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Subject[PATCH v7 1/2] procfs: show hierarchy of pid namespace
Date
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 check/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>

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.

Signed-off-by: Chen Hanxiao <chenhanxiao@cn.fujitsu.com>
---
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/pidns_hierarchy.c | 280 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 287 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/pidns_hierarchy.c b/fs/proc/pidns_hierarchy.c
new file mode 100644
index 0000000..4629bfd
--- /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>
+
+/*
+ * /proc/pidns_hierarchy
+ *
+ * show the hierarchy of pid namespace in:
+ * <init_PID> <parent_of_init_PID> <relative PID level>
+ *
+ * init_PID: child reaper in ns
+ * parent_of_init_PID: init_PID's parent, also child reaper
+ * relative PID level: pid level relative to caller's ns
+ */
+
+#define NS_HIERARCHY "pidns_hierarchy"
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+
+/* list for host pid collection */
+struct pidns_list {
+ struct list_head list;
+ struct pid *pid;
+ int show_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 show_level)
+{
+ struct pidns_list *ent;
+
+ ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+ if (!ent)
+ return -ENOMEM;
+
+ ent->pid = pid;
+ ent->show_level = show_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_show_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 subset of each other.
+ * But part of them may be same.
+ * We need to set the show_level of each pids:
+ * pid0: A->B->C pid1: A->B->D
+ * show_level 2 0
+ * We use show_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->show_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->show_level = i - 1;
+ }
+ }
+}
+
+/*
+ * collect pids and stored in pidns_pid_list,
+ * then remove duplicated ones,
+ * add the rest to 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_show_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->show_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,
+};
+
+static int __init pidns_hierarchy_init(void)
+{
+ proc_create(NS_HIERARCHY, S_IWUGO,
+ NULL, &proc_nspid_nslist_fops);
+
+ return 0;
+}
+fs_initcall(pidns_hierarchy_init);
--
1.9.3
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