1 files changed, 43 insertions, 10 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 2dd333b0fe7f..a7bea8c8bd46 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1937,6 +1937,21 @@ dput_out:
         return retval;
 }
 
+static struct mnt_namespace *alloc_mnt_ns(void)
+{
+        struct mnt_namespace *new_ns;
+
+        new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+        if (!new_ns)
+                return ERR_PTR(-ENOMEM);
+        atomic_set(&new_ns->count, 1);
+        new_ns->root = NULL;
+        INIT_LIST_HEAD(&new_ns->list);
+        init_waitqueue_head(&new_ns->poll);
+        new_ns->event = 0;
+        return new_ns;
+}
+
 /*
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
@@ -1948,14 +1963,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
         struct vfsmount *p, *q;
 
-        new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
-        if (!new_ns)
-                return ERR_PTR(-ENOMEM);
-
-        atomic_set(&new_ns->count, 1);
-        INIT_LIST_HEAD(&new_ns->list);
-        init_waitqueue_head(&new_ns->poll);
-        new_ns->event = 0;
+        new_ns = alloc_mnt_ns();
+        if (IS_ERR(new_ns))
+                return new_ns;
 
         down_write(&namespace_sem);
         /* First pass: copy the tree topology */
@@ -2019,6 +2029,24 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
         return new_ns;
 }
 
+/**
+ * create_mnt_ns - creates a private namespace and adds a root filesystem
+ * @mnt: pointer to the new root filesystem mountpoint
+ */
+struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
+{
+        struct mnt_namespace *new_ns;
+
+        new_ns = alloc_mnt_ns();
+        if (!IS_ERR(new_ns)) {
+                mnt->mnt_ns = new_ns;
+                new_ns->root = mnt;
+                list_add(&new_ns->list, &new_ns->root->mnt_list);
+        }
+        return new_ns;
+}
+EXPORT_SYMBOL(create_mnt_ns);
+
 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
                 char __user *, type, unsigned long, flags, void __user *, data)
 {
@@ -2246,10 +2274,14 @@ void __init mnt_init(void)
         init_mount_tree();
 }
 
-void __put_mnt_ns(struct mnt_namespace *ns)
+void put_mnt_ns(struct mnt_namespace *ns)
 {
-        struct vfsmount *root = ns->root;
+        struct vfsmount *root;
         LIST_HEAD(umount_list);
+
+        if (!atomic_dec_and_lock(&ns->count, &vfsmount_lock))
+                return;
+        root = ns->root;
         ns->root = NULL;
         spin_unlock(&vfsmount_lock);
         down_write(&namespace_sem);
@@ -2260,3 +2292,4 @@ void __put_mnt_ns(struct mnt_namespace *ns)
         release_mounts(&umount_list);
         kfree(ns);
 }
+EXPORT_SYMBOL(put_mnt_ns);