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Diffstat (limited to 'Documentation/filesystems/sysfs-tagging.rst')
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diff --git a/Documentation/filesystems/sysfs-tagging.rst b/Documentation/filesystems/sysfs-tagging.rst deleted file mode 100644 index 8888a05c398e..000000000000 --- a/Documentation/filesystems/sysfs-tagging.rst +++ /dev/null @@ -1,48 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -============= -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namespace - - initial_ns() which returns the initial namesapce - -- call kobj_ns_exit() when an individual tag is no longer valid |