Oleg Nesterov wrote:
On 07/26, Pavel Emelyanov wrote:
--- linux-2.6.23-rc1-mm1.orig/include/linux/pid.h 2007-07-26 16:34:45.000000000 +0400
+++ linux-2.6.23-rc1-mm1-7/include/linux/pid.h 2007-07-26 16:36:37.000000000 +0400
@@ -40,15 +40,21 @@ enum pid_type
* processes.
*/
-struct pid
-{
- atomic_t count;
+struct upid {
/* Try to keep pid_chain in the same cacheline as nr for find_pid */
int nr;
+ struct pid_namespace *ns;
struct hlist_node pid_chain;
+};
+
+struct pid
+{
+ atomic_t count;
/* lists of tasks that use this pid */
struct hlist_head tasks[PIDTYPE_MAX];
struct rcu_head rcu;
+ int level;
+ struct upid numbers[1];
};
Well. Definitely, the kernel can't be compiled with this patch applied,
this seems to be against the rules...
Yes. U forgot to mention, that this patchset is git-bisect-not-safe :)
I sent the safe split earlier, but it was harder to make and understand,
so I decided not to waste the time and sent a badly-split set just to get
comments about the approach. The ways a big patch is split wouldn't affect
the comments about the ideas, bugs, etc.
So. The task has a single (PIDTYPE_MAX) pid no matter how many namespaces
can see it, and "struct pid" has an array of numbers for each namespace.
Still I can't understand why do we need upid->ns, can't we kill it?
Suppose we add "struct pid_namespace *parent_ns" to "struct pid_namespace",
init_pid_ns.parent_ns == NULL.
We already have it :)
Now,
struct upid {
int nr;
struct hlist_node pid_chain;
};
struct pid
{
atomic_t count;
struct hlist_head tasks[PIDTYPE_MAX];
struct rcu_head rcu;
struct pid_namespace *active_ns;
struct upid numbers[0];
};
We populate pid->numbers in "reverse" order, so that pid->numbers[0] lives
in pid->active_ns.
Now, for example,
void free_pid(struct pid *pid)
{
struct pid_namespace *ns;
unsigned long flags;
int i;
spin_lock_irqsave(&pidmap_lock, flags);
for (i = 0, ns = pid->active_ns; ns; i++, ns = ns->parent_ns)
hlist_del_rcu(&pid->numbers[i].pid_chain);
spin_unlock_irqrestore(&pidmap_lock, flags);
for (i = 0, ns = pid->active_ns; ns; i++, ns = ns->parent_ns)
free_pidmap(ns, pid->numbers[i].nr);
call_rcu(&pid->rcu, delayed_put_pid);
}
Possible?
Possible, but how will
struct pid *find_pid_nr_ns(int nr, struct pid_namespace *ns);
look then? The only way (I see) is to make
hlist_for_each_entry (upid, ...)
if (upid->nr == nr && upid->ns == ns)
return container_of(upid, struct pid, ...)
Oleg.
Thanks,
Pavel
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