diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2602f1386160..0d20279024fb 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1295,6 +1295,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	int size_bias = 0;
 	int avail_size;
 	size_t ret = 0;
+	int mfrags;
 
 	pr_debug("msk=%p ssk=%p sending dfrag at seq=%llu len=%u already sent=%u",
 		 msk, ssk, dfrag->data_seq, dfrag->data_len, info->sent);
@@ -1302,6 +1303,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	/* compute send limit */
 	info->mss_now = tcp_send_mss(ssk, &info->size_goal, info->flags);
 	avail_size = info->size_goal;
+	mfrags = READ_ONCE(sysctl_max_skb_frags);
 	skb = tcp_write_queue_tail(ssk);
 	if (skb) {
 		/* Limit the write to the size available in the
@@ -1317,7 +1319,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 		}
 
 		must_collapse = (info->size_goal - skb->len > 0) &&
-				(skb_shinfo(skb)->nr_frags < sysctl_max_skb_frags);
+				(skb_shinfo(skb)->nr_frags < mfrags);
 		if (must_collapse) {
 			size_bias = skb->len;
 			avail_size = info->size_goal - skb->len;
@@ -1325,7 +1327,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	}
 
 alloc_skb:
-	if (!must_collapse && !ssk->sk_tx_skb_cache &&
+	if (!must_collapse &&
 	    !mptcp_alloc_tx_skb(sk, ssk, info->data_lock_held))
 		return 0;
 
@@ -1363,6 +1365,11 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 	}
 
 	mpext = skb_ext_find(tail, SKB_EXT_MPTCP);
+	if (!mpext)
+		pr_warn("must_collapse=%d old skb=%p avail_size=%d zero_window_probe=%d ws=%d state=%d frags=%d:%d",
+			must_collapse, skb, avail_size, zero_window_probe,
+			mptcp_subflow_ctx(ssk)->rel_write_seq,
+			ssk->sk_state, mfrags, READ_ONCE(sysctl_max_skb_frags));
 	if (WARN_ON_ONCE(!mpext)) {
 		/* should never reach here, stream corrupted */
 		return -EINVAL;