Re: [PATCH 1/1] containers: implement nsproxy containers subsystem
From: Pavel Emelianov
Date: Tue Jun 05 2007 - 05:58:18 EST
Serge E. Hallyn wrote:
>>From 190ea72d213393dd1440643b2b87b5b2128dff87 Mon Sep 17 00:00:00 2001
> From: Serge E. Hallyn <serue@xxxxxxxxxx>
> Date: Mon, 4 Jun 2007 14:18:52 -0400
> Subject: [PATCH 1/1] containers: implement nsproxy containers subsystem
>
> When a task enters a new namespace via a clone() or unshare(), a new
> container is created and the task moves into it. This enables
I have a design question.
How the child that has a new namespace guesses what id
this namespace has in containers?
> tracking - and applying resource controls - to virtual servers,
> resource jobs, often logins (using per-user namespaces), and in
> general any application of per-process namespaces.
>
> This version uses an ida to generate a unique id for auto-created
> containers, i.e. those created through container_clone(). After
> a container is created, it can be renamed to a more useful name if
> so desired. The original id isn't released until the container is
> destroyed. (This could be fixed at container_rename() if it was
> deemed desireable)
>
> There is just one ida for all containers, because an ida per container
> to track ids used for child containers would take a great deal of
> space, and probably isn't very useful.
>
> Changelog:
> Use an ida to generate unique ids for auto-created containers.
>
> Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>
> ---
> include/linux/container.h | 2 +
> include/linux/container_subsys.h | 6 ++
> include/linux/nsproxy.h | 7 +++
> init/Kconfig | 9 ++++
> kernel/Makefile | 1 +
> kernel/container.c | 52 ++++++++++++++++----
> kernel/ns_container.c | 99 ++++++++++++++++++++++++++++++++++++++
> kernel/nsproxy.c | 16 ++++++
> 8 files changed, 183 insertions(+), 9 deletions(-)
> create mode 100644 kernel/ns_container.c
>
> diff --git a/include/linux/container.h b/include/linux/container.h
> index 37c0bdf..2f8ee47 100644
> --- a/include/linux/container.h
> +++ b/include/linux/container.h
> @@ -87,6 +87,8 @@ struct container {
> /* Private pointers for each registered subsystem */
> struct container_subsys_state *subsys[CONTAINER_SUBSYS_COUNT];
>
> + int unique_id; /* usually -1, set to >=0 in container_clone() */
> +
> struct containerfs_root *root;
> struct container *top_container;
>
> diff --git a/include/linux/container_subsys.h b/include/linux/container_subsys.h
> index 8fea7cf..9861751 100644
> --- a/include/linux/container_subsys.h
> +++ b/include/linux/container_subsys.h
> @@ -24,3 +24,9 @@ SUBSYS(debug)
> #endif
>
> /* */
> +
> +#ifdef CONFIG_CONTAINER_NS
> +SUBSYS(ns)
> +#endif
> +
> +/* */
> diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
> index 189e0dc..8be975b 100644
> --- a/include/linux/nsproxy.h
> +++ b/include/linux/nsproxy.h
> @@ -54,4 +54,11 @@ static inline void exit_task_namespaces(struct task_struct *p)
> put_nsproxy(ns);
> }
> }
> +
> +#ifdef CONFIG_CONTAINER_NS
> +int ns_container_clone(struct task_struct *tsk);
> +#else
> +static inline int ns_container_clone(struct task_struct *tsk) { return 0; }
> +#endif
> +
> #endif
> diff --git a/init/Kconfig b/init/Kconfig
> index 5861ad9..d79c505 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -355,6 +355,15 @@ config CONTAINER_CPUACCT
> Provides a simple Resource Controller for monitoring the
> total CPU consumed by the tasks in a container
>
> +config CONTAINER_NS
> + bool "Namespace container subsystem"
> + select CONTAINERS
> + help
> + Provides a simple namespace container subsystem to
> + provide hierarchical naming of sets of namespaces,
> + for instance virtual servers and checkpoint/restart
> + jobs.
