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Message-ID: <6a5dyxarvdri6ykizyvr3mmfe5h2hsljcm426o6odao7ljujxn@xwk6n46qr6ww>
Date: Mon, 22 Sep 2025 15:41:41 +0200
From: Jan Kara <jack@...e.cz>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Amir Goldstein <amir73il@...il.com>,
Josef Bacik <josef@...icpanda.com>, Jeff Layton <jlayton@...nel.org>, Mike Yuan <me@...dnzj.com>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, Lennart Poettering <mzxreary@...inter.de>,
Aleksa Sarai <cyphar@...har.com>, Alexander Viro <viro@...iv.linux.org.uk>,
Jan Kara <jack@...e.cz>, Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
Michal Koutný <mkoutny@...e.com>, Jakub Kicinski <kuba@...nel.org>,
Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH 2/3] ns: simplify ns_common_init() further
On Mon 22-09-25 14:42:36, Christian Brauner wrote:
> Simply derive the ns operations from the namespace type.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>
Nice! As much as I already feel pity for the guy who'll be reading all
these macros to figure out how some ns gets initialized :) feel free to
add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/namespace.c | 4 ++--
> include/linux/ns_common.h | 30 ++++++++++++++++++++++++++----
> ipc/namespace.c | 2 +-
> kernel/cgroup/namespace.c | 2 +-
> kernel/pid_namespace.c | 2 +-
> kernel/time/namespace.c | 2 +-
> kernel/user_namespace.c | 2 +-
> kernel/utsname.c | 2 +-
> net/core/net_namespace.c | 9 +--------
> 9 files changed, 35 insertions(+), 20 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 271cd6294c8a..d65917ec5544 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -4104,9 +4104,9 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
> }
>
> if (anon)
> - ret = ns_common_init_inum(new_ns, &mntns_operations, MNT_NS_ANON_INO);
> + ret = ns_common_init_inum(new_ns, MNT_NS_ANON_INO);
> else
> - ret = ns_common_init(new_ns, &mntns_operations);
> + ret = ns_common_init(new_ns);
> if (ret) {
> kfree(new_ns);
> dec_mnt_namespaces(ucounts);
> diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> index aea8528d799a..56492cd9ff8d 100644
> --- a/include/linux/ns_common.h
> +++ b/include/linux/ns_common.h
> @@ -25,6 +25,17 @@ extern struct time_namespace init_time_ns;
> extern struct user_namespace init_user_ns;
> extern struct uts_namespace init_uts_ns;
>
> +extern const struct proc_ns_operations netns_operations;
> +extern const struct proc_ns_operations utsns_operations;
> +extern const struct proc_ns_operations ipcns_operations;
> +extern const struct proc_ns_operations pidns_operations;
> +extern const struct proc_ns_operations pidns_for_children_operations;
> +extern const struct proc_ns_operations userns_operations;
> +extern const struct proc_ns_operations mntns_operations;
> +extern const struct proc_ns_operations cgroupns_operations;
> +extern const struct proc_ns_operations timens_operations;
> +extern const struct proc_ns_operations timens_for_children_operations;
> +
> struct ns_common {
> struct dentry *stashed;
> const struct proc_ns_operations *ops;
> @@ -84,10 +95,21 @@ void __ns_common_free(struct ns_common *ns);
> struct user_namespace *: &init_user_ns, \
> struct uts_namespace *: &init_uts_ns)
>
> -#define ns_common_init(__ns, __ops) \
> - __ns_common_init(to_ns_common(__ns), __ops, (((__ns) == ns_init_ns(__ns)) ? ns_init_inum(__ns) : 0))
> -
> -#define ns_common_init_inum(__ns, __ops, __inum) __ns_common_init(to_ns_common(__ns), __ops, __inum)
> +#define to_ns_operations(__ns) \
> + _Generic((__ns), \
> + struct cgroup_namespace *: (IS_ENABLED(CONFIG_CGROUPS) ? &cgroupns_operations : NULL), \
> + struct ipc_namespace *: (IS_ENABLED(CONFIG_IPC_NS) ? &ipcns_operations : NULL), \
> + struct mnt_namespace *: &mntns_operations, \
> + struct net *: (IS_ENABLED(CONFIG_NET_NS) ? &netns_operations : NULL), \
