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Message-ID: <20240122112603.3270097-5-edumazet@google.com>
Date: Mon, 22 Jan 2024 11:25:58 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>,
Martin KaFai Lau <kafai@...com>, Guillaume Nault <gnault@...hat.com>, netdev@...r.kernel.org,
eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 4/9] inet_diag: allow concurrent operations
inet_diag_lock_handler() current implementation uses a mutex
to protect inet_diag_table[] array against concurrent changes.
This makes inet_diag dump serialized, thus less scalable
than legacy /proc files.
It is time to switch to full RCU protection.
As a bonus, if a target is statically linked instead of being
modular, inet_diag_lock_handler() & inet_diag_unlock_handler()
reduce to reads only.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/ipv4/inet_diag.c | 80 ++++++++++++++++++++++----------------------
1 file changed, 40 insertions(+), 40 deletions(-)
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 9804e9608a5a0294b3ffabc4b5bb87ac1b96b09e..abf7dc9827969d7e8061420be8629730ccce5449 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -32,7 +32,7 @@
#include <linux/inet_diag.h>
#include <linux/sock_diag.h>
-static const struct inet_diag_handler **inet_diag_table;
+static const struct inet_diag_handler __rcu **inet_diag_table;
struct inet_diag_entry {
const __be32 *saddr;
@@ -48,28 +48,28 @@ struct inet_diag_entry {
#endif
};
-static DEFINE_MUTEX(inet_diag_table_mutex);
-
static const struct inet_diag_handler *inet_diag_lock_handler(int proto)
{
- if (proto < 0 || proto >= IPPROTO_MAX) {
- mutex_lock(&inet_diag_table_mutex);
- return ERR_PTR(-ENOENT);
- }
+ const struct inet_diag_handler *handler;
+
+ if (proto < 0 || proto >= IPPROTO_MAX)
+ return NULL;
if (!READ_ONCE(inet_diag_table[proto]))
sock_load_diag_module(AF_INET, proto);
- mutex_lock(&inet_diag_table_mutex);
- if (!inet_diag_table[proto])
- return ERR_PTR(-ENOENT);
+ rcu_read_lock();
+ handler = rcu_dereference(inet_diag_table[proto]);
+ if (handler && !try_module_get(handler->owner))
+ handler = NULL;
+ rcu_read_unlock();
- return inet_diag_table[proto];
+ return handler;
}
static void inet_diag_unlock_handler(const struct inet_diag_handler *handler)
{
- mutex_unlock(&inet_diag_table_mutex);
+ module_put(handler->owner);
}
void inet_diag_msg_common_fill(struct inet_diag_msg *r, struct sock *sk)
@@ -104,9 +104,12 @@ static size_t inet_sk_attr_size(struct sock *sk,
const struct inet_diag_handler *handler;
size_t aux = 0;
- handler = inet_diag_table[req->sdiag_protocol];
+ rcu_read_lock();
+ handler = rcu_dereference(inet_diag_table[req->sdiag_protocol]);
+ DEBUG_NET_WARN_ON_ONCE(!handler);
if (handler && handler->idiag_get_aux_size)
aux = handler->idiag_get_aux_size(sk, net_admin);
+ rcu_read_unlock();
return nla_total_size(sizeof(struct tcp_info))
+ nla_total_size(sizeof(struct inet_diag_msg))
@@ -244,10 +247,16 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
struct nlmsghdr *nlh;
struct nlattr *attr;
void *info = NULL;
+ int protocol;
cb_data = cb->data;
- handler = inet_diag_table[inet_diag_get_protocol(req, cb_data)];
- BUG_ON(!handler);
+ protocol = inet_diag_get_protocol(req, cb_data);
+
+ /* inet_diag_lock_handler() made sure inet_diag_table[] is stable. */
+ handler = rcu_dereference_protected(inet_diag_table[protocol], 1);
+ DEBUG_NET_WARN_ON_ONCE(!handler);
+ if (!handler)
+ return -ENXIO;
nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
cb->nlh->nlmsg_type, sizeof(*r), nlmsg_flags);
@@ -605,9 +614,10 @@ static int inet_diag_cmd_exact(int cmd, struct sk_buff *in_skb,
protocol = inet_diag_get_protocol(req, &dump_data);
handler = inet_diag_lock_handler(protocol);
- if (IS_ERR(handler)) {
- err = PTR_ERR(handler);
- } else if (cmd == SOCK_DIAG_BY_FAMILY) {
+ if (!handler)
+ return -ENOENT;
+
+ if (cmd == SOCK_DIAG_BY_FAMILY) {
struct netlink_callback cb = {
.nlh = nlh,
.skb = in_skb,
@@ -1259,12 +1269,12 @@ static int __inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
again:
prev_min_dump_alloc = cb->min_dump_alloc;
handler = inet_diag_lock_handler(protocol);
- if (!IS_ERR(handler))
+ if (handler) {
handler->dump(skb, cb, r);
- else
- err = PTR_ERR(handler);
- inet_diag_unlock_handler(handler);
-
+ inet_diag_unlock_handler(handler);
+ } else {
+ err = -ENOENT;
+ }
/* The skb is not large enough to fit one sk info and
* inet_sk_diag_fill() has requested for a larger skb.
*/
@@ -1457,10 +1467,9 @@ int inet_diag_handler_get_info(struct sk_buff *skb, struct sock *sk)
}
handler = inet_diag_lock_handler(sk->sk_protocol);
- if (IS_ERR(handler)) {
- inet_diag_unlock_handler(handler);
+ if (!handler) {
nlmsg_cancel(skb, nlh);
- return PTR_ERR(handler);
+ return -ENOENT;
}
attr = handler->idiag_info_size
@@ -1495,20 +1504,12 @@ static const struct sock_diag_handler inet6_diag_handler = {
int inet_diag_register(const struct inet_diag_handler *h)
{
const __u16 type = h->idiag_type;
- int err = -EINVAL;
if (type >= IPPROTO_MAX)
- goto out;
+ return -EINVAL;
- mutex_lock(&inet_diag_table_mutex);
- err = -EEXIST;
- if (!inet_diag_table[type]) {
- WRITE_ONCE(inet_diag_table[type], h);
- err = 0;
- }
- mutex_unlock(&inet_diag_table_mutex);
-out:
- return err;
+ return !cmpxchg((const struct inet_diag_handler **)&inet_diag_table[type],
+ NULL, h) ? 0 : -EEXIST;
}
EXPORT_SYMBOL_GPL(inet_diag_register);
@@ -1519,9 +1520,8 @@ void inet_diag_unregister(const struct inet_diag_handler *h)
if (type >= IPPROTO_MAX)
return;
- mutex_lock(&inet_diag_table_mutex);
- WRITE_ONCE(inet_diag_table[type], NULL);
- mutex_unlock(&inet_diag_table_mutex);
+ xchg((const struct inet_diag_handler **)&inet_diag_table[type],
+ NULL);
}
EXPORT_SYMBOL_GPL(inet_diag_unregister);
--
2.43.0.429.g432eaa2c6b-goog
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