> +
> config PROC_PID_CPUSET
> bool "Include legacy /proc/<pid>/cpuset file"
> depends on CPUSETS
> diff --git a/kernel/Makefile b/kernel/Makefile
> index f73b3d3..34f2345 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -40,6 +40,7 @@ obj-$(CONFIG_CONTAINERS) += container.o
> obj-$(CONFIG_CONTAINER_DEBUG) += container_debug.o
> obj-$(CONFIG_CPUSETS) += cpuset.o
> obj-$(CONFIG_CONTAINER_CPUACCT) += cpu_acct.o
> +obj-$(CONFIG_CONTAINER_NS) += ns_container.o
> obj-$(CONFIG_IKCONFIG) += configs.o
> obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
> obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
> diff --git a/kernel/container.c b/kernel/container.c
> index 6f80487..0d46d66 100644
> --- a/kernel/container.c
> +++ b/kernel/container.c
> @@ -55,6 +55,7 @@
> #include <linux/time.h>
> #include <linux/backing-dev.h>
> #include <linux/sort.h>
> +#include <linux/idr.h>
>
> #include <asm/uaccess.h>
> #include <asm/atomic.h>
> @@ -64,6 +65,8 @@
>
> static DEFINE_MUTEX(container_mutex);
>
> +static struct ida container_ida;
> +
> /* Generate an array of container subsystem pointers */
> #define SUBSYS(_x) &_x ## _subsys,
>
> @@ -1818,6 +1821,7 @@ static long container_create(struct container *parent, struct dentry *dentry,
> INIT_LIST_HEAD(&cont->children);
> INIT_LIST_HEAD(&cont->css_groups);
> INIT_LIST_HEAD(&cont->release_list);
> + cont->unique_id = -1;
>
> cont->parent = parent;
> cont->root = parent->root;
> @@ -1941,6 +1945,9 @@ static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
> dput(d);
> root->number_of_containers--;
>
> + if (cont->unique_id != -1)
> + ida_remove(&container_ida, cont->unique_id);
> +
> if (!list_empty(&cont->release_list))
> list_del(&cont->release_list);
> set_bit(CONT_RELEASABLE, &parent->flags);
> @@ -2040,6 +2047,8 @@ int __init container_init_early(void)
> if (ss->early_init)
> container_init_subsys(ss);
> }
> +
> + ida_init(&container_ida);
> return 0;
> }
>
> @@ -2302,12 +2311,6 @@ void container_exit(struct task_struct *tsk, int run_callbacks)
> put_css_group_taskexit(cg);
> }
>
> -static atomic_t namecnt;
> -static void get_unused_name(char *buf)
> -{
> - sprintf(buf, "node%d", atomic_inc_return(&namecnt));
> -}
> -
> /**
> * container_clone - duplicate the current container in the hierarchy
> * that the given subsystem is attached to, and move this task into
> @@ -2322,6 +2325,7 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
> struct inode *inode;
> struct css_group *cg;
> struct containerfs_root *root;
> + int new_id;
>
> /* We shouldn't be called by an unregistered subsystem */
> BUG_ON(!subsys->active);
> @@ -2340,6 +2344,19 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
> }
> cg = tsk->containers;
> parent = task_container(tsk, subsys->subsys_id);
> +
> + ret = ida_get_new(&container_ida, &new_id);
> + if (ret == -EAGAIN) {
> + if (!ida_pre_get(&container_ida, GFP_KERNEL))
> + return -ENOMEM;
> + ret = ida_get_new(&container_ida, &new_id);
> + }
> + if (ret) {
> + ret = -EBUSY;
> + goto out_no_name;
> + }
> + sprintf(nodename, "node%d", new_id);
> +
> /* Pin the hierarchy */
> atomic_inc(&parent->root->sb->s_active);
>
> @@ -2347,8 +2364,8 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
> get_css_group(cg);
> mutex_unlock(&container_mutex);
>
> +
> /* Now do the VFS work to create a container */
> - get_unused_name(nodename);
> inode = parent->dentry->d_inode;
>
> /* Hold the parent directory mutex across this operation to
> @@ -2403,6 +2420,10 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
>
> /* All seems fine. Finish by moving the task into the new container */
> ret = attach_task(child, tsk);
> +
> + if (!ret)
> + child->unique_id = new_id;
> +
> mutex_unlock(&container_mutex);
>
> out_release:
> @@ -2410,19 +2431,32 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
>
> mutex_lock(&container_mutex);
> put_css_group(cg);
> +
> + out_no_name:
> mutex_unlock(&container_mutex);
> deactivate_super(parent->root->sb);
> return ret;
> }
>
> -/* See if "cont" is a descendant of the current task's container in
> - * the appropriate hierarchy */
> +/*
> + * See if "cont" is a descendant of the current task's container in
> + * the appropriate hierarchy
> + *
> + * If we are sending in dummytop, then presumably we are creating
> + * the top container in the subsystem.
