FAILED: patch "[PATCH] mptcp: sched: check both directions for backup" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] mptcp: sched: check both directions for backup" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x b6a66e521a2032f7fcba2af5a9bcbaeaa19b7ca3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024080759-deploy-send-dfa5@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

b6a66e521a20 ("mptcp: sched: check both directions for backup")
3ce0852c86b9 ("mptcp: enforce HoL-blocking estimation")
ff5a0b421cb2 ("mptcp: faster active backup recovery")
6da14d74e2bd ("mptcp: cleanup sysctl data and helpers")
1e1d9d6f119c ("mptcp: handle pending data on closed subflow")
71b7dec27f34 ("mptcp: less aggressive retransmission strategy")
33d41c9cd74c ("mptcp: more accurate timeout")
d2f77960e5b0 ("mptcp: add sysctl allow_join_initial_addr_port")
8ce568ed06ce ("mptcp: drop tx skb cache")
fc3c82eebf8e ("mptcp: add a new sysctl checksum_enabled")
752e906732c6 ("mptcp: add csum_enabled in mptcp_sock")
744ee14054c8 ("mptcp: restrict values of 'enabled' sysctl")
804c72eeecd2 ("mptcp: support SYSCTL only if enabled")
ae514983f2e4 ("mptcp: remove redundant initialization in pm_nl_init_net()")
6876a18d3361 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b6a66e521a2032f7fcba2af5a9bcbaeaa19b7ca3 Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Sat, 27 Jul 2024 12:01:23 +0200
Subject: [PATCH] mptcp: sched: check both directions for backup

The 'mptcp_subflow_context' structure has two items related to the
backup flags:

 - 'backup': the subflow has been marked as backup by the other peer

 - 'request_bkup': the backup flag has been set by the host

Before this patch, the scheduler was only looking at the 'backup' flag.
That can make sense in some cases, but it looks like that's not what we
wanted for the general use, because either the path-manager was setting
both of them when sending an MP_PRIO, or the receiver was duplicating
the 'backup' flag in the subflow request.

Note that the use of these two flags in the path-manager are going to be
fixed in the next commits, but this change here is needed not to modify
the behaviour.

Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/trace/events/mptcp.h b/include/trace/events/mptcp.h
index 09e72215b9f9..085b749cdd97 100644
--- a/include/trace/events/mptcp.h
+++ b/include/trace/events/mptcp.h
@@ -34,7 +34,7 @@ TRACE_EVENT(mptcp_subflow_get_send,
 		struct sock *ssk;
 
 		__entry->active = mptcp_subflow_active(subflow);
-		__entry->backup = subflow->backup;
+		__entry->backup = subflow->backup || subflow->request_bkup;
 
 		if (subflow->tcp_sock && sk_fullsock(subflow->tcp_sock))
 			__entry->free = sk_stream_memory_free(subflow->tcp_sock);
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a26c2c840fd9..a2fc54ed68c0 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1422,13 +1422,15 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 	}
 
 	mptcp_for_each_subflow(msk, subflow) {
+		bool backup = subflow->backup || subflow->request_bkup;
+
 		trace_mptcp_subflow_get_send(subflow);
 		ssk =  mptcp_subflow_tcp_sock(subflow);
 		if (!mptcp_subflow_active(subflow))
 			continue;
 
 		tout = max(tout, mptcp_timeout_from_subflow(subflow));
-		nr_active += !subflow->backup;
+		nr_active += !backup;
 		pace = subflow->avg_pacing_rate;
 		if (unlikely(!pace)) {
 			/* init pacing rate from socket */
@@ -1439,9 +1441,9 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 		}
 
 		linger_time = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32, pace);
-		if (linger_time < send_info[subflow->backup].linger_time) {
-			send_info[subflow->backup].ssk = ssk;
-			send_info[subflow->backup].linger_time = linger_time;
+		if (linger_time < send_info[backup].linger_time) {
+			send_info[backup].ssk = ssk;
+			send_info[backup].linger_time = linger_time;
 		}
 	}
 	__mptcp_set_timeout(sk, tout);

[PATCH 5.10.y] mptcp: sched: check both directions for backup

[Matthieu Baerts (NGI0)]

commit b6a66e521a2032f7fcba2af5a9bcbaeaa19b7ca3 upstream.

The 'mptcp_subflow_context' structure has two items related to the
backup flags:

 - 'backup': the subflow has been marked as backup by the other peer

 - 'request_bkup': the backup flag has been set by the host

Before this patch, the scheduler was only looking at the 'backup' flag.
That can make sense in some cases, but it looks like that's not what we
wanted for the general use, because either the path-manager was setting
both of them when sending an MP_PRIO, or the receiver was duplicating
the 'backup' flag in the subflow request.

Note that the use of these two flags in the path-manager are going to be
fixed in the next commits, but this change here is needed not to modify
the behaviour.

Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[ Conflicts in protocol.c, because the context has changed in commit
  3ce0852c86b9 ("mptcp: enforce HoL-blocking estimation") and in commit
  33d41c9cd74c ("mptcp: more accurate timeout"), which are not in this
  version. This commit is unrelated to this modification.
  Note that the tracepoint is not in this version, see commit
  e10a98920976 ("mptcp: add tracepoint in mptcp_subflow_get_send"). ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index a36493bbf895..a343b3077458 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1124,11 +1124,13 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
 		send_info[i].ratio = -1;
 	}
 	mptcp_for_each_subflow(msk, subflow) {
+		bool backup = subflow->backup || subflow->request_bkup;
+
 		ssk =  mptcp_subflow_tcp_sock(subflow);
 		if (!mptcp_subflow_active(subflow))
 			continue;
 
-		nr_active += !subflow->backup;
+		nr_active += !backup;
 		*sndbuf = max(tcp_sk(ssk)->snd_wnd, *sndbuf);
 		if (!sk_stream_memory_free(subflow->tcp_sock))
 			continue;
@@ -1139,9 +1141,9 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk,
 
 		ratio = div_u64((u64)READ_ONCE(ssk->sk_wmem_queued) << 32,
 				pace);
-		if (ratio < send_info[subflow->backup].ratio) {
-			send_info[subflow->backup].ssk = ssk;
-			send_info[subflow->backup].ratio = ratio;
+		if (ratio < send_info[backup].ratio) {
+			send_info[backup].ssk = ssk;
+			send_info[backup].ratio = ratio;
 		}
 	}
 
-- 
2.45.2