p54usb: Fix to prevent SKB memory allocation errors with 4K page size

On x86_64 architecture with 4K page size and SLUB debugging enabled, stress
testing on p54usb has resulted in skb allocation failures of O(1) and extreme
page fragmentation. Reducing rx_mtu fixes this problem by reducing the size of
all receive skb allocations to be of O(0). This change does not impact
performance in any way.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
index 82354b974a04..06c64744df27 100644
--- a/drivers/net/wireless/p54/p54common.c
+++ b/drivers/net/wireless/p54/p54common.c
@@ -138,6 +138,7 @@ int p54_parse_firmware(struct ieee80211_hw *dev, const struct firmware *fw)
         u8 *fw_version = NULL;
         size_t len;
         int i;
+        int maxlen;
 
         if (priv->rx_start)
                 return 0;
@@ -195,6 +196,16 @@ int p54_parse_firmware(struct ieee80211_hw *dev, const struct firmware *fw)
                         else
                                 priv->rx_mtu = (size_t)
                                         0x620 - priv->tx_hdr_len;
+                        maxlen = priv->tx_hdr_len + /* USB devices */
+                                 sizeof(struct p54_rx_data) +
+                                 4 + /* rx alignment */
+                                 IEEE80211_MAX_FRAG_THRESHOLD;
+                        if (priv->rx_mtu > maxlen && PAGE_SIZE == 4096) {
+                                printk(KERN_INFO "p54: rx_mtu reduced from %d "
+                                                 "to %d\n", priv->rx_mtu,
+                                                 maxlen);
+                                priv->rx_mtu = maxlen;
+                        }
                         break;
                         }
                 case BR_CODE_EXPOSED_IF: