"Serge E. Hallyn" <[EMAIL PROTECTED]> writes:
> Quoting Serge E. Hallyn ([EMAIL PROTECTED]):
>> > Just skimming through your patch I don't expect we will need the list
>> > of children, and not having should reduct our locking burden.
>>
>> Hmm, that's true. I can't see a reason for that. Thanks!
>
> BTW here is the new, slightly smaller patch:
>
>>From d17fbd87d97f64a0e879a7efbe5e1835fc573eae Mon Sep 17 00:00:00 2001
> From: Serge Hallyn <[EMAIL PROTECTED]>
> Date: Thu, 19 Jun 2008 20:18:17 -0500
> Subject: [PATCH 1/1] user namespaces: introduce user_struct->user_namespace
> relationship
>
> When a task does clone(CLONE_NEWNS), the task's user is the 'creator' of the
> new user_namespace, and the user_namespace is tacked onto a list of those
> created by this user.
>
> When we create or put a user in a namespace, we also do so for all creator
> users up the creator chain.
>
> Changelog:
> Jun 20: Eric Biederman pointed out the sibling/child_user_ns
> list is unnecessary!
>
> Signed-off-by: Serge Hallyn <[EMAIL PROTECTED]>
> ---
> include/linux/sched.h | 1 +
> include/linux/user_namespace.h | 1 +
> kernel/user.c | 66
> +++++++++++++++++++++++++++++++++++++++-
> kernel/user_namespace.c | 15 +++------
> 4 files changed, 72 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 799bbdd..da1bcc6 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -604,6 +604,7 @@ struct user_struct {
> /* Hash table maintenance information */
> struct hlist_node uidhash_node;
> uid_t uid;
> + struct user_namespace *user_namespace;
>
> #ifdef CONFIG_USER_SCHED
> struct task_group *tg;
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index b5f41d4..f9477c3 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -13,6 +13,7 @@ struct user_namespace {
> struct kref kref;
> struct hlist_head uidhash_table[UIDHASH_SZ];
> struct user_struct *root_user;
> + struct user_struct *creator;
> };
>
> extern struct user_namespace init_user_ns;
> diff --git a/kernel/user.c b/kernel/user.c
> index 865ecf5..e583be4 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -21,6 +21,7 @@ struct user_namespace init_user_ns = {
> .kref = {
> .refcount = ATOMIC_INIT(2),
> },
> + .creator = &root_user,
> .root_user = &root_user,
> };
> EXPORT_SYMBOL_GPL(init_user_ns);
> @@ -53,6 +54,7 @@ struct user_struct root_user = {
> .files = ATOMIC_INIT(0),
> .sigpending = ATOMIC_INIT(0),
> .locked_shm = 0,
> + .user_namespace = &init_user_ns,
> #ifdef CONFIG_USER_SCHED
> .tg = &init_task_group,
> #endif
> @@ -71,6 +73,18 @@ static void uid_hash_remove(struct user_struct *up)
> hlist_del_init(&up->uidhash_node);
> }
>
> +void inc_user_and_creators(struct user_struct *user)
> +{
> + struct user_namespace *ns = user->user_namespace;
> + while (user) {
> + atomic_inc(&user->__count);
> + if (ns == ns->creator->user_namespace)
> + return;
> + user = ns->creator;
> + ns = user->user_namespace;
> + }
> +}
> +
This functionality appears unnecessary. Holding a count on the user
and the user holding a count on it's user_namespace and the user_namespace
holding a count on it's creator should be sufficient.
Or am I missing something?
Eric
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