v4.19.13 snapshot.
diff --git a/kernel/pid.c b/kernel/pid.c
new file mode 100644
index 0000000..cdf63e5
--- /dev/null
+++ b/kernel/pid.c
@@ -0,0 +1,468 @@
+/*
+ * Generic pidhash and scalable, time-bounded PID allocator
+ *
+ * (C) 2002-2003 Nadia Yvette Chambers, IBM
+ * (C) 2004 Nadia Yvette Chambers, Oracle
+ * (C) 2002-2004 Ingo Molnar, Red Hat
+ *
+ * pid-structures are backing objects for tasks sharing a given ID to chain
+ * against. There is very little to them aside from hashing them and
+ * parking tasks using given ID's on a list.
+ *
+ * The hash is always changed with the tasklist_lock write-acquired,
+ * and the hash is only accessed with the tasklist_lock at least
+ * read-acquired, so there's no additional SMP locking needed here.
+ *
+ * We have a list of bitmap pages, which bitmaps represent the PID space.
+ * Allocating and freeing PIDs is completely lockless. The worst-case
+ * allocation scenario when all but one out of 1 million PIDs possible are
+ * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
+ * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
+ *
+ * Pid namespaces:
+ * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
+ * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
+ * Many thanks to Oleg Nesterov for comments and help
+ *
+ */
+
+#include <linux/mm.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/rculist.h>
+#include <linux/bootmem.h>
+#include <linux/hash.h>
+#include <linux/pid_namespace.h>
+#include <linux/init_task.h>
+#include <linux/syscalls.h>
+#include <linux/proc_ns.h>
+#include <linux/proc_fs.h>
+#include <linux/sched/task.h>
+#include <linux/idr.h>
+
+struct pid init_struct_pid = {
+ .count = ATOMIC_INIT(1),
+ .tasks = {
+ { .first = NULL },
+ { .first = NULL },
+ { .first = NULL },
+ },
+ .level = 0,
+ .numbers = { {
+ .nr = 0,
+ .ns = &init_pid_ns,
+ }, }
+};
+
+int pid_max = PID_MAX_DEFAULT;
+
+#define RESERVED_PIDS 300
+
+int pid_max_min = RESERVED_PIDS + 1;
+int pid_max_max = PID_MAX_LIMIT;
+
+/*
+ * PID-map pages start out as NULL, they get allocated upon
+ * first use and are never deallocated. This way a low pid_max
+ * value does not cause lots of bitmaps to be allocated, but
+ * the scheme scales to up to 4 million PIDs, runtime.
+ */
+struct pid_namespace init_pid_ns = {
+ .kref = KREF_INIT(2),
+ .idr = IDR_INIT(init_pid_ns.idr),
+ .pid_allocated = PIDNS_ADDING,
+ .level = 0,
+ .child_reaper = &init_task,
+ .user_ns = &init_user_ns,
+ .ns.inum = PROC_PID_INIT_INO,
+#ifdef CONFIG_PID_NS
+ .ns.ops = &pidns_operations,
+#endif
+};
+EXPORT_SYMBOL_GPL(init_pid_ns);
+
+/*
+ * Note: disable interrupts while the pidmap_lock is held as an
+ * interrupt might come in and do read_lock(&tasklist_lock).
+ *
+ * If we don't disable interrupts there is a nasty deadlock between
+ * detach_pid()->free_pid() and another cpu that does
+ * spin_lock(&pidmap_lock) followed by an interrupt routine that does
+ * read_lock(&tasklist_lock);
+ *
+ * After we clean up the tasklist_lock and know there are no
+ * irq handlers that take it we can leave the interrupts enabled.
+ * For now it is easier to be safe than to prove it can't happen.
+ */
+
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
+
+void put_pid(struct pid *pid)
+{
+ struct pid_namespace *ns;
+
+ if (!pid)
+ return;
+
+ ns = pid->numbers[pid->level].ns;
+ if ((atomic_read(&pid->count) == 1) ||
+ atomic_dec_and_test(&pid->count)) {
+ kmem_cache_free(ns->pid_cachep, pid);
+ put_pid_ns(ns);
+ }
+}
+EXPORT_SYMBOL_GPL(put_pid);
+
+static void delayed_put_pid(struct rcu_head *rhp)
+{
+ struct pid *pid = container_of(rhp, struct pid, rcu);
+ put_pid(pid);
+}
+
+void free_pid(struct pid *pid)
+{
+ /* We can be called with write_lock_irq(&tasklist_lock) held */
+ int i;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pidmap_lock, flags);
+ for (i = 0; i <= pid->level; i++) {
+ struct upid *upid = pid->numbers + i;
+ struct pid_namespace *ns = upid->ns;
+ switch (--ns->pid_allocated) {
+ case 2:
+ case 1:
+ /* When all that is left in the pid namespace
+ * is the reaper wake up the reaper. The reaper
+ * may be sleeping in zap_pid_ns_processes().
