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Subject[PATCH] cgroup : remove the ns_cgroup
Date
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.

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>
---
Documentation/cgroups/cgroups.txt | 2 +-
arch/mips/configs/bcm47xx_defconfig | 1 -
arch/mn10300/configs/asb2364_defconfig | 1 -
arch/powerpc/configs/ppc6xx_defconfig | 1 -
arch/powerpc/configs/pseries_defconfig | 1 -
arch/sh/configs/apsh4ad0a_defconfig | 1 -
arch/sh/configs/sdk7786_defconfig | 1 -
arch/sh/configs/se7206_defconfig | 1 -
arch/sh/configs/shx3_defconfig | 1 -
arch/sh/configs/urquell_defconfig | 1 -
arch/x86/configs/i386_defconfig | 1 -
arch/x86/configs/x86_64_defconfig | 1 -
include/linux/cgroup.h | 3 -
include/linux/cgroup_subsys.h | 6 --
include/linux/nsproxy.h | 9 ---
init/Kconfig | 8 --
kernel/Makefile | 1 -
kernel/cgroup.c | 116 -------------------------------
kernel/cpuset.c | 7 +-
kernel/fork.c | 6 --
kernel/ns_cgroup.c | 118 --------------------------------
kernel/nsproxy.c | 4 -
22 files changed, 4 insertions(+), 287 deletions(-)
delete mode 100644 kernel/ns_cgroup.c

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 44b8b7a..ac759b6 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -618,7 +618,7 @@ always handled well.
void post_clone(struct cgroup_subsys *ss, struct cgroup *cgrp)
(cgroup_mutex held by caller)

