This patch adds:

/proc/containers - general system info

/proc/*/container - per-task container membership info

Signed-off-by: Paul Menage <menage@google.com>

---
 fs/proc/base.c     |    7 ++
 kernel/container.c |  128 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)

Index: container-2.6.21-rc7-mm1/fs/proc/base.c
===================================================================
--- container-2.6.21-rc7-mm1.orig/fs/proc/base.c
+++ container-2.6.21-rc7-mm1/fs/proc/base.c
@@ -68,6 +68,7 @@
 #include <linux/security.h>
 #include <linux/ptrace.h>
 #include <linux/seccomp.h>
+#include <linux/container.h>
 #include <linux/cpuset.h>
 #include <linux/audit.h>
 #include <linux/poll.h>
@@ -1980,6 +1981,9 @@ static const struct pid_entry tgid_base_
 #ifdef CONFIG_CPUSETS
 	REG("cpuset",     S_IRUGO, cpuset),
 #endif
+#ifdef CONFIG_CONTAINERS
+	REG("container",  S_IRUGO, container),
+#endif
 	INF("oom_score",  S_IRUGO, oom_score),
 	REG("oom_adj",    S_IRUGO|S_IWUSR, oom_adjust),
 #ifdef CONFIG_AUDITSYSCALL
@@ -2270,6 +2274,9 @@ static const struct pid_entry tid_base_s
 #ifdef CONFIG_CPUSETS
 	REG("cpuset",    S_IRUGO, cpuset),
 #endif
+#ifdef CONFIG_CONTAINERS
+	REG("container",  S_IRUGO, container),
+#endif
 	INF("oom_score", S_IRUGO, oom_score),
 	REG("oom_adj",   S_IRUGO|S_IWUSR, oom_adjust),
 #ifdef CONFIG_AUDITSYSCALL
Index: container-2.6.21-rc7-mm1/kernel/container.c
===================================================================
--- container-2.6.21-rc7-mm1.orig/kernel/container.c
+++ container-2.6.21-rc7-mm1/kernel/container.c
@@ -247,6 +247,7 @@ static int container_mkdir(struct inode 
 static int container_rmdir(struct inode *unused_dir, struct dentry *dentry);
 static int container_populate_dir(struct container *cont);
 static struct inode_operations container_dir_inode_operations;
+struct file_operations proc_containerstats_operations;
 
 static struct backing_dev_info container_backing_dev_info = {
 	.ra_pages = 0,		/* No readahead */
@@ -1507,6 +1508,7 @@ int __init container_init(void)
 {
 	int err;
 	int i;
+	struct proc_dir_entry *entry;
 
 	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
 		struct container_subsys *ss = subsys[i];
@@ -1518,10 +1520,136 @@ int __init container_init(void)
 	if (err < 0)
 		goto out;
 
+	entry = create_proc_entry("containers", 0, NULL);
+	if (entry)
+		entry->proc_fops = &proc_containerstats_operations;
+
 out:
 	return err;
 }
 
+/*
+ * proc_container_show()
+ *  - Print task's container paths into seq_file, one line for each hierarchy
+ *  - Used for /proc/<pid>/container.
+ *  - No need to task_lock(tsk) on this tsk->container reference, as it
+ *    doesn't really matter if tsk->container changes after we read it,
+ *    and we take container_mutex, keeping attach_task() from changing it
+ *    anyway.  No need to check that tsk->container != NULL, thanks to
+ *    the_top_container_hack in container_exit(), which sets an exiting tasks
+ *    container to top_container.
+ */
+
+/* TODO: Use a proper seq_file iterator */
+static int proc_container_show(struct seq_file *m, void *v)
+{
+	struct pid *pid;
+	struct task_struct *tsk;
+	char *buf;
+	int retval;
+	struct containerfs_root *root;
+
+	retval = -ENOMEM;
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto out;
+
+	retval = -ESRCH;
+	pid = m->private;
+	tsk = get_pid_task(pid, PIDTYPE_PID);
+	if (!tsk)
+		goto out_free;
+
+	retval = 0;
+
+	mutex_lock(&container_mutex);
+
+	for_each_root(root) {
+		struct container_subsys *ss;
+		struct container *cont;
+		int subsys_id;
+		int count = 0;
+		/* Skip this hierarchy if it has no active subsystems */
+		if (!root->subsys_bits) continue;
+		for_each_subsys(root, ss) {
+			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
+		}
+		seq_putc(m, ':');
+		get_first_subsys(&root->top_container, NULL, &subsys_id);
+		cont = task_container(tsk, subsys_id);
+		retval = container_path(cont, buf, PAGE_SIZE);
+		if (retval < 0)
+			goto out_unlock;
+		seq_puts(m, buf);
+		seq_putc(m, '\n');
+	}
+
+out_unlock:
+	mutex_unlock(&container_mutex);
+	put_task_struct(tsk);
+out_free:
+	kfree(buf);
+out:
+	return retval;
+}
+
+static int container_open(struct inode *inode, struct file *file)
+{
+	struct pid *pid = PROC_I(inode)->pid;
+	return single_open(file, proc_container_show, pid);
+}
+
+struct file_operations proc_container_operations = {
+	.open		= container_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+/* Display information about each subsystem and each hierarchy */
+static int proc_containerstats_show(struct seq_file *m, void *v)
+{
+	int i;
+	struct containerfs_root *root;
+	mutex_lock(&container_mutex);
+	seq_puts(m, "Hierarchies:\n");
+	for_each_root(root) {
+		struct container_subsys *ss;
+		int first = 1;
+		seq_printf(m, "%p: bits=%lx containers=%d (", root,
+			   root->subsys_bits, root->number_of_containers);
+		for_each_subsys(root, ss) {
+			seq_printf(m, "%s%s", first ? "" : ", ", ss->name);
+			first = false;
+		}
+		seq_putc(m, ')');
+		if (root->sb) {
+			seq_printf(m, " s_active=%d",
+				   atomic_read(&root->sb->s_active));
+		}
+		seq_putc(m, '\n');
+	}
+	seq_puts(m, "Subsystems:\n");
+	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+		struct container_subsys *ss = subsys[i];
+		seq_printf(m, "%d: name=%s hierarchy=%p\n",
+			   i, ss->name, ss->root);
+	}
+	mutex_unlock(&container_mutex);
+	return 0;
+}
+
+static int containerstats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, proc_containerstats_show, 0);
+}
+
+struct file_operations proc_containerstats_operations = {
+	.open = containerstats_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
 /**
  * container_fork - attach newly forked task to its parents container.
  * @tsk: pointer to task_struct of forking parent process.

--
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