+ */
+ wake_up_process(ns->child_reaper);
+ break;
+ case PIDNS_ADDING:
+ /* Handle a fork failure of the first process */
+ WARN_ON(ns->child_reaper);
+ ns->pid_allocated = 0;
+ /* fall through */
+ case 0:
+ schedule_work(&ns->proc_work);
+ break;
+ }
+
+ idr_remove(&ns->idr, upid->nr);
+ }
+ spin_unlock_irqrestore(&pidmap_lock, flags);
+
+ call_rcu(&pid->rcu, delayed_put_pid);
+}
+
+struct pid *alloc_pid(struct pid_namespace *ns)
+{
+ struct pid *pid;
+ enum pid_type type;
+ int i, nr;
+ struct pid_namespace *tmp;
+ struct upid *upid;
+ int retval = -ENOMEM;
+
+ pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
+ if (!pid)
+ return ERR_PTR(retval);
+
+ tmp = ns;
+ pid->level = ns->level;
+
+ for (i = ns->level; i >= 0; i--) {
+ int pid_min = 1;
+
+ idr_preload(GFP_KERNEL);
+ spin_lock_irq(&pidmap_lock);
+
+ /*
+ * init really needs pid 1, but after reaching the maximum
+ * wrap back to RESERVED_PIDS
+ */
+ if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
+ pid_min = RESERVED_PIDS;
+
+ /*
+ * Store a null pointer so find_pid_ns does not find
+ * a partially initialized PID (see below).
+ */
+ nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
+ pid_max, GFP_ATOMIC);
+ spin_unlock_irq(&pidmap_lock);
+ idr_preload_end();
+
+ if (nr < 0) {
+ retval = (nr == -ENOSPC) ? -EAGAIN : nr;
+ goto out_free;
+ }
+
+ pid->numbers[i].nr = nr;
+ pid->numbers[i].ns = tmp;
+ tmp = tmp->parent;
+ }
+
+ if (unlikely(is_child_reaper(pid))) {
+ if (pid_ns_prepare_proc(ns))
+ goto out_free;
+ }
+
+ get_pid_ns(ns);
+ atomic_set(&pid->count, 1);
+ for (type = 0; type < PIDTYPE_MAX; ++type)
+ INIT_HLIST_HEAD(&pid->tasks[type]);
+
+ upid = pid->numbers + ns->level;
+ spin_lock_irq(&pidmap_lock);
+ if (!(ns->pid_allocated & PIDNS_ADDING))
+ goto out_unlock;
+ for ( ; upid >= pid->numbers; --upid) {
+ /* Make the PID visible to find_pid_ns. */
+ idr_replace(&upid->ns->idr, pid, upid->nr);
+ upid->ns->pid_allocated++;
+ }
+ spin_unlock_irq(&pidmap_lock);
+
+ return pid;
+
+out_unlock:
+ spin_unlock_irq(&pidmap_lock);
+ put_pid_ns(ns);
+
+out_free:
+ spin_lock_irq(&pidmap_lock);
+ while (++i <= ns->level)
+ idr_remove(&ns->idr, (pid->numbers + i)->nr);
+
+ /* On failure to allocate the first pid, reset the state */
+ if (ns->pid_allocated == PIDNS_ADDING)
+ idr_set_cursor(&ns->idr, 0);
+
+ spin_unlock_irq(&pidmap_lock);
+
+ kmem_cache_free(ns->pid_cachep, pid);
+ return ERR_PTR(retval);
+}
+
+void disable_pid_allocation(struct pid_namespace *ns)
+{
+ spin_lock_irq(&pidmap_lock);
+ ns->pid_allocated &= ~PIDNS_ADDING;
+ spin_unlock_irq(&pidmap_lock);
+}
+
+struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
+{
+ return idr_find(&ns->idr, nr);
+}
+EXPORT_SYMBOL_GPL(find_pid_ns);
+
+struct pid *find_vpid(int nr)
+{
+ return find_pid_ns(nr, task_active_pid_ns(current));
+}
+EXPORT_SYMBOL_GPL(find_vpid);
+
+static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
+{
+ return (type == PIDTYPE_PID) ?
+ &task->thread_pid :
+ &task->signal->pids[type];
+}
+
+/*
+ * attach_pid() must be called with the tasklist_lock write-held.
