The common code with some packet and index manipulations is extracted and
moved to newly implemented helper to make the code more readable and avoid
duplication. This is a preparation for skb allocation failure handling.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Suggested-by: Simon Horman <horms@kernel.org>
Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
---
Compile tested only.

v4:
  - Split patch up as suggested by Jakub
    (https://lore.kernel.org/all/20241004073311.223efca4@kernel.org/)
v3: https://lore.kernel.org/all/20240930053328.9618-1-amishin@t-argos.ru/
  - Implement helper which frees current packet resources and increase
    index and descriptor as suggested by Simon
    (https://lore.kernel.org/all/20240919134812.GB1571683@kernel.org/)
  - v3 has been reviewed-by Simon Horman
    (https://lore.kernel.org/all/20240930162622.GF1310185@kernel.org/)
v1: https://lore.kernel.org/all/20240906063907.9591-1-amishin@t-argos.ru/

 .../net/ethernet/marvell/octeon_ep/octep_rx.c | 55 +++++++++++--------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
index 4746a6b258f0..62db101b2147 100644
--- a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
+++ b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
@@ -336,6 +336,30 @@ static int octep_oq_check_hw_for_pkts(struct octep_device *oct,
 	return new_pkts;
 }
 
+/**
+ * octep_oq_next_pkt() - Move to the next packet in Rx queue.
+ *
+ * @oq: Octeon Rx queue data structure.
+ * @buff_info: Current packet buffer info.
+ * @read_idx: Current packet index in the ring.
+ * @desc_used: Current packet descriptor number.
+ *
+ * Free the resources associated with a packet.
+ * Increment packet index in the ring and packet descriptor number.
+ */
+static void octep_oq_next_pkt(struct octep_oq *oq,
+			      struct octep_rx_buffer *buff_info,
+			      u32 *read_idx, u32 *desc_used)
+{
+	dma_unmap_page(oq->dev, oq->desc_ring[*read_idx].buffer_ptr,
+		       PAGE_SIZE, DMA_FROM_DEVICE);
+	buff_info->page = NULL;
+	(*read_idx)++;
+	(*desc_used)++;
+	if (*read_idx == oq->max_count)
+		*read_idx = 0;
+}
+
 /**
  * __octep_oq_process_rx() - Process hardware Rx queue and push to stack.
  *
@@ -367,10 +391,7 @@ static int __octep_oq_process_rx(struct octep_device *oct,
 	desc_used = 0;
 	for (pkt = 0; pkt < pkts_to_process; pkt++) {
 		buff_info = (struct octep_rx_buffer *)&oq->buff_info[read_idx];
-		dma_unmap_page(oq->dev, oq->desc_ring[read_idx].buffer_ptr,
-			       PAGE_SIZE, DMA_FROM_DEVICE);
 		resp_hw = page_address(buff_info->page);
-		buff_info->page = NULL;
 
 		/* Swap the length field that is in Big-Endian to CPU */
 		buff_info->len = be64_to_cpu(resp_hw->length);
@@ -394,36 +415,27 @@ static int __octep_oq_process_rx(struct octep_device *oct,
 			data_offset = OCTEP_OQ_RESP_HW_SIZE;
 			rx_ol_flags = 0;
 		}
+
+		skb = build_skb((void *)resp_hw, PAGE_SIZE);
+		skb_reserve(skb, data_offset);
+
+		octep_oq_next_pkt(oq, buff_info, &read_idx, &desc_used);
+
 		rx_bytes += buff_info->len;
 
 		if (buff_info->len <= oq->max_single_buffer_size) {
-			skb = build_skb((void *)resp_hw, PAGE_SIZE);
-			skb_reserve(skb, data_offset);
 			skb_put(skb, buff_info->len);
-			read_idx++;
-			desc_used++;
-			if (read_idx == oq->max_count)
-				read_idx = 0;
 		} else {
 			struct skb_shared_info *shinfo;
 			u16 data_len;
 
