pid namespaces: define and use task_active_pid_ns() wrapper (2894d650) · Commits · 戴 / test

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@us.ibm.com> Acked-by:

Pavel Emelianov <xemul@openvz.org> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Serge Hallyn <serue@us.ibm.com> Cc: Herbert Poetzel <herbert@13thfloor.at> Cc: Kirill Korotaev <dev@sw.ru> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/exec.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -776,7 +776,7 @@ static int de_thread(struct task_struct *tsk)
		* 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);

fs/proc/proc_misc.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -91,7 +91,8 @@ static int loadavg_read_proc(char page, char *start, off_t off,
		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);
		}

include/linux/pid_namespace.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,11 @@ static inline void put_pid_ns(struct pid_namespace *ns)
		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;

kernel/nsproxy.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -87,7 +87,7 @@ static struct nsproxy *create_new_namespaces(unsigned long flags,
		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;

kernel/pid.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -214,7 +214,7 @@ struct pid *alloc_pid(void)
		int nr = -1;
		struct pid_namespace *ns;

		ns = current->nsproxy->pid_ns;
		ns = task_active_pid_ns(current);
		pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
		if (!pid)
		goto out;
		@@ -364,7 +364,7 @@ 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;

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