iwl4965: better skb management in rx path

4965 version of Eric patch "iwl3945: better skb management in rx path".
It fixes several problems :

1) skb->truesize is underestimated.
   We really consume PAGE_SIZE bytes for a fragment,
   not the frame length.
2) 128 bytes of initial headroom is a bit low and forces reallocations.
3) We can avoid consuming a full page for small enough frames.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/net/wireless/iwlegacy/4965-mac.c b/drivers/net/wireless/iwlegacy/4965-mac.c
index b9b2bb51e605..c4b22e190a54 100644
--- a/drivers/net/wireless/iwlegacy/4965-mac.c
+++ b/drivers/net/wireless/iwlegacy/4965-mac.c
@@ -574,9 +574,11 @@ il4965_translate_rx_status(struct il_priv *il, u32 decrypt_in)
         return decrypt_out;
 }
 
+#define SMALL_PACKET_SIZE 256
+
 static void
 il4965_pass_packet_to_mac80211(struct il_priv *il, struct ieee80211_hdr *hdr,
-                               u16 len, u32 ampdu_status, struct il_rx_buf *rxb,
+                               u32 len, u32 ampdu_status, struct il_rx_buf *rxb,
                                struct ieee80211_rx_status *stats)
 {
         struct sk_buff *skb;
@@ -598,21 +600,25 @@ il4965_pass_packet_to_mac80211(struct il_priv *il, struct ieee80211_hdr *hdr,
             il_set_decrypted_flag(il, hdr, ampdu_status, stats))
                 return;
 
-        skb = dev_alloc_skb(128);
+        skb = dev_alloc_skb(SMALL_PACKET_SIZE);
         if (!skb) {
                 IL_ERR("dev_alloc_skb failed\n");
                 return;
         }
 
-        skb_add_rx_frag(skb, 0, rxb->page, (void *)hdr - rxb_addr(rxb), len,
-                        len);
+        if (len <= SMALL_PACKET_SIZE) {
+                memcpy(skb_put(skb, len), hdr, len);
+        } else {
+                skb_add_rx_frag(skb, 0, rxb->page, (void *)hdr - rxb_addr(rxb),
+                                len, PAGE_SIZE << il->hw_params.rx_page_order);
+                il->alloc_rxb_page--;
+                rxb->page = NULL;
+        }
 
         il_update_stats(il, false, fc, len);
         memcpy(IEEE80211_SKB_RXCB(skb), stats, sizeof(*stats));
 
         ieee80211_rx(il->hw, skb);
-        il->alloc_rxb_page--;
-        rxb->page = NULL;
 }
 
 /* Called for N_RX (legacy ABG frames), or