sfc: Reduce size of efx_rx_buffer by unionising skb and page

[bwh: Forward-ported to net-next-2.6.]
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

diff --git a/drivers/net/sfc/net_driver.h b/drivers/net/sfc/net_driver.h
index 15b9068..59ff32a 100644 (file)
--- a/drivers/net/sfc/net_driver.h
+++ b/drivers/net/sfc/net_driver.h
@@ -216,13 +216,17 @@ struct efx_tx_queue {
  *     If both this and skb are %NULL, the buffer slot is currently free.
  * @data: Pointer to ethernet header
  * @len: Buffer length, in bytes.
+ * @is_page: Indicates if @page is valid. If false, @skb is valid.
  */
 struct efx_rx_buffer {
        dma_addr_t dma_addr;
-       struct sk_buff *skb;
-       struct page *page;
+       union {
+               struct sk_buff *skb;
+               struct page *page;
+       } u;
        char *data;
        unsigned int len;
+       bool is_page;
 };
 
 /**

diff --git a/drivers/net/sfc/rx.c b/drivers/net/sfc/rx.c
index 3925fd6..bcbd2ec 100644 (file)
--- a/drivers/net/sfc/rx.c
+++ b/drivers/net/sfc/rx.c
@@ -129,6 +129,7 @@ static int efx_init_rx_buffers_skb(struct efx_rx_queue *rx_queue)
        struct efx_nic *efx = rx_queue->efx;
        struct net_device *net_dev = efx->net_dev;
        struct efx_rx_buffer *rx_buf;
+       struct sk_buff *skb;
        int skb_len = efx->rx_buffer_len;
        unsigned index, count;
 
@@ -136,24 +137,24 @@ static int efx_init_rx_buffers_skb(struct efx_rx_queue *rx_queue)
                index = rx_queue->added_count & rx_queue->ptr_mask;
                rx_buf = efx_rx_buffer(rx_queue, index);
 
-               rx_buf->skb = netdev_alloc_skb(net_dev, skb_len);
-               if (unlikely(!rx_buf->skb))
+               rx_buf->u.skb = skb = netdev_alloc_skb(net_dev, skb_len);
+               if (unlikely(!skb))
                        return -ENOMEM;
-               rx_buf->page = NULL;
 
                /* Adjust the SKB for padding and checksum */
-               skb_reserve(rx_buf->skb, NET_IP_ALIGN);
+               skb_reserve(skb, NET_IP_ALIGN);
+               rx_buf->data = (char *)skb->data;
                rx_buf->len = skb_len - NET_IP_ALIGN;
-               rx_buf->data = (char *)rx_buf->skb->data;
-               rx_buf->skb->ip_summed = CHECKSUM_UNNECESSARY;
+               rx_buf->is_page = false;
+               skb->ip_summed = CHECKSUM_UNNECESSARY;
 
                rx_buf->dma_addr = pci_map_single(efx->pci_dev,
                                                  rx_buf->data, rx_buf->len,
                                                  PCI_DMA_FROMDEVICE);
                if (unlikely(pci_dma_mapping_error(efx->pci_dev,
                                                   rx_buf->dma_addr))) {
-                       dev_kfree_skb_any(rx_buf->skb);
-                       rx_buf->skb = NULL;
+                       dev_kfree_skb_any(skb);
+                       rx_buf->u.skb = NULL;
                        return -EIO;
                }
 
@@ -211,10 +212,10 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
                index = rx_queue->added_count & rx_queue->ptr_mask;
                rx_buf = efx_rx_buffer(rx_queue, index);
                rx_buf->dma_addr = dma_addr + EFX_PAGE_IP_ALIGN;
-               rx_buf->skb = NULL;
-               rx_buf->page = page;
+               rx_buf->u.page = page;
                rx_buf->data = page_addr + EFX_PAGE_IP_ALIGN;
                rx_buf->len = efx->rx_buffer_len - EFX_PAGE_IP_ALIGN;
+               rx_buf->is_page = true;
                ++rx_queue->added_count;
                ++rx_queue->alloc_page_count;
                ++state->refcnt;
@@ -235,19 +236,17 @@ static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
 static void efx_unmap_rx_buffer(struct efx_nic *efx,
                                struct efx_rx_buffer *rx_buf)
 {
-       if (rx_buf->page) {
+       if (rx_buf->is_page && rx_buf->u.page) {
                struct efx_rx_page_state *state;
 
