Phonet: restore flow control credits when sending fails

This patch restores the below flow control patch submitted by Rémi
Denis-Courmont, which accidentaly got lost due to Pipe controller patch
on Phonet.

	commit 1a98214f
	Author: Rémi Denis-Courmont <remi.denis-courmont@nokia.com>
	Date:   Mon Aug 30 12:57:03 2010 +0000

	Phonet: restore flow control credits when sending fails
Signed-off-by: NRémi Denis-Courmont <remi.denis-courmont@nokia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NKumar Sanghvi <kumar.sanghvi@stericsson.com>
Acked-by: NLinus Walleij <linus.walleij@stericsson.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/phonet/pep.c

@@ -1288,6 +1288,7 @@ static int pipe_skb_send(struct sock *sk, struct sk_buff *skb)
 {
 	struct pep_sock *pn = pep_sk(sk);
 	struct pnpipehdr *ph;
+	int err;
 #ifdef CONFIG_PHONET_PIPECTRLR
 	struct sockaddr_pn spn = {
 		.spn_family = AF_PHONET,
@@ -1314,10 +1315,15 @@ static int pipe_skb_send(struct sock *sk, struct sk_buff *skb)
 		ph->message_id = PNS_PIPE_DATA;
 	ph->pipe_handle = pn->pipe_handle;
 #ifdef CONFIG_PHONET_PIPECTRLR
-	return pn_skb_send(sk, skb, &spn);
+	err = pn_skb_send(sk, skb, &spn);
 #else
-	return pn_skb_send(sk, skb, &pipe_srv);
+	err = pn_skb_send(sk, skb, &pipe_srv);
 #endif
+
+	if (err && pn_flow_safe(pn->tx_fc))
+		atomic_inc(&pn->tx_credits);
+	return err;
+
 }
 
 static int pep_sendmsg(struct kiocb *iocb, struct sock *sk,