net/af_iucv: don't use paged skbs for TX on HiperSockets

With commit e53743994e21
("af_iucv: use paged SKBs for big outbound messages"),
we transmit paged skbs for both of AF_IUCV's transport modes
(IUCV or HiperSockets).
The qeth driver for Layer 3 HiperSockets currently doesn't
support NETIF_F_SG, so these skbs would just be linearized again
by the stack.
Avoid that overhead by using paged skbs only for IUCV transport.

cc stable, since this also circumvents a significant skb leak when
sending large messages (where the skb then needs to be linearized).

Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # v4.8+
Fixes: e53743994e21 ("af_iucv: use paged SKBs for big outbound messages")
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index cfb9e5f..13190b3 100644 (file)
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1044,7 +1044,8 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
 {
        struct sock *sk = sock->sk;
        struct iucv_sock *iucv = iucv_sk(sk);
-       size_t headroom, linear;
+       size_t headroom = 0;
+       size_t linear;
        struct sk_buff *skb;
        struct iucv_message txmsg = {0};
        struct cmsghdr *cmsg;
@@ -1122,18 +1123,20 @@ static int iucv_sock_sendmsg(struct socket *sock, struct msghdr *msg,
         * this is fine for SOCK_SEQPACKET (unless we want to support
         * segmented records using the MSG_EOR flag), but
         * for SOCK_STREAM we might want to improve it in future */
-       headroom = (iucv->transport == AF_IUCV_TRANS_HIPER)
-                  ? sizeof(struct af_iucv_trans_hdr) + ETH_HLEN : 0;
-       if (headroom + len < PAGE_SIZE) {
+       if (iucv->transport == AF_IUCV_TRANS_HIPER) {
+               headroom = sizeof(struct af_iucv_trans_hdr) + ETH_HLEN;
                linear = len;
        } else {
-               /* In nonlinear "classic" iucv skb,
-                * reserve space for iucv_array
-                */
-               if (iucv->transport != AF_IUCV_TRANS_HIPER)
-                       headroom += sizeof(struct iucv_array) *
-                                   (MAX_SKB_FRAGS + 1);
-               linear = PAGE_SIZE - headroom;
+               if (len < PAGE_SIZE) {
+                       linear = len;
+               } else {
+                       /* In nonlinear "classic" iucv skb,
+                        * reserve space for iucv_array
+                        */
+                       headroom = sizeof(struct iucv_array) *
+                                  (MAX_SKB_FRAGS + 1);
+                       linear = PAGE_SIZE - headroom;
+               }
        }
        skb = sock_alloc_send_pskb(sk, headroom + linear, len - linear,
                                   noblock, &err, 0);