This patch is sent as an answer to a previous thread around the ns_cgroup.
https://lists.linux-foundation.org/pipermail/containers/2009-June/018627.html
It adds a control file 'clone_children' for a cgroup.
This control file is a boolean specifying if the child cgroup should
be a clone of the parent cgroup or not. The default value is 'false'.
This flag makes the child cgroup to call the post_clone callback of all
the subsystem, if it is available.
At present, the cpuset is the only one which had implemented the post_clone
callback.
Signed-off-by: Daniel Lezcano <daniel.lezc...@free.fr>
Cc: Paul Menage <men...@google.com>
Cc: Serge E. Hallyn <se...@us.ibm.com>
---
Documentation/cgroups/cgroups.txt | 14 ++++++++++++--
include/linux/cgroup.h | 4 ++++
kernel/cgroup.c | 26 ++++++++++++++++++++++++++
3 files changed, 42 insertions(+), 2 deletions(-)
Index: linux-2.6/include/linux/cgroup.h
===================================================================
--- linux-2.6.orig/include/linux/cgroup.h
+++ linux-2.6/include/linux/cgroup.h
@@ -139,6 +139,10 @@ enum {
* A thread in rmdir() is wating for this cgroup.
*/
CGRP_WAIT_ON_RMDIR,
+ /*
+ * Clone cgroup values when creating a new child cgroup
+ */
+ CGRP_CLONE_CHILDREN,
};
/* which pidlist file are we talking about? */
Index: linux-2.6/kernel/cgroup.c
===================================================================
--- linux-2.6.orig/kernel/cgroup.c
+++ linux-2.6/kernel/cgroup.c
@@ -2789,6 +2789,23 @@ static int cgroup_write_notify_on_releas
return 0;
}
+static u64 cgroup_clone_children_read(struct cgroup *cgrp,
+ struct cftype *cft)
+{
+ return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+}
+
+static int cgroup_clone_children_write(struct cgroup *cgrp,
+ struct cftype *cft,
+ u64 val)
+{
+ if (val)
+ set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+ else
+ clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+ return 0;
+}
+
/*
* for the common functions, 'private' gives the type of file
*/
@@ -2814,6 +2831,11 @@ static struct cftype files[] = {
.read_u64 = cgroup_read_notify_on_release,
.write_u64 = cgroup_write_notify_on_release,
},
+ {
+ .name = "clone_children",
+ .read_u64 = cgroup_clone_children_read,
+ .write_u64 = cgroup_clone_children_write,
+ },
};
static struct cftype cft_release_agent = {
@@ -2946,6 +2968,10 @@ static long cgroup_create(struct cgroup
if (alloc_css_id(ss, parent, cgrp))
goto err_destroy;
/* At error, ->destroy() callback has to free assigned ID. */
+
+ if (test_bit(CGRP_CLONE_CHILDREN, &parent->flags))
+ if (ss->post_clone)
+ ss->post_clone(ss, cgrp);
}
cgroup_lock_hierarchy(root);
Index: linux-2.6/Documentation/cgroups/cgroups.txt
===================================================================
--- linux-2.6.orig/Documentation/cgroups/cgroups.txt
+++ linux-2.6/Documentation/cgroups/cgroups.txt
@@ -18,7 +18,8 @@ CONTENTS:
1.2 Why are cgroups needed ?
1.3 How are cgroups implemented ?
1.4 What does notify_on_release do ?
- 1.5 How do I use cgroups ?
+ 1.5 What does clone_children do ?
+ 1.6 How do I use cgroups ?
2. Usage Examples and Syntax
2.1 Basic Usage
2.2 Attaching processes
@@ -292,7 +293,16 @@ notify_on_release in the root cgroup at
value of their parents notify_on_release setting. The default value of
a cgroup hierarchy's release_agent path is empty.
-1.5 How do I use cgroups ?
+1.5 What does clone_children do ?
+---------------------------------
+
+If the clone_children flag is enabled (1) in a cgroup, then all
+cgroups created beneath will call the post_clone callbacks for each
+subsystem of the newly created cgroup. Usually when this callback is
+implemented for a subsystem, it copies the values of the parent
+subsystem, this is the case for the cpuset.
+
+1.6 How do I use cgroups ?
--------------------------
To start a new job that is to be contained within a cgroup, using
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