| Message ID | 20250205-tun-v5-6-15d0b32e87fa@daynix.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | tun: Unify vnet implementation | expand |
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>
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); > 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.
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,
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(-)