[PATCH net] i40e: sync next_to_clean and next_to_process for programming status desc

[Tirthendu Sarkar <tirthendu.sarkar@intel.com>]

When a programming status desc is encountered on the rx_ring,
next_to_process is bumped along with cleaned_count but next_to_clean is
not. This causes I40E_DESC_UNUSED() macro to misbehave resulting in
overwriting whole ring with new buffers.

Update next_to_clean to point to next_to_process on seeing a programming
status desc if not in the middle of handling a multi-frag packet. Also,
bump cleaned_count only for such case as otherwise next_to_clean buffer
may be returned to hardware on reaching clean_threshold.

Fixes: e9031f2da1ae ("i40e: introduce next_to_process to i40e_ring")
Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reported-by: hq.dev+kernel@msdfc.xyz
Reported by: Solomon Peachy <pizza@shaftnet.org>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217678
Tested-by: hq.dev+kernel@msdfc.xyz
Tested by: Indrek Järve <incx@dustbite.net>
Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@intel.com>
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 0b3a27f118fb..50c70a8e470a 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -2544,7 +2544,14 @@ static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget,
 			rx_buffer = i40e_rx_bi(rx_ring, ntp);
 			i40e_inc_ntp(rx_ring);
 			i40e_reuse_rx_page(rx_ring, rx_buffer);
-			cleaned_count++;
+			/* Update ntc and bump cleaned count if not in the
+			 * middle of mb packet.
+			 */
+			if (rx_ring->next_to_clean == ntp) {
+				rx_ring->next_to_clean =
+					rx_ring->next_to_process;
+				cleaned_count++;
+			}
 			continue;
 		}
 
-- 
2.34.1