[Devel] [PATCH 1/6] Define and use task_active_pid_ns() wrapper
Pavel Emelianov
xemul at openvz.org
Thu Jul 12 22:19:44 PDT 2007
sukadev at us.ibm.com wrote:
> Subject: [PATCH 1/6] Define and use task_active_pid_ns() wrapper
>
> From: Sukadev Bhattiprolu <sukadev at us.ibm.com>
>
> With multiple pid namespaces, a process is known by some pid_t in
> every ancestor pid namespace. Every time the process forks, the
> child process also gets a pid_t in every ancestor pid namespace.
>
> While a process is visible in >=1 pid namespaces, it can see pid_t's
> in only one pid namespace. We call this pid namespace it's "active
> pid namespace", and it is always the youngest pid namespace in which
> the process is known.
>
> This patch defines and uses a wrapper to find the active pid namespace
> of a process. The implementation of the wrapper will be changed in
> when support for multiple pid namespaces are added.
>
> Changelog:
> 2.6.22-rc4-mm2-pidns1:
> - [Pavel Emelianov, Alexey Dobriyan] Back out the change to use
> task_active_pid_ns() in child_reaper() since task->nsproxy
> can be NULL during task exit (so child_reaper() continues to
> use init_pid_ns).
>
> to implement child_reaper() since init_pid_ns.child_reaper to
> implement child_reaper() since tsk->nsproxy can be NULL during exit.
>
> 2.6.21-rc6-mm1:
> - Rename task_pid_ns() to task_active_pid_ns() to reflect that a
> process can have multiple pid namespaces.
>
> Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
Acked-by: Pavel Emelianov <xemul at openvz.org>
But I'm not sure Andrew will like the construction like
some_function()->xxx;
I used to do so in memory controller, but he asked to fix...
> ---
> fs/exec.c | 2 +-
> fs/proc/proc_misc.c | 3 ++-
> include/linux/pid_namespace.h | 5 +++++
> kernel/exit.c | 5 +++--
> kernel/nsproxy.c | 2 +-
> kernel/pid.c | 4 ++--
> 6 files changed, 14 insertions(+), 7 deletions(-)
>
> Index: lx26-22-rc6-mm1/include/linux/pid_namespace.h
> ===================================================================
> --- lx26-22-rc6-mm1.orig/include/linux/pid_namespace.h 2007-07-05 18:53:43.000000000 -0700
> +++ lx26-22-rc6-mm1/include/linux/pid_namespace.h 2007-07-05 18:53:48.000000000 -0700
> @@ -37,6 +37,11 @@ static inline void put_pid_ns(struct pid
> kref_put(&ns->kref, free_pid_ns);
> }
>
> +static inline struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
> +{
> + return tsk->nsproxy->pid_ns;
> +}
> +
> static inline struct task_struct *child_reaper(struct task_struct *tsk)
> {
> return init_pid_ns.child_reaper;
> Index: lx26-22-rc6-mm1/fs/exec.c
> ===================================================================
> --- lx26-22-rc6-mm1.orig/fs/exec.c 2007-07-05 18:53:43.000000000 -0700
> +++ lx26-22-rc6-mm1/fs/exec.c 2007-07-05 18:53:48.000000000 -0700
> @@ -827,7 +827,7 @@ static int de_thread(struct task_struct
> * so it is safe to do it under read_lock.
> */
> if (unlikely(tsk->group_leader == child_reaper(tsk)))
> - tsk->nsproxy->pid_ns->child_reaper = tsk;
> + task_active_pid_ns(tsk)->child_reaper = tsk;
>
> zap_other_threads(tsk);
> read_unlock(&tasklist_lock);
> Index: lx26-22-rc6-mm1/fs/proc/proc_misc.c
> ===================================================================
> --- lx26-22-rc6-mm1.orig/fs/proc/proc_misc.c 2007-07-05 18:53:43.000000000 -0700
> +++ lx26-22-rc6-mm1/fs/proc/proc_misc.c 2007-07-05 18:53:48.000000000 -0700
> @@ -94,7 +94,8 @@ static int loadavg_read_proc(char *page,
> LOAD_INT(a), LOAD_FRAC(a),
> LOAD_INT(b), LOAD_FRAC(b),
> LOAD_INT(c), LOAD_FRAC(c),
> - nr_running(), nr_threads, current->nsproxy->pid_ns->last_pid);
> + nr_running(), nr_threads,
> + task_active_pid_ns(current)->last_pid);
> return proc_calc_metrics(page, start, off, count, eof, len);
> }
>
> Index: lx26-22-rc6-mm1/kernel/exit.c
> ===================================================================
> --- lx26-22-rc6-mm1.orig/kernel/exit.c 2007-07-05 18:53:43.000000000 -0700
> +++ lx26-22-rc6-mm1/kernel/exit.c 2007-07-05 18:53:48.000000000 -0700
> @@ -909,8 +909,9 @@ fastcall NORET_TYPE void do_exit(long co
> if (unlikely(!tsk->pid))
> panic("Attempted to kill the idle task!");
> if (unlikely(tsk == child_reaper(tsk))) {
> - if (tsk->nsproxy->pid_ns != &init_pid_ns)
> - tsk->nsproxy->pid_ns->child_reaper = init_pid_ns.child_reaper;
> + if (task_active_pid_ns(tsk) != &init_pid_ns)
> + task_active_pid_ns(tsk)->child_reaper =
> + init_pid_ns.child_reaper;
> else
> panic("Attempted to kill init!");
> }
> Index: lx26-22-rc6-mm1/kernel/pid.c
> ===================================================================
> --- lx26-22-rc6-mm1.orig/kernel/pid.c 2007-07-05 18:53:43.000000000 -0700
> +++ lx26-22-rc6-mm1/kernel/pid.c 2007-07-05 18:53:48.000000000 -0700
> @@ -213,7 +213,7 @@ struct pid *alloc_pid(void)
> if (!pid)
> goto out;
>
> - nr = alloc_pidmap(current->nsproxy->pid_ns);
> + nr = alloc_pidmap(task_active_pid_ns(current));
> if (nr < 0)
> goto out_free;
>
> @@ -358,7 +358,7 @@ struct pid *find_ge_pid(int nr)
> pid = find_pid(nr);
> if (pid)
> break;
> - nr = next_pidmap(current->nsproxy->pid_ns, nr);
> + nr = next_pidmap(task_active_pid_ns(current), nr);
> } while (nr > 0);
>
> return pid;
> Index: lx26-22-rc6-mm1/kernel/nsproxy.c
> ===================================================================
> --- lx26-22-rc6-mm1.orig/kernel/nsproxy.c 2007-07-05 18:53:42.000000000 -0700
> +++ lx26-22-rc6-mm1/kernel/nsproxy.c 2007-07-05 18:54:07.000000000 -0700
> @@ -86,7 +86,7 @@ static struct nsproxy *create_new_namesp
> goto out_ipc;
> }
>
> - new_nsp->pid_ns = copy_pid_ns(flags, tsk->nsproxy->pid_ns);
> + new_nsp->pid_ns = copy_pid_ns(flags, task_active_pid_ns(tsk));
> if (IS_ERR(new_nsp->pid_ns)) {
> err = PTR_ERR(new_nsp->pid_ns);
> goto out_pid;
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