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, 6 insertions, 15 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-hcmd.c b/drivers/net/wireless/iwlwifi/iwl-hcmd.c
index 532c8d6cd8da..22a21a1c7f49 100644
--- a/drivers/net/wireless/iwlwifi/iwl-hcmd.c
+++ b/drivers/net/wireless/iwlwifi/iwl-hcmd.c
@@ -103,17 +103,8 @@ EXPORT_SYMBOL(get_cmd_string);
 
 static void iwl_generic_cmd_callback(struct iwl_priv *priv,
                                      struct iwl_device_cmd *cmd,
-                                     struct sk_buff *skb)
+                                     struct iwl_rx_packet *pkt)
 {
-        struct iwl_rx_packet *pkt = NULL;
-
-        if (!skb) {
-                IWL_ERR(priv, "Error: Response NULL in %s.\n",
-                                get_cmd_string(cmd->hdr.cmd));
-                return;
-        }
-
-        pkt = (struct iwl_rx_packet *)skb->data;
         if (pkt->hdr.flags & IWL_CMD_FAILED_MSK) {
                 IWL_ERR(priv, "Bad return from %s (0x%08X)\n",
                         get_cmd_string(cmd->hdr.cmd), pkt->hdr.flags);
@@ -215,7 +206,7 @@ int iwl_send_cmd_sync(struct iwl_priv *priv, struct iwl_host_cmd *cmd)
                 ret = -EIO;
                 goto fail;
         }
-        if ((cmd->flags & CMD_WANT_SKB) && !cmd->reply_skb) {
+        if ((cmd->flags & CMD_WANT_SKB) && !cmd->reply_page) {
                 IWL_ERR(priv, "Error: Response NULL in '%s'\n",
                           get_cmd_string(cmd->id));
                 ret = -EIO;
@@ -237,9 +228,9 @@ cancel:
                                                         ~CMD_WANT_SKB;
         }
 fail:
-        if (cmd->reply_skb) {
-                dev_kfree_skb_any(cmd->reply_skb);
-                cmd->reply_skb = NULL;
+        if (cmd->reply_page) {
+                free_pages(cmd->reply_page, priv->hw_params.rx_page_order);
+                cmd->reply_page = 0;
         }
 out:
         clear_bit(STATUS_HCMD_SYNC_ACTIVE, &priv->status);
@@ -272,7 +263,7 @@ int iwl_send_cmd_pdu_async(struct iwl_priv *priv,
                            u8 id, u16 len, const void *data,
                            void (*callback)(struct iwl_priv *priv,
                                             struct iwl_device_cmd *cmd,
-                                            struct sk_buff *skb))
+                                            struct iwl_rx_packet *pkt))
 {
         struct iwl_host_cmd cmd = {
                 .id = id,