net: macb: Increment rx bd head after allocating skb and buffer

stable inclusion
from stable-v5.10.118
commit 1bc27eb71b55e738d5e54ee16a7c561b30441cf5
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L686

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1bc27eb71b55e738d5e54ee16a7c561b30441cf5

--------------------------------

[ Upstream commit 9500acc6 ]

In gem_rx_refill rx_prepared_head is incremented at the beginning of
the while loop preparing the skb and data buffers. If the skb or data
buffer allocation fails, this BD will be unusable BDs until the head
loops back to the same BD (and obviously buffer allocation succeeds).
In the unlikely event that there's a string of allocation failures,
there will be an equal number of unusable BDs and an inconsistent RX
BD chain. Hence increment the head at the end of the while loop to be
clean.

Fixes: 4df95131 ("net/macb: change RX path for GEM")
Signed-off-by: NHarini Katakam <harini.katakam@xilinx.com>
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NRadhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Reviewed-by: NClaudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220512171900.32593-1-harini.katakam@xilinx.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

drivers/net/ethernet/cadence/macb_main.c

@@ -1092,7 +1092,6 @@ static void gem_rx_refill(struct macb_queue *queue)
 		/* Make hw descriptor updates visible to CPU */
 		rmb();
 
-		queue->rx_prepared_head++;
 		desc = macb_rx_desc(queue, entry);
 
 		if (!queue->rx_skbuff[entry]) {
@@ -1131,6 +1130,7 @@ static void gem_rx_refill(struct macb_queue *queue)
 			dma_wmb();
 			desc->addr &= ~MACB_BIT(RX_USED);
 		}
+		queue->rx_prepared_head++;
 	}
 
 	/* Make descriptor updates visible to hardware */