mptcp: re-enable sndbuf autotune

After commit 6e628cd3a8f7 ("mptcp: use mptcp release_cb for
delayed tasks"), MPTCP never sets the flag bit SOCK_NOSPACE
on its subflow. As a side effect, autotune never takes place,
as it happens inside tcp_new_space(), which in turn is called
only when the mentioned bit is set.

Let's sendmsg() set the subflows NOSPACE bit when looking for
more memory and use the subflow write_space callback to propagate
the snd buf update and wake-up the user-space.

Additionally, this allows dropping a bunch of duplicate code and
makes the SNDBUF_LIMITED chrono relevant again for MPTCP subflows.

Fixes: 6e628cd3a8f7 ("mptcp: use mptcp release_cb for delayed tasks")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index c5c80f9..d07e603 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -730,10 +730,14 @@ wake:
 
 void __mptcp_flush_join_list(struct mptcp_sock *msk)
 {
+       struct mptcp_subflow_context *subflow;
+
        if (likely(list_empty(&msk->join_list)))
                return;
 
        spin_lock_bh(&msk->join_list_lock);
+       list_for_each_entry(subflow, &msk->join_list, node)
+               mptcp_propagate_sndbuf((struct sock *)msk, mptcp_subflow_tcp_sock(subflow));
        list_splice_tail_init(&msk->join_list, &msk->conn_list);
        spin_unlock_bh(&msk->join_list_lock);
 }
@@ -1033,13 +1037,6 @@ out:
                        __mptcp_update_wmem(sk);
                        sk_mem_reclaim_partial(sk);
                }
-
-               if (sk_stream_is_writeable(sk)) {
-                       /* pairs with memory barrier in mptcp_poll */
-                       smp_mb();
-                       if (test_and_clear_bit(MPTCP_NOSPACE, &msk->flags))
-                               sk_stream_write_space(sk);
-               }
        }
 
        if (snd_una == READ_ONCE(msk->snd_nxt)) {
@@ -1358,8 +1355,7 @@ struct subflow_send_info {
        u64 ratio;
 };
 
-static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
-                                          u32 *sndbuf)
+static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 {
        struct subflow_send_info send_info[2];
        struct mptcp_subflow_context *subflow;
@@ -1370,24 +1366,17 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
 
        sock_owned_by_me((struct sock *)msk);
 
-       *sndbuf = 0;
        if (__mptcp_check_fallback(msk)) {
                if (!msk->first)
                        return NULL;
-               *sndbuf = msk->first->sk_sndbuf;
                return sk_stream_memory_free(msk->first) ? msk->first : NULL;
        }
 
        /* re-use last subflow, if the burst allow that */
        if (msk->last_snd && msk->snd_burst > 0 &&
            sk_stream_memory_free(msk->last_snd) &&
-           mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) {
-               mptcp_for_each_subflow(msk, subflow) {
-                       ssk =  mptcp_subflow_tcp_sock(subflow);
-                       *sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
-               }
+           mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd)))
                return msk->last_snd;
-       }
 
        /* pick the subflow with the lower wmem/wspace ratio */
        for (i = 0; i < 2; ++i) {
@@ -1400,7 +1389,6 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
                        continue;
 
                nr_active += !subflow->backup;
-               *sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
                if (!sk_stream_memory_free(subflow->tcp_sock))
                        continue;
 
@@ -1430,6 +1418,7 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
                                       sk_stream_wspace(msk->last_snd));
                return msk->last_snd;
        }
+
        return NULL;
 }
 
@@ -1450,7 +1439,6 @@ static void mptcp_push_pending(struct sock *sk, unsigned int flags)
        };
        struct mptcp_data_frag *dfrag;
        int len, copied = 0;
-       u32 sndbuf;
 
        while ((dfrag = mptcp_send_head(sk))) {
                info.sent = dfrag->already_sent;
@@ -1461,12 +1449,7 @@ static void mptcp_push_pending(struct sock *sk, unsigned int flags)
 
                        prev_ssk = ssk;
                        __mptcp_flush_join_list(msk);
-                       ssk = mptcp_subflow_get_send(msk, &sndbuf);
-
-                       /* do auto tuning */
-                       if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK) &&
-                           sndbuf > READ_ONCE(sk->sk_sndbuf))
-                               WRITE_ONCE(sk->sk_sndbuf, sndbuf);
+                       ssk = mptcp_subflow_get_send(msk);
 
