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SubjectRE: [resend][PATCH v9 1/3] procfs: show hierarchy of pid namespace
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> -----Original Message-----
> From: containers-bounces@lists.linux-foundation.org
> [mailto:containers-bounces@lists.linux-foundation.org] On Behalf Of Chen Hanxiao
> Sent: Tuesday, December 23, 2014 6:21 PM
> To: Eric W. Biederman; Serge Hallyn; Andrew Morton; Pavel Emelyanov
> Cc: Richard Weinberger; containers@lists.linux-foundation.org;
> linux-kernel@vger.kernel.org; Oleg Nesterov; David Howells; Mateusz Guzik
> Subject: [resend][PATCH v9 1/3] procfs: show hierarchy of pid namespace
>
> We lack of pid hierarchy information, and this will lead to:
> a) we don't know pids' relationship, who is whose child:
> /proc/PID/ns/pid only tell us whether two pids live in different ns
> b) bring trouble to nested lxc container checkpoint/restore/migration
> c) bring trouble to pid translation between containers;
>
> This patch will show the hierarchy of pid namespace
> by pidns_hierarchy like:
>
> <init_PID> <parent_of_init_PID> <relative PID level>
>

Hi Eric, Pavel

Any comments?

Regards,
- Chen

> Ex:
> [root@localhost ~]#cat /proc/pidns_hierarchy
> 18060 1 1
> 18102 18060 2
> 1534 18102 3
> 1600 18102 3
> 1550 1 1
> *Note: numbers represent the pid 1 in different ns
>
> It shows the pid hierarchy below:
>
> init_pid_ns 1
> │
> ┌────────────┐
> ns1 ns2
> │ │
> 1550 18060
> │
> │
> ns3
> │
> 18102
> │
> ┌──────────┐
> ns4 ns5
> │ │
> 1534 1600
>
> Every pid printed in pidns_hierarchy
> is the init pid of that pid ns level.
>
> Acked-by: Richard Weinberer <richard@nod.at>
>
> Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
> ---
> v9: fix codes be included if CONFIG_PID_NS=n
> v8: use max() from kernel.h
> fix some improper comments
> v7: change stype to be consistent with current interface like
> <init_PID> <parent_of_init_PID> <relative PID level>
> remove EXPERT dependent in Kconfig
> v6: fix a get_pid leak and do some cleanups;
> v5: collect pid by find_ge_pid;
> use local list inside nslist_proc_show;
> use get_pid, remove mutex lock.
> v4: simplify pid collection and some performance optimizamtion
> fix another race issue.
> v3: fix a race issue and memory leak issue
> v2: use a procfs text file instead of dirs under /proc
>
> fs/proc/Kconfig | 6 +
> fs/proc/Makefile | 1 +
> fs/proc/internal.h | 9 ++
> fs/proc/pidns_hierarchy.c | 280 ++++++++++++++++++++++++++++++++++++++++++++++
> fs/proc/root.c | 1 +
> 5 files changed, 297 insertions(+)
> create mode 100644 fs/proc/pidns_hierarchy.c
>
> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
> index 2183fcf..82dda55 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"
> + depends on PROC_FS
> + help
> + Show pid namespace hierarchy information
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index 7151ea4..33e384b 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -30,3 +30,4 @@ 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/internal.h b/fs/proc/internal.h
> index 6fcdba5..18e0773 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -280,6 +280,15 @@ struct proc_maps_private {
> #endif
> };
>
> +/*
> + * pidns_hierarchy.c
> + */
> +#ifdef CONFIG_PROC_PID_HIERARCHY
> + extern void proc_pidns_hierarchy_init(void);
> +#else
> + static inline void proc_pidns_hierarchy_init(void) {}
> +#endif
> +
> struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode);
>
> extern const struct file_operations proc_pid_maps_operations;
> diff --git a/fs/proc/pidns_hierarchy.c b/fs/proc/pidns_hierarchy.c
> new file mode 100644
> index 0000000..ab1c665
> --- /dev/null