+ */
+void attach_pid(struct task_struct *task, enum pid_type type)
+{
+ struct pid *pid = *task_pid_ptr(task, type);
+ hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]);
+}
+
+static void __change_pid(struct task_struct *task, enum pid_type type,
+ struct pid *new)
+{
+ struct pid **pid_ptr = task_pid_ptr(task, type);
+ struct pid *pid;
+ int tmp;
+
+ pid = *pid_ptr;
+
+ hlist_del_rcu(&task->pid_links[type]);
+ *pid_ptr = new;
+
+ for (tmp = PIDTYPE_MAX; --tmp >= 0; )
+ if (!hlist_empty(&pid->tasks[tmp]))
+ return;
+
+ free_pid(pid);
+}
+
+void detach_pid(struct task_struct *task, enum pid_type type)
+{
+ __change_pid(task, type, NULL);
+}
+
+void change_pid(struct task_struct *task, enum pid_type type,
+ struct pid *pid)
+{
+ __change_pid(task, type, pid);
+ attach_pid(task, type);
+}
+
+/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
+void transfer_pid(struct task_struct *old, struct task_struct *new,
+ enum pid_type type)
+{
+ if (type == PIDTYPE_PID)
+ new->thread_pid = old->thread_pid;
+ hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]);
+}
+
+struct task_struct *pid_task(struct pid *pid, enum pid_type type)
+{
+ struct task_struct *result = NULL;
+ if (pid) {
+ struct hlist_node *first;
+ first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
+ lockdep_tasklist_lock_is_held());
+ if (first)
+ result = hlist_entry(first, struct task_struct, pid_links[(type)]);
+ }
+ return result;
+}
+EXPORT_SYMBOL(pid_task);
+
+/*
+ * Must be called under rcu_read_lock().
+ */
+struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
+{
+ RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
+ "find_task_by_pid_ns() needs rcu_read_lock() protection");
+ return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
+}
+
+struct task_struct *find_task_by_vpid(pid_t vnr)
+{
+ return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
+}
+
+struct task_struct *find_get_task_by_vpid(pid_t nr)
+{
+ struct task_struct *task;
+
+ rcu_read_lock();
+ task = find_task_by_vpid(nr);
+ if (task)
+ get_task_struct(task);
+ rcu_read_unlock();
+
+ return task;
+}
+
+struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
+{
+ struct pid *pid;
+ rcu_read_lock();
+ pid = get_pid(rcu_dereference(*task_pid_ptr(task, type)));
+ rcu_read_unlock();
+ return pid;
+}
+EXPORT_SYMBOL_GPL(get_task_pid);
+
+struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
+{
+ struct task_struct *result;
+ rcu_read_lock();
+ result = pid_task(pid, type);
+ if (result)
+ get_task_struct(result);
+ rcu_read_unlock();
+ return result;
+}
+EXPORT_SYMBOL_GPL(get_pid_task);
+
+struct pid *find_get_pid(pid_t nr)
+{
+ struct pid *pid;
+
+ rcu_read_lock();
+ pid = get_pid(find_vpid(nr));
+ rcu_read_unlock();
+
+ return pid;
+}
+EXPORT_SYMBOL_GPL(find_get_pid);
+
+pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
+{
+ struct upid *upid;
+ pid_t nr = 0;
+
+ if (pid && ns->level <= pid->level) {
+ upid = &pid->numbers[ns->level];
+ if (upid->ns == ns)
+ nr = upid->nr;
+ }
+ return nr;
+}
+EXPORT_SYMBOL_GPL(pid_nr_ns);
+
+pid_t pid_vnr(struct pid *pid)
+{
+ return pid_nr_ns(pid, task_active_pid_ns(current));
+}
+EXPORT_SYMBOL_GPL(pid_vnr);
+
+pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
+ struct pid_namespace *ns)
+{
+ pid_t nr = 0;
+
+ rcu_read_lock();
+ if (!ns)
+ ns = task_active_pid_ns(current);
+ if (likely(pid_alive(task)))
+ nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
+ rcu_read_unlock();
+
+ return nr;
+}
+EXPORT_SYMBOL(__task_pid_nr_ns);
+
+struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
+{
+ return ns_of_pid(task_pid(tsk));
+}
+EXPORT_SYMBOL_GPL(task_active_pid_ns);
+
+/*
+ * Used by proc to find the first pid that is greater than or equal to nr.
+ *
+ * If there is a pid at nr this function is exactly the same as find_pid_ns.
+ */
+struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
+{
+ return idr_get_next(&ns->idr, &nr);
+}
+
+void __init pid_idr_init(void)
+{
+ /* Verify no one has done anything silly: */
+ BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
+
+ /* bump default and minimum pid_max based on number of cpus */
+ pid_max = min(pid_max_max, max_t(int, pid_max,
+ PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
+ pid_max_min = max_t(int, pid_max_min,
+ PIDS_PER_CPU_MIN * num_possible_cpus());
+ pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
+
+ idr_init(&init_pid_ns.idr);
+
+ init_pid_ns.pid_cachep = KMEM_CACHE(pid,
+ SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
+}