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, 59 insertions, 61 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c b/drivers/net/wireless/iwlwifi/iwl3945-base.c
index 515f29b8a7a7..5977a57a234c 100644
--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
@@ -745,7 +745,7 @@ static int iwl3945_get_measurement(struct iwl_priv *priv,
                                u8 type)
 {
         struct iwl_spectrum_cmd spectrum;
-        struct iwl_rx_packet *res;
+        struct iwl_rx_packet *pkt;
         struct iwl_host_cmd cmd = {
                 .id = REPLY_SPECTRUM_MEASUREMENT_CMD,
                 .data = (void *)&spectrum,
@@ -790,18 +790,18 @@ static int iwl3945_get_measurement(struct iwl_priv *priv,
         if (rc)
                 return rc;
 
-        res = (struct iwl_rx_packet *)cmd.reply_skb->data;
-        if (res->hdr.flags & IWL_CMD_FAILED_MSK) {
+        pkt = (struct iwl_rx_packet *)cmd.reply_page;
+        if (pkt->hdr.flags & IWL_CMD_FAILED_MSK) {
                 IWL_ERR(priv, "Bad return from REPLY_RX_ON_ASSOC command\n");
                 rc = -EIO;
         }
 
-        spectrum_resp_status = le16_to_cpu(res->u.spectrum.status);
+        spectrum_resp_status = le16_to_cpu(pkt->u.spectrum.status);
         switch (spectrum_resp_status) {
         case 0:         /* Command will be handled */
-                if (res->u.spectrum.id != 0xff) {
+                if (pkt->u.spectrum.id != 0xff) {
                         IWL_DEBUG_INFO(priv, "Replaced existing measurement: %d\n",
-                                                res->u.spectrum.id);
+                                                pkt->u.spectrum.id);
                         priv->measurement_status &= ~MEASUREMENT_READY;
                 }
                 priv->measurement_status |= MEASUREMENT_ACTIVE;
@@ -813,7 +813,7 @@ static int iwl3945_get_measurement(struct iwl_priv *priv,
                 break;
         }
 
-        dev_kfree_skb_any(cmd.reply_skb);
+        free_pages(cmd.reply_page, priv->hw_params.rx_page_order);
 
         return rc;
 }
@@ -822,7 +822,7 @@ static int iwl3945_get_measurement(struct iwl_priv *priv,
 static void iwl3945_rx_reply_alive(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_alive_resp *palive;
         struct delayed_work *pwork;
 
@@ -859,7 +859,7 @@ static void iwl3945_rx_reply_add_sta(struct iwl_priv *priv,
                                  struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-        struct iwl_rx_packet *pkt = (void *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
 #endif
 
         IWL_DEBUG_RX(priv, "Received REPLY_ADD_STA: 0x%02X\n", pkt->u.status);
@@ -895,7 +895,7 @@ static void iwl3945_rx_beacon_notif(struct iwl_priv *priv,
                                 struct iwl_rx_mem_buffer *rxb)
 {
 #ifdef CONFIG_IWLWIFI_DEBUG
-        struct iwl_rx_packet *pkt = (void *)rxb->skb->data;
+        struct iwl_rx_packet *pkt = rxb_addr(rxb);
         struct iwl3945_beacon_notif *beacon = &(pkt->u.beacon_status);
         u8 rate = beacon->beacon_notify_hdr.rate;
 
@@ -918,7 +918,7 @@ static void iwl3945_rx_beacon_notif(struct iwl_priv *priv,
 static void iwl3945_rx_card_state_notif(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);
         u32 flags = le32_to_cpu(pkt->u.card_state_notif.flags);
         unsigned long status = priv->status;
 
@@ -1082,7 +1082,7 @@ static int iwl3945_rx_queue_restock(struct iwl_priv *priv)
                 list_del(element);
 
                 /* Point to Rx buffer via next RBD in circular buffer */
-                rxq->bd[rxq->write] = iwl3945_dma_addr2rbd_ptr(priv, rxb->real_dma_addr);
+                rxq->bd[rxq->write] = iwl3945_dma_addr2rbd_ptr(priv, rxb->page_dma);
                 rxq->queue[rxq->write] = rxb;
                 rxq->write = (rxq->write + 1) & RX_QUEUE_MASK;
                 rxq->free_count--;
@@ -1122,7 +1122,7 @@ static void iwl3945_rx_allocate(struct iwl_priv *priv, gfp_t priority)
         struct iwl_rx_queue *rxq = &priv->rxq;
         struct list_head *element;
         struct iwl_rx_mem_buffer *rxb;
-        struct sk_buff *skb;
+        struct page *page;
         unsigned long flags;
 
         while (1) {
@@ -1136,9 +1136,13 @@ static void iwl3945_rx_allocate(struct iwl_priv *priv, gfp_t priority)
 
