iwlwifi: use paged Rx

This switches the iwlwifi driver to use paged skb from linear skb for Rx
buffer. So that it relieves some Rx buffer allocation pressure for the
memory subsystem. Currently iwlwifi (4K for 3945) requests 8K bytes for
Rx buffer. Due to the trailing skb_shared_info in the skb->data,
alloc_skb() will do the next order allocation, which is 16K bytes. This
is suboptimal and more likely to fail when the system is under memory
usage pressure. Switching to paged Rx skb lets us allocate the RXB
directly by alloc_pages(), so that only order 1 allocation is required.

It also adjusts the area spin_lock (with IRQ disabled) protected in the
tasklet because tasklet guarentees to run only on one CPU and the new
unprotected code can be preempted by the IRQ handler. This saves us from
spawning another workqueue to make skb_linearize/__pskb_pull_tail happy
(which cannot be called in hard irq context).

Finally, mac80211 doesn't support paged Rx yet. So we linearize the skb
for all the management frames and software decryption or defragmentation
required data frames before handed to mac80211. For all the other frames,
we __pskb_pull_tail 64 bytes in the linear area of the skb for mac80211
to handle them properly.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c
index 41f9a0621250..4fca65a2fe9c 100644
--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -111,7 +111,7 @@ EXPORT_SYMBOL(iwl_scan_cancel_timeout);
 static int iwl_send_scan_abort(struct iwl_priv *priv)
 {
         int ret = 0;
-        struct iwl_rx_packet *res;
+        struct iwl_rx_packet *pkt;
         struct iwl_host_cmd cmd = {
                 .id = REPLY_SCAN_ABORT_CMD,
                 .flags = CMD_WANT_SKB,
@@ -131,21 +131,21 @@ static int iwl_send_scan_abort(struct iwl_priv *priv)
                 return ret;
         }
 
-        res = (struct iwl_rx_packet *)cmd.reply_skb->data;
-        if (res->u.status != CAN_ABORT_STATUS) {
+        pkt = (struct iwl_rx_packet *)cmd.reply_page;
+        if (pkt->u.status != CAN_ABORT_STATUS) {
                 /* The scan abort will return 1 for success or
                  * 2 for "failure".  A failure condition can be
                  * due to simply not being in an active scan which
                  * can occur if we send the scan abort before we
                  * the microcode has notified us that a scan is
                  * completed. */
-                IWL_DEBUG_INFO(priv, "SCAN_ABORT returned %d.\n", res->u.status);
+                IWL_DEBUG_INFO(priv, "SCAN_ABORT returned %d.\n", pkt->u.status);
                 clear_bit(STATUS_SCAN_ABORTING, &priv->status);
                 clear_bit(STATUS_SCAN_HW, &priv->status);
         }
 
-        priv->alloc_rxb_skb--;
-        dev_kfree_skb_any(cmd.reply_skb);
+        priv->alloc_rxb_page--;
+        free_pages(cmd.reply_page, priv->hw_params.rx_page_order);
 
         return ret;
 }
@@ -155,7 +155,7 @@ static void iwl_rx_reply_scan(struct iwl_priv *priv,
                               struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl_scanreq_notification *notif =
             (struct iwl_scanreq_notification *)pkt->u.raw;
 
@@ -167,7 +167,7 @@ static void iwl_rx_reply_scan(struct iwl_priv *priv,
 static void iwl_rx_scan_start_notif(struct iwl_priv *priv,
                                     struct iwl_rx_mem_buffer *rxb)
 {
-        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl_scanstart_notification *notif =
             (struct iwl_scanstart_notification *)pkt->u.raw;
         priv->scan_start_tsf = le32_to_cpu(notif->tsf_low);
@@ -186,7 +186,7 @@ static void iwl_rx_scan_results_notif(struct iwl_priv *priv,
                                       struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl_scanresults_notification *notif =
             (struct iwl_scanresults_notification *)pkt->u.raw;
 
@@ -213,7 +213,7 @@ static void iwl_rx_scan_complete_notif(struct iwl_priv *priv,
                                        struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl_scancomplete_notification *scan_notif = (void *)pkt->u.raw;
 
         IWL_DEBUG_SCAN(priv, "Scan complete: %d channels (TSF 0x%08X:%08X) - %d\n",