mirror of
https://github.com/torvalds/linux.git
synced 2024-12-03 17:41:22 +00:00
9ba41327d8
- sysfs_dirent is now kernfs_node - see commit324a56e16e("kernfs: s/sysfs_dirent/kernfs_node/ and rename its friends accordingly") - sysfs_super_info is now kernfs_super_info - see commitc525aaddc3("kernfs: s/sysfs/kernfs/ in various data structures") - the 's_' prefix was dropped from various fields - see commitadc5e8b58f("kernfs: drop s_ prefix from kernfs_node members") Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
43 lines
1.8 KiB
Plaintext
43 lines
1.8 KiB
Plaintext
Sysfs tagging
|
|
-------------
|
|
|
|
(Taken almost verbatim from Eric Biederman's netns tagging patch
|
|
commit msg)
|
|
|
|
The problem. Network devices show up in sysfs and with the network
|
|
namespace active multiple devices with the same name can show up in
|
|
the same directory, ouch!
|
|
|
|
To avoid that problem and allow existing applications in network
|
|
namespaces to see the same interface that is currently presented in
|
|
sysfs, sysfs now has tagging directory support.
|
|
|
|
By using the network namespace pointers as tags to separate out the
|
|
the sysfs directory entries we ensure that we don't have conflicts
|
|
in the directories and applications only see a limited set of
|
|
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
|
|
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
|
|
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
|
|
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
|
|
- 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
|