[3.11.y.z extended stable] Patch "iwl3945: better skb management in rx path" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Thu Dec 5 11:25:10 UTC 2013


This is a note to let you know that I have just added a patch titled

    iwl3945: better skb management in rx path

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 59fc5d95f70e7739c240c112b50778ffe3cfc545 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Fri, 28 Jun 2013 08:05:06 -0700
Subject: iwl3945: better skb management in rx path

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 at google.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Cc: Paul Stewart <pstew at google.com>
Acked-by: Stanislaw Gruszka <sgruszka at redhat.com>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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)
--
1.8.3.2





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