                        /* try to keep the subflow socket lock across
                         * consecutive xmit on the same socket
@@ -1533,11 +1516,6 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk)
                while (len > 0) {
                        int ret = 0;
 
-                       /* do auto tuning */
-                       if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK) &&
-                           ssk->sk_sndbuf > READ_ONCE(sk->sk_sndbuf))
-                               WRITE_ONCE(sk->sk_sndbuf, ssk->sk_sndbuf);
-
                        if (unlikely(mptcp_must_reclaim_memory(sk, ssk))) {
                                __mptcp_update_wmem(sk);
                                sk_mem_reclaim_partial(sk);
@@ -1575,6 +1553,15 @@ out:
        }
 }
 
+static void mptcp_set_nospace(struct sock *sk)
+{
+       /* enable autotune */
+       set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+
+       /* will be cleared on avail space */
+       set_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags);
+}
+
 static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
        struct mptcp_sock *msk = mptcp_sk(sk);
@@ -1676,7 +1663,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
                continue;
 
 wait_for_memory:
-               set_bit(MPTCP_NOSPACE, &msk->flags);
+               mptcp_set_nospace(sk);
                mptcp_push_pending(sk, msg->msg_flags);
                ret = sk_stream_wait_memory(sk, &timeo);
                if (ret)
@@ -3268,6 +3255,7 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 
                mptcp_copy_inaddrs(newsk, msk->first);
                mptcp_rcv_space_init(msk, msk->first);
+               mptcp_propagate_sndbuf(newsk, msk->first);
 
                /* set ssk->sk_socket of accept()ed flows to mptcp socket.
                 * This is needed so NOSPACE flag can be set from tcp stack.
@@ -3308,7 +3296,7 @@ static __poll_t mptcp_check_writeable(struct mptcp_sock *msk)
        if (sk_stream_is_writeable(sk))
                return EPOLLOUT | EPOLLWRNORM;
 
-       set_bit(MPTCP_NOSPACE, &msk->flags);
+       mptcp_set_nospace(sk);
        smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
        if (sk_stream_is_writeable(sk))
                return EPOLLOUT | EPOLLWRNORM;

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 65d200a..871534d 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -522,6 +522,25 @@ static inline bool mptcp_data_fin_enabled(const struct mptcp_sock *msk)
               READ_ONCE(msk->write_seq) == READ_ONCE(msk->snd_nxt);
 }
 
+static inline bool mptcp_propagate_sndbuf(struct sock *sk, struct sock *ssk)
+{
+       if ((sk->sk_userlocks & SOCK_SNDBUF_LOCK) || ssk->sk_sndbuf <= READ_ONCE(sk->sk_sndbuf))
+               return false;
+
+       WRITE_ONCE(sk->sk_sndbuf, ssk->sk_sndbuf);
+       return true;
+}
+
+static inline void mptcp_write_space(struct sock *sk)
+{
+       if (sk_stream_is_writeable(sk)) {
+               /* pairs with memory barrier in mptcp_poll */
+               smp_mb();
+               if (test_and_clear_bit(MPTCP_NOSPACE, &mptcp_sk(sk)->flags))
+                       sk_stream_write_space(sk);
+       }
+}
+
 void mptcp_destroy_common(struct mptcp_sock *msk);
 
 void __init mptcp_token_init(void);

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 2231371..1ca0c82 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -343,6 +343,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
        if (subflow->conn_finished)
                return;
 
+       mptcp_propagate_sndbuf(parent, sk);
        subflow->rel_write_seq = 1;
        subflow->conn_finished = 1;
        subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
@@ -1040,7 +1041,10 @@ static void subflow_data_ready(struct sock *sk)
 
 static void subflow_write_space(struct sock *ssk)
 {
-       /* we take action in __mptcp_clean_una() */
+       struct sock *sk = mptcp_subflow_ctx(ssk)->conn;
+
+       mptcp_propagate_sndbuf(sk, ssk);
+       mptcp_write_space(sk);
 }
 
 static struct inet_connection_sock_af_ops *
@@ -1302,6 +1306,7 @@ static void subflow_state_change(struct sock *sk)
        __subflow_state_change(sk);
 
        if (subflow_simultaneous_connect(sk)) {
+               mptcp_propagate_sndbuf(parent, sk);
                mptcp_do_fallback(sk);
                mptcp_rcv_space_init(mptcp_sk(parent), sk);
                pr_fallback(mptcp_sk(parent));