3 files changed, 55 insertions, 2 deletions

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index b34823ff1646..190018b0c649 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/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
@@ -293,7 +294,16 @@ notify_on_release in the root cgroup at system boot is disabled
 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
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 709dfb901d11..ed4ba111bc8d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -154,6 +154,10 @@ 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? */
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9270d532ec3c..4b218a46ddd3 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -243,6 +243,11 @@ static int notify_on_release(const struct cgroup *cgrp)
         return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 }
 
+static int clone_children(const struct cgroup *cgrp)
+{
+        return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+}
+
 /*
  * for_each_subsys() allows you to iterate on each subsystem attached to
  * an active hierarchy
@@ -1040,6 +1045,8 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
                 seq_puts(seq, ",noprefix");
         if (strlen(root->release_agent_path))
                 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
+        if (clone_children(&root->top_cgroup))
+                seq_puts(seq, ",clone_children");
         if (strlen(root->name))
                 seq_printf(seq, ",name=%s", root->name);
         mutex_unlock(&cgroup_mutex);
@@ -1050,6 +1057,7 @@ struct cgroup_sb_opts {
         unsigned long subsys_bits;
         unsigned long flags;
         char *release_agent;
+        bool clone_children;
         char *name;
         /* User explicitly requested empty subsystem */
         bool none;
@@ -1097,6 +1105,8 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
                         opts->none = true;
                 } else if (!strcmp(token, "noprefix")) {
                         set_bit(ROOT_NOPREFIX, &opts->flags);
+                } else if (!strcmp(token, "clone_children")) {
+                        opts->clone_children = true;
                 } else if (!strncmp(token, "release_agent=", 14)) {
                         /* Specifying two release agents is forbidden */
                         if (opts->release_agent)
@@ -1355,6 +1365,8 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
                 strcpy(root->release_agent_path, opts->release_agent);
         if (opts->name)
                 strcpy(root->name, opts->name);
+        if (opts->clone_children)
+                set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
         return root;
 }
 
@@ -3173,6 +3185,23 @@ fail:
         return ret;
 }
 
+static u64 cgroup_clone_children_read(struct cgroup *cgrp,
+                                    struct cftype *cft)
+{
+        return clone_children(cgrp);
+}
+
+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
  */
@@ -3203,6 +3232,11 @@ static struct cftype files[] = {
                 .write_string = cgroup_write_event_control,
                 .mode = S_IWUGO,
         },
+        {
+                .name = "cgroup.clone_children",
+                .read_u64 = cgroup_clone_children_read,
+                .write_u64 = cgroup_clone_children_write,
+        },
 };
 
 static struct cftype cft_release_agent = {
@@ -3332,6 +3366,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         if (notify_on_release(parent))
                 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 
+        if (clone_children(parent))
+                set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
+
         for_each_subsys(root, ss) {
                 struct cgroup_subsys_state *css = ss->create(ss, cgrp);
 
@@ -3346,6 +3383,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
                                 goto err_destroy;
                 }
                 /* At error, ->destroy() callback has to free assigned ID. */
+                if (clone_children(parent) && ss->post_clone)
+                        ss->post_clone(ss, cgrp);
         }
 
         cgroup_lock_hierarchy(root);