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, 2 insertions, 2 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-5000.c b/drivers/net/wireless/iwlwifi/iwl-5000.c
index ab5b9d8d66b..17555c7c1d6 100644
--- a/drivers/net/wireless/iwlwifi/iwl-5000.c
+++ b/drivers/net/wireless/iwlwifi/iwl-5000.c
@@ -423,7 +423,7 @@ static int iwl5000_send_calib_cfg(struct iwl_priv *priv)
 static void iwl5000_rx_calib_result(struct iwl_priv *priv,
 			     struct iwl_rx_mem_buffer *rxb)
 {
-	struct iwl_rx_packet *pkt = (void *)rxb->skb->data;
+	struct iwl_rx_packet *pkt = rxb_addr(rxb);
 	struct iwl_calib_hdr *hdr = (struct iwl_calib_hdr *)pkt->u.raw;
 	int len = le32_to_cpu(pkt->len_n_flags) & FH_RSCSR_FRAME_SIZE_MSK;
 	int index;
@@ -1143,7 +1143,7 @@ static int iwl5000_tx_status_reply_tx(struct iwl_priv *priv,
 static void iwl5000_rx_reply_tx(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);