user/sven/linux.git/include/uapi/linux/nsfs.h, branch v6.17

mntns: use stable inode number for initial mount ns

2025-06-11T09:59:08Z

Apart from the network and mount namespace all other namespaces expose a stable inode number and userspace has been relying on that for a very long time now. It's very much heavily used API. Align the mount namespace and use a stable inode number from the reserved procfs inode number space so this is consistent across all namespaces. Link: https://lore.kernel.org/20250606-work-nsfs-v1-3-b8749c9a8844@kernel.org Signed-off-by: Christian Brauner

netns: use stable inode number for initial mount ns

2025-06-11T09:59:08Z

Apart from the network and mount namespace all other namespaces expose a stable inode number and userspace has been relying on that for a very long time now. It's very much heavily used API. Align the network namespace and use a stable inode number from the reserved procfs inode number space so this is consistent across all namespaces. Link: https://lore.kernel.org/20250606-work-nsfs-v1-2-b8749c9a8844@kernel.org Reviewed-by: Jakub Kicinski Signed-off-by: Christian Brauner

nsfs: move root inode number to uapi

2025-06-11T09:59:08Z

Userspace relies on the root inode numbers to identify the initial namespaces. That's already a hard dependency. So we cannot change that anymore. Move the initial inode numbers to a public header. Link: https://github.com/systemd/systemd/commit/d293fade24b34ccc2f5716b0ff5513e9533cf0c4 Link: https://lore.kernel.org/20250606-work-nsfs-v1-1-b8749c9a8844@kernel.org Signed-off-by: Christian Brauner

Merge tag 'vfs-6.12.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T09:15:26Z

Pull vfs mount updates from Christian Brauner: "Recently, we added the ability to list mounts in other mount namespaces and the ability to retrieve namespace file descriptors without having to go through procfs by deriving them from pidfds. This extends nsfs in two ways: (1) Add the ability to retrieve information about a mount namespace via NS_MNT_GET_INFO. This will return the mount namespace id and the number of mounts currently in the mount namespace. The number of mounts can be used to size the buffer that needs to be used for listmount() and is in general useful without having to actually iterate through all the mounts. The structure is extensible. (2) Add the ability to iterate through all mount namespaces over which the caller holds privilege returning the file descriptor for the next or previous mount namespace. To retrieve a mount namespace the caller must be privileged wrt to it's owning user namespace. This means that PID 1 on the host can list all mounts in all mount namespaces or that a container can list all mounts of its nested containers. Optionally pass a structure for NS_MNT_GET_INFO with NS_MNT_GET_{PREV,NEXT} to retrieve information about the mount namespace in one go. (1) and (2) can be implemented for other namespace types easily. Together with recent api additions this means one can iterate through all mounts in all mount namespaces without ever touching procfs. The commit message in 49224a345c48 ('Merge patch series "nsfs: iterate through mount namespaces"') contains example code how to do this" * tag 'vfs-6.12.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: nsfs: iterate through mount namespaces file: add fput() cleanup helper fs: add put_mnt_ns() cleanup helper fs: allow mount namespace fd

nsfs: fix ioctl declaration

2024-08-12T20:03:26Z

The kernel is writing an object of type __u64, so the ioctl has to be defined to _IOR(NSIO, 0x5, __u64) instead of _IO(NSIO, 0x5). Reported-by: Dmitry V. Levin Link: https://lore.kernel.org/r/20240730164554.GA18486@altlinux.org Signed-off-by: Christian Brauner

nsfs: iterate through mount namespaces

2024-08-09T10:46:59Z

It is already possible to list mounts in other mount namespaces and to retrieve namespace file descriptors without having to go through procfs by deriving them from pidfds. Augment these abilities by adding the ability to retrieve information about a mount namespace via NS_MNT_GET_INFO. This will return the mount namespace id and the number of mounts currently in the mount namespace. The number of mounts can be used to size the buffer that needs to be used for listmount() and is in general useful without having to actually iterate through all the mounts. The structure is extensible. And add the ability to iterate through all mount namespaces over which the caller holds privilege returning the file descriptor for the next or previous mount namespace. To retrieve a mount namespace the caller must be privileged wrt to it's owning user namespace. This means that PID 1 on the host can list all mounts in all mount namespaces or that a container can list all mounts of its nested containers. Optionally pass a structure for NS_MNT_GET_INFO with NS_MNT_GET_{PREV,NEXT} to retrieve information about the mount namespace in one go. Both ioctls can be implemented for other namespace types easily. Together with recent api additions this means one can iterate through all mounts in all mount namespaces without ever touching procfs. Link: https://lore.kernel.org/r/20240719-work-mount-namespace-v1-5-834113cab0d2@kernel.org Reviewed-by: Josef Bacik Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner

