[PATCH net-next v6 6/7] tap: Keep hdr_len in tap_get_user()

[Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>]

hdr_len is repeatedly used so keep it in a local variable.

Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
---
 drivers/net/tap.c | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 5aa41d5f7765a6dcf185bccd3cba2299bad89398..8cb002616a6143b54258b65b483fed0c3af2c7a0 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -645,6 +645,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 	int err;
 	struct virtio_net_hdr vnet_hdr = { 0 };
 	int vnet_hdr_len = 0;
+	int hdr_len = 0;
 	int copylen = 0;
 	int depth;
 	bool zerocopy = false;
@@ -663,13 +664,13 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 		if (!copy_from_iter_full(&vnet_hdr, sizeof(vnet_hdr), from))
 			goto err;
 		iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
-		if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
-		     tap16_to_cpu(q, vnet_hdr.csum_start) +
-		     tap16_to_cpu(q, vnet_hdr.csum_offset) + 2 >
-			     tap16_to_cpu(q, vnet_hdr.hdr_len))
-			vnet_hdr.hdr_len = cpu_to_tap16(q,
-				 tap16_to_cpu(q, vnet_hdr.csum_start) +
-				 tap16_to_cpu(q, vnet_hdr.csum_offset) + 2);
+		hdr_len = tap16_to_cpu(q, vnet_hdr.hdr_len);
+		if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+			hdr_len = max(tap16_to_cpu(q, vnet_hdr.csum_start) +
+				      tap16_to_cpu(q, vnet_hdr.csum_offset) + 2,
+				      hdr_len);
+			vnet_hdr.hdr_len = cpu_to_tap16(q, hdr_len);
+		}
 		err = -EINVAL;
 		if (tap16_to_cpu(q, vnet_hdr.hdr_len) > len)
 			goto err;
@@ -682,12 +683,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 	if (msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
 		struct iov_iter i;
 
-		copylen = vnet_hdr.hdr_len ?
-			tap16_to_cpu(q, vnet_hdr.hdr_len) : GOODCOPY_LEN;
-		if (copylen > good_linear)
-			copylen = good_linear;
-		else if (copylen < ETH_HLEN)
-			copylen = ETH_HLEN;
+		copylen = clamp(hdr_len ?: GOODCOPY_LEN, ETH_HLEN, good_linear);
 		linear = copylen;
 		i = *from;
 		iov_iter_advance(&i, copylen);
@@ -697,11 +693,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 
 	if (!zerocopy) {
 		copylen = len;
-		linear = tap16_to_cpu(q, vnet_hdr.hdr_len);
-		if (linear > good_linear)
-			linear = good_linear;
-		else if (linear < ETH_HLEN)
-			linear = ETH_HLEN;
+		linear = clamp(hdr_len, ETH_HLEN, good_linear);
 	}
 
 	skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,

-- 
2.48.1