Revert "sysfs: drop kobj_ns_type handling"

This reverts commit cb26a311578e67769e92a39a0a63476533cb7e12.

It mysteriously causes NetworkManager to not find the wireless device
for me. As far as I can tell, Tejun *meant* for this commit to not make
any semantic changes, but there clearly are some. So revert it, taking
into account some of the calling convention changes that happened in
this area in subsequent commits.

Cc: Tejun Heo <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/sysfs/dir.c

···
 	/* add new node and rebalance the tree */
 	rb_link_node(&sd->s_rb, parent, node);
 	rb_insert_color(&sd->s_rb, &sd->s_parent->s_dir.children);
-
-	/* if @sd has ns tag, mark the parent to enable ns filtering */
-	if (sd->s_ns)
-		sd->s_parent->s_flags |= SYSFS_FLAG_HAS_NS;
-
 	return 0;
 }
 
···
 		sd->s_parent->s_dir.subdirs--;
 
 	rb_erase(&sd->s_rb, &sd->s_parent->s_dir.children);
-
-	/*
-	 * Either all or none of the children have tags.  Clearing HAS_NS
-	 * when there's no child left is enough to keep the flag synced.
-	 */
-	if (RB_EMPTY_ROOT(&sd->s_parent->s_dir.children))
-		sd->s_parent->s_flags &= ~SYSFS_FLAG_HAS_NS;
 }
 
 /**
···
 static int sysfs_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct sysfs_dirent *sd;
+	int type;
 
 	if (flags & LOOKUP_RCU)
 		return -ECHILD;
···
 		goto out_bad;
 
 	/* The sysfs dirent has been moved to a different namespace */
-	if (sd->s_ns && sd->s_ns != sysfs_info(dentry->d_sb)->ns)
-		goto out_bad;
+	type = KOBJ_NS_TYPE_NONE;
+	if (sd->s_parent) {
+		type = sysfs_ns_type(sd->s_parent);
+		if (type != KOBJ_NS_TYPE_NONE &&
+				sysfs_info(dentry->d_sb)->ns[type] != sd->s_ns)
+			goto out_bad;
+	}
 
 	mutex_unlock(&sysfs_mutex);
 out_valid:
···
 {
 	struct sysfs_inode_attrs *ps_iattr;
 	int ret;
+
+	if (!!sysfs_ns_type(parent_sd) != !!sd->s_ns) {
+		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
+			sysfs_ns_type(parent_sd) ? "required" : "invalid",
+			parent_sd->s_name, sd->s_name);
+		return -EINVAL;
+	}
 
 	sd->s_hash = sysfs_name_hash(sd->s_name, sd->s_ns);
 	sd->s_parent = sysfs_get(parent_sd);
···
 	struct rb_node *node = parent_sd->s_dir.children.rb_node;
 	unsigned int hash;
 
+	if (!!sysfs_ns_type(parent_sd) != !!ns) {
+		WARN(1, KERN_WARNING "sysfs: ns %s in '%s' for '%s'\n",
+			sysfs_ns_type(parent_sd) ? "required" : "invalid",
+			parent_sd->s_name, name);
+		return NULL;
+	}
+
 	hash = sysfs_name_hash(name, ns);
 	while (node) {
 		struct sysfs_dirent *sd;
···
 EXPORT_SYMBOL_GPL(sysfs_get_dirent_ns);
 
 static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
+		      enum kobj_ns_type type,
 		      const char *name, const void *ns,
 		      struct sysfs_dirent **p_sd)
 {
···
 	if (!sd)
 		return -ENOMEM;
 
+	sd->s_flags |= (type << SYSFS_NS_TYPE_SHIFT);
 	sd->s_ns = ns;
 	sd->s_dir.kobj = kobj;
 
···
 int sysfs_create_subdir(struct kobject *kobj, const char *name,
 			struct sysfs_dirent **p_sd)
 {
-	return create_dir(kobj, kobj->sd, name, NULL, p_sd);
+	return create_dir(kobj, kobj->sd,
+			  KOBJ_NS_TYPE_NONE, name, NULL, p_sd);
+}
+
+/**
+ *	sysfs_read_ns_type: return associated ns_type
+ *	@kobj: the kobject being queried
+ *
+ *	Each kobject can be tagged with exactly one namespace type
+ *	(i.e. network or user).  Return the ns_type associated with
+ *	this object if any
+ */
+static enum kobj_ns_type sysfs_read_ns_type(struct kobject *kobj)
+{
+	const struct kobj_ns_type_operations *ops;
+	enum kobj_ns_type type;
+
+	ops = kobj_child_ns_ops(kobj);
+	if (!ops)
+		return KOBJ_NS_TYPE_NONE;
+
+	type = ops->type;
+	BUG_ON(type <= KOBJ_NS_TYPE_NONE);
+	BUG_ON(type >= KOBJ_NS_TYPES);
+	BUG_ON(!kobj_ns_type_registered(type));
+
+	return type;
 }
 