-			skb = build_skb((void *)resp_hw, PAGE_SIZE);
-			skb_reserve(skb, data_offset);
 			/* Head fragment includes response header(s);
 			 * subsequent fragments contains only data.
 			 */
 			skb_put(skb, oq->max_single_buffer_size);
-			read_idx++;
-			desc_used++;
-			if (read_idx == oq->max_count)
-				read_idx = 0;
-
 			shinfo = skb_shinfo(skb);
 			data_len = buff_info->len - oq->max_single_buffer_size;
 			while (data_len) {
-				dma_unmap_page(oq->dev, oq->desc_ring[read_idx].buffer_ptr,
-					       PAGE_SIZE, DMA_FROM_DEVICE);
 				buff_info = (struct octep_rx_buffer *)
 					    &oq->buff_info[read_idx];
 				if (data_len < oq->buffer_size) {
@@ -438,11 +450,8 @@ static int __octep_oq_process_rx(struct octep_device *oct,
 						buff_info->page, 0,
 						buff_info->len,
 						buff_info->len);
-				buff_info->page = NULL;
-				read_idx++;
-				desc_used++;
-				if (read_idx == oq->max_count)
-					read_idx = 0;
+
+				octep_oq_next_pkt(oq, buff_info, &read_idx, &desc_used);
 			}
 		}
 
-- 
2.30.2

On 10/12/24 11:49, Aleksandr Mishin wrote:
> diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
> index 4746a6b258f0..62db101b2147 100644
> --- a/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
> +++ b/drivers/net/ethernet/marvell/octeon_ep/octep_rx.c
> @@ -336,6 +336,30 @@ static int octep_oq_check_hw_for_pkts(struct octep_device *oct,
>   	return new_pkts;
>   }
>   
> +/**
> + * octep_oq_next_pkt() - Move to the next packet in Rx queue.
> + *
> + * @oq: Octeon Rx queue data structure.
> + * @buff_info: Current packet buffer info.
> + * @read_idx: Current packet index in the ring.
> + * @desc_used: Current packet descriptor number.
> + *
> + * Free the resources associated with a packet.
> + * Increment packet index in the ring and packet descriptor number.
> + */
> +static void octep_oq_next_pkt(struct octep_oq *oq,
> +			      struct octep_rx_buffer *buff_info,
> +			      u32 *read_idx, u32 *desc_used)
> +{
> +	dma_unmap_page(oq->dev, oq->desc_ring[*read_idx].buffer_ptr,
> +		       PAGE_SIZE, DMA_FROM_DEVICE);
> +	buff_info->page = NULL;
> +	(*read_idx)++;
> +	(*desc_used)++;
> +	if (*read_idx == oq->max_count)
> +		*read_idx = 0;
> +}
> +
>   /**
>    * __octep_oq_process_rx() - Process hardware Rx queue and push to stack.
>    *
> @@ -367,10 +391,7 @@ static int __octep_oq_process_rx(struct octep_device *oct,
>   	desc_used = 0;
>   	for (pkt = 0; pkt < pkts_to_process; pkt++) {
>   		buff_info = (struct octep_rx_buffer *)&oq->buff_info[read_idx];
> -		dma_unmap_page(oq->dev, oq->desc_ring[read_idx].buffer_ptr,
> -			       PAGE_SIZE, DMA_FROM_DEVICE);
>   		resp_hw = page_address(buff_info->page);
> -		buff_info->page = NULL;
>   
>   		/* Swap the length field that is in Big-Endian to CPU */
>   		buff_info->len = be64_to_cpu(resp_hw->length);
> @@ -394,36 +415,27 @@ static int __octep_oq_process_rx(struct octep_device *oct,
>   			data_offset = OCTEP_OQ_RESP_HW_SIZE;
>   			rx_ol_flags = 0;
>   		}
> +
> +		skb = build_skb((void *)resp_hw, PAGE_SIZE);
> +		skb_reserve(skb, data_offset);
> +
> +		octep_oq_next_pkt(oq, buff_info, &read_idx, &desc_used);

I'm sorry for not catching the following in the previous iteration (the 
split indeed helped with the review):

build_skb() will write into the paged buffer, I think you should unmap 
it with octep_oq_next_pkt() before the skb creation.

That in turn will have side effect on the following patch (the 'do {} 
while' loop should become a plain 'while' one).

Thanks,

Paolo