pid_namespace: make freeing struct pid_namespace rcu-delayed
makes procfs ->premission() instances safety in RCU mode independent
from vfsmount_lock.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index e277266..7246ef3 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -23,6 +23,7 @@
struct pid_namespace {
struct kref kref;
struct pidmap pidmap[PIDMAP_ENTRIES];
+ struct rcu_head rcu;
int last_pid;
unsigned int nr_hashed;
struct task_struct *child_reaper;
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 4208655..06c62de 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -132,6 +132,12 @@
return ERR_PTR(err);
}
+static void delayed_free_pidns(struct rcu_head *p)
+{
+ kmem_cache_free(pid_ns_cachep,
+ container_of(p, struct pid_namespace, rcu));
+}
+
static void destroy_pid_namespace(struct pid_namespace *ns)
{
int i;
@@ -140,7 +146,7 @@
for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page);
put_user_ns(ns->user_ns);
- kmem_cache_free(pid_ns_cachep, ns);
+ call_rcu(&ns->rcu, delayed_free_pidns);
}
struct pid_namespace *copy_pid_ns(unsigned long flags,