From: Mauro Carvalho Chehab Date: Mon, 27 Apr 2020 21:17:18 +0000 (+0200) Subject: docs: filesystems: convert sysfs-tagging.txt to ReST X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ec4551f45036d23a34d4f13ab3ce2ea345a13de7;p=linux.git docs: filesystems: convert sysfs-tagging.txt to ReST - Add a SPDX header; - Adjust document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to filesystems/index.rst. Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/45a01fa5edd5c6ee8fc0754fc74f7ef65a3e5581.1588021877.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst index 7afb58dff43bd..14e298d84c8a6 100644 --- a/Documentation/filesystems/index.rst +++ b/Documentation/filesystems/index.rst @@ -35,6 +35,7 @@ algorithms work. seq_file sharedsubtree sysfs-pci + sysfs-tagging automount-support diff --git a/Documentation/filesystems/sysfs-tagging.rst b/Documentation/filesystems/sysfs-tagging.rst new file mode 100644 index 0000000000000..8888a05c398ef --- /dev/null +++ b/Documentation/filesystems/sysfs-tagging.rst @@ -0,0 +1,48 @@ +.. 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 diff --git a/Documentation/filesystems/sysfs-tagging.txt b/Documentation/filesystems/sysfs-tagging.txt deleted file mode 100644 index c7c8e64389584..0000000000000 --- a/Documentation/filesystems/sysfs-tagging.txt +++ /dev/null @@ -1,42 +0,0 @@ -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