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SubjectRe: [PATCH 05/23] user: Use generic ns_common::count
On Thu, Jul 30, 2020 at 02:59:47PM +0300, Kirill Tkhai wrote:
> Convert user namespace to use generic counter.
>
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> ---

Looks good!
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

> include/linux/user_namespace.h | 5 ++---
> kernel/user.c | 2 +-
> kernel/user_namespace.c | 4 ++--
> 3 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
> index 6ef1c7109fc4..64cf8ebdc4ec 100644
> --- a/include/linux/user_namespace.h
> +++ b/include/linux/user_namespace.h
> @@ -57,7 +57,6 @@ struct user_namespace {
> struct uid_gid_map uid_map;
> struct uid_gid_map gid_map;
> struct uid_gid_map projid_map;
> - atomic_t count;
> struct user_namespace *parent;
> int level;
> kuid_t owner;
> @@ -109,7 +108,7 @@ void dec_ucount(struct ucounts *ucounts, enum ucount_type type);
> static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
> {
> if (ns)
> - atomic_inc(&ns->count);
> + refcount_inc(&ns->ns.count);
> return ns;
> }
>
> @@ -119,7 +118,7 @@ extern void __put_user_ns(struct user_namespace *ns);
>
> static inline void put_user_ns(struct user_namespace *ns)
> {
> - if (ns && atomic_dec_and_test(&ns->count))
> + if (ns && refcount_dec_and_test(&ns->ns.count))
> __put_user_ns(ns);
> }
>
> diff --git a/kernel/user.c b/kernel/user.c
> index b1635d94a1f2..a2478cddf536 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -55,7 +55,7 @@ struct user_namespace init_user_ns = {
> },
> },
> },
> - .count = ATOMIC_INIT(3),
> + .ns.count = REFCOUNT_INIT(3),

Note-to-self: I really wish we'd had a comment in cases where the
refcount isn't set to 1 but to something like 3. Otherwise one always
needs to dig up the reasons why. :)

> .owner = GLOBAL_ROOT_UID,
> .group = GLOBAL_ROOT_GID,
> .ns.inum = PROC_USER_INIT_INO,
> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
> index 87804e0371fe..7c2bbe8f3e45 100644
> --- a/kernel/user_namespace.c
> +++ b/kernel/user_namespace.c
> @@ -111,7 +111,7 @@ int create_user_ns(struct cred *new)
> goto fail_free;
> ns->ns.ops = &userns_operations;
>
> - atomic_set(&ns->count, 1);
> + refcount_set(&ns->ns.count, 1);
> /* Leave the new->user_ns reference with the new user namespace. */
> ns->parent = parent_ns;
> ns->level = parent_ns->level + 1;
> @@ -197,7 +197,7 @@ static void free_user_ns(struct work_struct *work)
> kmem_cache_free(user_ns_cachep, ns);
> dec_user_namespaces(ucounts);
> ns = parent;
> - } while (atomic_dec_and_test(&parent->count));
> + } while (refcount_dec_and_test(&parent->ns.count));
> }
>
> void __put_user_ns(struct user_namespace *ns)
>
>

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