Smack: create a sysfs mount point for smackfs

There are a number of "conventions" for where to put LSM filesystems.
Smack adheres to none of them. Create a mount point at /sys/fs/smackfs
for mounting smackfs so that Smack can be conventional.

Targeted for git://git.gitorious.org/smack-next/kernel.gitSigned-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smackfs.c

@@ -2063,6 +2063,19 @@ static const struct file_operations smk_revoke_subj_ops = {
 	.llseek		= generic_file_llseek,
 };
 
+static struct kset *smackfs_kset;
+/**
+ * smk_init_sysfs - initialize /sys/fs/smackfs
+ *
+ */
+static int smk_init_sysfs(void)
+{
+	smackfs_kset = kset_create_and_add("smackfs", NULL, fs_kobj);
+	if (!smackfs_kset)
+		return -ENOMEM;
+	return 0;
+}
+
 /**
  * smk_fill_super - fill the /smackfs superblock
  * @sb: the empty superblock
@@ -2183,6 +2196,10 @@ static int __init init_smk_fs(void)
 	if (!security_module_enable(&smack_ops))
 		return 0;
 
+	err = smk_init_sysfs();
+	if (err)
+		printk(KERN_ERR "smackfs: sysfs mountpoint problem.\n");
+
 	err = register_filesystem(&smk_fs_type);
 	if (!err) {
 		smackfs_mount = kern_mount(&smk_fs_type);