[PATCH 1/2][RFC] containers: improve automatic container naming

[PATCH 1/2][RFC] containers: improve automatic container naming

[Serge E. Hallyn]

This compiles and boots, but is not intended for inclusion in -mm (yet),
just as an RFC for the naming scheme to fix the bug Andrew pointed out.

Seem ok overall?

thanks,
-serge

>From 8e9b972f7482415777e982d3bc9a0d55cbaf862b Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@us.ibm.com>
Date: Fri, 1 Jun 2007 15:32:15 -0400
Subject: [PATCH 1/2] containers: improve automatic container naming

The automatic naming of containers created using container_clone()
is currently broken (not protected from wraparound) and inconvenient.

Add a per-container counter for use in naming children of the container.
Before two unshares in a row by one process, and a third in another,
would result in

	/node1/node2
	/node3

The current scheme should result in

	/node1/node1
	/node2

Also, keep a hash table populated with used names, to protect
against counter wrap-around.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
 include/linux/container.h |    8 +++
 kernel/container.c        |  116 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 120 insertions(+), 4 deletions(-)

diff --git a/include/linux/container.h b/include/linux/container.h
index 37c0bdf..61c750d 100644
--- a/include/linux/container.h
+++ b/include/linux/container.h
@@ -75,6 +75,14 @@ struct container {
 	atomic_t count;
 
 	/*
+	 * these are to support automatic naming of automatically
+	 * created containers
+	 */
+	int auto_cnt_set;  /* 1 if thie container is using up a auto_cnt */
+	unsigned long auto_cnt; /* the auto_cnt it's using up */
+	unsigned long next_childcnt; /* next avail cnt for child containers */
+
+	/*
 	 * We link our 'sibling' struct into our parent's 'children'.
 	 * Our children link their 'sibling' into our 'children'.
 	 */
diff --git a/kernel/container.c b/kernel/container.c
index 6f80487..2b2f6f2 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/hash.h>
 
 #include <asm/uaccess.h>
 #include <asm/atomic.h>
@@ -1819,6 +1820,9 @@ static long container_create(struct container *parent, struct dentry *dentry,
 	INIT_LIST_HEAD(&cont->css_groups);
 	INIT_LIST_HEAD(&cont->release_list);
 
+	cont->auto_cnt_set = 0;
+	cont->next_childcnt = 0;
+
 	cont->parent = parent;
 	cont->root = parent->root;
 	cont->top_container = parent->top_container;
@@ -1894,6 +1898,71 @@ static inline int container_has_css_refs(struct container *cont)
 	return 0;
 }
 
+#define cnthash_shift 3
+#define childcnt_hash(ptr, nr) hash_long(nr+(unsigned long)ptr, cnthash_shift)
+static DEFINE_SPINLOCK(childcntlock);
+
+struct container_child_hash_elem {
+	struct container *parent;
+	unsigned long cnt;
+	struct hlist_node list;
+};
+
+static struct hlist_head cntnum_hash_list[1 << cnthash_shift];
+
+static void init_cntnum_hash(void)
+{
+	int i;
+
+	for (i=0; i<1 << cnthash_shift; i++)
+		INIT_HLIST_HEAD(&cntnum_hash_list[i]);
+}
+
+static inline struct container_child_hash_elem *find_cntnum_hash(
+		struct container *parent, unsigned long count)
+{
+	struct container_child_hash_elem *he;
+	struct hlist_head *h;
+	struct hlist_node *tmp;
+
+	h = &cntnum_hash_list[childcnt_hash(parent, count)];
+	hlist_for_each_entry(he, tmp, h, list) {
+		if (he->parent == parent && he->cnt == count)
+			return he;
+	}
+	return NULL;
+}
+
+#define UNSET_HASH 0
+#define SET_HASH 1
+static inline int set_cntnum_hash(struct container *parent,
+        unsigned long count, int set)
+{
+	struct container_child_hash_elem *he;
+	int idx;
+
+	he = find_cntnum_hash(parent, count);
+	if (he) {
+		if (!set) {
+			hlist_del(&he->list);
+			kfree(he);
+			return 0;
+		}
+		return -ENOENT;
+	}
+	if (!set)
+		return -ENOENT;
+	he = kmalloc(sizeof(*he), GFP_KERNEL);
+	if (!he)
+		return -ENOMEM;
+	he->parent = parent;
+	he->cnt = count;
+	INIT_HLIST_NODE(&he->list);
+	idx = childcnt_hash(parent, count);
+	hlist_add_head(&he->list, &cntnum_hash_list[idx]);
+	return 0;
+}
+
 static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
 {
 	struct container *cont = dentry->d_fsdata;
@@ -1941,6 +2010,15 @@ static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
 	dput(d);
 	root->number_of_containers--;
 