> + struct pid_namespace *: (IS_ENABLED(CONFIG_PID_NS) ? &pidns_operations : NULL), \
> + struct time_namespace *: (IS_ENABLED(CONFIG_TIME_NS) ? &timens_operations : NULL), \
> + struct user_namespace *: (IS_ENABLED(CONFIG_USER_NS) ? &userns_operations : NULL), \
> + struct uts_namespace *: (IS_ENABLED(CONFIG_UTS_NS) ? &utsns_operations : NULL))
> +
> +#define ns_common_init(__ns) \
> + __ns_common_init(to_ns_common(__ns), to_ns_operations(__ns), (((__ns) == ns_init_ns(__ns)) ? ns_init_inum(__ns) : 0))
> +
> +#define ns_common_init_inum(__ns, __inum) __ns_common_init(to_ns_common(__ns), to_ns_operations(__ns), __inum)
>
> #define ns_common_free(__ns) __ns_common_free(to_ns_common((__ns)))
>
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index bd85d1c9d2c2..d89dfd718d2b 100644
> --- a/ipc/namespace.c
> +++ b/ipc/namespace.c
> @@ -62,7 +62,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
> if (ns == NULL)
> goto fail_dec;
>
> - err = ns_common_init(ns, &ipcns_operations);
> + err = ns_common_init(ns);
> if (err)
> goto fail_free;
>
> diff --git a/kernel/cgroup/namespace.c b/kernel/cgroup/namespace.c
> index 16ead7508371..04c98338ac08 100644
> --- a/kernel/cgroup/namespace.c
> +++ b/kernel/cgroup/namespace.c
> @@ -27,7 +27,7 @@ static struct cgroup_namespace *alloc_cgroup_ns(void)
> new_ns = kzalloc(sizeof(struct cgroup_namespace), GFP_KERNEL_ACCOUNT);
> if (!new_ns)
> return ERR_PTR(-ENOMEM);
> - ret = ns_common_init(new_ns, &cgroupns_operations);
> + ret = ns_common_init(new_ns);
> if (ret)
> return ERR_PTR(ret);
> ns_tree_add(new_ns);
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 162f5fb63d75..a262a3f19443 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -103,7 +103,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
> if (ns->pid_cachep == NULL)
> goto out_free_idr;
>
> - err = ns_common_init(ns, &pidns_operations);
> + err = ns_common_init(ns);
> if (err)
> goto out_free_idr;
>
> diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
> index 7aa4d6fedd49..9f26e61be044 100644
> --- a/kernel/time/namespace.c
> +++ b/kernel/time/namespace.c
> @@ -97,7 +97,7 @@ static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
> if (!ns->vvar_page)
> goto fail_free;
>
> - err = ns_common_init(ns, &timens_operations);
> + err = ns_common_init(ns);
> if (err)
> goto fail_free_page;
>
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index f9df45c46235..e1559e8a8a02 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -126,7 +126,7 @@ int create_user_ns(struct cred *new)
>
> ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
>
> - ret = ns_common_init(ns, &userns_operations);
> + ret = ns_common_init(ns);
> if (ret)
> goto fail_free;
>
> diff --git a/kernel/utsname.c b/kernel/utsname.c
> index 95d733eb2c98..00001592ad13 100644
> --- a/kernel/utsname.c
> +++ b/kernel/utsname.c
> @@ -50,7 +50,7 @@ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
> if (!ns)
> goto fail_dec;
>
> - err = ns_common_init(ns, &utsns_operations);
> + err = ns_common_init(ns);
> if (err)
> goto fail_free;
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index d5e3fd819163..bdea7d5fac56 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -400,16 +400,9 @@ static __net_init void preinit_net_sysctl(struct net *net)
> /* init code that must occur even if setup_net() is not called. */
> static __net_init int preinit_net(struct net *net, struct user_namespace *user_ns)
> {
> - const struct proc_ns_operations *ns_ops;
> int ret;
>
> -#ifdef CONFIG_NET_NS
> - ns_ops = &netns_operations;
> -#else
> - ns_ops = NULL;
> -#endif
> -
> - ret = ns_common_init(net, ns_ops);
> + ret = ns_common_init(net);
> if (ret)
> return ret;
>
>
> --
> 2.47.3
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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