[PATCH net-next v2] tun: replace get_cpu_ptr with this_cpu_ptr when bh disabled

[Prashant Bhole]

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 <jasow...@redhat.com>
Signed-off-by: Prashant Bhole <bhole_prashant...@lab.ntt.co.jp>
---
v1 -> v2: Added comment to explain why this change is safe

 drivers/net/tun.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 6760b86547df..cb90859d0433 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2494,12 +2494,14 @@ static int tun_xdp_one(struct tun_struct *tun,
        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 += skb->len;
        u64_stats_update_end(&stats->syncp);
-       put_cpu_ptr(stats);
 
        if (rxhash)
                tun_flow_update(tun, rxhash, tfile);
-- 
2.17.2