-               EFX_BUG_ON_PARANOID(rx_buf->skb);
-
-               state = page_address(rx_buf->page);
+               state = page_address(rx_buf->u.page);
                if (--state->refcnt == 0) {
                        pci_unmap_page(efx->pci_dev,
                                       state->dma_addr,
                                       efx_rx_buf_size(efx),
                                       PCI_DMA_FROMDEVICE);
                }
-       } else if (likely(rx_buf->skb)) {
+       } else if (!rx_buf->is_page && rx_buf->u.skb) {
                pci_unmap_single(efx->pci_dev, rx_buf->dma_addr,
                                 rx_buf->len, PCI_DMA_FROMDEVICE);
        }
@@ -256,12 +255,12 @@ static void efx_unmap_rx_buffer(struct efx_nic *efx,
 static void efx_free_rx_buffer(struct efx_nic *efx,
                               struct efx_rx_buffer *rx_buf)
 {
-       if (rx_buf->page) {
-               __free_pages(rx_buf->page, efx->rx_buffer_order);
-               rx_buf->page = NULL;
-       } else if (likely(rx_buf->skb)) {
-               dev_kfree_skb_any(rx_buf->skb);
-               rx_buf->skb = NULL;
+       if (rx_buf->is_page && rx_buf->u.page) {
+               __free_pages(rx_buf->u.page, efx->rx_buffer_order);
+               rx_buf->u.page = NULL;
+       } else if (!rx_buf->is_page && rx_buf->u.skb) {
+               dev_kfree_skb_any(rx_buf->u.skb);
+               rx_buf->u.skb = NULL;
        }
 }
 
@@ -277,7 +276,7 @@ static void efx_fini_rx_buffer(struct efx_rx_queue *rx_queue,
 static void efx_resurrect_rx_buffer(struct efx_rx_queue *rx_queue,
                                    struct efx_rx_buffer *rx_buf)
 {
-       struct efx_rx_page_state *state = page_address(rx_buf->page);
+       struct efx_rx_page_state *state = page_address(rx_buf->u.page);
        struct efx_rx_buffer *new_buf;
        unsigned fill_level, index;
 
@@ -292,16 +291,16 @@ static void efx_resurrect_rx_buffer(struct efx_rx_queue *rx_queue,
        }
 
        ++state->refcnt;
-       get_page(rx_buf->page);
+       get_page(rx_buf->u.page);
 
        index = rx_queue->added_count & rx_queue->ptr_mask;
        new_buf = efx_rx_buffer(rx_queue, index);
        new_buf->dma_addr = rx_buf->dma_addr ^ (PAGE_SIZE >> 1);
-       new_buf->skb = NULL;
-       new_buf->page = rx_buf->page;
+       new_buf->u.page = rx_buf->u.page;
        new_buf->data = (void *)
                ((__force unsigned long)rx_buf->data ^ (PAGE_SIZE >> 1));
        new_buf->len = rx_buf->len;
+       new_buf->is_page = true;
        ++rx_queue->added_count;
 }
 
@@ -315,16 +314,15 @@ static void efx_recycle_rx_buffer(struct efx_channel *channel,
        struct efx_rx_buffer *new_buf;
        unsigned index;
 
-       if (rx_buf->page != NULL && efx->rx_buffer_len <= EFX_RX_HALF_PAGE &&
-           page_count(rx_buf->page) == 1)
+       if (rx_buf->is_page && efx->rx_buffer_len <= EFX_RX_HALF_PAGE &&
+           page_count(rx_buf->u.page) == 1)
                efx_resurrect_rx_buffer(rx_queue, rx_buf);
 
        index = rx_queue->added_count & rx_queue->ptr_mask;
        new_buf = efx_rx_buffer(rx_queue, index);
 
        memcpy(new_buf, rx_buf, sizeof(*new_buf));
-       rx_buf->page = NULL;
-       rx_buf->skb = NULL;
+       rx_buf->u.page = NULL;
        ++rx_queue->added_count;
 }
 
