Return-path: Received: from mail-ea0-f180.google.com ([209.85.215.180]:62440 "EHLO mail-ea0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751519Ab3F1PFA (ORCPT ); Fri, 28 Jun 2013 11:05:00 -0400 Message-ID: <1372431906.3301.283.camel@edumazet-glaptop> (sfid-20130628_170513_843002_63FC6BD1) Subject: [PATCH v3] iwl3945: better skb management in rx path From: Eric Dumazet To: Paul Stewart Cc: "John W. Linville" , "Steinar H. Gunderson" , linux-wireless , netdev Date: Fri, 28 Jun 2013 08:05:06 -0700 In-Reply-To: <1372431024.3301.277.camel@edumazet-glaptop> References: <1372421021.3301.263.camel@edumazet-glaptop> <1372431024.3301.277.camel@edumazet-glaptop> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: From: Eric Dumazet 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 Signed-off-by: Eric Dumazet Cc: Paul Stewart --- v3: use regular memcpy(skb_put(...),...) v2: SMALL_PACKET_SIZE define drivers/net/wireless/iwlegacy/3945.c | 31 +++++++++++++++---------- 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/drivers/net/wireless/iwlegacy/3945.c b/drivers/net/wireless/iwlegacy/3945.c index c092033..f09e257 100644 --- a/drivers/net/wireless/iwlegacy/3945.c +++ b/drivers/net/wireless/iwlegacy/3945.c @@ -475,6 +475,8 @@ il3945_is_network_packet(struct il_priv *il, struct ieee80211_hdr *header) } } +#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) @@ -483,14 +485,13 @@ il3945_pass_packet_to_mac80211(struct il_priv *il, struct il_rx_buf *rxb, 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; } @@ -506,26 +507,32 @@ il3945_pass_packet_to_mac80211(struct il_priv *il, struct il_rx_buf *rxb, D_INFO("Woke queues - frame received on passive channel\n"); } - 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)