Merge remote-tracking branch 'regulator/for-linus' into regulator-next

1 files changed, 32 insertions, 0 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index e5e1c7d1839..6d3a1963879 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2483,11 +2483,43 @@ struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
 		__mnt_make_longterm(mnt);
 		new_ns->root = mnt;
 		list_add(&new_ns->list, &new_ns->root->mnt_list);
+	} else {
+		mntput(mnt);
 	}
 	return new_ns;
 }
 EXPORT_SYMBOL(create_mnt_ns);
 
+struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
+{
+	struct mnt_namespace *ns;
+	struct super_block *s;
+	struct path path;
+	int err;
+
+	ns = create_mnt_ns(mnt);
+	if (IS_ERR(ns))
+		return ERR_CAST(ns);
+
+	err = vfs_path_lookup(mnt->mnt_root, mnt,
+			name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
+
+	put_mnt_ns(ns);
+
+	if (err)
+		return ERR_PTR(err);
+
+	/* trade a vfsmount reference for active sb one */
+	s = path.mnt->mnt_sb;
+	atomic_inc(&s->s_active);
+	mntput(path.mnt);
+	/* lock the sucker */
+	down_write(&s->s_umount);
+	/* ... and return the root of (sub)tree on it */
+	return path.dentry;
+}
+EXPORT_SYMBOL(mount_subtree);
+
 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
 		char __user *, type, unsigned long, flags, void __user *, data)
 {