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

commit dc5367bcc556e97555fc94a32cd1aadbebdff47e upstream.

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>
Fixes: e53743994e21 ("af_iucv: use paged SKBs for big outbound messages")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 14 insertions, 11 deletions

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c
index 02b45a8e8b35..91cbbf1c3f82 100644
--- a/net/iucv/af_iucv.c
+++ b/net/iucv/af_iucv.c
@@ -1036,7 +1036,8 @@ 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;
@@ -1114,18 +1115,20 @@ 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);