-Called at the end of cgroup_clone() to do any parameter
+Called during cgroup_create() to do any parameter
initialization which might be required before a task could attach. For
example in cpusets, no task may attach before 'cpus' and 'mems' are set
up.
diff --git a/arch/mips/configs/bcm47xx_defconfig b/arch/mips/configs/bcm47xx_defconfig
index 927d58b..c4338e0 100644
--- a/arch/mips/configs/bcm47xx_defconfig
+++ b/arch/mips/configs/bcm47xx_defconfig
@@ -16,7 +16,6 @@ CONFIG_TASK_IO_ACCOUNTING=y
CONFIG_AUDIT=y
CONFIG_TINY_RCU=y
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_RELAY=y
CONFIG_BLK_DEV_INITRD=y
diff --git a/arch/mn10300/configs/asb2364_defconfig b/arch/mn10300/configs/asb2364_defconfig
index 83ce2f2..d38391a 100644
--- a/arch/mn10300/configs/asb2364_defconfig
+++ b/arch/mn10300/configs/asb2364_defconfig
@@ -8,7 +8,6 @@ CONFIG_TASK_XACCT=y
CONFIG_TASK_IO_ACCOUNTING=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
diff --git a/arch/powerpc/configs/ppc6xx_defconfig b/arch/powerpc/configs/ppc6xx_defconfig
index 9d64a68..9b253f6 100644
--- a/arch/powerpc/configs/ppc6xx_defconfig
+++ b/arch/powerpc/configs/ppc6xx_defconfig
@@ -10,7 +10,6 @@ CONFIG_TASK_XACCT=y
CONFIG_TASK_IO_ACCOUNTING=y
CONFIG_AUDIT=y
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_RESOURCE_COUNTERS=y
diff --git a/arch/powerpc/configs/pseries_defconfig b/arch/powerpc/configs/pseries_defconfig
index f87f0e1..972587f 100644
--- a/arch/powerpc/configs/pseries_defconfig
+++ b/arch/powerpc/configs/pseries_defconfig
@@ -15,7 +15,6 @@ CONFIG_AUDITSYSCALL=y
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CPUSETS=y
diff --git a/arch/sh/configs/apsh4ad0a_defconfig b/arch/sh/configs/apsh4ad0a_defconfig
index e71a531..f722a3d 100644
--- a/arch/sh/configs/apsh4ad0a_defconfig
+++ b/arch/sh/configs/apsh4ad0a_defconfig
@@ -7,7 +7,6 @@ CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
diff --git a/arch/sh/configs/sdk7786_defconfig b/arch/sh/configs/sdk7786_defconfig
index dc4a2eb..9fdabe2 100644
--- a/arch/sh/configs/sdk7786_defconfig
+++ b/arch/sh/configs/sdk7786_defconfig
@@ -12,7 +12,6 @@ CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_CGROUPS=y
CONFIG_CGROUP_DEBUG=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CPUSETS=y
diff --git a/arch/sh/configs/se7206_defconfig b/arch/sh/configs/se7206_defconfig
index a468ff2..72c3fad 100644
--- a/arch/sh/configs/se7206_defconfig
+++ b/arch/sh/configs/se7206_defconfig
@@ -8,7 +8,6 @@ CONFIG_RCU_TRACE=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_CGROUPS=y
CONFIG_CGROUP_DEBUG=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_RESOURCE_COUNTERS=y
diff --git a/arch/sh/configs/shx3_defconfig b/arch/sh/configs/shx3_defconfig
index 3f92d37..6bb4130 100644
--- a/arch/sh/configs/shx3_defconfig
+++ b/arch/sh/configs/shx3_defconfig
@@ -9,7 +9,6 @@ CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
diff --git a/arch/sh/configs/urquell_defconfig b/arch/sh/configs/urquell_defconfig
index 7b3daec..8bfa4d0 100644
--- a/arch/sh/configs/urquell_defconfig
+++ b/arch/sh/configs/urquell_defconfig
@@ -9,7 +9,6 @@ CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_CGROUPS=y
CONFIG_CGROUP_DEBUG=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CPUSETS=y
diff --git a/arch/x86/configs/i386_defconfig b/arch/x86/configs/i386_defconfig
index 6f98726..2bf1805 100644
--- a/arch/x86/configs/i386_defconfig
+++ b/arch/x86/configs/i386_defconfig
@@ -10,7 +10,6 @@ CONFIG_TASK_IO_ACCOUNTING=y
CONFIG_AUDIT=y
CONFIG_LOG_BUF_SHIFT=18
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CPUSETS=y
CONFIG_CGROUP_CPUACCT=y
diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
index ee01a9d..22a0dc8 100644
--- a/arch/x86/configs/x86_64_defconfig
+++ b/arch/x86/configs/x86_64_defconfig
@@ -11,7 +11,6 @@ CONFIG_TASK_IO_ACCOUNTING=y
CONFIG_AUDIT=y
CONFIG_LOG_BUF_SHIFT=18
CONFIG_CGROUPS=y
-CONFIG_CGROUP_NS=y
CONFIG_CGROUP_FREEZER=y
CONFIG_CPUSETS=y
CONFIG_CGROUP_CPUACCT=y
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ce104e3..d0509a3 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -552,9 +552,6 @@ static inline struct cgroup* task_cgroup(struct task_struct *task,
return task_subsys_state(task, subsys_id)->cgroup;
}

-int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss,
- char *nodename);
-
/* A cgroup_iter should be treated as an opaque object */
struct cgroup_iter {
struct list_head *cg_link;
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index ccefff0..4ba5259 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -19,12 +19,6 @@ SUBSYS(debug)

/* */

-#ifdef CONFIG_CGROUP_NS
-SUBSYS(ns)
-#endif
-
-/* */
-
#ifdef CONFIG_CGROUP_SCHED
SUBSYS(cpu_cgroup)
#endif
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 7b370c7..50d20ab 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -81,13 +81,4 @@ static inline void get_nsproxy(struct nsproxy *ns)
atomic_inc(&ns->count);
}

-#ifdef CONFIG_CGROUP_NS
-int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid);
-#else
-static inline int ns_cgroup_clone(struct task_struct *tsk, struct pid *pid)
-{
- return 0;
-}
-#endif
-
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 1379adc..7acdfb4 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -582,14 +582,6 @@ config CGROUP_DEBUG

Say N if unsure.