 /**
···
  */
 int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
 {
+	enum kobj_ns_type type;
 	struct sysfs_dirent *parent_sd, *sd;
 	int error = 0;
 
···
 	if (!parent_sd)
 		return -ENOENT;
 
-	error = create_dir(kobj, parent_sd, kobject_name(kobj), ns, &sd);
+	type = sysfs_read_ns_type(kobj);
+
+	error = create_dir(kobj, parent_sd, type, kobject_name(kobj), ns, &sd);
 	if (!error)
 		kobj->sd = sd;
 	return error;
···
 	struct sysfs_dirent *parent_sd = parent->d_fsdata;
 	struct sysfs_dirent *sd;
 	struct inode *inode;
-	const void *ns = NULL;
+	enum kobj_ns_type type;
+	const void *ns;
 
 	mutex_lock(&sysfs_mutex);
 
-	if (parent_sd->s_flags & SYSFS_FLAG_HAS_NS)
-		ns = sysfs_info(dir->i_sb)->ns;
+	type = sysfs_ns_type(parent_sd);
+	ns = sysfs_info(dir->i_sb)->ns[type];
 
 	sd = sysfs_find_dirent(parent_sd, dentry->d_name.name, ns);
 
···
 	struct dentry *dentry = file->f_path.dentry;
 	struct sysfs_dirent *parent_sd = dentry->d_fsdata;
 	struct sysfs_dirent *pos = file->private_data;
-	const void *ns = NULL;
+	enum kobj_ns_type type;
+	const void *ns;
+
+	type = sysfs_ns_type(parent_sd);
+	ns = sysfs_info(dentry->d_sb)->ns[type];
 
 	if (!dir_emit_dots(file, ctx))
 		return 0;
 	mutex_lock(&sysfs_mutex);
-
-	if (parent_sd->s_flags & SYSFS_FLAG_HAS_NS)
-		ns = sysfs_info(dentry->d_sb)->ns;
-
 	for (pos = sysfs_dir_pos(ns, parent_sd, ctx->pos, pos);
 	     pos;
 	     pos = sysfs_dir_next_pos(ns, parent_sd, ctx->pos, pos)) {

fs/sysfs/mount.c

···
 struct sysfs_dirent sysfs_root = {
 	.s_name		= "",
 	.s_count	= ATOMIC_INIT(1),
-	.s_flags	= SYSFS_DIR,
+	.s_flags	= SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT),
 	.s_mode		= S_IFDIR | S_IRUGO | S_IXUGO,
 	.s_ino		= 1,
 };
···
 {
 	struct sysfs_super_info *sb_info = sysfs_info(sb);
 	struct sysfs_super_info *info = data;
+	enum kobj_ns_type type;
+	int found = 1;
 
-	return sb_info->ns == info->ns;
+	for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
+		if (sb_info->ns[type] != info->ns[type])
+			found = 0;
+	}
+	return found;
 }
 
 static int sysfs_set_super(struct super_block *sb, void *data)
···
 
 static void free_sysfs_super_info(struct sysfs_super_info *info)
 {
-	kobj_ns_drop(KOBJ_NS_TYPE_NET, info->ns);
+	int type;
+	for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
+		kobj_ns_drop(type, info->ns[type]);
 	kfree(info);
 }
 
···
 	int flags, const char *dev_name, void *data)
 {
 	struct sysfs_super_info *info;
+	enum kobj_ns_type type;
 	struct super_block *sb;
 	int error;
 
···
 		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
 			return ERR_PTR(-EPERM);
 
-		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
-			return ERR_PTR(-EPERM);
+		for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
+			if (!kobj_ns_current_may_mount(type))
+				return ERR_PTR(-EPERM);
+		}
 	}
 
 	info = kzalloc(sizeof(*info), GFP_KERNEL);
 	if (!info)
 		return ERR_PTR(-ENOMEM);
 
-	info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
+		info->ns[type] = kobj_ns_grab_current(type);
 
 	sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
 	if (IS_ERR(sb) || sb->s_fs_info != info)

fs/sysfs/symlink.c

···
 	struct sysfs_dirent *target_sd = NULL;
 	struct sysfs_dirent *sd = NULL;
 	struct sysfs_addrm_cxt acxt;
+	enum kobj_ns_type ns_type;
 	int error;
 
