IB: Change CQE "csum_ok" field to a bit flag

Use a bit in wc_flags rather then a whole integer to hold the
"checksum OK" flag.  By itself, this change doesn't reduce the size of
struct ib_wc on 64bit machines -- it stays on 56 bytes because of
padding.  However, it will allow to add more fields in the future
without enlarging the struct.  Also, it will let us have a unified
approach with future libibverbs checksum offload reporting, because a
bit flag doesn't break the library ABI.

This patch was suggested during conversation with Liran Liss
<liranl@mellanox.com>.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx4/cq.c

@@ -720,7 +720,8 @@ repoll:
 		wc->dlid_path_bits = (g_mlpath_rqpn >> 24) & 0x7f;
 		wc->wc_flags	  |= g_mlpath_rqpn & 0x80000000 ? IB_WC_GRH : 0;
 		wc->pkey_index     = be32_to_cpu(cqe->immed_rss_invalid) & 0x7f;
-		wc->csum_ok	   = mlx4_ib_ipoib_csum_ok(cqe->status, cqe->checksum);
+		wc->wc_flags	  |= mlx4_ib_ipoib_csum_ok(cqe->status,
+					cqe->checksum) ? IB_WC_IP_CSUM_OK : 0;
 		if (rdma_port_get_link_layer(wc->qp->device,
 				(*cur_qp)->port) == IB_LINK_LAYER_ETHERNET)
 			wc->sl  = be16_to_cpu(cqe->sl_vid) >> 13;

drivers/infiniband/hw/mthca/mthca_cq.c

@@ -643,7 +643,8 @@ static inline int mthca_poll_one(struct mthca_dev *dev,
 		entry->wc_flags   |= cqe->g_mlpath & 0x80 ? IB_WC_GRH : 0;
 		checksum = (be32_to_cpu(cqe->rqpn) >> 24) |
 				((be32_to_cpu(cqe->my_ee) >> 16) & 0xff00);
-		entry->csum_ok = (cqe->sl_ipok & 1 && checksum == 0xffff);
+		entry->wc_flags	  |=  (cqe->sl_ipok & 1 && checksum == 0xffff) ?
+							IB_WC_IP_CSUM_OK : 0;
 	}
 
 	entry->status = IB_WC_SUCCESS;

drivers/infiniband/hw/qib/qib_rc.c

@@ -2048,7 +2048,6 @@ send_last:
 		wc.pkey_index = 0;
 		wc.dlid_path_bits = 0;
 		wc.port_num = 0;
-		wc.csum_ok = 0;
 		/* Signal completion event if the solicited bit is set. */
 		qib_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
 			     (ohdr->bth[0] &

drivers/infiniband/hw/qib/qib_uc.c

@@ -422,7 +422,6 @@ last_imm:
 		wc.pkey_index = 0;
 		wc.dlid_path_bits = 0;
 		wc.port_num = 0;
-		wc.csum_ok = 0;
 		/* Signal completion event if the solicited bit is set. */
 		qib_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
 			     (ohdr->bth[0] &

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -296,7 +296,8 @@ static void ipoib_ib_handle_rx_wc(struct net_device *dev, struct ib_wc *wc)
 	dev->stats.rx_bytes += skb->len;
 
 	skb->dev = dev;
-	if ((dev->features & NETIF_F_RXCSUM) && likely(wc->csum_ok))
+	if ((dev->features & NETIF_F_RXCSUM) &&
+			likely(wc->wc_flags & IB_WC_IP_CSUM_OK))
 		skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 	napi_gro_receive(&priv->napi, skb);

include/rdma/ib_verbs.h

@@ -518,6 +518,7 @@ enum ib_wc_flags {
 	IB_WC_GRH		= 1,
 	IB_WC_WITH_IMM		= (1<<1),
 	IB_WC_WITH_INVALIDATE	= (1<<2),
+	IB_WC_IP_CSUM_OK	= (1<<3),
 };
 
 struct ib_wc {
@@ -538,7 +539,6 @@ struct ib_wc {
 	u8			sl;
 	u8			dlid_path_bits;
 	u8			port_num;	/* valid only for DR SMPs on switches */
-	int			csum_ok;
 };
 
 enum ib_cq_notify_flags {