Switch over pid namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical.
Unified · Split
| @@ -8,7 +8,6 @@ · 7 unmodified lines | |||
| 8 | #include <linux/workqueue.h> | 8 | #include <linux/workqueue.h> |
| 9 | #include <linux/threads.h> | 9 | #include <linux/threads.h> |
| 10 | #include <linux/nsproxy.h> | 10 | #include <linux/nsproxy.h> |
| 11 | #include <linux/kref.h> | ||
| 12 | #include <linux/ns_common.h> | 11 | #include <linux/ns_common.h> |
| 13 | #include <linux/idr.h> | 12 | #include <linux/idr.h> |
| 14 | 13 | ||
| @@ -18,7 +17,6 @@ · 3 unmodified lines | |||
| 18 | struct fs_pin; | 17 | struct fs_pin; |
| 19 | 18 | ||
| 20 | struct pid_namespace { | 19 | struct pid_namespace { |
| 21 | struct kref kref; | ||
| 22 | struct idr idr; | 20 | struct idr idr; |
| 23 | struct rcu_head rcu; | 21 | struct rcu_head rcu; |
| 24 | unsigned int pid_allocated; | 22 | unsigned int pid_allocated; |
| @@ -43,7 +41,7 @@ extern struct pid_namespace init_pid_ns; · 18 unmodified lines | |||
| 43 | static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns) | 41 | static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns) |
| 44 | { | 42 | { |
| 45 | if (ns != &init_pid_ns) | 43 | if (ns != &init_pid_ns) |
| 46 | kref_get(&ns->kref); | 44 | refcount_inc(&ns->ns.count); |
| 47 | return ns; | 45 | return ns; |
| 48 | } | 46 | } |
| 49 | 47 | ||
| @@ -72,7 +72,7 @@ int pid_max_max = PID_MAX_LIMIT; · 71 unmodified lines | |||
| 72 | * the scheme scales to up to 4 million PIDs, runtime. | 72 | * the scheme scales to up to 4 million PIDs, runtime. |
| 73 | */ | 73 | */ |
| 74 | struct pid_namespace init_pid_ns = { | 74 | struct pid_namespace init_pid_ns = { |
| 75 | .kref = KREF_INIT(2), | 75 | .ns.count = REFCOUNT_INIT(2), |
| 76 | .idr = IDR_INIT(init_pid_ns.idr), | 76 | .idr = IDR_INIT(init_pid_ns.idr), |
| 77 | .pid_allocated = PIDNS_ADDING, | 77 | .pid_allocated = PIDNS_ADDING, |
| 78 | .level = 0, | 78 | .level = 0, |
| @@ -102,7 +102,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns · 101 unmodified lines | |||
| 102 | goto out_free_idr; | 102 | goto out_free_idr; |
| 103 | ns->ns.ops = &pidns_operations; | 103 | ns->ns.ops = &pidns_operations; |
| 104 | 104 | ||
| 105 | kref_init(&ns->kref); | 105 | refcount_set(&ns->ns.count, 1); |
| 106 | ns->level = level; | 106 | ns->level = level; |
| 107 | ns->parent = get_pid_ns(parent_pid_ns); | 107 | ns->parent = get_pid_ns(parent_pid_ns); |
| 108 | ns->user_ns = get_user_ns(user_ns); | 108 | ns->user_ns = get_user_ns(user_ns); |
| @@ -148,22 +148,15 @@ struct pid_namespace *copy_pid_ns(unsigned long flags, · 39 unmodified lines | |||
| 148 | return create_pid_namespace(user_ns, old_ns); | 148 | return create_pid_namespace(user_ns, old_ns); |
| 149 | } | 149 | } |
| 150 | 150 | ||
| 151 | static void free_pid_ns(struct kref *kref) | ||
| 152 | { | ||
| 153 | struct pid_namespace *ns; | ||
| 154 | |||
| 155 | ns = container_of(kref, struct pid_namespace, kref); | ||
| 156 | destroy_pid_namespace(ns); | ||
| 157 | } | ||
| 158 | |||
| 159 | void put_pid_ns(struct pid_namespace *ns) | 151 | void put_pid_ns(struct pid_namespace *ns) |
| 160 | { | 152 | { |
| 161 | struct pid_namespace *parent; | 153 | struct pid_namespace *parent; |
| 162 | 154 | ||
| 163 | while (ns != &init_pid_ns) { | 155 | while (ns != &init_pid_ns) { |
| 164 | parent = ns->parent; | 156 | parent = ns->parent; |
| 165 | if (!kref_put(&ns->kref, free_pid_ns)) | 157 | if (!refcount_dec_and_test(&ns->ns.count)) |
| 166 | break; | 158 | break; |
| 159 | destroy_pid_namespace(ns); | ||
| 167 | ns = parent; | 160 | ns = parent; |
| 168 | } | 161 | } |
| 169 | } | 162 | } |