Re: [cip-dev] [PATCH 4.19.y-cip 1/6] Backport netfilter: nf_tables: autoload modules from the abort path

Amy Fong
2022-01-10T14:11:06Z

From dda33be9e3fadf0b47e2afc8a0b381c3667622c3 Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw@strlen.de>
Date: Wed, 29 Aug 2018 14:41:32 +0200
Subject: [PATCH 1/5] netfilter: nf_tables: asynchronous release

Release the committed transaction log from a work queue, moving
expensive synchronize_rcu out of the locked section and providing
opportunity to batch this.

On my test machine this cuts runtime of nft-test.py in half.
Based on earlier patch from Pablo Neira Ayuso.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit 0935d558840099b3679c67bb7468dc78fcbad940)
---
include/net/netfilter/nf_tables.h | 2 ++
net/netfilter/nf_tables_api.c | 56 +++++++++++++++++++++++++++----
2 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 93253ba1eeac..c60d281c9a58 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1316,12 +1316,14 @@ static inline void nft_set_elem_clear_busy(struct nft_set_ext *ext)
*
* @list: used internally
* @msg_type: message type
+ * @put_net: ctx->net needs to be put
* @ctx: transaction context
* @data: internal information related to the transaction
*/
struct nft_trans {
struct list_head list;
int msg_type;
+ bool put_net;
struct nft_ctx ctx;
char data[0];
};
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 9cc8e92f4b00..02e577e8fb8a 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -29,6 +29,8 @@
static LIST_HEAD(nf_tables_expressions);
static LIST_HEAD(nf_tables_objects);
static LIST_HEAD(nf_tables_flowtables);
+static LIST_HEAD(nf_tables_destroy_list);
+static DEFINE_SPINLOCK(nf_tables_destroy_list_lock);
static u64 table_handle;

enum {
@@ -66,6 +68,8 @@ static void nft_validate_state_update(struct net *net, u8 new_validate_state)

net->nft.validate_state = new_validate_state;
}
+static void nf_tables_trans_destroy_work(struct work_struct *w);
+static DECLARE_WORK(trans_destroy_work, nf_tables_trans_destroy_work);

static void nft_ctx_init(struct nft_ctx *ctx,
struct net *net,
@@ -2503,7 +2507,6 @@ static void nf_tables_rule_destroy(const struct nft_ctx *ctx,
{
struct nft_expr *expr, *next;

- lockdep_assert_held(&ctx->net->nft.commit_mutex);
/*
* Careful: some expressions might not be initialized in case this
* is called on error from nf_tables_newrule().
@@ -6300,19 +6303,28 @@ static void nft_commit_release(struct nft_trans *trans)
nf_tables_flowtable_destroy(nft_trans_flowtable(trans));
break;
}
+
+ if (trans->put_net)
+ put_net(trans->ctx.net);
+
kfree(trans);
}

-static void nf_tables_commit_release(struct net *net)
+static void nf_tables_trans_destroy_work(struct work_struct *w)
{
struct nft_trans *trans, *next;
+ LIST_HEAD(head);
+
+ spin_lock(&nf_tables_destroy_list_lock);
+ list_splice_init(&nf_tables_destroy_list, &head);
+ spin_unlock(&nf_tables_destroy_list_lock);

- if (list_empty(&net->nft.commit_list))
+ if (list_empty(&head))
return;

synchronize_rcu();

- list_for_each_entry_safe(trans, next, &net->nft.commit_list, list) {
+ list_for_each_entry_safe(trans, next, &head, list) {
list_del(&trans->list);
nft_commit_release(trans);
}
@@ -6443,6 +6455,37 @@ static void nft_chain_del(struct nft_chain *chain)
list_del_rcu(&chain->list);
}

+static void nf_tables_commit_release(struct net *net)
+{
+ struct nft_trans *trans;
+
+ /* all side effects have to be made visible.
+ * For example, if a chain named 'foo' has been deleted, a
+ * new transaction must not find it anymore.
+ *
+ * Memory reclaim happens asynchronously from work queue
+ * to prevent expensive synchronize_rcu() in commit phase.
+ */
+ if (list_empty(&net->nft.commit_list)) {
+ mutex_unlock(&net->nft.commit_mutex);
+ return;
+ }
+
+ trans = list_last_entry(&net->nft.commit_list,
+ struct nft_trans, list);
+ get_net(trans->ctx.net);
+ WARN_ON_ONCE(trans->put_net);
+
+ trans->put_net = true;
+ spin_lock(&nf_tables_destroy_list_lock);
+ list_splice_tail_init(&net->nft.commit_list, &nf_tables_destroy_list);
+ spin_unlock(&nf_tables_destroy_list_lock);
+
+ mutex_unlock(&net->nft.commit_mutex);
+
+ schedule_work(&trans_destroy_work);
+}
+
static int nf_tables_commit(struct net *net, struct sk_buff *skb)
{
struct nft_trans *trans, *next;
@@ -6604,9 +6647,8 @@ static int nf_tables_commit(struct net *net, struct sk_buff *skb)
}
}

- nf_tables_commit_release(net);
nf_tables_gen_notify(net, skb, NFT_MSG_NEWGEN);
- mutex_unlock(&net->nft.commit_mutex);
+ nf_tables_commit_release(net);

return 0;
}
@@ -7387,6 +7429,7 @@ static int __init nf_tables_module_init(void)
{
int err;

+ spin_lock_init(&nf_tables_destroy_list_lock);
err = register_pernet_subsys(&nf_tables_net_ops);
if (err < 0)
return err;
@@ -7426,6 +7469,7 @@ static void __exit nf_tables_module_exit(void)
unregister_netdevice_notifier(&nf_tables_flowtable_notifier);
nft_chain_filter_fini();
unregister_pernet_subsys(&nf_tables_net_ops);
+ cancel_work_sync(&trans_destroy_work);
rcu_barrier();
nf_tables_core_module_exit();
}
--
2.34.1