[PATCH net-next v2 4/5] r8152: support skb_add_rx_frag

[Hayes Wang]

Use skb_add_rx_frag() to reduce the memory copy for rx data.

Use a new list of rx_used to store the rx buffer which couldn't be
reused yet.

Besides, the total number of rx buffer may be increased or decreased
dynamically. And it is limited by RTL8152_MAX_RX_AGG.

Signed-off-by: Hayes Wang <hayeswang@xxxxxxxxxxx>
---
 drivers/net/usb/r8152.c | 120 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 105 insertions(+), 15 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index f41cb728e999..2ae04522cd5a 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -584,6 +584,9 @@ enum rtl_register_content {
 #define TX_ALIGN		4
 #define RX_ALIGN		8
 
+#define RTL8152_MAX_RX_AGG	(10 * RTL8152_MAX_RX)
+#define RTL8152_RXFG_HEADSZ	256
+
 #define INTR_LINK		0x0004
 
 #define RTL8152_REQT_READ	0xc0
@@ -720,7 +723,7 @@ struct r8152 {
 	struct net_device *netdev;
 	struct urb *intr_urb;
 	struct tx_agg tx_info[RTL8152_MAX_TX];
-	struct list_head rx_info;
+	struct list_head rx_info, rx_used;
 	struct list_head rx_done, tx_free;
 	struct sk_buff_head tx_queue, rx_queue;
 	spinlock_t rx_lock, tx_lock;
@@ -1476,7 +1479,7 @@ static void free_rx_agg(struct r8152 *tp, struct rx_agg *agg)
 	list_del(&agg->info_list);
 
 	usb_free_urb(agg->urb);
-	__free_pages(agg->page, get_order(tp->rx_buf_sz));
+	put_page(agg->page);
 	kfree(agg);
 
 	atomic_dec(&tp->rx_count);
@@ -1494,7 +1497,7 @@ static struct rx_agg *alloc_rx_agg(struct r8152 *tp, gfp_t mflags)
 	if (!rx_agg)
 		return NULL;
 
-	rx_agg->page = alloc_pages(mflags, order);
+	rx_agg->page = alloc_pages(mflags | __GFP_COMP, order);
 	if (!rx_agg->page)
 		goto free_rx;
 
@@ -1947,6 +1950,46 @@ static u8 r8152_rx_csum(struct r8152 *tp, struct rx_desc *rx_desc)
 	return checksum;
 }
 
+static inline bool rx_count_exceed(struct r8152 *tp)
+{
+	return atomic_read(&tp->rx_count) > RTL8152_MAX_RX;
+}
+
+static inline int agg_offset(struct rx_agg *agg, void *addr)
+{
+	return (int)(addr - agg->buffer);
+}
+
+static struct rx_agg *rtl_get_free_rx(struct r8152 *tp, gfp_t mflags)
+{
+	struct rx_agg *agg, *agg_next, *agg_free = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tp->rx_lock, flags);
+
+	list_for_each_entry_safe(agg, agg_next, &tp->rx_used, list) {
+		if (page_count(agg->page) == 1) {
+			if (!agg_free) {
+				list_del_init(&agg->list);
+				agg_free = agg;
+				continue;
+			}
+			if (rx_count_exceed(tp)) {
+				list_del_init(&agg->list);
+				free_rx_agg(tp, agg);
+			}
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&tp->rx_lock, flags);
+
+	if (!agg_free && atomic_read(&tp->rx_count) < RTL8152_MAX_RX_AGG)
+		agg_free = alloc_rx_agg(tp, mflags);
+
+	return agg_free;
+}
+
 static int rx_bottom(struct r8152 *tp, int budget)
 {
 	unsigned long flags;
@@ -1982,7 +2025,7 @@ static int rx_bottom(struct r8152 *tp, int budget)
 
 	list_for_each_safe(cursor, next, &rx_queue) {
 		struct rx_desc *rx_desc;
-		struct rx_agg *agg;
+		struct rx_agg *agg, *agg_free;
 		int len_used = 0;
 		struct urb *urb;
 		u8 *rx_data;
@@ -1994,6 +2037,8 @@ static int rx_bottom(struct r8152 *tp, int budget)
 		if (urb->actual_length < ETH_ZLEN)
 			goto submit;
 
+		agg_free = rtl_get_free_rx(tp, GFP_ATOMIC);
+
 		rx_desc = agg->buffer;
 		rx_data = agg->buffer;
 		len_used += sizeof(struct rx_desc);
@@ -2001,7 +2046,7 @@ static int rx_bottom(struct r8152 *tp, int budget)
 		while (urb->actual_length > len_used) {
 			struct net_device *netdev = tp->netdev;
 			struct net_device_stats *stats = &netdev->stats;
-			unsigned int pkt_len;
+			unsigned int pkt_len, rx_frag_head_sz;
 			struct sk_buff *skb;
 
 			/* limite the skb numbers for rx_queue */
@@ -2019,22 +2064,37 @@ static int rx_bottom(struct r8152 *tp, int budget)
 			pkt_len -= ETH_FCS_LEN;
 			rx_data += sizeof(struct rx_desc);
 
