[PATCH RFC 07/25] net: Make sys sublist pernet_operations executed out of net_mutex

Kirill Tkhai
2017-11-17T18:28:30Z

Move net_mutex to setup_net() and cleanup_net(), and
do not hold it, while sys sublist methods are executed.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
net/core/net_namespace.c | 44 +++++++++++++++++++++++++++++++++++---------
1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index f4f4aaa5ce1f..7aec8c1afe50 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -84,11 +84,11 @@ static int net_assign_generic(struct net *net, unsigned int id, void *data)
{
struct net_generic *ng, *old_ng;

- BUG_ON(!mutex_is_locked(&net_mutex));
+ BUG_ON(!rwsem_is_locked(&net_sem));
BUG_ON(id < MIN_PERNET_OPS_ID);

old_ng = rcu_dereference_protected(net->gen,
- lockdep_is_held(&net_mutex));
+ lockdep_is_held(&net_sem));
if (old_ng->s.len > id) {
old_ng->ptr[id] = data;
return 0;
@@ -300,6 +300,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
{
/* Must be called with net_mutex held */
const struct pernet_operations *ops, *saved_ops;
+ bool locked = false;
int error = 0;
LIST_HEAD(net_exit_list);

@@ -311,14 +312,34 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
spin_lock_init(&net->nsid_lock);

list_for_each_entry(ops, &pernet_list, list) {
+ if (&ops->list == first_subsys) {
+ BUG_ON(locked);
+ error = mutex_lock_killable(&net_mutex);
+ if (error)
+ goto out_undo;
+ locked = true;
+ }
+
error = ops_init(ops, net);
if (error < 0)
goto out_undo;
}
+
+ if (!locked) {
+ /*
+ * This may happen only on early boot, so we don't
+ * care about possibility to interrupt the locking.
+ */
+ mutex_lock(&net_mutex);
+ locked = true;
+ }
+
rtnl_lock();
list_add_tail_rcu(&net->list, &net_namespace_list);
rtnl_unlock();
out:
+ if (locked)
+ mutex_unlock(&net_mutex);
return error;

out_undo:
@@ -433,12 +454,7 @@ struct net *copy_net_ns(unsigned long flags,
rv = down_read_killable(&net_sem);
if (rv < 0)
goto put_userns;
- rv = mutex_lock_killable(&net_mutex);
- if (rv < 0)
- goto up_read;
rv = setup_net(net, user_ns);
- mutex_unlock(&net_mutex);
-up_read:
up_read(&net_sem);
if (rv < 0) {
put_userns:
@@ -460,6 +476,7 @@ static void cleanup_net(struct work_struct *work)
struct net *net, *tmp;
struct list_head net_kill_list;
LIST_HEAD(net_exit_list);
+ bool locked;

/* Atomically snapshot the list of namespaces to cleanup */
spin_lock_irq(&cleanup_list_lock);
@@ -468,6 +485,7 @@ static void cleanup_net(struct work_struct *work)

down_read(&net_sem);
mutex_lock(&net_mutex);
+ locked = true;

/* Don't let anyone else find us. */
rtnl_lock();
@@ -500,10 +518,18 @@ static void cleanup_net(struct work_struct *work)
synchronize_rcu();

/* Run all of the network namespace exit methods */
- list_for_each_entry_reverse(ops, &pernet_list, list)
+ list_for_each_entry_reverse(ops, &pernet_list, list) {
ops_exit_list(ops, &net_exit_list);

- mutex_unlock(&net_mutex);
+ if (&ops->list == first_subsys) {
+ BUG_ON(!locked);
+ mutex_unlock(&net_mutex);
+ locked = false;
+ }
+ }
+
+ if (locked)
+ mutex_unlock(&net_mutex);

/* Free the net generic variables */
list_for_each_entry_reverse(ops, &pernet_list, list)