                 if (rxq->free_count > RX_LOW_WATERMARK)
                         priority |= __GFP_NOWARN;
+
+                if (priv->hw_params.rx_page_order > 0)
+                        priority |= __GFP_COMP;
+
                 /* Alloc a new receive buffer */
-                skb = alloc_skb(priv->hw_params.rx_buf_size, priority);
-                if (!skb) {
+                page = alloc_pages(priority, priv->hw_params.rx_page_order);
+                if (!page) {
                         if (net_ratelimit())
                                 IWL_DEBUG_INFO(priv, "Failed to allocate SKB buffer.\n");
                         if ((rxq->free_count <= RX_LOW_WATERMARK) &&
@@ -1155,7 +1159,7 @@ static void iwl3945_rx_allocate(struct iwl_priv *priv, gfp_t priority)
                 spin_lock_irqsave(&rxq->lock, flags);
                 if (list_empty(&rxq->rx_used)) {
                         spin_unlock_irqrestore(&rxq->lock, flags);
-                        dev_kfree_skb_any(skb);
+                        __free_pages(page, priv->hw_params.rx_page_order);
                         return;
                 }
                 element = rxq->rx_used.next;
@@ -1163,26 +1167,18 @@ static void iwl3945_rx_allocate(struct iwl_priv *priv, gfp_t priority)
                 list_del(element);
                 spin_unlock_irqrestore(&rxq->lock, flags);
 
-                rxb->skb = skb;
-
-                /* If radiotap head is required, reserve some headroom here.
-                 * The physical head count is a variable rx_stats->phy_count.
-                 * We reserve 4 bytes here. Plus these extra bytes, the
-                 * headroom of the physical head should be enough for the
-                 * radiotap head that iwl3945 supported. See iwl3945_rt.
-                 */
-                skb_reserve(rxb->skb, 4);
-
+                rxb->page = page;
                 /* Get physical address of RB/SKB */
-                rxb->real_dma_addr = pci_map_single(priv->pci_dev,
-                                                rxb->skb->data,
-                                                priv->hw_params.rx_buf_size,
-                                                PCI_DMA_FROMDEVICE);
+                rxb->page_dma = pci_map_page(priv->pci_dev, page, 0,
+                                PAGE_SIZE << priv->hw_params.rx_page_order,
+                                PCI_DMA_FROMDEVICE);
 
                 spin_lock_irqsave(&rxq->lock, flags);
+
                 list_add_tail(&rxb->list, &rxq->rx_free);
-                priv->alloc_rxb_skb++;
                 rxq->free_count++;
+                priv->alloc_rxb_page++;
+
                 spin_unlock_irqrestore(&rxq->lock, flags);
         }
 }
@@ -1198,14 +1194,14 @@ void iwl3945_rx_queue_reset(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
         for (i = 0; i < RX_FREE_BUFFERS + RX_QUEUE_SIZE; i++) {
                 /* In the reset function, these buffers may have been allocated
                  * to an SKB, so we need to unmap and free potential storage */
-                if (rxq->pool[i].skb != NULL) {
-                        pci_unmap_single(priv->pci_dev,
-                                         rxq->pool[i].real_dma_addr,
-                                         priv->hw_params.rx_buf_size,
-                                         PCI_DMA_FROMDEVICE);
-                        priv->alloc_rxb_skb--;
-                        dev_kfree_skb(rxq->pool[i].skb);
-                        rxq->pool[i].skb = NULL;
+                if (rxq->pool[i].page != NULL) {
+                        pci_unmap_page(priv->pci_dev, rxq->pool[i].page_dma,
+                                PAGE_SIZE << priv->hw_params.rx_page_order,
+                                PCI_DMA_FROMDEVICE);
+                        priv->alloc_rxb_page--;
+                        __free_pages(rxq->pool[i].page,
+                                     priv->hw_params.rx_page_order);
+                        rxq->pool[i].page = NULL;
                 }
                 list_add_tail(&rxq->pool[i].list, &rxq->rx_used);
         }
@@ -1213,8 +1209,8 @@ void iwl3945_rx_queue_reset(struct iwl_priv *priv, struct iwl_rx_queue *rxq)
         /* Set us so that we have processed and used all buffers, but have
          * not restocked the Rx queue with fresh buffers */
         rxq->read = rxq->write = 0;
-        rxq->free_count = 0;
         rxq->write_actual = 0;
+        rxq->free_count = 0;
         spin_unlock_irqrestore(&rxq->lock, flags);
 }
 