+	if (cont->auto_cnt_set) {
+		spin_lock(&childcntlock);
+		if (set_cntnum_hash(parent, cont->auto_cnt, UNSET_HASH))
+			printk(KERN_NOTICE "%s: could not unset %lu\n",
+				__FUNCTION__, cont->auto_cnt);
+		cont->auto_cnt_set = 0;
+		spin_unlock(&childcntlock);
+	}
+
 	if (!list_empty(&cont->release_list))
 		list_del(&cont->release_list);
 	set_bit(CONT_RELEASABLE, &parent->flags);
@@ -2063,6 +2141,8 @@ int __init container_init(void)
 	err = register_filesystem(&container_fs_type);
 	if (err < 0)
 		goto out;
+	
+	init_cntnum_hash();
 
 	entry = create_proc_entry("containers", 0, NULL);
 	if (entry)
@@ -2302,10 +2382,31 @@ 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)
+/*
+ * the while (find_cntnum_hash) loop will only be hit after
+ * we wrap around on next_childnct, which should never happen.
+ */
+static int get_unused_name(struct container *parent, unsigned long *out_cnt,
+		char *buf)
 {
-	sprintf(buf, "node%d", atomic_inc_return(&namecnt));
+	unsigned long cnt;
+	int err = 0;
+
+	spin_lock(&childcntlock);
+	cnt = parent->next_childcnt;
+	while (find_cntnum_hash(parent, cnt))
+		cnt++;
+	err = set_cntnum_hash(parent, cnt, SET_HASH);
+	if (err)
+		goto out_unlock;
+
+	sprintf(buf, "node%lu", cnt);
+	parent->next_childcnt = cnt+1;
+	*out_cnt = cnt;
+
+out_unlock:
+	spin_unlock(&childcntlock);
+	return err;
 }
 
 /**
@@ -2318,6 +2419,7 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	struct dentry *dentry;
 	int ret = 0;
 	char nodename[32];
+	unsigned long auto_cntnum;
 	struct container *parent, *child;
 	struct inode *inode;
 	struct css_group *cg;
@@ -2348,7 +2450,10 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	mutex_unlock(&container_mutex);
 
 	/* Now do the VFS work to create a container */
-	get_unused_name(nodename);
+	ret = get_unused_name(parent, &auto_cntnum, nodename);
+	if (ret)
+		goto out_container_mutex;
+
 	inode = parent->dentry->d_inode;
 
 	/* Hold the parent directory mutex across this operation to
@@ -2380,6 +2485,8 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 		ret = -ENOMEM;
 		goto out_release;
 	}
+	child->auto_cnt_set = 1;
+	child->auto_cnt = auto_cntnum;
 
 	/* The container now exists. Retake container_mutex and check
 	 * that we're still in the same state that we thought we
@@ -2408,6 +2515,7 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
  out_release:
 	mutex_unlock(&inode->i_mutex);
 
+ out_container_mutex:
 	mutex_lock(&container_mutex);
 	put_css_group(cg);
 	mutex_unlock(&container_mutex);
-- 
1.5.1.1.GIT

[PATCH 2/2][RFC] containers interface to nsproxy subsystem

[Serge E. Hallyn]

Again, not compiles and boots, but not sufficiently tested for
inclusion.

thanks,
-serge

>From 6c03518dbda04bf20a9ddeefb291bf1c63e32ec1 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@us.ibm.com>
Date: Fri, 1 Jun 2007 17:30:16 -0400
Subject: [PATCH 2/2] Container interface to nsproxy subsystem

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

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
 include/linux/container_subsys.h |    6 ++
 include/linux/nsproxy.h          |    7 +++
 init/Kconfig                     |    9 ++++
 kernel/Makefile                  |    1 +
 kernel/container.c               |   15 +++++-
 kernel/ns_container.c            |   96 ++++++++++++++++++++++++++++++++++++++
 kernel/nsproxy.c                 |   16 ++++++
 7 files changed, 148 insertions(+), 2 deletions(-)
 create mode 100644 kernel/ns_container.c

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 2b2f6f2..ac5879f 100644
--- a/kernel/container.c
+++ b/kernel/container.c
@@ -2523,14 +2523,25 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	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..afa50d9
--- /dev/null
+++ b/kernel/ns_container.c
@@ -0,0 +1,96 @@
+/*
+ * ns_container.c - namespace container subsystem
+ *
+ * Copyright 2006, 2007 IBM Corp
+ */
+
+#include <linux/module.h>
+#include <linux/container.h>
+#include <linux/fs.h>
+
+struct nscont {
+	struct container_subsys_state css;
+	spinlock_t lock;
+};
+
+struct container_subsys ns_subsys;
+
+static inline struct nscont *container_nscont(struct container *cont)
+{
+	return container_of(container_subsys_state(cont, ns_subsys_id),
+			    struct nscont, css);
+}
+
+int ns_container_clone(struct task_struct *tsk)
+{
+	return container_clone(tsk, &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 tsk's destination container
+ *       (hence either you are in the same container as tsk, or in an
+ *        ancestor container thereof)
+ */
+int ns_can_attach(struct container_subsys *ss,
+		  struct container *cont, struct task_struct *tsk)
+{
+	struct container *c;
+
+	if (current != tsk) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		if (!container_is_descendant(cont))
+			return -EPERM;
+	}
+
+	if (atomic_read(&cont->count) != 0)
+		return -EPERM;
+
+	c = task_container(tsk, ns_subsys_id);
+	if (c && c != cont->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 *cont)
+{
+	struct nscont *ns;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (!container_is_descendant(cont))
+		return -EPERM;
+
+	ns = kzalloc(sizeof(*ns), GFP_KERNEL);
+	if (!ns) return -ENOMEM;
+	spin_lock_init(&ns->lock);
+	cont->subsys[ns_subsys.subsys_id] = &ns->css;
+	return 0;
+}
+
+static void ns_destroy(struct container_subsys *ss,
+		       struct container *cont)
+{
+	struct nscont *ns = container_nscont(cont);
+	kfree(ns);
+}
+
+struct container_subsys ns_subsys = {
+	.name = "ns",
+	.create = ns_create,
+	.destroy  = ns_destroy,
+	.can_attach = ns_can_attach,
+	.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;
 }
-- 
1.5.1.1.GIT