> +++ b/fs/proc/pidns_hierarchy.c
> @@ -0,0 +1,280 @@
> +#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>
> +#include <linux/seq_file.h>
> +#include <linux/kernel.h>
> +
> +/*
> + * /proc/pidns_hierarchy
> + *
> + * show the hierarchy of pid namespace as:
> + * <init_PID> <parent_of_init_PID> <relative PID level>
> + *
> + * init_PID: child reaper in ns
> + * parent_of_init_PID: init_PID's parent, child reaper too
> + * relative PID level: pid level relative to caller's ns
> + */
> +
> +#define NS_HIERARCHY "pidns_hierarchy"
> +
> +/* list for host pid collection */
> +struct pidns_list {
> + struct list_head list;
> + struct pid *pid;
> + unsigned int level;
> +};
> +
> +static void free_pidns_list(struct list_head *head)
> +{
> + struct pidns_list *tmp, *pos;
> +
> + list_for_each_entry_safe(pos, tmp, head, list) {
> + list_del(&pos->list);
> + put_pid(pos->pid);
> + kfree(pos);
> + }
> +}
> +
> +static int
> +pidns_list_add(struct pid *pid, struct list_head *list_head,
> + int level)
> +{
> + struct pidns_list *ent;
> +
> + ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> + if (!ent)
> + return -ENOMEM;
> +
> + ent->pid = pid;
> + ent->level = level;
> + list_add_tail(&ent->list, list_head);
> +
> + return 0;
> +}
> +
> +static int
> +pidns_list_filter(struct list_head *pidns_pid_list,
> + struct list_head *pidns_pid_tree)
> +{
> + struct pidns_list *pos, *pos_t;
> + struct pid_namespace *ns0, *ns1;
> + struct pid *pid0, *pid1;
> + int rc, flag = 0;
> +
> + /*
> + * screen pids with relationship
> + * in pidns_pid_list, we may add pids like:
> + * ns0 ns1 ns2
> + * pid1->pid2->pid3
> + * we should screen pid1, pid2 and keep pid3
> + */
> + list_for_each_entry(pos, pidns_pid_list, list) {
> + list_for_each_entry(pos_t, pidns_pid_list, list) {
> + flag = 0;
> + pid0 = pos->pid;
> + pid1 = pos_t->pid;
> + ns0 = pid0->numbers[pid0->level].ns;
> + ns1 = pid1->numbers[pid1->level].ns;
> + if (pos->pid->level < pos_t->pid->level)
> + for (; ns1 != NULL; ns1 = ns1->parent)
> + if (ns0 == ns1) {
> + flag = 1;
> + break;
> + }
> + /* a redundant pid found */
> + if (flag == 1)
> + break;
> + }
> +
> + if (flag == 0) {
> + get_pid(pos->pid);
> + rc = pidns_list_add(pos->pid, pidns_pid_tree, 0);
> + if (rc) {
> + put_pid(pos->pid);
> + goto cleanup;
> + }
> + }
> + }
> +
> + /*
> + * Now all useful stuffs are in pidns_pid_tree,
> + * free pidns_pid_list
> + */
> + free_pidns_list(pidns_pid_list);
> +
> + return 0;
> +
> +cleanup:
> + free_pidns_list(pidns_pid_tree);
> + return rc;
> +}
> +
> +static void
> +pidns_list_set_level(struct list_head *pidns_list_in,
> + struct pid_namespace *curr_ns)
> +{
> + struct pidns_list *pos, *pos_t;
> + struct pid *pid0, *pid1;
> + int i;
> +
> + /*
> + * From the pid hierarchy point of view,
> + * we already had a list of pids who are not
> + * the subsets of each other.
> + * But part of them may be same.
> + * We need to set the level of each pids:
> + * pid0: A->B->C pid1: A->B->D
> + * level: 2 0
> + * We use level to identify
> + * the public part of each pids.
> + */
> + list_for_each_entry(pos, pidns_list_in, list) {
> + list_for_each_entry(pos_t, pidns_list_in, list) {
> + pid0 = pos->pid;
> + pid1 = pos_t->pid;
> + if (pid0 == pid1)
> + continue;
> + if (pos_t->level > 0)
> + continue;
> + for (i = curr_ns->level + 1; i <= pid0->level; i++) {
> + /* skip the public parts */
> + if (pid0->numbers[i].ns ==
> + pid1->numbers[i].ns)
> + continue;
> + else
> + break;
> + }
> + pos->level = i - 1;
> + }
> + }
> +}
> +
> +/*
> + * Finds all init pids, places them into
> + * pidns_pid_list and then stores the hierarchy
> + * into pidns_pid_tree.
