[Devel] [RFC] [PATCH 3/3] containers: hook /proc/$$/container into containerfs

[Serge E. Hallyn]

From: Serge E. Hallyn <serue at us.ibm.com>
Subject: [RFC] [PATCH 3/3] containers: hook /proc/$$/container into containerfs

Create a symlink from /proc/$$/container into the containerfs.
What works:

	1.  ls -l /proc/$$/container
	  shows the full hierarchical name of the container;

	2.  mount -t containerfs none /container
	  results in a file tree under /container representing the
	  full container hierarchy

	3.  cd /proc/$$/container; ls
	  results in a listing of child containers

What doesn't work:
	The /proc/$$/container link always appears dead (red
	in bash on my fedora test system) because it points
	into a kern_mounted fs.

Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
---
 fs/proc/base.c            |   18 ++++++++++++++++++
 include/linux/container.h |    1 +
 kernel/container.c        |    2 +-
 3 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 77a57b5..00c7618 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -73,6 +73,7 @@ #include <linux/audit.h>
 #include <linux/poll.h>
 #include <linux/nsproxy.h>
 #include <linux/oom.h>
+#include <linux/container.h>
 #include "internal.h"
 
 /* NOTE:
@@ -189,6 +190,21 @@ static int proc_root_link(struct inode *
 	return result;
 }
 
+static int proc_container_link(struct inode *inode, struct dentry **dentry,
+						 struct vfsmount **mnt)
+{
+	struct task_struct *task = get_proc_task(inode);
+	int result = -ENOENT;
+
+	if (task) {
+		*dentry = dget(task->nsproxy->container->dentry);
+		*mnt = mntget(containerfs_mount);
+		put_task_struct(task);
+		result = 0;
+	}
+	return result;
+}
+
 #define MAY_PTRACE(task) \
 	(task == current || \
 	(task->parent == current && \
@@ -1879,6 +1895,7 @@ #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 	INF("io",	S_IRUGO, pid_io_accounting),
 #endif
+	LNK("container",  container),
 };
 
 static int proc_tgid_base_readdir(struct file * filp,
@@ -2157,6 +2174,7 @@ #endif
 #ifdef CONFIG_FAULT_INJECTION
 	REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),
 #endif
+	LNK("container",  container),
 };
 
 static int proc_tid_base_readdir(struct file * filp,
diff --git a/include/linux/container.h b/include/linux/container.h
index c224a53..d5d143c 100644
--- a/include/linux/container.h
+++ b/include/linux/container.h
@@ -17,6 +17,7 @@ struct container {
 	struct kref ref;
 };
 extern struct container init_container;
+extern struct vfsmount *containerfs_mount;
 
 void put_container(struct container *c);
 struct container *new_container(struct container *parent,
diff --git a/kernel/container.c b/kernel/container.c
index 6206e72..5ce82b1 100644
--- a/kernel/container.c
+++ b/kernel/container.c
@@ -26,7 +26,7 @@ #define CONTAINERFS_MAGIC 0xb6663caf
 struct nsproxy;
 
 struct container init_container = INIT_CONTAINER(init_container);
-static struct vfsmount *containerfs_mount;
+struct vfsmount *containerfs_mount;
 static void containerfs_remove(struct dentry *dentry);
 static struct dentry *containerfs_create_dir(struct container *container);
 
-- 
1.4.1

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