be2net: Fix to avoid a crash seen on PPC with LRO and Jumbo frames.

While testing the driver on PPC, we ran into a crash with LRO, Jumbo frames.
With CONFIG_PPC_64K_PAGES configured (a default in PPC), MAX_SKB_FRAGS drops to 3 and we were crossing the array limits on skb_shinfo(skb)->frags[].
Now we coalesce the frags from the same physical page into one slot in
skb_shinfo(skb)->frags[] and go to the next index when the frag is from

different physical page.

This patch is against the net-2.6 tree.

Signed-off-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 35 insertions, 16 deletions

diff --git a/drivers/net/benet/be.h b/drivers/net/benet/be.h
index f703758f0a6e..5b4bf3d2cdc2 100644
--- a/drivers/net/benet/be.h
+++ b/drivers/net/benet/be.h
@@ -73,7 +73,7 @@ static inline char *nic_name(struct pci_dev *pdev)
 #define RX_FRAGS_REFILL_WM      (RX_Q_LEN - MAX_RX_POST)
 
 #define BE_MAX_LRO_DESCRIPTORS  16
-#define BE_MAX_FRAGS_PER_FRAME  16
+#define BE_MAX_FRAGS_PER_FRAME  (min((u32) 16, (u32) MAX_SKB_FRAGS))
 
 struct be_dma_mem {
         void *va;
diff --git a/drivers/net/benet/be_ethtool.c b/drivers/net/benet/be_ethtool.c
index 9592f22e4c8c..cccc5419ad72 100644
--- a/drivers/net/benet/be_ethtool.c
+++ b/drivers/net/benet/be_ethtool.c
@@ -162,8 +162,8 @@ be_set_coalesce(struct net_device *netdev, struct ethtool_coalesce *coalesce)
                 return -EINVAL;
 
         adapter->max_rx_coal = coalesce->rx_max_coalesced_frames;
-        if (adapter->max_rx_coal > MAX_SKB_FRAGS)
-                adapter->max_rx_coal = MAX_SKB_FRAGS - 1;
+        if (adapter->max_rx_coal > BE_MAX_FRAGS_PER_FRAME)
+                adapter->max_rx_coal = BE_MAX_FRAGS_PER_FRAME;
 
         /* if AIC is being turned on now, start with an EQD of 0 */
         if (rx_eq->enable_aic == 0 &&
diff --git a/drivers/net/benet/be_main.c b/drivers/net/benet/be_main.c
index 66c10c87f517..308eb09ca56b 100644
--- a/drivers/net/benet/be_main.c
+++ b/drivers/net/benet/be_main.c
@@ -666,7 +666,7 @@ static void skb_fill_rx_data(struct be_adapter *adapter,
 {
         struct be_queue_info *rxq = &adapter->rx_obj.q;
         struct be_rx_page_info *page_info;
-        u16 rxq_idx, i, num_rcvd;
+        u16 rxq_idx, i, num_rcvd, j;
         u32 pktsize, hdr_len, curr_frag_len;
         u8 *start;
 
@@ -709,22 +709,33 @@ static void skb_fill_rx_data(struct be_adapter *adapter,
 
         /* More frags present for this completion */
         pktsize -= curr_frag_len; /* account for above copied frag */
-        for (i = 1; i < num_rcvd; i++) {
+        for (i = 1, j = 0; i < num_rcvd; i++) {
                 index_inc(&rxq_idx, rxq->len);
                 page_info = get_rx_page_info(adapter, rxq_idx);
 
                 curr_frag_len = min(pktsize, rx_frag_size);
 
-                skb_shinfo(skb)->frags[i].page = page_info->page;
-                skb_shinfo(skb)->frags[i].page_offset = page_info->page_offset;
-                skb_shinfo(skb)->frags[i].size = curr_frag_len;
+                /* Coalesce all frags from the same physical page in one slot */
+                if (page_info->page_offset == 0) {
+                        /* Fresh page */
+                        j++;
+                        skb_shinfo(skb)->frags[j].page = page_info->page;
+                        skb_shinfo(skb)->frags[j].page_offset =
+                                                        page_info->page_offset;
+                        skb_shinfo(skb)->frags[j].size = 0;
+                        skb_shinfo(skb)->nr_frags++;
+                } else {
+                        put_page(page_info->page);
+                }
+
+                skb_shinfo(skb)->frags[j].size += curr_frag_len;
                 skb->len += curr_frag_len;
                 skb->data_len += curr_frag_len;
-                skb_shinfo(skb)->nr_frags++;
                 pktsize -= curr_frag_len;
 
                 memset(page_info, 0, sizeof(*page_info));
         }
+        BUG_ON(j > MAX_SKB_FRAGS);
 
 done:
         be_rx_stats_update(adapter, pktsize, num_rcvd);
@@ -786,7 +797,7 @@ static void be_rx_compl_process_lro(struct be_adapter *adapter,
         struct skb_frag_struct rx_frags[BE_MAX_FRAGS_PER_FRAME];
         struct be_queue_info *rxq = &adapter->rx_obj.q;
         u32 num_rcvd, pkt_size, remaining, vlanf, curr_frag_len;
-        u16 i, rxq_idx = 0, vid;
+        u16 i, rxq_idx = 0, vid, j;
 
         num_rcvd = AMAP_GET_BITS(struct amap_eth_rx_compl, numfrags, rxcp);
         pkt_size = AMAP_GET_BITS(struct amap_eth_rx_compl, pktsize, rxcp);
@@ -794,20 +805,28 @@ static void be_rx_compl_process_lro(struct be_adapter *adapter,
         rxq_idx = AMAP_GET_BITS(struct amap_eth_rx_compl, fragndx, rxcp);
 
         remaining = pkt_size;
-        for (i = 0; i < num_rcvd; i++) {
+        for (i = 0, j = -1; i < num_rcvd; i++) {
                 page_info = get_rx_page_info(adapter, rxq_idx);
 
                 curr_frag_len = min(remaining, rx_frag_size);
 
-                rx_frags[i].page = page_info->page;
-                rx_frags[i].page_offset = page_info->page_offset;
-                rx_frags[i].size = curr_frag_len;
-                remaining -= curr_frag_len;
+                /* Coalesce all frags from the same physical page in one slot */
+                if (i == 0 || page_info->page_offset == 0) {
+                        /* First frag or Fresh page */
+                        j++;
+                        rx_frags[j].page = page_info->page;
+                        rx_frags[j].page_offset = page_info->page_offset;
+                        rx_frags[j].size = 0;
+                } else {
+                        put_page(page_info->page);
+                }
+                rx_frags[j].size += curr_frag_len;
 
+                remaining -= curr_frag_len;
                 index_inc(&rxq_idx, rxq->len);
-
                 memset(page_info, 0, sizeof(*page_info));
         }
+        BUG_ON(j > MAX_SKB_FRAGS);
 
         if (likely(!vlanf)) {
                 lro_receive_frags(&adapter->rx_obj.lro_mgr, rx_frags, pkt_size,