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Message-ID: <lsq.1510009382.675989450@decadent.org.uk>
Date: Mon, 06 Nov 2017 23:03:02 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
"Florian Fainelli" <f.fainelli@...il.com>,
"Jaedon Shin" <jaedon.shin@...il.com>,
"Petri Gynther" <pgynther@...gle.com>
Subject: [PATCH 3.16 012/294] net: bcmgenet: rewrite bcmgenet_rx_refill()
3.16.50-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Petri Gynther <pgynther@...gle.com>
commit d6707bec598649450ee0887bf11896e525777874 upstream.
Currently, bcmgenet_desc_rx() calls bcmgenet_rx_refill() at the end of
Rx packet processing loop, after the current Rx packet has already been
passed to napi_gro_receive(). However, bcmgenet_rx_refill() might fail
to allocate a new Rx skb, thus leaving a hole on the Rx queue where no
valid Rx buffer exists.
To eliminate this situation:
1. Rewrite bcmgenet_rx_refill() to retain the current Rx skb on the Rx
queue if a new replacement Rx skb can't be allocated and DMA-mapped.
In this case, the data on the current Rx skb is effectively dropped.
2. Modify bcmgenet_desc_rx() to call bcmgenet_rx_refill() at the top of
Rx packet processing loop, so that the new replacement Rx skb is
already in place before the current Rx skb is processed.
Signed-off-by: Petri Gynther <pgynther@...gle.com>
Tested-by: Jaedon Shin <jaedon.shin@...il.com>--
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Tested-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.16:
- There's no alloc_rx_buff_failed statistic
- Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1275,33 +1275,41 @@ out:
return ret;
}
-
-static int bcmgenet_rx_refill(struct bcmgenet_priv *priv,
- struct enet_cb *cb)
+static struct sk_buff *bcmgenet_rx_refill(struct bcmgenet_priv *priv,
+ struct enet_cb *cb)
{
struct device *kdev = &priv->pdev->dev;
struct sk_buff *skb;
+ struct sk_buff *rx_skb;
dma_addr_t mapping;
- int ret;
+ /* Allocate a new Rx skb */
skb = netdev_alloc_skb(priv->dev,
priv->rx_buf_len + SKB_ALIGNMENT);
- if (!skb)
- return -ENOMEM;
+ if (!skb) {
+ netif_err(priv, rx_err, priv->dev,
+ "%s: Rx skb allocation failed\n", __func__);
+ return NULL;
+ }
- /* a caller did not release this control block */
- WARN_ON(cb->skb != NULL);
- cb->skb = skb;
- mapping = dma_map_single(kdev, skb->data,
- priv->rx_buf_len, DMA_FROM_DEVICE);
- ret = dma_mapping_error(kdev, mapping);
- if (ret) {
- bcmgenet_free_cb(cb);
+ /* DMA-map the new Rx skb */
+ mapping = dma_map_single(kdev, skb->data, priv->rx_buf_len,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(kdev, mapping)) {
+ dev_kfree_skb_any(skb);
netif_err(priv, rx_err, priv->dev,
- "%s DMA map failed\n", __func__);
- return ret;
+ "%s: Rx skb DMA mapping failed\n", __func__);
+ return NULL;
}
+ /* Grab the current Rx skb from the ring and DMA-unmap it */
+ rx_skb = cb->skb;
+ if (likely(rx_skb))
+ dma_unmap_single(kdev, dma_unmap_addr(cb, dma_addr),
+ priv->rx_buf_len, DMA_FROM_DEVICE);
+
+ /* Put the new Rx skb on the ring */
+ cb->skb = skb;
dma_unmap_addr_set(cb, dma_addr, mapping);
/* assign packet, prepare descriptor, and advance pointer */
@@ -1314,7 +1322,8 @@ static int bcmgenet_rx_refill(struct bcm
priv->rx_bd_assign_ptr = priv->rx_bds +
(priv->rx_bd_assign_index * DMA_DESC_SIZE);
- return 0;
+ /* Return the current Rx skb to caller */
+ return rx_skb;
}
/* bcmgenet_desc_rx - descriptor based rx process.
