From: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Date: Tue, 11 Dec 2018 02:43:07 +0000 (+0900)
Subject: tun: replace get_cpu_ptr with this_cpu_ptr when bh disabled
X-Git-Tag: v5.4-rc1~1957^2~100
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6342ca644713601b42dcb8f35e3751afc0943373;p=platform%2Fkernel%2Flinux-rpi.git

tun: replace get_cpu_ptr with this_cpu_ptr when bh disabled

tun_xdp_one() runs with local bh disabled. So there is no need to
disable preemption by calling get_cpu_ptr while updating stats. This
patch replaces the use of get_cpu_ptr() with this_cpu_ptr() as a
micro-optimization. Also removes related put_cpu_ptr call.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 72577aa..a4fdad4 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2495,12 +2495,14 @@ build:
 	skb_record_rx_queue(skb, tfile->queue_index);
 	netif_receive_skb(skb);
 
-	stats = get_cpu_ptr(tun->pcpu_stats);
+	/* No need for get_cpu_ptr() here since this function is
+	 * always called with bh disabled
+	 */
+	stats = this_cpu_ptr(tun->pcpu_stats);
 	u64_stats_update_begin(&stats->syncp);
 	stats->rx_packets++;
 	stats->rx_bytes += datasize;
 	u64_stats_update_end(&stats->syncp);
-	put_cpu_ptr(stats);
 
 	if (rxhash)
 		tun_flow_update(tun, rxhash, tfile);