Reuse the mbuf that was just retrieved from the receive ring if mbuf

exhaustion is encountered. There was a fix made previously for this
problem but the solution (breaking out of the receive loop) does not
seem to work. mbuf reuse strategy is already adopted by other drivers
such as if_bge.  The problem was recreated and the patch is also
verified in the same test environment.

1 files changed, 17 insertions, 8 deletions

diff --git a/sys/dev/fxp/if_fxp.c b/sys/dev/fxp/if_fxp.c
index a652fb6..e4bb212 100644
--- a/sys/dev/fxp/if_fxp.c
+++ b/sys/dev/fxp/if_fxp.c
@@ -231,7 +231,7 @@ static int		fxp_ioctl(struct ifnet *ifp, u_long command,
 			    caddr_t data);
 static void 		fxp_watchdog(struct fxp_softc *sc);
 static int		fxp_add_rfabuf(struct fxp_softc *sc,
-    			    struct fxp_rx *rxp);
+    			    struct fxp_rx *rxp, struct mbuf *oldm);
 static int		fxp_mc_addrs(struct fxp_softc *sc);
 static void		fxp_mc_setup(struct fxp_softc *sc);
 static uint16_t		fxp_eeprom_getword(struct fxp_softc *sc, int offset,
@@ -715,7 +715,7 @@ fxp_attach(device_t dev)
 			device_printf(dev, "can't create DMA map for RX\n");
 			goto fail;
 		}
-		if (fxp_add_rfabuf(sc, rxp) != 0) {
+		if (fxp_add_rfabuf(sc, rxp, NULL) != 0) {
 			error = ENOMEM;
 			goto fail;
 		}
@@ -1652,7 +1652,7 @@ fxp_intr_body(struct fxp_softc *sc, struct ifnet *ifp, uint8_t statack,
 		 * If this fails, the old buffer is recycled
 		 * instead.
 		 */
-		fxp_rc = fxp_add_rfabuf(sc, rxp);
+		fxp_rc = fxp_add_rfabuf(sc, rxp, m);
 		if (fxp_rc == 0) {
 			int total_len;
 
@@ -2245,17 +2245,26 @@ fxp_ifmedia_sts(struct ifnet *ifp, struct ifmediareq *ifmr)
  * data pointer is fixed up to point just past it.
  */
 static int
-fxp_add_rfabuf(struct fxp_softc *sc, struct fxp_rx *rxp)
+fxp_add_rfabuf(struct fxp_softc *sc, struct fxp_rx *rxp, struct mbuf *oldm)
 {
 	struct mbuf *m;
 	struct fxp_rfa *rfa, *p_rfa;
 	struct fxp_rx *p_rx;
 	bus_dmamap_t tmp_map;
-	int error;
+	int error, reused_mbuf=0;
 
 	m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
-	if (m == NULL)
-		return (ENOBUFS);
+	if (m == NULL) {
+		if (oldm == NULL)
+			return ENOBUFS;
+		m = oldm;
+		m->m_data = m->m_ext.ext_buf;
+		/*
+		 * return error so the receive loop will 
+		 * not pass the packet to upper layer
+		 */
+		reused_mbuf = EAGAIN;
+	}
 
 	/*
 	 * Move the data pointer up so that the incoming data packet
@@ -2320,7 +2329,7 @@ fxp_add_rfabuf(struct fxp_softc *sc, struct fxp_rx *rxp)
 		sc->fxp_desc.rx_head = rxp;
 	}
 	sc->fxp_desc.rx_tail = rxp;
-	return (0);
+	return (reused_mbuf);
 }
 
 static int