Quoting Chen Hanxiao (chenhanx...@cn.fujitsu.com):
> This patch will show the hierarchy of pid namespace
> under /proc/pidns like:
> /proc/pidns
> ├── hierarchy
> │ ├── pidns4026532399
> │ │ ├── pidns -> /proc/2863/ns/pid
> │ │ └── pidns4026532515
> │ │ └── pidns -> /proc/10611/ns/pid
> │ └── pidns4026532504
> │ └── pidns -> /proc/4450/ns/pid
> └── refresh
>
> a) hierarchy dir:
> use to show hierarchy infomation using dir and symlinks.
> dirs are named as pidns($inum)
> a symlink is created under pidns($inum), and linked to
> that pid namespace.
>
> b) refresh
> trigger key.
> We need to write sth to /proc/nspid/refresh,
> then we could get hierarchy info
> under /proc/pidns/hierarchy.
Ouch. There may not be a better way, but it sure would be nice if
we could simply have the list update in real-time.
If we have to 'echo 1 > /proc/pidns/refresh' to update the fs tree under
/proc/pidns/ to reflect new pidns activity, then why not just make this
a text file? I suppose if it were a textfile you'd be encouraging ppl
to 'cat pidlist | while read line; do grep line /proc/pidns; done',
which would cause a refresh of that file for every grep?
My concern with this approach is that it is unlike any other pseudo-fs
that I know of, and people may simply expect the fs contents to be
uptodate rather than a snapshot.
> Signed-off-by: Chen Hanxiao <chenhanx...@cn.fujitsu.com>
> ---
> fs/proc/Kconfig | 6 ++
> fs/proc/Makefile | 1 +
> fs/proc/pidns_hierarchy.c | 161
> ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 168 insertions(+)
> create mode 100644 fs/proc/pidns_hierarchy.c
>
> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
> index 2183fcf..e2e2292 100644
> --- a/fs/proc/Kconfig
> +++ b/fs/proc/Kconfig
> @@ -71,3 +71,9 @@ config PROC_PAGE_MONITOR
> /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap,
> /proc/kpagecount, and /proc/kpageflags. Disabling these
> interfaces will reduce the size of the kernel by approximately 4kb.
> +
> +config PROC_PID_HIERARCHY
> + bool "Enable /proc/pidns_hierarchy support" if EXPERT
> + depends on PROC_FS
> + help
> + Show pid namespace hierarchy infomation
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index 239493e..733599b 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -29,3 +29,4 @@ proc-$(CONFIG_PROC_KCORE) += kcore.o
> proc-$(CONFIG_PROC_VMCORE) += vmcore.o
> proc-$(CONFIG_PRINTK) += kmsg.o
> proc-$(CONFIG_PROC_PAGE_MONITOR) += page.o
> +proc-$(CONFIG_PROC_PID_HIERARCHY) += pidns_hierarchy.o
> diff --git a/fs/proc/pidns_hierarchy.c b/fs/proc/pidns_hierarchy.c
> new file mode 100644
> index 0000000..d35340f
> --- /dev/null
> +++ b/fs/proc/pidns_hierarchy.c
> @@ -0,0 +1,161 @@
> +/*
> + * proc_pidns_hierarchy.c -- handles pidns hierarchy
> + *
> + * Copyright 2014
> + */
> +
> +#include <linux/init.h>
> +#include <linux/errno.h>
> +#include <linux/proc_fs.h>
> +#include <linux/module.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/pid_namespace.h>
> +
> +/*
> + * The /proc/pidns directory
> + */
> +
> +#define BASE_DIR "pidns" /* Subdir in /proc */
> +#define HIERARCHY_DIR "pidns/hierarchy" /* hierarchy dir */
> +#define REFRESH_KEY "pidns/refresh" /* refresh key */
> +#define NAME "pidns_hierarchy" /* Module name */
> +
> +static LIST_HEAD(pidns_list);
> +static DEFINE_RWLOCK(pidns_lock);
