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authorPaul Menage <menage@google.com>2007-10-18 23:39:34 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-19 11:53:36 -0700
commit697f41610863c9264a7ae26dac9a387c9dda8c84 (patch)
tree9d4321f93abe36920a8e9d5239d120803f6cabbc /kernel/cgroup.c
parentb4f48b6363c81ca743ef46943ef23fd72e60f679 (diff)
Task Control Groups: add cgroup_clone() interface
Add support for cgroup_clone(), a way to create new cgroups intended to be used for systems such as namespace unsharing. A new subsystem callback, post_clone(), is added to allow subsystems to automatically configure cloned cgroups. Signed-off-by: Paul Menage <menage@google.com> Cc: Serge E. Hallyn <serue@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Paul Jackson <pj@sgi.com> Cc: Kirill Korotaev <dev@openvz.org> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7bb520aaf0a3..cc68fe68a60e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1708,3 +1708,138 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
tsk->cgroups = init_task.cgroups;
task_unlock(tsk);
}
+
+/**
+ * cgroup_clone - duplicate the current cgroup in the hierarchy
+ * that the given subsystem is attached to, and move this task into
+ * the new child
+ */
+int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
+{
+ struct dentry *dentry;
+ int ret = 0;
+ char nodename[MAX_CGROUP_TYPE_NAMELEN];
+ struct cgroup *parent, *child;
+ struct inode *inode;
+ struct css_set *cg;
+ struct cgroupfs_root *root;
+ struct cgroup_subsys *ss;
+
+ /* We shouldn't be called by an unregistered subsystem */
+ BUG_ON(!subsys->active);
+
+ /* First figure out what hierarchy and cgroup we're dealing
+ * with, and pin them so we can drop cgroup_mutex */
+ mutex_lock(&cgroup_mutex);
+ again:
+ root = subsys->root;
+ if (root == &rootnode) {
+ printk(KERN_INFO
+ "Not cloning cgroup for unused subsystem %s\n",
+ subsys->name);
+ mutex_unlock(&cgroup_mutex);
+ return 0;
+ }
+ cg = &tsk->cgroups;
+ parent = task_cgroup(tsk, subsys->subsys_id);
+
+ snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid);
+
+ /* Pin the hierarchy */
+ atomic_inc(&parent->root->sb->s_active);
+
+ mutex_unlock(&cgroup_mutex);
+
+ /* Now do the VFS work to create a cgroup */
+ inode = parent->dentry->d_inode;
+
+ /* Hold the parent directory mutex across this operation to
+ * stop anyone else deleting the new cgroup */
+ mutex_lock(&inode->i_mutex);
+ dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
+ if (IS_ERR(dentry)) {
+ printk(KERN_INFO
+ "Couldn't allocate dentry for %s: %ld\n", nodename,
+ PTR_ERR(dentry));
+ ret = PTR_ERR(dentry);
+ goto out_release;
+ }
+
+ /* Create the cgroup directory, which also creates the cgroup */
+ ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
+ child = __d_cont(dentry);
+ dput(dentry);
+ if (ret) {
+ printk(KERN_INFO
+ "Failed to create cgroup %s: %d\n", nodename,
+ ret);
+ goto out_release;
+ }
+
+ if (!child) {
+ printk(KERN_INFO
+ "Couldn't find new cgroup %s\n", nodename);
+ ret = -ENOMEM;
+ goto out_release;
+ }
+
+ /* The cgroup now exists. Retake cgroup_mutex and check
+ * that we're still in the same state that we thought we
+ * were. */
+ mutex_lock(&cgroup_mutex);
+ if ((root != subsys->root) ||
+ (parent != task_cgroup(tsk, subsys->subsys_id))) {
+ /* Aargh, we raced ... */
+ mutex_unlock(&inode->i_mutex);
+
+ deactivate_super(parent->root->sb);
+ /* The cgroup is still accessible in the VFS, but
+ * we're not going to try to rmdir() it at this
+ * point. */
+ printk(KERN_INFO
+ "Race in cgroup_clone() - leaking cgroup %s\n",
+ nodename);
+ goto again;
+ }
+
+ /* do any required auto-setup */
+ for_each_subsys(root, ss) {
+ if (ss->post_clone)
+ ss->post_clone(ss, child);
+ }
+
+ /* All seems fine. Finish by moving the task into the new cgroup */
+ ret = attach_task(child, tsk);
+ mutex_unlock(&cgroup_mutex);
+
+ out_release:
+ mutex_unlock(&inode->i_mutex);
+ deactivate_super(parent->root->sb);
+ return ret;
+}
+
+/*
+ * See if "cont" is a descendant of the current task's cgroup in
+ * the appropriate hierarchy
+ *
+ * If we are sending in dummytop, then presumably we are creating
+ * the top cgroup in the subsystem.
+ *
+ * Called only by the ns (nsproxy) cgroup.
+ */
+int cgroup_is_descendant(const struct cgroup *cont)
+{
+ int ret;
+ struct cgroup *target;
+ int subsys_id;
+
+ if (cont == dummytop)
+ return 1;
+
+ get_first_subsys(cont, NULL, &subsys_id);
+ target = task_cgroup(current, subsys_id);
+ while (cont != target && cont!= cont->top_cgroup)
+ cont = cont->parent;
+ ret = (cont == target);
+ return ret;
+}

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