diff options
| -rw-r--r-- | kernel/pid_namespace.c | 67 |
1 files changed, 24 insertions, 43 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 0b53eef7d34b..773b2b31734f 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -23,55 +23,39 @@ #include <linux/sched/signal.h> #include <linux/idr.h> -struct pid_cache { - int nr_ids; - char name[16]; - struct kmem_cache *cachep; - struct list_head list; -}; - -static LIST_HEAD(pid_caches_lh); static DEFINE_MUTEX(pid_caches_mutex); static struct kmem_cache *pid_ns_cachep; +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ +#define MAX_PID_NS_LEVEL 32 +/* Write once array, filled from the beginning. */ +static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL]; /* * creates the kmem cache to allocate pids from. - * @nr_ids: the number of numerical ids this pid will have to carry + * @level: pid namespace level */ -static struct kmem_cache *create_pid_cachep(int nr_ids) +static struct kmem_cache *create_pid_cachep(unsigned int level) { - struct pid_cache *pcache; - struct kmem_cache *cachep; - + /* Level 0 is init_pid_ns.pid_cachep */ + struct kmem_cache **pkc = &pid_cache[level - 1]; + struct kmem_cache *kc; + char name[4 + 10 + 1]; + unsigned int len; + + kc = READ_ONCE(*pkc); + if (kc) + return kc; + + snprintf(name, sizeof(name), "pid_%u", level + 1); + len = sizeof(struct pid) + level * sizeof(struct upid); mutex_lock(&pid_caches_mutex); - list_for_each_entry(pcache, &pid_caches_lh, list) - if (pcache->nr_ids == nr_ids) - goto out; - - pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); - if (pcache == NULL) - goto err_alloc; - - snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); - cachep = kmem_cache_create(pcache->name, - sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid), - 0, SLAB_HWCACHE_ALIGN, NULL); - if (cachep == NULL) - goto err_cachep; - - pcache->nr_ids = nr_ids; - pcache->cachep = cachep; - list_add(&pcache->list, &pid_caches_lh); -out: + /* Name collision forces to do allocation under mutex. */ + if (!*pkc) + *pkc = kmem_cache_create(name, len, 0, SLAB_HWCACHE_ALIGN, 0); mutex_unlock(&pid_caches_mutex); - return pcache->cachep; - -err_cachep: - kfree(pcache); -err_alloc: - mutex_unlock(&pid_caches_mutex); - return NULL; + /* current can fail, but someone else can succeed. */ + return READ_ONCE(*pkc); } static void proc_cleanup_work(struct work_struct *work) @@ -80,9 +64,6 @@ static void proc_cleanup_work(struct work_struct *work) pid_ns_release_proc(ns); } -/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ -#define MAX_PID_NS_LEVEL 32 - static struct ucounts *inc_pid_namespaces(struct user_namespace *ns) { return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES); @@ -119,7 +100,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns idr_init(&ns->idr); - ns->pid_cachep = create_pid_cachep(level + 1); + ns->pid_cachep = create_pid_cachep(level); if (ns->pid_cachep == NULL) goto out_free_idr; |