From: Eric Dumazet <eduma...@google.com>
Current struct pernet_operations exit() handlers are highly
discouraged to call synchronize_rcu().
There are cases where we need them, and exit_batch() does
not help the common case where a single netns is dismantled.
This patch leverages the existing synchronize_rcu() call
in cleanup_net()
Calling optional ->pre_exit() method before ->exit() or
->exit_batch() allows to benefit from a single synchronize_rcu()
call.
Note that the synchronize_rcu() calls added in this patch
are only in error paths or slow paths.
Tested:
$ time for i in {1..1000}; do unshare -n /bin/false;done
real 0m2.612s
user 0m0.171s
sys 0m2.216s
Signed-off-by: Eric Dumazet <eduma...@google.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
https://virtuozzo.atlassian.net/browse/PSBM-155867
(cherry picked from commit d7d99872c144a2c2f5d9c9d83627fa833836cba5)
Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com>
---
include/net/net_namespace.h | 6 ++++++
net/core/net_namespace.c | 28 ++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index d00dc43efd526..57830afc25cfb 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -364,7 +364,13 @@ struct net *get_net_ns_by_id(struct net *net, int id);
struct pernet_operations {
struct list_head list;
+ /*
+ * Note that a combination of pre_exit() and exit() can
+ * be used, since a synchronize_rcu() is guaranteed between
+ * the calls.
+ */
int (*init)(struct net *net);
+ void (*pre_exit)(struct net *net);
void (*exit)(struct net *net);
void (*exit_batch)(struct list_head *net_exit_list);
int *id;
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 644e38948d102..16d3a111d8824 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -139,6 +139,17 @@ static void ops_free(const struct pernet_operations *ops,
struct net *net)
}
}
+static void ops_pre_exit_list(const struct pernet_operations *ops,
+ struct list_head *net_exit_list)
+{
+ struct net *net;
+
+ if (ops->pre_exit) {
+ list_for_each_entry(net, net_exit_list, exit_list)
+ ops->pre_exit(net);
+ }
+}
+
static void ops_exit_list(const struct pernet_operations *ops,
struct list_head *net_exit_list)
{
@@ -338,6 +349,12 @@ static __net_init int setup_net(struct net *net, struct
user_namespace *user_ns)
* for the pernet modules whose init functions did not fail.
*/
list_add(&net->exit_list, &net_exit_list);
+ saved_ops = ops;
+ list_for_each_entry_continue_reverse(ops, &pernet_list, list)
+ ops_pre_exit_list(ops, &net_exit_list);
+
+ synchronize_rcu();
+
saved_ops = ops;
list_for_each_entry_continue_reverse(ops, &pernet_list, list)
ops_exit_list(ops, &net_exit_list);
@@ -509,10 +526,15 @@ static void cleanup_net(struct work_struct *work)
list_add_tail(&net->exit_list, &net_exit_list);
}
+ /* Run all of the network namespace pre_exit methods */
+ list_for_each_entry_reverse(ops, &pernet_list, list)
+ ops_pre_exit_list(ops, &net_exit_list);
+
/*
* Another CPU might be rcu-iterating the list, wait for it.
* This needs to be before calling the exit() notifiers, so
* the rcu_barrier() below isn't sufficient alone.
+ * Also the pre_exit() and exit() methods need this barrier.
*/
synchronize_rcu();
@@ -883,6 +905,8 @@ static int __register_pernet_operations(struct list_head
*list,
out_undo:
/* If I have an error cleanup all namespaces I initialized */
list_del(&ops->list);
+ ops_pre_exit_list(ops, &net_exit_list);
+ synchronize_rcu();
ops_exit_list(ops, &net_exit_list);
ops_free_list(ops, &net_exit_list);
return error;
@@ -896,6 +920,8 @@ static void __unregister_pernet_operations(struct
pernet_operations *ops)
list_del(&ops->list);
for_each_net(net)
list_add_tail(&net->exit_list, &net_exit_list);
+ ops_pre_exit_list(ops, &net_exit_list);
+ synchronize_rcu();
ops_exit_list(ops, &net_exit_list);
ops_free_list(ops, &net_exit_list);
}
@@ -912,6 +938,8 @@ static void __unregister_pernet_operations(struct
pernet_operations *ops)
{
LIST_HEAD(net_exit_list);
list_add(&init_net.exit_list, &net_exit_list);
+ ops_pre_exit_list(ops, &net_exit_list);
+ synchronize_rcu();
ops_exit_list(ops, &net_exit_list);
ops_free_list(ops, &net_exit_list);
}
--
2.46.0
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