-config CGROUP_NS
- bool "Namespace cgroup subsystem"
- 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_FREEZER
bool "Freezer cgroup subsystem"
help
diff --git a/kernel/Makefile b/kernel/Makefile
index 353d3fe..bd1b486 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -62,7 +62,6 @@ obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup.o
obj-$(CONFIG_CGROUP_FREEZER) += cgroup_freezer.o
obj-$(CONFIG_CPUSETS) += cpuset.o
-obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
obj-$(CONFIG_UTS_NS) += utsname.o
obj-$(CONFIG_USER_NS) += user_namespace.o
obj-$(CONFIG_PID_NS) += pid_namespace.o
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b24d702..9b92442 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4267,122 +4267,6 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
}

/**
- * 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
* @task: the task in question
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4349935..10f1835 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1828,10 +1828,9 @@ static int cpuset_populate(struct cgroup_subsys *ss, struct cgroup *cont)
}

/*
- * post_clone() is called at the end of cgroup_clone().
- * 'cgroup' was just created automatically as a result of
- * a cgroup_clone(), and the current task is about to
- * be moved into 'cgroup'.
+ * post_clone() is called during cgroup_create() when the
+ * clone_children mount argument was specified. The cgroup
+ * can not yet have any tasks.
*
* Currently we refuse to set up the cgroup - thereby
* refusing the task to be entered, and as a result refusing
diff --git a/kernel/fork.c b/kernel/fork.c
index 25e4291..4326cbe 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1193,12 +1193,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
if (clone_flags & CLONE_THREAD)
p->tgid = current->tgid;

- if (current->nsproxy != p->nsproxy) {
- retval = ns_cgroup_clone(p, pid);
- if (retval)
- goto bad_fork_free_pid;
- }
-
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
/*
* Clear TID on mm_release()?
diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
deleted file mode 100644
index 2c98ad9..0000000
--- a/kernel/ns_cgroup.c
+++ /dev/null
@@ -1,118 +0,0 @@
-/*
- * ns_cgroup.c - namespace cgroup subsystem
- *
- * Copyright 2006, 2007 IBM Corp
- */
-
-#include <linux/module.h>
-#include <linux/cgroup.h>
-#include <linux/fs.h>
-#include <linux/proc_fs.h>
-#include <linux/slab.h>
-#include <linux/nsproxy.h>
-
-struct ns_cgroup {
- struct cgroup_subsys_state css;
-};
-
-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, struct pid *pid)
-{
- char name[PROC_NUMBUF];
-
- snprintf(name, PROC_NUMBUF, "%d", pid_vnr(pid));
- return cgroup_clone(task, &ns_subsys, name);
-}
-
-/*
- * Rules:
- * 1. you can only enter a cgroup which is a descendant 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, bool threadgroup)
-{
- if (current != task) {
- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
-
- if (!cgroup_is_descendant(new_cgroup, current))
- return -EPERM;
- }
-
- if (!cgroup_is_descendant(new_cgroup, task))
- return -EPERM;
-
- if (threadgroup) {
- struct task_struct *c;
- rcu_read_lock();
- list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
- if (!cgroup_is_descendant(new_cgroup, c)) {
- rcu_read_unlock();
- return -EPERM;
- }
- }
- rcu_read_unlock();
- }
-
- 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, current))
- return ERR_PTR(-EPERM);
- if (test_bit(CGRP_CLONE_CHILDREN, &cgroup->flags)) {
- printk("ns_cgroup can't be created with parent "
- "'clone_children' set.\n");
- return ERR_PTR(-EINVAL);
- }
-
- printk_once("ns_cgroup deprecated: consider using the "
- "'clone_children' flag without the ns_cgroup.\n");
-
- ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
- if (!ns_cgroup)
- return ERR_PTR(-ENOMEM);
- 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,
-};
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f74e6c0..014a90d 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -198,10 +198,6 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
goto out;
}

- err = ns_cgroup_clone(current, task_pid(current));
- if (err)
- put_nsproxy(*new_nsp);
-
out:
return err;
}
--
1.7.1


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