i40e: add pre-xdp page_count in rx_buffer

Page count of rx_buffer needs to be stored prior to XDP call to prevent
page recycling in case that buffer would be freed within xdp redirect
path. Instead of storing it on the stack, now it is stored in the
rx_buffer struct. This will help in processing multi-buffers as the page
counts of all rx_buffers (of the same packet) don't need to be stored on
stack.

Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
Tested-by: Chandan Kumar Rout <chandanx.rout@intel.com> (A Contingent Worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1970,7 +1970,6 @@ static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb,
  * i40e_can_reuse_rx_page - Determine if page can be reused for another Rx
  * @rx_buffer: buffer containing the page
  * @rx_stats: rx stats structure for the rx ring
- * @rx_buffer_pgcnt: buffer page refcount pre xdp_do_redirect() call
  *
  * If page is reusable, we have a green light for calling i40e_reuse_rx_page,
  * which will assign the current buffer to the buffer that next_to_alloc is
@@ -1981,8 +1980,7 @@ static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb,
  * or busy if it could not be reused.
  */
 static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
-				   struct i40e_rx_queue_stats *rx_stats,
-				   int rx_buffer_pgcnt)
+				   struct i40e_rx_queue_stats *rx_stats)
 {
 	unsigned int pagecnt_bias = rx_buffer->pagecnt_bias;
 	struct page *page = rx_buffer->page;
@@ -1995,7 +1993,7 @@ static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer,
 
 #if (PAGE_SIZE < 8192)
 	/* if we are only owner of page we can reuse it */
-	if (unlikely((rx_buffer_pgcnt - pagecnt_bias) > 1)) {
+	if (unlikely((rx_buffer->page_count - pagecnt_bias) > 1)) {
 		rx_stats->page_busy_count++;
 		return false;
 	}
@@ -2058,19 +2056,17 @@ static void i40e_add_rx_frag(struct i40e_ring *rx_ring,
  * i40e_get_rx_buffer - Fetch Rx buffer and synchronize data for use
  * @rx_ring: rx descriptor ring to transact packets on
  * @size: size of buffer to add to skb
- * @rx_buffer_pgcnt: buffer page refcount
  *
  * This function will pull an Rx buffer from the ring and synchronize it
  * for use by the CPU.
  */
 static struct i40e_rx_buffer *i40e_get_rx_buffer(struct i40e_ring *rx_ring,
-						 const unsigned int size,
-						 int *rx_buffer_pgcnt)
+						 const unsigned int size)
 {
 	struct i40e_rx_buffer *rx_buffer;
 
 	rx_buffer = i40e_rx_bi(rx_ring, rx_ring->next_to_clean);
-	*rx_buffer_pgcnt =
+	rx_buffer->page_count =
 #if (PAGE_SIZE < 8192)
 		page_count(rx_buffer->page);
 #else
@@ -2226,16 +2222,14 @@ static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
  * i40e_put_rx_buffer - Clean up used buffer and either recycle or free
  * @rx_ring: rx descriptor ring to transact packets on
  * @rx_buffer: rx buffer to pull data from
- * @rx_buffer_pgcnt: rx buffer page refcount pre xdp_do_redirect() call
  *
  * This function will clean up the contents of the rx_buffer.  It will
  * either recycle the buffer or unmap it and free the associated resources.
  */
 static void i40e_put_rx_buffer(struct i40e_ring *rx_ring,
-			       struct i40e_rx_buffer *rx_buffer,
-			       int rx_buffer_pgcnt)
+			       struct i40e_rx_buffer *rx_buffer)
 {
-	if (i40e_can_reuse_rx_page(rx_buffer, &rx_ring->rx_stats, rx_buffer_pgcnt)) {
+	if (i40e_can_reuse_rx_page(rx_buffer, &rx_ring->rx_stats)) {
 		/* hand second half of page back to the ring */
 		i40e_reuse_rx_page(rx_ring, rx_buffer);
 	} else {
@@ -2457,7 +2451,6 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 	while (likely(total_rx_packets < (unsigned int)budget)) {
 		struct i40e_rx_buffer *rx_buffer;
 		union i40e_rx_desc *rx_desc;
-		int rx_buffer_pgcnt;
 		unsigned int size;
 		u64 qword;
 
@@ -2500,7 +2493,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 			break;
 
 		i40e_trace(clean_rx_irq, rx_ring, rx_desc, skb);
-		rx_buffer = i40e_get_rx_buffer(rx_ring, size, &rx_buffer_pgcnt);
+		rx_buffer = i40e_get_rx_buffer(rx_ring, size);
 
 		/* retrieve a buffer from the ring */
 		if (!skb) {
@@ -2541,7 +2534,7 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 			break;
 		}
 
-		i40e_put_rx_buffer(rx_ring, rx_buffer, rx_buffer_pgcnt);
+		i40e_put_rx_buffer(rx_ring, rx_buffer);
 		cleaned_count++;
 
 		i40e_inc_ntc(rx_ring);

drivers/net/ethernet/intel/i40e/i40e_txrx.h

@@ -277,6 +277,7 @@ struct i40e_rx_buffer {
 	struct page *page;
 	__u32 page_offset;
 	__u16 pagecnt_bias;
+	__u32 page_count;
 };
 
 struct i40e_queue_stats {