@@ -428,7 +426,7 @@ static void efx_rx_packet__check_len(struct efx_rx_queue *rx_queue,
                 * data at the end of the skb will be trashed. So
                 * we have no choice but to leak the fragment.
                 */
-               *leak_packet = (rx_buf->skb != NULL);
+               *leak_packet = !rx_buf->is_page;
                efx_schedule_reset(efx, RESET_TYPE_RX_RECOVERY);
        } else {
                if (net_ratelimit())
@@ -454,13 +452,12 @@ static void efx_rx_packet_gro(struct efx_channel *channel,
        gro_result_t gro_result;
 
        /* Pass the skb/page into the GRO engine */
-       if (rx_buf->page) {
+       if (rx_buf->is_page) {
                struct efx_nic *efx = channel->efx;
-               struct page *page = rx_buf->page;
+               struct page *page = rx_buf->u.page;
                struct sk_buff *skb;
 
-               EFX_BUG_ON_PARANOID(rx_buf->skb);
-               rx_buf->page = NULL;
+               rx_buf->u.page = NULL;
 
                skb = napi_get_frags(napi);
                if (!skb) {
@@ -487,11 +484,10 @@ static void efx_rx_packet_gro(struct efx_channel *channel,
 
                gro_result = napi_gro_frags(napi);
        } else {
-               struct sk_buff *skb = rx_buf->skb;
+               struct sk_buff *skb = rx_buf->u.skb;
 
-               EFX_BUG_ON_PARANOID(!skb);
                EFX_BUG_ON_PARANOID(!checksummed);
-               rx_buf->skb = NULL;
+               rx_buf->u.skb = NULL;
 
                gro_result = napi_gro_receive(napi, skb);
        }
@@ -514,8 +510,6 @@ void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
 
        rx_buf = efx_rx_buffer(rx_queue, index);
        EFX_BUG_ON_PARANOID(!rx_buf->data);
-       EFX_BUG_ON_PARANOID(rx_buf->skb && rx_buf->page);
-       EFX_BUG_ON_PARANOID(!(rx_buf->skb || rx_buf->page));
 
        /* This allows the refill path to post another buffer.
         * EFX_RXD_HEAD_ROOM ensures that the slot we are using
@@ -587,32 +581,32 @@ void __efx_rx_packet(struct efx_channel *channel,
                return;
        }
 
-       if (rx_buf->skb) {
-               prefetch(skb_shinfo(rx_buf->skb));
+       if (!rx_buf->is_page) {
+               skb = rx_buf->u.skb;
+
+               prefetch(skb_shinfo(skb));
 
-               skb_reserve(rx_buf->skb, efx->type->rx_buffer_hash_size);
-               skb_put(rx_buf->skb, rx_buf->len);
+               skb_reserve(skb, efx->type->rx_buffer_hash_size);
+               skb_put(skb, rx_buf->len);
 
                if (efx->net_dev->features & NETIF_F_RXHASH)
-                       rx_buf->skb->rxhash = efx_rx_buf_hash(rx_buf);
+                       skb->rxhash = efx_rx_buf_hash(rx_buf);
 
                /* Move past the ethernet header. rx_buf->data still points
                 * at the ethernet header */
-               rx_buf->skb->protocol = eth_type_trans(rx_buf->skb,
-                                                      efx->net_dev);
+               skb->protocol = eth_type_trans(skb, efx->net_dev);
 
-               skb_record_rx_queue(rx_buf->skb, channel->channel);
+               skb_record_rx_queue(skb, channel->channel);
        }
 
-       if (likely(checksummed || rx_buf->page)) {
+       if (likely(checksummed || rx_buf->is_page)) {
                efx_rx_packet_gro(channel, rx_buf, checksummed);
                return;
        }
 
        /* We now own the SKB */
-       skb = rx_buf->skb;
-       rx_buf->skb = NULL;
-       EFX_BUG_ON_PARANOID(!skb);
+       skb = rx_buf->u.skb;
+       rx_buf->u.skb = NULL;
 
        /* Set the SKB flags */
        skb_checksum_none_assert(skb);