sysfs-tagging.txt: fix pre-kernfs references

in the directories and applications only see a limited set of

the network devices.

Each sysfs directory entry may be tagged with zero or one

namespaces.  A sysfs_dirent is augmented with a void *s_ns.  If a

directory entry is tagged, then sysfs_dirent->s_flags will have a

flag between KOBJ_NS_TYPE_NONE and KOBJ_NS_TYPES, and s_ns will

point to the namespace to which it belongs.

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

and KOBJ_NS_TYPES, and ns will point to the namespace to which it

belongs.

Each sysfs superblock's sysfs_super_info contains an array void

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

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

sysfs_dirent->s_ns pointers pointing to it.

kernfs_node->ns pointers pointing to it.

Users of this interface:

- define a type in the kobj_ns_type enumeration.