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, 5 insertions, 5 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-tx.c b/drivers/net/wireless/iwlwifi/iwl-tx.c
index d0bd7cd024a..5c43d7c43b3 100644
--- a/drivers/net/wireless/iwlwifi/iwl-tx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-tx.c
@@ -1153,7 +1153,7 @@ static void iwl_hcmd_queue_reclaim(struct iwl_priv *priv, int txq_id,
  */
 void iwl_tx_cmd_complete(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);
 	u16 sequence = le16_to_cpu(pkt->hdr.sequence);
 	int txq_id = SEQ_TO_QUEUE(sequence);
 	int index = SEQ_TO_INDEX(sequence);
@@ -1180,10 +1180,10 @@ void iwl_tx_cmd_complete(struct iwl_priv *priv, struct iwl_rx_mem_buffer *rxb)
 
 	/* Input error checking is done when commands are added to queue. */
 	if (meta->flags & CMD_WANT_SKB) {
-		meta->source->reply_skb = rxb->skb;
-		rxb->skb = NULL;
+		meta->source->reply_page = (unsigned long)rxb_addr(rxb);
+		rxb->page = NULL;
 	} else if (meta->callback)
-		meta->callback(priv, cmd, rxb->skb);
+		meta->callback(priv, cmd, pkt);
 
 	iwl_hcmd_queue_reclaim(priv, txq_id, index, cmd_index);
 
@@ -1442,7 +1442,7 @@ static int iwl_tx_status_reply_compressed_ba(struct iwl_priv *priv,
 void iwl_rx_reply_compressed_ba(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_compressed_ba_resp *ba_resp = &pkt->u.compressed_ba;
 	struct iwl_tx_queue *txq = NULL;
 	struct iwl_ht_agg *agg;