> + */
> +static int proc_pidns_list_refresh(struct pid_namespace *curr_ns,
> + struct list_head *pidns_pid_list,
> + struct list_head *pidns_pid_tree)
> +{
> + struct pid *pid;
> + int new_nr, nr = 0;
> + int rc;
> +
> + /* collect pids in current namespace */
> + while (nr < PID_MAX_LIMIT) {
> + rcu_read_lock();
> + pid = find_ge_pid(nr, curr_ns);
> + if (!pid) {
> + rcu_read_unlock();
> + break;
> + }
> +
> + new_nr = pid_vnr(pid);
> + if (!is_child_reaper(pid)) {
> + nr = new_nr + 1;
> + rcu_read_unlock();
> + continue;
> + }
> + get_pid(pid);
> + rcu_read_unlock();
> + rc = pidns_list_add(pid, pidns_pid_list, 0);
> + if (rc) {
> + put_pid(pid);
> + goto cleanup;
> + }
> + nr = new_nr + 1;
> + }
> +
> + /*
> + * Only one pid found as the child reaper,
> + * so current pid namespace do not have sub-namespace,
> + * return 0 directly.
> + */
> + if (list_is_singular(pidns_pid_list)) {
> + rc = 0;
> + goto cleanup;
> + }
> +
> + /*
> + * screen duplicate pids from pidns_pid_list
> + * and form a new list pidns_pid_tree.
> + */
> + rc = pidns_list_filter(pidns_pid_list, pidns_pid_tree);
> + if (rc)
> + goto cleanup;
> +
> + return 0;
> +
> +cleanup:
> + free_pidns_list(pidns_pid_list);
> + return rc;
> +}
> +
> +static int nslist_proc_show(struct seq_file *m, void *v)
> +{
> + struct pidns_list *pos;
> + struct pid_namespace *ns, *curr_ns;
> + struct pid *pid;
> + char pid_buf[16], ppid_buf[16];
> + int i, rc;
> +
> + LIST_HEAD(pidns_pid_list);
> + LIST_HEAD(pidns_pid_tree);
> +
> + curr_ns = task_active_pid_ns(current);
> +
> + rc = proc_pidns_list_refresh(curr_ns,
> + &pidns_pid_list, &pidns_pid_tree);
> + if (rc)
> + return rc;
> +
> + pidns_list_set_level(&pidns_pid_tree, curr_ns);
> +
> + /* print pid namespace's hierarchy */
> + list_for_each_entry(pos, &pidns_pid_tree, list) {
> + pid = pos->pid;
> + for (i = max(curr_ns->level, pos->level) + 1;
> + i <= pid->level; i++) {
> + ns = pid->numbers[i].ns;
> + /* show PID '1' in specific pid ns */
> + snprintf(pid_buf, 16, "%u",
> + pid_vnr(find_pid_ns(1, ns)));
> + ns = pid->numbers[i - 1].ns;
> + snprintf(ppid_buf, 16, "%u",
> + pid_vnr(find_pid_ns(1, ns)));
> + seq_printf(m, "%s\t%s\t%d\n", pid_buf, ppid_buf,
> + i - curr_ns->level);
> + }
> + }
> +
> + free_pidns_list(&pidns_pid_tree);
> +
> + return 0;
> +}
> +
> +static int nslist_proc_open(struct inode *inode, struct file *file)
> +{
> + return single_open(file, nslist_proc_show, NULL);
> +}
> +
> +static const struct file_operations proc_nspid_nslist_fops = {
> + .open = nslist_proc_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +/*
> + * Called by proc_root_init() to initialize the /proc/pidns_hierarchy
> + */
> +void __init proc_pidns_hierarchy_init(void)
> +{
> + proc_create(NS_HIERARCHY, S_IRUGO,
> + NULL, &proc_nspid_nslist_fops);
> +}
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index e74ac9f..bcb55c7 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -190,6 +190,7 @@ void __init proc_root_init(void)
> proc_tty_init();
> proc_mkdir("bus", NULL);
> proc_sys_init();
> + proc_pidns_hierarchy_init();
> }
>
> static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct
> kstat *stat
> --
> 1.9.3
>
> _______________________________________________
> Containers mailing list
> Containers@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/containers
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