linux-kernel - Re: [PATCH 00/17] ns: header cleanups and initial namespace reference count improvements

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Message-ID: <byhojbx5x73zxickqy4uje6fmcn3nuugau7afia6thsyomfnlx@exrz3jpwdfgs>
Date: Thu, 13 Nov 2025 12:03:44 +0100
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>, 
	Jeff Layton <jlayton@...nel.org>, Jann Horn <jannh@...gle.com>, Mike Yuan <me@...dnzj.com>, 
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, Lennart Poettering <mzxreary@...inter.de>, 
	Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
	Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
	bpf@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 00/17] ns: header cleanups and initial namespace
 reference count improvements

On Mon 10-11-25 16:08:12, Christian Brauner wrote:
> Cleanup the namespace headers by splitting them into types and helpers.
> Better separate common namepace types and functions from namespace tree
> types and functions.
> 
> Fix the reference counts of initial namespaces so we don't do any
> pointless cacheline ping-pong for them when we know they can never go
> away. Add a bunch of asserts for both the passive and active reference
> counts to catch any changes that would break it.
> 
> Signed-off-by: Christian Brauner <brauner@...nel.org>

FWIW I've read the series and I like it. It looks like very nice cleanups.
I don't feel *very* confident with this code so it isn't worth much but
still feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
> Christian Brauner (17):
>       ns: move namespace types into separate header
>       nstree: decouple from ns_common header
>       nstree: move nstree types into separate header
>       nstree: add helper to operate on struct ns_tree_{node,root}
>       nstree: switch to new structures
>       nstree: simplify owner list iteration
>       nstree: use guards for ns_tree_lock
>       ns: make is_initial_namespace() argument const
>       ns: rename is_initial_namespace()
>       fs: use boolean to indicate anonymous mount namespace
>       ipc: enable is_ns_init_id() assertions
>       ns: make all reference counts on initial namespace a nop
>       ns: add asserts for initial namespace reference counts
>       ns: add asserts for initial namespace active reference counts
>       pid: rely on common reference count behavior
>       ns: drop custom reference count initialization for initial namespaces
>       selftests/namespaces: fix nsid tests
> 
>  fs/mount.h                                     |   3 +-
>  fs/namespace.c                                 |   9 +-
>  include/linux/ns/ns_common_types.h             | 196 ++++++++++++++++
>  include/linux/ns/nstree_types.h                |  55 +++++
>  include/linux/ns_common.h                      | 266 +++++-----------------
>  include/linux/nstree.h                         |  38 ++--
>  include/linux/pid_namespace.h                  |   3 +-
>  init/version-timestamp.c                       |   2 +-
>  ipc/msgutil.c                                  |   2 +-
>  ipc/namespace.c                                |   3 +-
>  kernel/cgroup/cgroup.c                         |   2 +-
>  kernel/nscommon.c                              |  15 +-
>  kernel/nstree.c                                | 304 ++++++++++++++-----------
>  kernel/pid.c                                   |   2 +-
>  kernel/pid_namespace.c                         |   2 +-
>  kernel/time/namespace.c                        |   2 +-
>  kernel/user.c                                  |   2 +-
>  tools/testing/selftests/namespaces/nsid_test.c | 107 +++++----
>  18 files changed, 576 insertions(+), 437 deletions(-)
> ---
> base-commit: c9255cbe738098e46c9125c6b409f7f8f4785bf6
> change-id: 20251110-work-namespace-nstree-fixes-f23931a00ba2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR