hdr_len is repeatedly used so keep it in a local variable.
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
drivers/net/tap.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 5aa41d5f7765a6dcf185bccd3cba2299bad89398..c55c432bac48d395aebc9ceeaa74f7d07e25af4c 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;
@@ -682,11 +683,8 @@ 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 = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
+ if (copylen < ETH_HLEN)
copylen = ETH_HLEN;
linear = copylen;
i = *from;
@@ -697,11 +695,9 @@ 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 = min(hdr_len, good_linear);
+ if (copylen < ETH_HLEN)
+ copylen = ETH_HLEN;
}
skb = tap_alloc_skb(&q->sk, TAP_RESERVE, copylen,
--
2.48.1Akihiko Odaki wrote:
> hdr_len is repeatedly used so keep it in a local variable.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> @@ -682,11 +683,8 @@ 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 = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
> + if (copylen < ETH_HLEN)
> copylen = ETH_HLEN;
I forgot earlier: this can also use single line statement
copylen = max(copylen, ETH_HLEN);
And perhaps easiest to follow is
copylen = hdr_len ?: GOODCOPY_LEN;
copylen = min(copylen, good_linear);
copylen = max(copylen, ETH_HLEN);
> linear = copylen;
> i = *from;
> @@ -697,11 +695,9 @@ 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 = min(hdr_len, good_linear);
> + if (copylen < ETH_HLEN)
> + copylen = ETH_HLEN;
Same
On 2025/02/06 6:21, Willem de Bruijn wrote:
> Akihiko Odaki wrote:
>> hdr_len is repeatedly used so keep it in a local variable.
>>
>> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
>
>> @@ -682,11 +683,8 @@ 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 = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
>> + if (copylen < ETH_HLEN)
>> copylen = ETH_HLEN;
>
> I forgot earlier: this can also use single line statement
>
> copylen = max(copylen, ETH_HLEN);
>
> And perhaps easiest to follow is
>
> copylen = hdr_len ?: GOODCOPY_LEN;
> copylen = min(copylen, good_linear);
> copylen = max(copylen, ETH_HLEN);
I introduced the min() usage as it now neatly fits in a line, but I
found even clamp() fits so I'll use it in the next version:
copylen = clamp(hdr_len ?: GOODCOPY_LEN, ETH_HLEN, good_linear);
Please tell me if you prefer hdr_len ?: GOODCOPY_LEN in a separate line:
copylen = hdr_len ?: GOODCOPY_LEN;
copylen = clamp(copylen, ETH_HLEN, good_linear);
>
>> linear = copylen;
>> i = *from;
>> @@ -697,11 +695,9 @@ 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 = min(hdr_len, good_linear);
>> + if (copylen < ETH_HLEN)
>> + copylen = ETH_HLEN;> > Same
I realized I mistakenly replaced linear with copylen here. Using clamp()
will remove redundant variable references and fix the bug.
Akihiko Odaki wrote:
> On 2025/02/06 6:21, Willem de Bruijn wrote:
> > Akihiko Odaki wrote:
> >> hdr_len is repeatedly used so keep it in a local variable.
> >>
> >> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> >
> >> @@ -682,11 +683,8 @@ 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 = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
> >> + if (copylen < ETH_HLEN)
> >> copylen = ETH_HLEN;
> >
> > I forgot earlier: this can also use single line statement
> >
> > copylen = max(copylen, ETH_HLEN);
> >
> > And perhaps easiest to follow is
> >
> > copylen = hdr_len ?: GOODCOPY_LEN;
> > copylen = min(copylen, good_linear);
> > copylen = max(copylen, ETH_HLEN);
>
> I introduced the min() usage as it now neatly fits in a line, but I
> found even clamp() fits so I'll use it in the next version:
> copylen = clamp(hdr_len ?: GOODCOPY_LEN, ETH_HLEN, good_linear);
>
> Please tell me if you prefer hdr_len ?: GOODCOPY_LEN in a separate line:
> copylen = hdr_len ?: GOODCOPY_LEN;
> copylen = clamp(copylen, ETH_HLEN, good_linear);
Oh nice. I had forgotten about clamp. Even better.
Akihiko Odaki wrote: > hdr_len is repeatedly used so keep it in a local variable. > > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> Reviewed-by: Willem de Bruijn <willemb@google.com>
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