[PATCH 3.10 171/173] iwl3945: better skb management in rx path

Greg Kroah-Hartman
2013-12-02T19:12:34Z

From: Eric Dumazet <edumazet@google.com>

commit 45fe142cefa864b685615bcb930159f6749c3667 upstream.

Steinar reported reallocations of skb->head with IPv6, leading to
a warning in skb_try_coalesce()

It turns out iwl3945 has 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.

Reported-by: Steinar H. Gunderson <sesse@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paul Stewart <pstew@google.com>
Acked-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/iwlegacy/3945.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

--- a/drivers/net/wireless/iwlegacy/3945.c
+++ b/drivers/net/wireless/iwlegacy/3945.c
@@ -462,6 +462,8 @@ il3945_is_network_packet(struct il_priv
}
}

+#define SMALL_PACKET_SIZE 256
+
static void
il3945_pass_packet_to_mac80211(struct il_priv *il, struct il_rx_buf *rxb,
struct ieee80211_rx_status *stats)
@@ -470,14 +472,13 @@ il3945_pass_packet_to_mac80211(struct il
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)IL_RX_DATA(pkt);
struct il3945_rx_frame_hdr *rx_hdr = IL_RX_HDR(pkt);
struct il3945_rx_frame_end *rx_end = IL_RX_END(pkt);
- u16 len = le16_to_cpu(rx_hdr->len);
+ u32 len = le16_to_cpu(rx_hdr->len);
struct sk_buff *skb;
__le16 fc = hdr->frame_control;
+ u32 fraglen = PAGE_SIZE << il->hw_params.rx_page_order;

/* We received data from the HW, so stop the watchdog */
- if (unlikely
- (len + IL39_RX_FRAME_SIZE >
- PAGE_SIZE << il->hw_params.rx_page_order)) {
+ if (unlikely(len + IL39_RX_FRAME_SIZE > fraglen)) {
D_DROP("Corruption detected!\n");
return;
}
@@ -488,26 +489,32 @@ il3945_pass_packet_to_mac80211(struct il
return;
}

- skb = dev_alloc_skb(128);
+ skb = dev_alloc_skb(SMALL_PACKET_SIZE);
if (!skb) {
IL_ERR("dev_alloc_skb failed\n");
return;
}

if (!il3945_mod_params.sw_crypto)
- il_set_decrypted_flag(il, (struct ieee80211_hdr *)rxb_addr(rxb),
+ il_set_decrypted_flag(il, (struct ieee80211_hdr *)pkt,
le32_to_cpu(rx_end->status), stats);

- skb_add_rx_frag(skb, 0, rxb->page,
- (void *)rx_hdr->payload - (void *)pkt, len,
- len);
-
+ /* If frame is small enough to fit into skb->head, copy it
+ * and do not consume a full page
+ */
+ if (len <= SMALL_PACKET_SIZE) {
+ memcpy(skb_put(skb, len), rx_hdr->payload, len);
+ } else {
+ skb_add_rx_frag(skb, 0, rxb->page,
+ (void *)rx_hdr->payload - (void *)pkt, len,
+ fraglen);
+ 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;
}

#define IL_DELAY_NEXT_SCAN_AFTER_ASSOC (HZ*6)