[PATCH 2/4] net: allow sk_prot->release_cb() without sock lock held

Jens Axboe
2022-04-12T23:29:29Z

Add helpers that allow ->release_cb() to acquire the socket bh lock
when needed. For normal sockets, ->release_cb() is always invoked with
that lock held. For nolock sockets it will not be held, so provide an
easy way to acquire it when necessary.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
include/net/sock.h | 10 ++++++++++
net/atm/common.c | 5 ++++-
net/ipv4/tcp_output.c | 2 ++
net/mptcp/protocol.c | 3 +++
net/smc/af_smc.c | 2 ++
5 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index e8283a65b757..99fcc4d7eed9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1696,6 +1696,16 @@ void release_sock(struct sock *sk);
SINGLE_DEPTH_NESTING)
#define bh_unlock_sock(__sk) spin_unlock(&((__sk)->sk_lock.slock))

+/* nolock helpers */
+#define bh_lock_sock_on_nolock(__sk) do { \
+ if ((__sk)->sk_no_lock) \
+ spin_lock_bh(&(__sk)->sk_lock.slock); \
+} while (0)
+#define bh_unlock_sock_on_nolock(__sk) do { \
+ if ((__sk)->sk_no_lock) \
+ spin_unlock_bh(&(__sk)->sk_lock.slock); \
+} while (0)
+
bool __lock_sock_fast(struct sock *sk) __acquires(&sk->sk_lock.slock);

/**
diff --git a/net/atm/common.c b/net/atm/common.c
index 1cfa9bf1d187..471363e929f6 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -126,8 +126,11 @@ static void vcc_release_cb(struct sock *sk)
{
struct atm_vcc *vcc = atm_sk(sk);

- if (vcc->release_cb)
+ if (vcc->release_cb) {
+ bh_lock_sock_on_nolock(sk);
vcc->release_cb(vcc);
+ bh_lock_sock_on_nolock(sk);
+ }
}

static struct proto vcc_proto = {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9ede847f4199..9f86ea63cbac 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1100,6 +1100,7 @@ void tcp_release_cb(struct sock *sk)
* But following code is meant to be called from BH handlers,
* so we should keep BH disabled, but early release socket ownership
*/
+ bh_lock_sock_on_nolock(sk);
sock_release_ownership(sk);

if (flags & TCPF_WRITE_TIMER_DEFERRED) {
@@ -1114,6 +1115,7 @@ void tcp_release_cb(struct sock *sk)
inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
__sock_put(sk);
}
+ bh_unlock_sock_on_nolock(sk);
}
EXPORT_SYMBOL(tcp_release_cb);

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 0cbea3b6d0a4..ae9078e8e137 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3065,6 +3065,8 @@ static void mptcp_release_cb(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);

+ bh_lock_sock_on_nolock(sk);
+
for (;;) {
unsigned long flags = (msk->cb_flags & MPTCP_FLAGS_PROCESS_CTX_NEED) |
msk->push_pending;
@@ -3103,6 +3105,7 @@ static void mptcp_release_cb(struct sock *sk)
__mptcp_error_report(sk);

__mptcp_update_rmem(sk);
+ bh_unlock_sock_on_nolock(sk);
}

/* MP_JOIN client subflow must wait for 4th ack before sending any data:
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index f0d118e9f155..3456dc6cd38b 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -201,10 +201,12 @@ static void smc_release_cb(struct sock *sk)
{
struct smc_sock *smc = smc_sk(sk);

+ bh_lock_sock_on_nolock(sk);
if (smc->conn.tx_in_release_sock) {
smc_tx_pending(&smc->conn);
smc->conn.tx_in_release_sock = false;
}
+ bh_unlock_sock_on_nolock(sk);
}

struct proto smc_proto = {
--
2.35.1