[PATCH RFC 1/8] mntns: introduce mntns_get_inum()

[Aristeu Rozanski <arozansk@redhat.com>]

This allows other parts of the kernel to have access to userspace
visible namespace identification.

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
---
 fs/namespace.c                |   14 ++++++++++++++
 include/linux/mnt_namespace.h |    2 ++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 50ca17d..b8a888f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2792,6 +2792,20 @@ static unsigned int mntns_inum(void *ns)
 	return mnt_ns->proc_inum;
 }
 
+unsigned int mntns_get_inum(struct task_struct *tsk)
+{
+	struct nsproxy *nsproxy;
+	int rc = 0;
+
+	rcu_read_lock();
+	nsproxy = task_nsproxy(tsk);
+	if (nsproxy)
+		rc = mntns_inum(nsproxy->mnt_ns);
+	rcu_read_unlock();
+
+	return rc;
+}
+
 const struct proc_ns_operations mntns_operations = {
 	.name		= "mnt",
 	.type		= CLONE_NEWNS,
diff --git a/include/linux/mnt_namespace.h b/include/linux/mnt_namespace.h
index 12b2ab5..b6afe65 100644
--- a/include/linux/mnt_namespace.h
+++ b/include/linux/mnt_namespace.h
@@ -5,10 +5,12 @@
 struct mnt_namespace;
 struct fs_struct;
 struct user_namespace;
+struct task_struct;
 
 extern struct mnt_namespace *copy_mnt_ns(unsigned long, struct mnt_namespace *,
 		struct user_namespace *, struct fs_struct *);
 extern void put_mnt_ns(struct mnt_namespace *ns);
+extern unsigned int mntns_get_inum(struct task_struct *tsk);
 
 extern const struct file_operations proc_mounts_operations;
 extern const struct file_operations proc_mountinfo_operations;
-- 
1.7.1