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Message-ID: <so6gpy2udirre26cghfchiayvaxzhtnhq3y3j2mndzkkosxpcv@2dnlcxurzbjo>
Date: Thu, 18 Sep 2025 11:45:20 +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>,
Daan De Meyer <daan.j.demeyer@...il.com>, 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 8/9] nscommon: simplify initialization
On Wed 17-09-25 12:28:07, Christian Brauner wrote:
> There's a lot of information that namespace implementers don't need to
> know about at all. Encapsulate this all in the initialization helper.
>
> Signed-off-by: Christian Brauner <brauner@...nel.org>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/namespace.c | 5 +++--
> include/linux/ns_common.h | 41 +++++++++++++++++++++++++++++++++++++++--
> ipc/namespace.c | 2 +-
> kernel/cgroup/namespace.c | 2 +-
> kernel/nscommon.c | 17 ++++++++---------
> kernel/pid_namespace.c | 2 +-
> kernel/time/namespace.c | 2 +-
> kernel/user_namespace.c | 2 +-
> kernel/utsname.c | 2 +-
> net/core/net_namespace.c | 2 +-
> 10 files changed, 57 insertions(+), 20 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 09e4ecd44972..31eb0e8f21eb 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -4105,8 +4105,9 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
> }
>
> if (anon)
> - new_ns->ns.inum = MNT_NS_ANON_INO;
> - ret = ns_common_init(&new_ns->ns, &mntns_operations, !anon);
> + ret = ns_common_init_inum(new_ns, &mntns_operations, MNT_NS_ANON_INO);
> + else
> + ret = ns_common_init(new_ns, &mntns_operations);
> if (ret) {
> kfree(new_ns);
> dec_mnt_namespaces(ucounts);
> diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
> index 78b17fe80b62..284bba2b7c43 100644
> --- a/include/linux/ns_common.h
> +++ b/include/linux/ns_common.h
> @@ -16,6 +16,15 @@ struct time_namespace;
> struct user_namespace;
> struct uts_namespace;
>
> +extern struct cgroup_namespace init_cgroup_ns;
> +extern struct ipc_namespace init_ipc_ns;
> +extern struct mnt_namespace *init_mnt_ns;
> +extern struct net init_net;
> +extern struct pid_namespace init_pid_ns;
> +extern struct time_namespace init_time_ns;
> +extern struct user_namespace init_user_ns;
> +extern struct uts_namespace init_uts_ns;
> +
> struct ns_common {
> struct dentry *stashed;
> const struct proc_ns_operations *ops;
> @@ -31,8 +40,7 @@ struct ns_common {
> };
> };
>
> -int ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops,
> - bool alloc_inum);
> +int __ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops, int inum);
>
> #define to_ns_common(__ns) \
> _Generic((__ns), \
> @@ -45,4 +53,33 @@ int ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops,
> struct user_namespace *: &(__ns)->ns, \
> struct uts_namespace *: &(__ns)->ns)
>
> +#define ns_init_inum(__ns) \
> + _Generic((__ns), \
> + struct cgroup_namespace *: CGROUP_NS_INIT_INO, \
> + struct ipc_namespace *: IPC_NS_INIT_INO, \
> + struct mnt_namespace *: MNT_NS_INIT_INO, \
> + struct net *: NET_NS_INIT_INO, \
> + struct pid_namespace *: PID_NS_INIT_INO, \
> + struct time_namespace *: TIME_NS_INIT_INO, \
> + struct user_namespace *: USER_NS_INIT_INO, \
> + struct uts_namespace *: UTS_NS_INIT_INO)
> +
> +#define ns_init_ns(__ns) \
> + _Generic((__ns), \
> + struct cgroup_namespace *: &init_cgroup_ns, \
> + struct ipc_namespace *: &init_ipc_ns, \
> + struct mnt_namespace *: init_mnt_ns, \
> + struct net *: &init_net, \
> + struct pid_namespace *: &init_pid_ns, \
> + struct time_namespace *: &init_time_ns, \
> + struct user_namespace *: &init_user_ns, \
> + struct uts_namespace *: &init_uts_ns)
> +
> +#define ns_common_init(__ns, __ops) \
> + __ns_common_init(&(__ns)->ns, __ops, \
> + (((__ns) == ns_init_ns(__ns)) ? ns_init_inum(__ns) : 0))
> +
> +#define ns_common_init_inum(__ns, __ops, __inum) \
> + __ns_common_init(&(__ns)->ns, __ops, __inum)
> +
> #endif
> diff --git a/ipc/namespace.c b/ipc/namespace.c
> index 89588819956b..0f8bbd18a475 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->ns, &ipcns_operations, true);
> + err = ns_common_init(ns, &ipcns_operations);
> if (err)
> goto fail_free;
>
> diff --git a/kernel/cgroup/namespace.c b/kernel/cgroup/namespace.c
> index 5a327914b565..d928c557e28b 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->ns, &cgroupns_operations, true);
> + ret = ns_common_init(new_ns, &cgroupns_operations);
> if (ret)
> return ERR_PTR(ret);
> ns_tree_add(new_ns);
> diff --git a/kernel/nscommon.c b/kernel/nscommon.c
> index e10fad8afe61..c3a90bb665ad 100644
> --- a/kernel/nscommon.c
> +++ b/kernel/nscommon.c
> @@ -1,21 +1,20 @@
> // SPDX-License-Identifier: GPL-2.0-only
>
> #include <linux/ns_common.h>
> +#include <linux/proc_ns.h>
>
> -int ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops,
> - bool alloc_inum)
> +int __ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops, int inum)
> {
> - if (alloc_inum && !ns->inum) {
> - int ret;
> - ret = proc_alloc_inum(&ns->inum);
> - if (ret)
> - return ret;
> - }
> refcount_set(&ns->count, 1);
> ns->stashed = NULL;
> ns->ops = ops;
> ns->ns_id = 0;
> RB_CLEAR_NODE(&ns->ns_tree_node);
> INIT_LIST_HEAD(&ns->ns_list_node);
> - return 0;
> +
> + if (inum) {
> + ns->inum = inum;
> + return 0;
> + }
> + return proc_alloc_inum(&ns->inum);
> }
> diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
> index 9b327420309e..170757c265c2 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->ns, &pidns_operations, true);
> + err = ns_common_init(ns, &pidns_operations);
> if (err)
> goto out_free_idr;
>
> diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c
> index 20b65f90549e..ce8e952104a7 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->ns, &timens_operations, true);
> + err = ns_common_init(ns, &timens_operations);
> if (err)
> goto fail_free_page;
>
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index cfb0e28f2779..db9f0463219c 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->ns, &userns_operations, true);
> + ret = ns_common_init(ns, &userns_operations);
> if (ret)
> goto fail_free;
>
> diff --git a/kernel/utsname.c b/kernel/utsname.c
> index a682830742d3..399888be66bd 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->ns, &utsns_operations, true);
> + err = ns_common_init(ns, &utsns_operations);
> if (err)
> goto fail_free;
>
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index 897f4927df9e..fdb266bbdf93 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -409,7 +409,7 @@ static __net_init int preinit_net(struct net *net, struct user_namespace *user_n
> ns_ops = NULL;
> #endif
>
> - ret = ns_common_init(&net->ns, ns_ops, true);
> + ret = ns_common_init(net, ns_ops);
> if (ret)
> return ret;
>
>
> --
> 2.47.3
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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