Fix up alc_encap() / alc_start():

- Remove unnecessary nsegs variable from alc_encap() and
  use map->dm_nsegs. Also remove unnecessary FreeBSD check
  for 0 DMA segments check.
- Remove printfs in alc_encap() failure paths that shouldn't
  be there.
- Add missing IF_PREPEND() from failure path coming off of
  alc_encap() within alc_start().
- Fix error handling within alc_encap(). Previously alc_encap()
  was attempting to unload a DMA map upon failure from
  bus_dmamap_load_mbuf() even though one wasn't loaded at that
  point and then always forcing mbufs through the EFBIG path.

Tested by Gabriel Linder.

From Brad

1 files changed, 23 insertions, 34 deletions

diff --git a/sys/dev/pci/if_alc.c b/sys/dev/pci/if_alc.c
index e8ecac8e3ce..3d4f834a4a2 100644
--- a/sys/dev/pci/if_alc.c
+++ b/sys/dev/pci/if_alc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_alc.c,v 1.18 2011/09/03 14:33:51 kevlo Exp $	*/
+/*	$OpenBSD: if_alc.c,v 1.19 2011/09/13 08:12:51 kevlo Exp $	*/
 /*-
  * Copyright (c) 2009, Pyun YongHyeon <yongari@FreeBSD.org>
  * All rights reserved.
@@ -1283,7 +1283,7 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head)
 	struct mbuf *m;
 	bus_dmamap_t map;
 	uint32_t cflags, poff, vtag;
-	int error, idx, nsegs, prod;
+	int error, idx, prod;
 
 	m = *m_head;
 	cflags = vtag = 0;
@@ -1295,46 +1295,25 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head)
 	map = txd->tx_dmamap;
 
 	error = bus_dmamap_load_mbuf(sc->sc_dmat, map, *m_head, BUS_DMA_NOWAIT);
-
+	if (error != 0 && error != EFBIG)
+		goto drop;
 	if (error != 0) {
-		bus_dmamap_unload(sc->sc_dmat, map);
-		error = EFBIG;
-	}
-	if (error == EFBIG) {
 		if (m_defrag(*m_head, M_DONTWAIT)) {
-			printf("%s: can't defrag TX mbuf\n",
-			    sc->sc_dev.dv_xname);
-			m_freem(*m_head);
-			*m_head = NULL;
-			return (ENOBUFS);
+			error = ENOBUFS;
+			goto drop;
 		}
 		error = bus_dmamap_load_mbuf(sc->sc_dmat, map, *m_head,
 		    BUS_DMA_NOWAIT);
-		if (error != 0) {
-			printf("%s: could not load defragged TX mbuf\n",
-			    sc->sc_dev.dv_xname);
-			m_freem(*m_head);
-			*m_head = NULL;
-			return (error);
-		}
-	} else if (error) {
-		printf("%s: could not load TX mbuf\n", sc->sc_dev.dv_xname);
-		return (error);
-	}
-
-	nsegs = map->dm_nsegs;
-
-	if (nsegs == 0) {
-		m_freem(*m_head);
-		*m_head = NULL;
-		return (EIO);
+		if (error != 0)
+			goto drop;
 	}
 
 	/* Check descriptor overrun. */
-	if (sc->alc_cdata.alc_tx_cnt + nsegs >= ALC_TX_RING_CNT - 3) {
+	if (sc->alc_cdata.alc_tx_cnt + map->dm_nsegs >= ALC_TX_RING_CNT - 3) {
 		bus_dmamap_unload(sc->sc_dmat, map);
 		return (ENOBUFS);
 	}
+
 	bus_dmamap_sync(sc->sc_dmat, map, 0, map->dm_mapsize,
 	    BUS_DMASYNC_PREWRITE);
 
@@ -1355,8 +1334,9 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head)
 		/* Set checksum start offset. */
 		cflags |= ((poff >> 1) << TD_PLOAD_OFFSET_SHIFT) &
 		    TD_PLOAD_OFFSET_MASK;
-	} 
-	for (; idx < nsegs; idx++) {
+	}
+
+	for (; idx < map->dm_nsegs; idx++) {
 		desc = &sc->alc_rdata.alc_tx_ring[prod];
 		desc->len =
 		    htole32(TX_BYTES(map->dm_segs[idx].ds_len) | vtag);
@@ -1365,6 +1345,7 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head)
 		sc->alc_cdata.alc_tx_cnt++;
 		ALC_DESC_INC(prod, ALC_TX_RING_CNT);
 	}
+
 	/* Update producer index. */
 	sc->alc_cdata.alc_tx_prod = prod;
 
@@ -1381,6 +1362,11 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head)
 	txd->tx_m = m;
 
 	return (0);
+
+ drop:
+	m_freem(*m_head);
+	*m_head = NULL;
+	return (error);
 }
 
 void
@@ -1412,8 +1398,11 @@ alc_start(struct ifnet *ifp)
 		 * for the NIC to drain the ring.
 		 */
 		if (alc_encap(sc, &m_head)) {
-			if (m_head == NULL)
+			if (m_head == NULL) {
+				ifp->if_oerrors++;
 				break;
+			}
+			IF_PREPEND(&ifp->if_snd, m_head);
 			ifp->if_flags |= IFF_OACTIVE;
 			break;
 		}