-			skb = napi_alloc_skb(napi, pkt_len);
+			if (!agg_free || RTL8152_RXFG_HEADSZ > pkt_len)
+				rx_frag_head_sz = pkt_len;
+			else
+				rx_frag_head_sz = RTL8152_RXFG_HEADSZ;
+
+			skb = napi_alloc_skb(napi, rx_frag_head_sz);
 			if (!skb) {
 				stats->rx_dropped++;
 				goto find_next_rx;
 			}
 
 			skb->ip_summed = r8152_rx_csum(tp, rx_desc);
-			memcpy(skb->data, rx_data, pkt_len);
-			skb_put(skb, pkt_len);
+			memcpy(skb->data, rx_data, rx_frag_head_sz);
+			skb_put(skb, rx_frag_head_sz);
+			pkt_len -= rx_frag_head_sz;
+			rx_data += rx_frag_head_sz;
+			if (pkt_len) {
+				skb_add_rx_frag(skb, 0, agg->page,
+						agg_offset(agg, rx_data),
+						pkt_len,
+						SKB_DATA_ALIGN(pkt_len));
+				get_page(agg->page);
+			}
+
 			skb->protocol = eth_type_trans(skb, netdev);
 			rtl_rx_vlan_tag(rx_desc, skb);
 			if (work_done < budget) {
 				napi_gro_receive(napi, skb);
 				work_done++;
 				stats->rx_packets++;
-				stats->rx_bytes += pkt_len;
+				stats->rx_bytes += skb->len;
 			} else {
 				__skb_queue_tail(&tp->rx_queue, skb);
 			}
@@ -2042,10 +2102,24 @@ static int rx_bottom(struct r8152 *tp, int budget)
 find_next_rx:
 			rx_data = rx_agg_align(rx_data + pkt_len + ETH_FCS_LEN);
 			rx_desc = (struct rx_desc *)rx_data;
-			len_used = (int)(rx_data - (u8 *)agg->buffer);
+			len_used = agg_offset(agg, rx_data);
 			len_used += sizeof(struct rx_desc);
 		}
 
+		WARN_ON(!agg_free && page_count(agg->page) > 1);
+
+		if (agg_free) {
+			spin_lock_irqsave(&tp->rx_lock, flags);
+			if (page_count(agg->page) == 1) {
+				list_add(&agg_free->list, &tp->rx_used);
+			} else {
+				list_add_tail(&agg->list, &tp->rx_used);
+				agg = agg_free;
+				urb = agg->urb;
+			}
+			spin_unlock_irqrestore(&tp->rx_lock, flags);
+		}
+
 submit:
 		if (!ret) {
 			ret = r8152_submit_rx(tp, agg, GFP_ATOMIC);
@@ -2373,13 +2447,14 @@ static int rtl_start_rx(struct r8152 *tp)
 	struct rx_agg *agg, *agg_next;
 	struct list_head tmp_list;
 	unsigned long flags;
-	int ret = 0;
+	int ret = 0, i = 0;
 
 	INIT_LIST_HEAD(&tmp_list);
 
 	spin_lock_irqsave(&tp->rx_lock, flags);
 
 	INIT_LIST_HEAD(&tp->rx_done);
+	INIT_LIST_HEAD(&tp->rx_used);
 
 	list_splice_init(&tp->rx_info, &tmp_list);
 
@@ -2388,10 +2463,18 @@ static int rtl_start_rx(struct r8152 *tp)
 	list_for_each_entry_safe(agg, agg_next, &tmp_list, info_list) {
 		INIT_LIST_HEAD(&agg->list);
 
-		if (ret < 0)
+		/* Only RTL8152_MAX_RX rx_agg need to be submitted. */
+		if (++i > RTL8152_MAX_RX) {
+			spin_lock_irqsave(&tp->rx_lock, flags);
+			list_add_tail(&agg->list, &tp->rx_used);
+			spin_unlock_irqrestore(&tp->rx_lock, flags);
+		} else if (unlikely(ret < 0)) {
+			spin_lock_irqsave(&tp->rx_lock, flags);
 			list_add_tail(&agg->list, &tp->rx_done);
-		else
+			spin_unlock_irqrestore(&tp->rx_lock, flags);
+		} else {
 			ret = r8152_submit_rx(tp, agg, GFP_KERNEL);
+		}
 	}
 
 	spin_lock_irqsave(&tp->rx_lock, flags);
@@ -2420,8 +2503,15 @@ static int rtl_stop_rx(struct r8152 *tp)
 	list_splice_init(&tp->rx_info, &tmp_list);
 	spin_unlock_irqrestore(&tp->rx_lock, flags);
 
-	list_for_each_entry_safe(agg, agg_next, &tmp_list, info_list)
-		usb_kill_urb(agg->urb);
+	list_for_each_entry_safe(agg, agg_next, &tmp_list, info_list) {
+		/* At least RTL8152_MAX_RX rx_agg have the page_count being
+		 * equal to 1, so the other ones could be freed safely.
+		 */
+		if (page_count(agg->page) > 1)
+			free_rx_agg(tp, agg);
+		else
+			usb_kill_urb(agg->urb);
+	}
 
 	/* Move back the list of temp to the rx_info */
 	spin_lock_irqsave(&tp->rx_lock, flags);
-- 
2.21.0