+.. SPDX-License-Identifier: GPL-2.0
+
+=============
Sysfs tagging
--------------
+=============
(Taken almost verbatim from Eric Biederman's netns tagging patch
commit msg)
the network devices.
Each sysfs directory entry may be tagged with a namespace via the
-void *ns member of its kernfs_node. If a directory entry is tagged,
-then kernfs_node->flags will have a flag between KOBJ_NS_TYPE_NONE
+``void *ns member`` of its ``kernfs_node``. If a directory entry is tagged,
+then ``kernfs_node->flags`` will have a flag between KOBJ_NS_TYPE_NONE
and KOBJ_NS_TYPES, and ns will point to the namespace to which it
belongs.
-Each sysfs superblock's kernfs_super_info contains an array void
-*ns[KOBJ_NS_TYPES]. When a task in a tagging namespace
+Each sysfs superblock's kernfs_super_info contains an array
+``void *ns[KOBJ_NS_TYPES]``. When a task in a tagging namespace
kobj_nstype first mounts sysfs, a new superblock is created. It
will be differentiated from other sysfs mounts by having its
-s_fs_info->ns[kobj_nstype] set to the new namespace. Note that
+``s_fs_info->ns[kobj_nstype]`` set to the new namespace. Note that
through bind mounting and mounts propagation, a task can easily view
the contents of other namespaces' sysfs mounts. Therefore, when a
namespace exits, it will call kobj_ns_exit() to invalidate any
kernfs_node->ns pointers pointing to it.
Users of this interface:
-- define a type in the kobj_ns_type enumeration.
-- call kobj_ns_type_register() with its kobj_ns_type_operations which has
+
+- define a type in the ``kobj_ns_type`` enumeration.
+- call kobj_ns_type_register() with its ``kobj_ns_type_operations`` which has
+
- current_ns() which returns current's namespace
- netlink_ns() which returns a socket's namespace
- initial_ns() which returns the initial namesapce
+
- call kobj_ns_exit() when an individual tag is no longer valid