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Message-id: <20200122005633.21229-14-cpaasch@apple.com>
Date: Tue, 21 Jan 2020 16:56:27 -0800
From: Christoph Paasch <cpaasch@...le.com>
To: netdev@...r.kernel.org
Cc: mptcp@...ts.01.org, Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next v3 13/19] mptcp: allow collapsing consecutive
sendpages on the same substream
From: Paolo Abeni <pabeni@...hat.com>
If the current sendmsg() lands on the same subflow we used last, we
can try to collapse the data.
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Christoph Paasch <cpaasch@...le.com>
---
net/mptcp/protocol.c | 75 +++++++++++++++++++++++++++++++++++---------
1 file changed, 60 insertions(+), 15 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ad9c73cc20e1..0b21ae25bd0f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -122,14 +122,27 @@ static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
return NULL;
}
+static inline bool mptcp_skb_can_collapse_to(const struct mptcp_sock *msk,
+ const struct sk_buff *skb,
+ const struct mptcp_ext *mpext)
+{
+ if (!tcp_skb_can_collapse_to(skb))
+ return false;
+
+ /* can collapse only if MPTCP level sequence is in order */
+ return mpext && mpext->data_seq + mpext->data_len == msk->write_seq;
+}
+
static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
- struct msghdr *msg, long *timeo)
+ struct msghdr *msg, long *timeo, int *pmss_now,
+ int *ps_goal)
{
- int mss_now = 0, size_goal = 0, ret = 0;
+ int mss_now, avail_size, size_goal, ret;
struct mptcp_sock *msk = mptcp_sk(sk);
struct mptcp_ext *mpext = NULL;
+ struct sk_buff *skb, *tail;
+ bool can_collapse = false;
struct page_frag *pfrag;
- struct sk_buff *skb;
size_t psize;
/* use the mptcp page cache so that we can easily move the data
@@ -145,8 +158,29 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
/* compute copy limit */
mss_now = tcp_send_mss(ssk, &size_goal, msg->msg_flags);
- psize = min_t(int, pfrag->size - pfrag->offset, size_goal);
+ *pmss_now = mss_now;
+ *ps_goal = size_goal;
+ avail_size = size_goal;
+ skb = tcp_write_queue_tail(ssk);
+ if (skb) {
+ mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
+
+ /* Limit the write to the size available in the
+ * current skb, if any, so that we create at most a new skb.
+ * Explicitly tells TCP internals to avoid collapsing on later
+ * queue management operation, to avoid breaking the ext <->
+ * SSN association set here
+ */
+ can_collapse = (size_goal - skb->len > 0) &&
+ mptcp_skb_can_collapse_to(msk, skb, mpext);
+ if (!can_collapse)
+ TCP_SKB_CB(skb)->eor = 1;
+ else
+ avail_size = size_goal - skb->len;
+ }
+ psize = min_t(size_t, pfrag->size - pfrag->offset, avail_size);
+ /* Copy to page */
pr_debug("left=%zu", msg_data_left(msg));
psize = copy_page_from_iter(pfrag->page, pfrag->offset,
min_t(size_t, msg_data_left(msg), psize),
@@ -155,14 +189,9 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
if (!psize)
return -EINVAL;
- /* Mark the end of the previous write so the beginning of the
- * next write (with its own mptcp skb extension data) is not
- * collapsed.
+ /* tell the TCP stack to delay the push so that we can safely
+ * access the skb after the sendpages call
*/
- skb = tcp_write_queue_tail(ssk);
- if (skb)
- TCP_SKB_CB(skb)->eor = 1;
-
ret = do_tcp_sendpages(ssk, pfrag->page, pfrag->offset, psize,
msg->msg_flags | MSG_SENDPAGE_NOTLAST);
if (ret <= 0)
@@ -170,6 +199,18 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
if (unlikely(ret < psize))
iov_iter_revert(&msg->msg_iter, psize - ret);
+ /* if the tail skb extension is still the cached one, collapsing
+ * really happened. Note: we can't check for 'same skb' as the sk_buff
+ * hdr on tail can be transmitted, freed and re-allocated by the
+ * do_tcp_sendpages() call
+ */
+ tail = tcp_write_queue_tail(ssk);
+ if (mpext && tail && mpext == skb_ext_find(tail, SKB_EXT_MPTCP)) {
+ WARN_ON_ONCE(!can_collapse);
+ mpext->data_len += ret;
+ goto out;
+ }
+
skb = tcp_write_queue_tail(ssk);
mpext = __skb_ext_set(skb, SKB_EXT_MPTCP, msk->cached_ext);
msk->cached_ext = NULL;
@@ -185,11 +226,11 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
mpext->data_seq, mpext->subflow_seq, mpext->data_len,
mpext->dsn64);
+out:
pfrag->offset += ret;
msk->write_seq += ret;
mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
- tcp_push(ssk, msg->msg_flags, mss_now, tcp_sk(ssk)->nonagle, size_goal);
return ret;
}
@@ -212,11 +253,11 @@ static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
+ int mss_now = 0, size_goal = 0, ret = 0;
struct mptcp_sock *msk = mptcp_sk(sk);
struct socket *ssock;
size_t copied = 0;
struct sock *ssk;
- int ret = 0;
long timeo;
if (msg->msg_flags & ~(MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL))
@@ -243,15 +284,19 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
lock_sock(ssk);
while (msg_data_left(msg)) {
- ret = mptcp_sendmsg_frag(sk, ssk, msg, &timeo);
+ ret = mptcp_sendmsg_frag(sk, ssk, msg, &timeo, &mss_now,
+ &size_goal);
if (ret < 0)
break;
copied += ret;
}
- if (copied > 0)
+ if (copied) {
ret = copied;
+ tcp_push(ssk, msg->msg_flags, mss_now, tcp_sk(ssk)->nonagle,
+ size_goal);
+ }
ssk_check_wmem(msk, ssk);
release_sock(ssk);
--
2.23.0
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