> + *
> + * Called only by the ns (nsproxy) container.
> + */
>
> int container_is_descendant(const struct container *cont)
> {
> int ret;
> struct container *target;
> int subsys_id;
> +
> + if (cont == dummytop)
> + return 1;
> +
> get_first_subsys(cont, NULL, &subsys_id);
> target = task_container(current, subsys_id);
> while (cont != target && cont!= cont->top_container) {
> diff --git a/kernel/ns_container.c b/kernel/ns_container.c
> new file mode 100644
> index 0000000..3465716
> --- /dev/null
> +++ b/kernel/ns_container.c
> @@ -0,0 +1,99 @@
> +/*
> + * ns_container.c - namespace container subsystem
> + *
> + * Copyright 2006, 2007 IBM Corp
> + */
> +
> +#include <linux/module.h>
> +#include <linux/container.h>
> +#include <linux/fs.h>
> +
> +struct ns_container {
> + struct container_subsys_state css;
> + spinlock_t lock;
> +};
> +
> +struct container_subsys ns_subsys;
> +
> +static inline struct ns_container *container_to_ns(
> + struct container *container)
> +{
> + return container_of(container_subsys_state(container, ns_subsys_id),
> + struct ns_container, css);
> +}
> +
> +int ns_container_clone(struct task_struct *task)
> +{
> + return container_clone(task, &ns_subsys);
> +}
> +
> +/*
> + * Rules:
> + * 1. you can only enter a container which is a child of your current
> + * container
> + * 2. you can only place another process into a container if
> + * a. you have CAP_SYS_ADMIN
> + * b. your container is an ancestor of task's destination container
> + * (hence either you are in the same container as task, or in an
> + * ancestor container thereof)
> + */
> +static int ns_can_attach(struct container_subsys *ss,
> + struct container *new_container, struct task_struct *task)
> +{
> + struct container *orig;
> +
> + if (current != task) {
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + if (!container_is_descendant(new_container))
> + return -EPERM;
> + }
> +
> + if (atomic_read(&new_container->count) != 0)
> + return -EPERM;
> +
> + orig = task_container(task, ns_subsys_id);
> + if (orig && orig != new_container->parent)
> + return -EPERM;
> +
> + return 0;
> +}
> +
> +/*
> + * Rules: you can only create a container if
> + * 1. you are capable(CAP_SYS_ADMIN)
> + * 2. the target container is a descendant of your own container
> + */
> +static int ns_create(struct container_subsys *ss, struct container *container)
> +{
> + struct ns_container *ns_container;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> + if (!container_is_descendant(container))
> + return -EPERM;
> +
> + ns_container = kzalloc(sizeof(*ns_container), GFP_KERNEL);
> + if (!ns_container) return -ENOMEM;
> + spin_lock_init(&ns_container->lock);
> + container->subsys[ns_subsys.subsys_id] = &ns_container->css;
> + return 0;
> +}
> +
> +static void ns_destroy(struct container_subsys *ss,
> + struct container *container)
> +{
> + struct ns_container *ns_container;
> +
> + ns_container = container_to_ns(container);
> + kfree(ns_container);
> +}
> +
> +struct container_subsys ns_subsys = {
> + .name = "ns",
> + .can_attach = ns_can_attach,
> + .create = ns_create,
> + .destroy = ns_destroy,
> + .subsys_id = ns_subsys_id,
> +};
> diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
> index 1bc4b55..afce808 100644
> --- a/kernel/nsproxy.c
> +++ b/kernel/nsproxy.c
> @@ -124,7 +124,14 @@ int copy_namespaces(int flags, struct task_struct *tsk)
> goto out;
> }
>
> + err = ns_container_clone(tsk);
> + if (err) {
> + put_nsproxy(new_ns);
> + goto out;
> + }
> +
> tsk->nsproxy = new_ns;
> +
> out:
> put_nsproxy(old_ns);
> return err;
> @@ -177,6 +184,15 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
> if (IS_ERR(*new_nsp)) {
> err = PTR_ERR(*new_nsp);
> put_nsproxy(old_ns);
> + goto out;
> + }
> +
> + err = ns_container_clone(current);
> + if (err) {
> + put_nsproxy(*new_nsp);
> + put_nsproxy(old_ns);
> }
> +
> +out:
> return err;
> }
-
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