 	BUG_ON(!name || !parent_sd);
···
 	if (!sd)
 		goto out_put;
 
-	sd->s_ns = target_sd->s_ns;
+	ns_type = sysfs_ns_type(parent_sd);
+	if (ns_type)
+		sd->s_ns = target_sd->s_ns;
 	sd->s_symlink.target_sd = target_sd;
 	target_sd = NULL;	/* reference is now owned by the symlink */
 
 	sysfs_addrm_start(&acxt);
-	if (warn)
-		error = sysfs_add_one(&acxt, sd, parent_sd);
-	else
-		error = __sysfs_add_one(&acxt, sd, parent_sd);
+	/* Symlinks must be between directories with the same ns_type */
+	if (!ns_type ||
+	    (ns_type == sysfs_ns_type(sd->s_symlink.target_sd->s_parent))) {
+		if (warn)
+			error = sysfs_add_one(&acxt, sd, parent_sd);
+		else
+			error = __sysfs_add_one(&acxt, sd, parent_sd);
+	} else {
+		error = -EINVAL;
+		WARN(1, KERN_WARNING
+			"sysfs: symlink across ns_types %s/%s -> %s/%s\n",
+			parent_sd->s_name,
+			sd->s_name,
+			sd->s_symlink.target_sd->s_parent->s_name,
+			sd->s_symlink.target_sd->s_name);
+	}
 	sysfs_addrm_finish(&acxt);
 
 	if (error)
···
 	 * sysfs_remove_dir() for details.
 	 */
 	spin_lock(&sysfs_symlink_target_lock);
-	if (targ->sd)
+	if (targ->sd && sysfs_ns_type(kobj->sd))
 		ns = targ->sd->s_ns;
 	spin_unlock(&sysfs_symlink_target_lock);
 	sysfs_hash_and_remove(kobj->sd, name, ns);

fs/sysfs/sysfs.h

···
 #define SYSFS_COPY_NAME			(SYSFS_DIR | SYSFS_KOBJ_LINK)
 #define SYSFS_ACTIVE_REF		(SYSFS_KOBJ_ATTR | SYSFS_KOBJ_BIN_ATTR)
 
-#define SYSFS_FLAG_MASK			~SYSFS_TYPE_MASK
-#define SYSFS_FLAG_HAS_NS		0x01000
+/* identify any namespace tag on sysfs_dirents */
+#define SYSFS_NS_TYPE_MASK		0xf00
+#define SYSFS_NS_TYPE_SHIFT		8
+
+#define SYSFS_FLAG_MASK			~(SYSFS_NS_TYPE_MASK|SYSFS_TYPE_MASK)
 #define SYSFS_FLAG_REMOVED		0x02000
 
 static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
 {
 	return sd->s_flags & SYSFS_TYPE_MASK;
+}
+
+/*
+ * Return any namespace tags on this dirent.
+ * enum kobj_ns_type is defined in linux/kobject.h
+ */
+static inline enum kobj_ns_type sysfs_ns_type(struct sysfs_dirent *sd)
+{
+	return (sd->s_flags & SYSFS_NS_TYPE_MASK) >> SYSFS_NS_TYPE_SHIFT;
 }
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
···
  */
 
 /*
- * Each sb is associated with one namespace tag, currently the network
- * namespace of the task which mounted this sysfs instance.  If multiple
- * tags become necessary, make the following an array and compare
- * sysfs_dirent tag against every entry.
+ * Each sb is associated with a set of namespace tags (i.e.
+ * the network namespace of the task which mounted this sysfs
+ * instance).
  */
 struct sysfs_super_info {
-	void *ns;
+	void *ns[KOBJ_NS_TYPES];
 };
 #define sysfs_info(SB) ((struct sysfs_super_info *)(SB->s_fs_info))
 extern struct sysfs_dirent sysfs_root;

lib/kobject.c

···
 const void *kobject_namespace(struct kobject *kobj)
 {
 	const struct kobj_ns_type_operations *ns_ops = kobj_ns_ops(kobj);
-	const void *ns;
 
 	if (!ns_ops || ns_ops->type == KOBJ_NS_TYPE_NONE)
 		return NULL;
 
-	ns = kobj->ktype->namespace(kobj);
-	WARN_ON(!ns);	/* @kobj in a namespace is required to have !NULL tag */
-	return ns;
+	return kobj->ktype->namespace(kobj);
 }
 
 /*