> +static struct proc_dir_entry *proc_root;
> +
> +struct ns_pid_list {
> + struct pid *pid;
> + struct list_head list;
> +};
> +
> +static void free_pidns_list(struct list_head *head)
> +{
> + struct ns_pid_list *tmp, *pos;
> +
> + list_for_each_entry_safe(pos, tmp, head, list) {
> + list_del(&pos->list);
> + kfree(pos);
> + }
> +}
> +
> +/*
> + * Only add pids with different ns
> + */
> +static int
> +ns_pid_list_really_add(struct pid *pid)
> +{
> + struct ns_pid_list *tmp, *pos;
> +
> + list_for_each_entry_safe(pos, tmp, &pidns_list, list)
> + if (ns_of_pid(pid) == ns_of_pid(pos->pid))
> + return 0;
> +
> + return 1;
> +}
> +
> +static int
> +ns_pid_list_add(struct pid *pid)
> +{
> + struct ns_pid_list *ent;
> +
> + ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> + if (!ent)
> + return -ENOMEM;
> + ent->pid = pid;
> + if (ns_pid_list_really_add(pid))
> + list_add_tail(&ent->list, &pidns_list);
> +
> + return 0;
> +}
> +
> +static void print_list(void)
> +{
> + struct ns_pid_list *tmp, *pos;
> + struct proc_dir_entry *parent, *parent_new;
> + struct pid_namespace *ns, *curr_ns;
> + struct pid *pid;
> + char name_buf[16], pid_buf[32];
> + int i, k;
> +
> + curr_ns = task_active_pid_ns(current);
> +
> + list_for_each_entry_safe(pos, tmp, &pidns_list, list) {
> + pid = pos->pid;
> + k = -1;
> + ns = pid->numbers[pid->level].ns;
> + /* Check whether pid has relationship with current ns */
> + for (; ns != NULL; ns = ns->parent)
> + if (ns == curr_ns)
> + k = curr_ns->level;
> + if (k == -1)
> + continue;
> + parent = proc_root;
> + for (i = k + 1; i <= pid->level; i++) {
> + ns = pid->numbers[i].ns;
> + snprintf(name_buf, 16, "pidns%u",
> + pid->numbers[i].ns->proc_inum);
> + snprintf(pid_buf, 32, "/proc/%u/ns/pid",
> + pid->numbers[0].nr);
> + /* don't duplicate ns dirs */
> + parent_new = proc_uniq_dir(parent, name_buf);
> + if (!parent_new) {
> + parent_new = proc_mkdir(name_buf, parent);
> + proc_symlink("pidns", parent_new, pid_buf);
> + }
> + parent = parent_new;
> + }
> + }
> +}
> +
> +void proc_pidns_list(void)
> +{
> + struct pid *pid;
> + struct task_struct *task = &init_task;
> +
> + remove_proc_subtree(HIERARCHY_DIR, NULL);
> + proc_root = proc_mkdir(HIERARCHY_DIR, NULL);
> + free_pidns_list(&pidns_list);
> +
> + do {
> + pid = task_pid(task);
> + if (pid) {
> + if (pid->level > 0)
> + ns_pid_list_add(pid);
> + }
> + } while ((task = next_task(task)) != &init_task);
> +
> + print_list();
> + printk(KERN_INFO "refresh finished\n");
> +}
> +
> +ssize_t proc_pidns_refresh_switch(struct file *file, const char __user *buf,
> + size_t size, loff_t *ppos)
> +{
> + write_lock(&pidns_lock);
> + proc_pidns_list();
> + write_unlock(&pidns_lock);
> + return 1;
> +}
> +
> +static const struct file_operations proc_pidns_refresh_fops = {
> + .write = proc_pidns_refresh_switch,
> +};
> +
> +static int __init pidns_hierarchy_init(void)
> +{
> +
> + if (!proc_mkdir(BASE_DIR, NULL))
> + return -ENOMEM;
> + proc_root = proc_mkdir(HIERARCHY_DIR, NULL);
> + if (!proc_root)
> + return -ENOMEM;
> +
> + proc_create(REFRESH_KEY, S_IWUGO,
> + NULL, &proc_pidns_refresh_fops);
> + printk(KERN_INFO "%s: loaded successfully\n", NAME);
> +
> + return 0;
> +}
> +fs_initcall(pidns_hierarchy_init);
> --
> 1.9.0
>
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