net: Optimize hard_start_xmit() return checking
Recent changes in the TX error propagation require additional checking and masking of values returned from hard_start_xmit(), mainly to separate cases where skb was consumed. This aim can be simplified by changing the order of NETDEV_TX and NET_XMIT codes, because the latter are treated similarly to negative (ERRNO) values. After this change much simpler dev_xmit_complete() is also used in sch_direct_xmit(), so it is moved to netdevice.h. Additionally NET_RX definitions in netdevice.h are moved up from between TX codes to avoid confusion while reading the TX comment. Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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cb43e23435
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3 changed files with 35 additions and 47 deletions
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@ -63,6 +63,10 @@ struct wireless_dev;
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#define HAVE_FREE_NETDEV /* free_netdev() */
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#define HAVE_NETDEV_PRIV /* netdev_priv() */
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/* Backlog congestion levels */
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#define NET_RX_SUCCESS 0 /* keep 'em coming, baby */
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#define NET_RX_DROP 1 /* packet dropped */
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/*
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* Transmit return codes: transmit return codes originate from three different
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* namespaces:
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@ -82,14 +86,10 @@ struct wireless_dev;
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/* qdisc ->enqueue() return codes. */
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#define NET_XMIT_SUCCESS 0x00
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#define NET_XMIT_DROP 0x10 /* skb dropped */
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#define NET_XMIT_CN 0x20 /* congestion notification */
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#define NET_XMIT_POLICED 0x30 /* skb is shot by police */
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#define NET_XMIT_MASK 0xf0 /* qdisc flags in net/sch_generic.h */
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/* Backlog congestion levels */
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#define NET_RX_SUCCESS 0 /* keep 'em coming, baby */
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#define NET_RX_DROP 1 /* packet dropped */
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#define NET_XMIT_DROP 0x01 /* skb dropped */
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#define NET_XMIT_CN 0x02 /* congestion notification */
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#define NET_XMIT_POLICED 0x03 /* skb is shot by police */
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#define NET_XMIT_MASK 0x0f /* qdisc flags in net/sch_generic.h */
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/* NET_XMIT_CN is special. It does not guarantee that this packet is lost. It
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* indicates that the device will soon be dropping packets, or already drops
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@ -98,16 +98,34 @@ struct wireless_dev;
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#define net_xmit_errno(e) ((e) != NET_XMIT_CN ? -ENOBUFS : 0)
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/* Driver transmit return codes */
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#define NETDEV_TX_MASK 0xf
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#define NETDEV_TX_MASK 0xf0
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enum netdev_tx {
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__NETDEV_TX_MIN = INT_MIN, /* make sure enum is signed */
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NETDEV_TX_OK = 0, /* driver took care of packet */
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NETDEV_TX_BUSY = 1, /* driver tx path was busy*/
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NETDEV_TX_LOCKED = 2, /* driver tx lock was already taken */
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NETDEV_TX_OK = 0x00, /* driver took care of packet */
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NETDEV_TX_BUSY = 0x10, /* driver tx path was busy*/
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NETDEV_TX_LOCKED = 0x20, /* driver tx lock was already taken */
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};
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typedef enum netdev_tx netdev_tx_t;
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/*
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* Current order: NETDEV_TX_MASK > NET_XMIT_MASK >= 0 is significant;
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* hard_start_xmit() return < NET_XMIT_MASK means skb was consumed.
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*/
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static inline bool dev_xmit_complete(int rc)
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{
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/*
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* Positive cases with an skb consumed by a driver:
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* - successful transmission (rc == NETDEV_TX_OK)
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* - error while transmitting (rc < 0)
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* - error while queueing to a different device (rc & NET_XMIT_MASK)
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*/
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if (likely(rc < NET_XMIT_MASK))
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return true;
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return false;
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}
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#endif
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#define MAX_ADDR_LEN 32 /* Largest hardware address length */
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@ -1924,23 +1924,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
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return rc;
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}
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static inline bool dev_xmit_complete(int rc)
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{
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/* successful transmission */
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if (rc == NETDEV_TX_OK)
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return true;
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/* error while transmitting, driver consumed skb */
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if (rc < 0)
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return true;
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/* error while queueing to a different device, driver consumed skb */
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if (rc & NET_XMIT_MASK)
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return true;
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return false;
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}
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/**
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* dev_queue_xmit - transmit a buffer
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* @skb: buffer to transmit
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@ -119,39 +119,26 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
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spin_unlock(root_lock);
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HARD_TX_LOCK(dev, txq, smp_processor_id());
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if (!netif_tx_queue_stopped(txq) &&
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!netif_tx_queue_frozen(txq)) {
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if (!netif_tx_queue_stopped(txq) && !netif_tx_queue_frozen(txq))
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ret = dev_hard_start_xmit(skb, dev, txq);
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/* an error implies that the skb was consumed */
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if (ret < 0)
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ret = NETDEV_TX_OK;
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/* all NET_XMIT codes map to NETDEV_TX_OK */
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ret &= ~NET_XMIT_MASK;
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}
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HARD_TX_UNLOCK(dev, txq);
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spin_lock(root_lock);
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switch (ret) {
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case NETDEV_TX_OK:
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/* Driver sent out skb successfully */
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if (dev_xmit_complete(ret)) {
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/* Driver sent out skb successfully or skb was consumed */
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ret = qdisc_qlen(q);
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break;
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case NETDEV_TX_LOCKED:
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} else if (ret == NETDEV_TX_LOCKED) {
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/* Driver try lock failed */
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ret = handle_dev_cpu_collision(skb, txq, q);
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break;
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default:
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} else {
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/* Driver returned NETDEV_TX_BUSY - requeue skb */
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if (unlikely (ret != NETDEV_TX_BUSY && net_ratelimit()))
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printk(KERN_WARNING "BUG %s code %d qlen %d\n",
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dev->name, ret, q->q.qlen);
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ret = dev_requeue_skb(skb, q);
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break;
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}
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if (ret && (netif_tx_queue_stopped(txq) ||
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