mirror of
https://github.com/checkpoint-restore/criu.git
synced 2026-07-21 09:10:10 +00:00
104 lines
3.5 KiB
Text
104 lines
3.5 KiB
Text
From: Cyrill Gorcunov <gorcunov@openvz.org>
|
|
Subject: [PATCH] sysctl: Add the kernel.ns_last_pid control
|
|
|
|
From: Pavel Emelyanov <xemul@parallels.com>
|
|
|
|
The sysctl works on the current task's pid namespace, getting and setting its
|
|
last_pid field.
|
|
|
|
Writing is allowed for CAP_SYS_ADMIN-capable tasks thus making it possible to
|
|
create a task with desired pid value. This ability is required badly for the
|
|
checkpoint/restore in userspace.
|
|
|
|
This approach suits all the parties for now.
|
|
|
|
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
|
|
Acked-by: Tejun Heo <tj@kernel.org>
|
|
CC: Oleg Nesterov <oleg@redhat.com>
|
|
CC: Andrew Morton <akpm@linux-foundation.org>
|
|
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
|
|
---
|
|
Documentation/sysctl/kernel.txt | 8 ++++++++
|
|
kernel/pid.c | 4 +++-
|
|
kernel/pid_namespace.c | 31 +++++++++++++++++++++++++++++++
|
|
3 files changed, 42 insertions(+), 1 deletion(-)
|
|
|
|
Index: linux-2.6.git/Documentation/sysctl/kernel.txt
|
|
===================================================================
|
|
--- linux-2.6.git.orig/Documentation/sysctl/kernel.txt
|
|
+++ linux-2.6.git/Documentation/sysctl/kernel.txt
|
|
@@ -401,6 +401,14 @@ PIDs of value pid_max or larger are not
|
|
|
|
==============================================================
|
|
|
|
+ns_last_pid:
|
|
+
|
|
+The last pid allocated in the current (the one task using this sysctl
|
|
+lives in) pid namespace. When selecting a pid for a next task on fork
|
|
+kernel tries to allocate a number starting from this one.
|
|
+
|
|
+==============================================================
|
|
+
|
|
powersave-nap: (PPC only)
|
|
|
|
If set, Linux-PPC will use the 'nap' mode of powersaving,
|
|
Index: linux-2.6.git/kernel/pid.c
|
|
===================================================================
|
|
--- linux-2.6.git.orig/kernel/pid.c
|
|
+++ linux-2.6.git/kernel/pid.c
|
|
@@ -137,7 +137,9 @@ static int pid_before(int base, int a, i
|
|
}
|
|
|
|
/*
|
|
- * We might be racing with someone else trying to set pid_ns->last_pid.
|
|
+ * We might be racing with someone else trying to set pid_ns->last_pid
|
|
+ * at the pid allocation time (there's also a sysctl for this, but racing
|
|
+ * with this one is OK, see comment in kernel/pid_namespace.c about it).
|
|
* We want the winner to have the "later" value, because if the
|
|
* "earlier" value prevails, then a pid may get reused immediately.
|
|
*
|
|
Index: linux-2.6.git/kernel/pid_namespace.c
|
|
===================================================================
|
|
--- linux-2.6.git.orig/kernel/pid_namespace.c
|
|
+++ linux-2.6.git/kernel/pid_namespace.c
|
|
@@ -191,9 +191,40 @@ void zap_pid_ns_processes(struct pid_nam
|
|
return;
|
|
}
|
|
|
|
+static int pid_ns_ctl_handler(struct ctl_table *table, int write,
|
|
+ void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
+{
|
|
+ struct ctl_table tmp = *table;
|
|
+
|
|
+ if (write && !capable(CAP_SYS_ADMIN))
|
|
+ return -EPERM;
|
|
+
|
|
+ /*
|
|
+ * Writing directly to ns' last_pid field is OK, since this field
|
|
+ * is volatile in a living namespace anyway and a code writing to
|
|
+ * it should synchronize its usage with external means.
|
|
+ */
|
|
+
|
|
+ tmp.data = ¤t->nsproxy->pid_ns->last_pid;
|
|
+ return proc_dointvec(&tmp, write, buffer, lenp, ppos);
|
|
+}
|
|
+
|
|
+static struct ctl_table pid_ns_ctl_table[] = {
|
|
+ {
|
|
+ .procname = "ns_last_pid",
|
|
+ .maxlen = sizeof(int),
|
|
+ .mode = 0666, /* permissions are checked in the handler */
|
|
+ .proc_handler = pid_ns_ctl_handler,
|
|
+ },
|
|
+ { }
|
|
+};
|
|
+
|
|
+static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
|
|
+
|
|
static __init int pid_namespaces_init(void)
|
|
{
|
|
pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
|
|
+ register_sysctl_paths(kern_path, pid_ns_ctl_table);
|
|
return 0;
|
|
}
|
|
|