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cgroup: remove the ns_cgroup

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The ns_cgroup is an annoying cgroup at the namespace / cgroup frontier and
leads to some problems:

  * cgroup creation is out-of-control
  * cgroup name can conflict when pids are looping
  * it is not possible to have a single process handling a lot of
    namespaces without falling in a exponential creation time
  * we may want to create a namespace without creating a cgroup

  The ns_cgroup was replaced by a compatibility flag 'clone_children',
  where a newly created cgroup will copy the parent cgroup values.
  The userspace has to manually create a cgroup and add a task to
  the 'tasks' file.

This patch removes the ns_cgroup as suggested in the following thread:

https://lists.linux-foundation.org/pipermail/containers/2009-June/018616.html

The 'cgroup_clone' function is removed because it is no longer used.

This is a userspace-visible change.  Commit 45531757b4 ("cgroup: notify
ns_cgroup deprecated") (merged into 2.6.27) caused the kernel to emit a
printk warning users that the feature is planned for removal.  Since that
time we have heard from XXX users who were affected by this.

Signed-off-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jamal Hadi Salim <hadi@cyberus.ca>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Menage <menage@google.com>
Acked-by: Matt Helsley <matthltc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Daniel Lezcano
2011-05-26 16:25:23 -07:00
committed by Linus Torvalds
parent d846687d7f
commit a77aea9201
22 changed files with 4 additions and 287 deletions
Download Patch File Download Diff File Expand all files Collapse all files

116
kernel/cgroup.c
View File

@@ -4629,122 +4629,6 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
put_css_set_taskexit(cg);
}
/**
* cgroup_clone - clone the cgroup the given subsystem is attached to
* @tsk: the task to be moved
* @subsys: the given subsystem
* @nodename: the name for the new cgroup
*
* 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,
char *nodename)
{
struct dentry *dentry;
int ret = 0;
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) {
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Pin the hierarchy */
if (!atomic_inc_not_zero(&root->sb->s_active)) {
/* We race with the final deactivate_super() */
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Keep the cgroup alive */
task_lock(tsk);
parent = task_cgroup(tsk, subsys->subsys_id);
cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
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
"cgroup: 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, 0755);
child = __d_cgrp(dentry);
dput(dentry);
if (ret) {
printk(KERN_INFO
"Failed to create cgroup %s: %d\n", nodename,
ret);
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);
put_css_set(cg);
deactivate_super(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 = cgroup_attach_task(child, tsk);
mutex_unlock(&cgroup_mutex);
out_release:
mutex_unlock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
deactivate_super(root->sb);
return ret;
}
/**
* cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
* @cgrp: the cgroup in question