33,6 +43,22 @@ will remove the default 'a *:* rwm' entry. Doing
 
 will add the 'a *:* rwm' entry to the whitelist.
 
+2.2 RDMA device controller
+
+RDMA resources are limited using devices.rdma.resource.max.<resource_name>.
+Doing
+	echo 200 > /sys/fs/cgroup/1/rdma.resource.max_qp
+will limit maximum number of QP across all the process of cgroup to 200.
+
+More examples:
+	echo 200 > /sys/fs/cgroup/1/rdma.resource.max_flow
+	echo 10  > /sys/fs/cgroup/1/rdma.resource.max_pd
+	echo 15  > /sys/fs/cgroup/1/rdma.resource.max_srq
+	echo 1   > /sys/fs/cgroup/1/rdma.resource.max_uctx
+
+RDMA resource current usage can be tracked using devices.rdma.resource.usage
+	cat /sys/fs/cgroup/1/devices.rdma.resource.usage
+
 3. Security
 
 Any task can move itself between cgroups.  This clearly won't
-- 
1.8.3.1