virtio_net: lower limit on buffer size

commit d85b758f72b0 ("virtio_net: fix support for small rings")
was supposed to increase the buffer size for small rings but had an
unintentional side effect of decreasing it for large rings. This seems
to break some setups - it's not yet clear why, but increasing buffer
size back to what it was before helps.

Fixes: d85b758f72b0 ("virtio_net: fix support for small rings")
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: "J. Bruce Fields" <bfields@fieldses.org>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3e9246cc49c3784ebc045868a53318d35bf01075..a871f45ecc79a438b2b43465d3719f240ff25cb5 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -869,7 +869,7 @@ static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
        unsigned int len;
 
        len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len),
-                               rq->min_buf_len - hdr_len, PAGE_SIZE - hdr_len);
+                               rq->min_buf_len, PAGE_SIZE - hdr_len);
        return ALIGN(len, L1_CACHE_BYTES);
 }
 
@@ -2144,7 +2144,8 @@ static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct virtqu
        unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len;
        unsigned int min_buf_len = DIV_ROUND_UP(buf_len, rq_size);
 
-       return max(min_buf_len, hdr_len);
+       return max(max(min_buf_len, hdr_len) - hdr_len,
+                  (unsigned int)GOOD_PACKET_LEN);
 }
 
 static int virtnet_find_vqs(struct virtnet_info *vi)