[PATCH 02/14] virtio_net: simplify virtnet_set_affinity()

[Yury Norov]

The inner loop may be replaced with the dedicated for_each_online_cpu_wrap.
It helps to avoid setting the same bits in the @mask more than once, in
case of group_size is greater than number of online CPUs.

Signed-off-by: Yury Norov <yury.no...@gmail.com>
---
 drivers/net/virtio_net.c | 12 +++++++-----
 include/linux/cpumask.h  |  4 ++++
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7646ddd9bef7..5e266486de1f 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3826,7 +3826,7 @@ static void virtnet_set_affinity(struct virtnet_info *vi)
        cpumask_var_t mask;
        int stragglers;
        int group_size;
-       int i, j, cpu;
+       int i, start = 0, cpu;
        int num_cpu;
        int stride;
 
@@ -3840,16 +3840,18 @@ static void virtnet_set_affinity(struct virtnet_info 
*vi)
        stragglers = num_cpu >= vi->curr_queue_pairs ?
                        num_cpu % vi->curr_queue_pairs :
                        0;
-       cpu = cpumask_first(cpu_online_mask);
 
        for (i = 0; i < vi->curr_queue_pairs; i++) {
                group_size = stride + (i < stragglers ? 1 : 0);
 
-               for (j = 0; j < group_size; j++) {
+               for_each_online_cpu_wrap(cpu, start) {
+                       if (!group_size--)
+                               break;
                        cpumask_set_cpu(cpu, mask);
-                       cpu = cpumask_next_wrap(cpu, cpu_online_mask,
-                                               nr_cpu_ids, false);
                }
+
+               start = cpu < nr_cpu_ids ? cpu + 1 : start;
+
                virtqueue_set_affinity(vi->rq[i].vq, mask);
                virtqueue_set_affinity(vi->sq[i].vq, mask);
                __netif_set_xps_queue(vi->dev, cpumask_bits(mask), i, XPS_CPUS);
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 5cf69a110c1c..30042351f15f 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -1036,6 +1036,8 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS);
 
 #define for_each_possible_cpu_wrap(cpu, start) \
        for ((void)(start), (cpu) = 0; (cpu) < 1; (cpu)++)
+#define for_each_online_cpu_wrap(cpu, start)   \
+       for ((void)(start), (cpu) = 0; (cpu) < 1; (cpu)++)
 #else
 #define for_each_possible_cpu(cpu) for_each_cpu((cpu), cpu_possible_mask)
 #define for_each_online_cpu(cpu)   for_each_cpu((cpu), cpu_online_mask)
@@ -1044,6 +1046,8 @@ extern const DECLARE_BITMAP(cpu_all_bits, NR_CPUS);
 
 #define for_each_possible_cpu_wrap(cpu, start) \
        for_each_cpu_wrap((cpu), cpu_possible_mask, (start))
+#define for_each_online_cpu_wrap(cpu, start)   \
+       for_each_cpu_wrap((cpu), cpu_online_mask, (start))
 #endif
 
 /* Wrappers for arch boot code to manipulate normally-constant masks */
-- 
2.43.0