@@ -1329,7 +1338,7 @@ static unsigned int bcmgenet_desc_rx(str
struct sk_buff *skb;
u32 dma_length_status;
unsigned long dma_flag;
- int len, err;
+ int len;
unsigned int rxpktprocessed = 0, rxpkttoprocess;
unsigned int p_index;
unsigned int chksum_ok = 0;
@@ -1351,26 +1360,14 @@ static unsigned int bcmgenet_desc_rx(str
(rxpktprocessed < budget)) {
cb = &priv->rx_cbs[priv->rx_read_ptr];
- skb = cb->skb;
+ skb = bcmgenet_rx_refill(priv, cb);
- /* We do not have a backing SKB, so we do not have a
- * corresponding DMA mapping for this incoming packet since
- * bcmgenet_rx_refill always either has both skb and mapping or
- * none.
- */
if (unlikely(!skb)) {
dev->stats.rx_dropped++;
dev->stats.rx_errors++;
- goto refill;
+ goto next;
}
- /* Unmap the packet contents such that we can use the
- * RSV from the 64 bytes descriptor when enabled and save
- * a 32-bits register read
- */
- dma_unmap_single(kdev, dma_unmap_addr(cb, dma_addr),
- priv->rx_buf_len, DMA_FROM_DEVICE);
-
if (!priv->desc_64b_en) {
dma_length_status = dmadesc_get_length_status(priv,
priv->rx_bds +
@@ -1398,10 +1395,10 @@ static unsigned int bcmgenet_desc_rx(str
"Droping fragmented packet!\n");
dev->stats.rx_dropped++;
dev->stats.rx_errors++;
- dev_kfree_skb_any(cb->skb);
- cb->skb = NULL;
- goto refill;
+ dev_kfree_skb_any(skb);
+ goto next;
}
+
/* report errors */
if (unlikely(dma_flag & (DMA_RX_CRC_ERROR |
DMA_RX_OV |
@@ -1420,11 +1417,8 @@ static unsigned int bcmgenet_desc_rx(str
dev->stats.rx_length_errors++;
dev->stats.rx_dropped++;
dev->stats.rx_errors++;
-
- /* discard the packet and advance consumer index.*/
- dev_kfree_skb_any(cb->skb);
- cb->skb = NULL;
- goto refill;
+ dev_kfree_skb_any(skb);
+ goto next;
} /* error packet */
chksum_ok = (dma_flag & priv->dma_rx_chk_bit) &&
@@ -1457,15 +1451,9 @@ static unsigned int bcmgenet_desc_rx(str
/* Notify kernel */
napi_gro_receive(&priv->napi, skb);
- cb->skb = NULL;
netif_dbg(priv, rx_status, dev, "pushed up to kernel\n");
- /* refill RX path on the current control block */
-refill:
- err = bcmgenet_rx_refill(priv, cb);
- if (err)
- netif_err(priv, rx_err, dev, "Rx refill failed\n");
-
+next:
rxpktprocessed++;
priv->rx_read_ptr++;
priv->rx_read_ptr &= (priv->num_rx_bds - 1);
@@ -1478,7 +1466,7 @@ refill:
static int bcmgenet_alloc_rx_buffers(struct bcmgenet_priv *priv)
{
struct enet_cb *cb;
- int ret = 0;
+ struct sk_buff *skb;
int i;
netif_dbg(priv, hw, priv->dev, "%s:\n", __func__);
@@ -1486,16 +1474,14 @@ static int bcmgenet_alloc_rx_buffers(str
/* loop here for each buffer needing assign */
for (i = 0; i < priv->num_rx_bds; i++) {
cb = &priv->rx_cbs[priv->rx_bd_assign_index];
- if (cb->skb)
- continue;
-
- ret = bcmgenet_rx_refill(priv, cb);
- if (ret)
- break;
-
+ skb = bcmgenet_rx_refill(priv, cb);
+ if (skb)
+ dev_kfree_skb_any(skb);
+ if (!cb->skb)
+ return -ENOMEM;
}
- return ret;
+ return 0;
}
static void bcmgenet_free_rx_buffers(struct bcmgenet_priv *priv)
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