Re: [PATCH 1/2][RFC] containers: improve automatic container naming

[Andrew Morton]

On Fri, 1 Jun 2007 16:48:09 -0500
"Serge E. Hallyn" <serue@us.ibm.com> wrote:

> This compiles and boots, but is not intended for inclusion in -mm (yet),
> just as an RFC for the naming scheme to fix the bug Andrew pointed out.
> 
> Seem ok overall?
> 
> thanks,
> -serge
> 
> >From 8e9b972f7482415777e982d3bc9a0d55cbaf862b Mon Sep 17 00:00:00 2001
> From: Serge E. Hallyn <serue@us.ibm.com>
> Date: Fri, 1 Jun 2007 15:32:15 -0400
> Subject: [PATCH 1/2] containers: improve automatic container naming
> 
> The automatic naming of containers created using container_clone()
> is currently broken (not protected from wraparound) and inconvenient.
> 
> Add a per-container counter for use in naming children of the container.
> Before two unshares in a row by one process, and a third in another,
> would result in
> 
> 	/node1/node2
> 	/node3
> 
> The current scheme should result in
> 
> 	/node1/node1
> 	/node2
> 
> Also, keep a hash table populated with used names, to protect
> against counter wrap-around.
> 
> ...
>
>  include/linux/container.h |    8 +++
>  kernel/container.c        |  116 +++++++++++++++++++++++++++++++++++++++++++--

gad, what's all this stuff?

I think an IDR tree would get you what you're after in much less code. 
Although it means that container IDs would get recycled quickly across a
remove+add.

Be aware that there are IDR enhancements in Greg's driver tree (and hence
in -mm) which are relevant to this application.


> +	if (cont->auto_cnt_set) {

Can we please stop using "cnt" and "cont" to refer to containers?  Let's
use "container", OK?

Re: [PATCH 1/2][RFC] containers: improve automatic container naming

[Serge E. Hallyn]

Quoting Andrew Morton (akpm@linux-foundation.org):
> On Fri, 1 Jun 2007 16:48:09 -0500
> "Serge E. Hallyn" <serue@us.ibm.com> wrote:
> 
> > This compiles and boots, but is not intended for inclusion in -mm (yet),
> > just as an RFC for the naming scheme to fix the bug Andrew pointed out.
> > 
> > Seem ok overall?
> > 
> > thanks,
> > -serge
> > 
> > >From 8e9b972f7482415777e982d3bc9a0d55cbaf862b Mon Sep 17 00:00:00 2001
> > From: Serge E. Hallyn <serue@us.ibm.com>
> > Date: Fri, 1 Jun 2007 15:32:15 -0400
> > Subject: [PATCH 1/2] containers: improve automatic container naming
> > 
> > The automatic naming of containers created using container_clone()
> > is currently broken (not protected from wraparound) and inconvenient.
> > 
> > Add a per-container counter for use in naming children of the container.
> > Before two unshares in a row by one process, and a third in another,
> > would result in
> > 
> > 	/node1/node2
> > 	/node3
> > 
> > The current scheme should result in
> > 
> > 	/node1/node1
> > 	/node2
> > 
> > Also, keep a hash table populated with used names, to protect
> > against counter wrap-around.
> > 
> > ...
> >
> >  include/linux/container.h |    8 +++
> >  kernel/container.c        |  116 +++++++++++++++++++++++++++++++++++++++++++--
> 
> gad, what's all this stuff?

The sound of me starting over.

> I think an IDR tree would get you what you're after in much less code. 

Ok, will look at that.  Thanks for the tip!

> Although it means that container IDs would get recycled quickly across a
> remove+add.
> 
> Be aware that there are IDR enhancements in Greg's driver tree (and hence
> in -mm) which are relevant to this application.
> 
> 
> > +	if (cont->auto_cnt_set) {
> 
> Can we please stop using "cnt" and "cont" to refer to containers?  Let's
> use "container", OK?

Ok.

thanks,
-serge