Merge tag 'vfs-6.11.nsfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-07-15T19:27:39Z

Pull namespace-fs updates from Christian Brauner: "This adds ioctls allowing to translate PIDs between PID namespaces. The motivating use-case comes from LXCFS which is a tiny fuse filesystem used to virtualize various aspects of procfs. LXCFS is run on the host. The files and directories it creates can be bind-mounted by e.g. a container at startup and mounted over the various procfs files the container wishes to have virtualized. When e.g. a read request for uptime is received, LXCFS will receive the pid of the reader. In order to virtualize the corresponding read, LXCFS needs to know the pid of the init process of the reader's pid namespace. In order to do this, LXCFS first needs to fork() two helper processes. The first helper process setns() to the readers pid namespace. The second helper process is needed to create a process that is a proper member of the pid namespace. The second helper process then creates a ucred message with ucred.pid set to 1 and sends it back to LXCFS. The kernel will translate the ucred.pid field to the corresponding pid number in LXCFS's pid namespace. This way LXCFS can learn the init pid number of the reader's pid namespace and can go on to virtualize. Since these two forks() are costly LXCFS maintains an init pid cache that caches a given pid for a fixed amount of time. The cache is pruned during new read requests. However, even with the cache the hit of the two forks() is singificant when a very large number of containers are running. So this adds a simple set of ioctls that let's a caller translate PIDs from and into a given PID namespace. This significantly improves performance with a very simple change. To protect against races pidfds can be used to check whether the process is still valid" * tag 'vfs-6.11.nsfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: nsfs: add pid translation ioctls

fs: add an ioctl to get the mnt ns id from nsfs

2024-06-28T07:53:31Z

In order to utilize the listmount() and statmount() extensions that allow us to call them on different namespaces we need a way to get the mnt namespace id from user space. Add an ioctl to nsfs that will allow us to extract the mnt namespace id in order to make these new extensions usable. Signed-off-by: Josef Bacik Link: https://lore.kernel.org/r/180449959d5a756af7306d6bda55f41b9d53e3cb.1719243756.git.josef@toxicpanda.com Signed-off-by: Christian Brauner

nsfs: add pid translation ioctls

2024-06-25T21:00:41Z

Add ioctl()s to translate pids between pid namespaces. LXCFS is a tiny fuse filesystem used to virtualize various aspects of procfs. LXCFS is run on the host. The files and directories it creates can be bind-mounted by e.g. a container at startup and mounted over the various procfs files the container wishes to have virtualized. When e.g. a read request for uptime is received, LXCFS will receive the pid of the reader. In order to virtualize the corresponding read, LXCFS needs to know the pid of the init process of the reader's pid namespace. In order to do this, LXCFS first needs to fork() two helper processes. The first helper process setns() to the readers pid namespace. The second helper process is needed to create a process that is a proper member of the pid namespace. The second helper process then creates a ucred message with ucred.pid set to 1 and sends it back to LXCFS. The kernel will translate the ucred.pid field to the corresponding pid number in LXCFS's pid namespace. This way LXCFS can learn the init pid number of the reader's pid namespace and can go on to virtualize. Since these two forks() are costly LXCFS maintains an init pid cache that caches a given pid for a fixed amount of time. The cache is pruned during new read requests. However, even with the cache the hit of the two forks() is singificant when a very large number of containers are running. With this simple patch we add an ns ioctl that let's a caller retrieve the init pid nr of a pid namespace through its pid namespace fd. This significantly improves performance with a very simple change. Support translation of pids and tgids. Other concepts can be added but there are no obvious users for this right now. To protect against races pidfds can be used to check whether the process is still valid. If needed, this can also be extended to work on pidfds directly. Link: https://lore.kernel.org/r/20240619-work-ns_ioctl-v1-1-7c0097e6bb6b@kernel.org Reviewed-by: Alexander Mikhalitsyn Signed-off-by: Christian Brauner

License cleanup: add SPDX license identifier to uapi header files with no license

2017-11-02T10:19:54Z

Many user space API headers are missing licensing information, which makes it hard for compliance tools to determine the correct license. By default are files without license information under the default license of the kernel, which is GPLV2. Marking them GPLV2 would exclude them from being included in non GPLV2 code, which is obviously not intended. The user space API headers fall under the syscall exception which is in the kernels COPYING file: NOTE! This copyright does *not* cover user programs that use kernel services by normal system calls - this is merely considered normal use of the kernel, and does *not* fall under the heading of "derived work". otherwise syscall usage would not be possible. Update the files which contain no license information with an SPDX license identifier. The chosen identifier is 'GPL-2.0 WITH Linux-syscall-note' which is the officially assigned identifier for the Linux syscall exception. SPDX license identifiers are a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. See the previous patch in this series for the methodology of how this patch was researched. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman