cgroups: implement namespace tracking subsystem

When a task enters a new namespace via a clone() or unshare(), a new cgroup
is created and the task moves into it.

This version names cgroups which are automatically created using
cgroup_clone() as "node_<pid>" where pid is the pid of the unsharing or
cloned process.  (Thanks Pavel for the idea) This is safe because if the
process unshares again, it will create

	/cgroups/(...)/node_<pid>/node_<pid>

The only possibilities (AFAICT) for a -EEXIST on unshare are

	1. pid wraparound
	2. a process fails an unshare, then tries again.

Case 1 is unlikely enough that I ignore it (at least for now).  In case 2, the
node_<pid> will be empty and can be rmdir'ed to make the subsequent unshare()
succeed.

Changelog:
	Name cloned cgroups as "node_<pid>".

[clg@fr.ibm.com: fix order of cgroup subsystems in init/Kconfig]
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: 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>
This commit is contained in:
Serge E. Hallyn 2007-10-18 23:39:45 -07:00 committed by Linus Torvalds
parent 846c7bb055
commit 858d72ead4
6 changed files with 146 additions and 8 deletions

View file

@ -24,3 +24,9 @@ SUBSYS(debug)
#endif
/* */
#ifdef CONFIG_CGROUP_NS
SUBSYS(ns)
#endif
/* */

View file

@ -55,4 +55,11 @@ static inline void exit_task_namespaces(struct task_struct *p)
put_nsproxy(ns);
}
}
#ifdef CONFIG_CGROUP_NS
int ns_cgroup_clone(struct task_struct *tsk);
#else
static inline int ns_cgroup_clone(struct task_struct *tsk) { return 0; }
#endif
#endif

View file

@ -288,6 +288,22 @@ config CGROUP_DEBUG
Say N if unsure
config CGROUP_NS
bool "Namespace cgroup subsystem"
depends on CGROUPS
help
Provides a simple namespace cgroup subsystem to
provide hierarchical naming of sets of namespaces,
for instance virtual servers and checkpoint/restart
jobs.
config CGROUP_CPUACCT
bool "Simple CPU accounting cgroup subsystem"
depends on CGROUPS
help
Provides a simple Resource Controller for monitoring the
total CPU consumed by the tasks in a cgroup
config CPUSETS
bool "Cpuset support"
depends on SMP && CGROUPS
@ -345,13 +361,6 @@ config PROC_PID_CPUSET
depends on CPUSETS
default y
config CGROUP_CPUACCT
bool "Simple CPU accounting cgroup subsystem"
depends on CGROUPS
help
Provides a simple Resource Controller for monitoring the
total CPU consumed by the tasks in a cgroup
config RELAY
bool "Kernel->user space relay support (formerly relayfs)"
help

View file

@ -40,6 +40,7 @@ obj-$(CONFIG_CGROUPS) += cgroup.o
obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
obj-$(CONFIG_CPUSETS) += cpuset.o
obj-$(CONFIG_CGROUP_CPUACCT) += cpu_acct.o
obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
obj-$(CONFIG_IKCONFIG) += configs.o
obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
obj-$(CONFIG_AUDIT) += audit.o auditfilter.o

100
kernel/ns_cgroup.c Normal file
View file

@ -0,0 +1,100 @@
/*
* ns_cgroup.c - namespace cgroup subsystem
*
* Copyright 2006, 2007 IBM Corp
*/
#include <linux/module.h>
#include <linux/cgroup.h>
#include <linux/fs.h>
struct ns_cgroup {
struct cgroup_subsys_state css;
spinlock_t lock;
};
struct cgroup_subsys ns_subsys;
static inline struct ns_cgroup *cgroup_to_ns(
struct cgroup *cgroup)
{
return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
struct ns_cgroup, css);
}
int ns_cgroup_clone(struct task_struct *task)
{
return cgroup_clone(task, &ns_subsys);
}
/*
* Rules:
* 1. you can only enter a cgroup which is a child of your current
* cgroup
* 2. you can only place another process into a cgroup if
* a. you have CAP_SYS_ADMIN
* b. your cgroup is an ancestor of task's destination cgroup
* (hence either you are in the same cgroup as task, or in an
* ancestor cgroup thereof)
*/
static int ns_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup, struct task_struct *task)
{
struct cgroup *orig;
if (current != task) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!cgroup_is_descendant(new_cgroup))
return -EPERM;
}
if (atomic_read(&new_cgroup->count) != 0)
return -EPERM;
orig = task_cgroup(task, ns_subsys_id);
if (orig && orig != new_cgroup->parent)
return -EPERM;
return 0;
}
/*
* Rules: you can only create a cgroup if
* 1. you are capable(CAP_SYS_ADMIN)
* 2. the target cgroup is a descendant of your own cgroup
*/
static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct ns_cgroup *ns_cgroup;
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
if (!cgroup_is_descendant(cgroup))
return ERR_PTR(-EPERM);
ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
if (!ns_cgroup)
return ERR_PTR(-ENOMEM);
spin_lock_init(&ns_cgroup->lock);
return &ns_cgroup->css;
}
static void ns_destroy(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct ns_cgroup *ns_cgroup;
ns_cgroup = cgroup_to_ns(cgroup);
kfree(ns_cgroup);
}
struct cgroup_subsys ns_subsys = {
.name = "ns",
.can_attach = ns_can_attach,
.create = ns_create,
.destroy = ns_destroy,
.subsys_id = ns_subsys_id,
};

View file

@ -156,7 +156,14 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
goto out;
}
err = ns_cgroup_clone(tsk);
if (err) {
put_nsproxy(new_ns);
goto out;
}
tsk->nsproxy = new_ns;
out:
put_nsproxy(old_ns);
return err;
@ -196,8 +203,16 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
*new_nsp = create_new_namespaces(unshare_flags, current,
new_fs ? new_fs : current->fs);
if (IS_ERR(*new_nsp))
if (IS_ERR(*new_nsp)) {
err = PTR_ERR(*new_nsp);
goto out;
}
err = ns_cgroup_clone(current);
if (err)
put_nsproxy(*new_nsp);
out:
return err;
}