@@ -1247,12 +1243,14 @@ static void iwl3945_rx_queue_free(struct iwl_priv *priv, struct iwl_rx_queue *rx
 {
         int i;
         for (i = 0; i < RX_QUEUE_SIZE + RX_FREE_BUFFERS; i++) {
-                if (rxq->pool[i].skb != NULL) {
-                        pci_unmap_single(priv->pci_dev,
-                                         rxq->pool[i].real_dma_addr,
-                                         priv->hw_params.rx_buf_size,
-                                         PCI_DMA_FROMDEVICE);
-                        dev_kfree_skb(rxq->pool[i].skb);
+                if (rxq->pool[i].page != NULL) {
+                        pci_unmap_page(priv->pci_dev, rxq->pool[i].page_dma,
+                                PAGE_SIZE << priv->hw_params.rx_page_order,
+                                PCI_DMA_FROMDEVICE);
+                        __free_pages(rxq->pool[i].page,
+                                     priv->hw_params.rx_page_order);
+                        rxq->pool[i].page = NULL;
+                        priv->alloc_rxb_page--;
                 }
         }
 
@@ -1388,10 +1386,10 @@ static void iwl3945_rx_handle(struct iwl_priv *priv)
 
                 rxq->queue[i] = NULL;
 
-                pci_unmap_single(priv->pci_dev, rxb->real_dma_addr,
-                                priv->hw_params.rx_buf_size,
-                                PCI_DMA_FROMDEVICE);
-                pkt = (struct iwl_rx_packet *)rxb->skb->data;
+                pci_unmap_page(priv->pci_dev, rxb->page_dma,
+                               PAGE_SIZE << priv->hw_params.rx_page_order,
+                               PCI_DMA_FROMDEVICE);
+                pkt = rxb_addr(rxb);
 
                 trace_iwlwifi_dev_rx(priv, pkt,
                         le32_to_cpu(pkt->len_n_flags) & FH_RSCSR_FRAME_SIZE_MSK);
@@ -1416,16 +1414,17 @@ static void iwl3945_rx_handle(struct iwl_priv *priv)
                         priv->isr_stats.rx_handlers[pkt->hdr.cmd]++;
                 } else {
                         /* No handling needed */
-                        IWL_DEBUG_RX(priv, "r %d i %d No handler needed for %s, 0x%02x\n",
+                        IWL_DEBUG_RX(priv,
+                                "r %d i %d No handler needed for %s, 0x%02x\n",
                                 r, i, get_cmd_string(pkt->hdr.cmd),
                                 pkt->hdr.cmd);
                 }
 
                 if (reclaim) {
-                        /* Invoke any callbacks, transfer the skb to caller, and
-                         * fire off the (possibly) blocking iwl_send_cmd()
+                        /* Invoke any callbacks, transfer the buffer to caller,
+                         * and fire off the (possibly) blocking iwl_send_cmd()
                          * as we reclaim the driver command queue */
-                        if (rxb && rxb->skb)
+                        if (rxb && rxb->page)
                                 iwl_tx_cmd_complete(priv, rxb);
                         else
                                 IWL_WARN(priv, "Claim null rxb?\n");
@@ -1434,10 +1433,10 @@ static void iwl3945_rx_handle(struct iwl_priv *priv)
                 /* For now we just don't re-use anything.  We can tweak this
                  * later to try and re-use notification packets and SKBs that
                  * fail to Rx correctly */
-                if (rxb->skb != NULL) {
-                        priv->alloc_rxb_skb--;
-                        dev_kfree_skb_any(rxb->skb);
-                        rxb->skb = NULL;
+                if (rxb->page != NULL) {
+                        priv->alloc_rxb_page--;
+                        __free_pages(rxb->page, priv->hw_params.rx_page_order);
+                        rxb->page = NULL;
                 }
 
                 spin_lock_irqsave(&rxq->lock, flags);
@@ -1678,6 +1677,8 @@ static void iwl3945_irq_tasklet(struct iwl_priv *priv)
         }
 #endif
 
+        spin_unlock_irqrestore(&priv->lock, flags);
+
         /* Since CSR_INT and CSR_FH_INT_STATUS reads and clears are not
          * atomic, make sure that inta covers all the interrupts that
          * we've discovered, even if FH interrupt came in just after
@@ -1699,8 +1700,6 @@ static void iwl3945_irq_tasklet(struct iwl_priv *priv)
 
                 handled |= CSR_INT_BIT_HW_ERR;
 
-                spin_unlock_irqrestore(&priv->lock, flags);
-
                 return;
         }
 
@@ -1792,7 +1791,6 @@ static void iwl3945_irq_tasklet(struct iwl_priv *priv)
                         "flags 0x%08lx\n", inta, inta_mask, inta_fh, flags);
         }
 #endif
-        spin_unlock_irqrestore(&priv->lock, flags);
 }
 
 static int iwl3945_get_channels_for_scan(struct iwl_priv *priv,