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Date: Mon, 24 Nov 2014 00:27:42 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: Al Viro <viro@...IV.linux.org.uk>
Cc: David Miller <davem@...emloft.net>, torvalds@...ux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
target-devel@...r.kernel.org, nab@...ux-iscsi.org,
hch@...radead.org
Subject: Re: [PATCH 08/17] {macvtap,tun}_get_user(): switch to iov_iter
On Sat, 2014-11-22 at 04:33 +0000, Al Viro wrote:
> allows to switch macvtap and tun from ->aio_write() to ->write_iter()
>
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> ---
> drivers/net/macvtap.c | 43 ++++++++++++++++++++-----------------------
> drivers/net/tun.c | 43 +++++++++++++++++++++++--------------------
> 2 files changed, 43 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index cdd820f..2bf08c6 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -640,12 +640,12 @@ static void macvtap_skb_to_vnet_hdr(const struct sk_buff *skb,
>
> /* Get packet from user space buffer */
> static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
> - const struct iovec *iv, unsigned long total_len,
> - size_t count, int noblock)
> + struct iov_iter *from, int noblock)
> {
> int good_linear = SKB_MAX_HEAD(NET_IP_ALIGN);
> struct sk_buff *skb;
> struct macvlan_dev *vlan;
> + unsigned long total_len = iov_iter_count(from);
> unsigned long len = total_len;
> int err;
> struct virtio_net_hdr vnet_hdr = { 0 };
> @@ -653,6 +653,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
> int copylen = 0;
> bool zerocopy = false;
> size_t linear;
> + ssize_t n;
>
> if (q->flags & IFF_VNET_HDR) {
> vnet_hdr_len = q->vnet_hdr_sz;
> @@ -662,10 +663,11 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
> goto err;
> len -= vnet_hdr_len;
>
> - err = memcpy_fromiovecend((void *)&vnet_hdr, iv, 0,
> - sizeof(vnet_hdr));
> - if (err < 0)
> + err = -EFAULT;
> + n = copy_from_iter(&vnet_hdr, sizeof(vnet_hdr), from);
> + if (n != sizeof(vnet_hdr))
> goto err;
> + iov_iter_advance(from, vnet_hdr_len - sizeof(vnet_hdr));
> if ((vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
> vnet_hdr.csum_start + vnet_hdr.csum_offset + 2 >
> vnet_hdr.hdr_len)
> @@ -680,17 +682,15 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
> if (unlikely(len < ETH_HLEN))
> goto err;
>
> - err = -EMSGSIZE;
> - if (unlikely(count > UIO_MAXIOV))
> - goto err;
> -
> if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY)) {
> + struct iov_iter i;
Blank line needed after a declaration.
> copylen = vnet_hdr.hdr_len ? vnet_hdr.hdr_len : GOODCOPY_LEN;
> if (copylen > good_linear)
> copylen = good_linear;
> linear = copylen;
> - if (iov_pages(iv, vnet_hdr_len + copylen, count)
> - <= MAX_SKB_FRAGS)
> + i = *from;
> + iov_iter_advance(&i, copylen);
> + if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
The maxpages argument should be MAX_SKB_FRAGS + 1 as we don't need the
exact number.
> zerocopy = true;
> }
>
> @@ -708,10 +708,9 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
> goto err;
>
> if (zerocopy)
> - err = zerocopy_sg_from_iovec(skb, iv, vnet_hdr_len, count);
> + err = zerocopy_sg_from_iter(skb, from);
> else {
> - err = skb_copy_datagram_from_iovec(skb, 0, iv, vnet_hdr_len,
> - len);
> + err = skb_copy_datagram_from_iter(skb, 0, from, len);
Does skb_copy_datagram_from_iter() really need a len parameter? Here it
is equal to iov_iter_count(from).
[...]
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1012,28 +1012,29 @@ static struct sk_buff *tun_alloc_skb(struct tun_file *tfile,
>
> /* Get packet from user space buffer */
> static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> - void *msg_control, const struct iovec *iv,
> - size_t total_len, size_t count, int noblock)
> + void *msg_control, struct iov_iter *from,
> + int noblock)
> {
> struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
> struct sk_buff *skb;
> + size_t total_len = iov_iter_count(from);
> size_t len = total_len, align = NET_SKB_PAD, linear;
> struct virtio_net_hdr gso = { 0 };
> int good_linear;
> - int offset = 0;
> int copylen;
> bool zerocopy = false;
> int err;
> u32 rxhash;
> + ssize_t n;
>
> if (!(tun->flags & TUN_NO_PI)) {
> if (len < sizeof(pi))
> return -EINVAL;
> len -= sizeof(pi);
>
> - if (memcpy_fromiovecend((void *)&pi, iv, 0, sizeof(pi)))
> + n = copy_from_iter(&pi, sizeof(pi), from);
> + if (n != sizeof(pi))
> return -EFAULT;
> - offset += sizeof(pi);
> }
>
> if (tun->flags & TUN_VNET_HDR) {
> @@ -1041,7 +1042,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> return -EINVAL;
> len -= tun->vnet_hdr_sz;
>
> - if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
> + n = copy_from_iter(&gso, sizeof(gso), from);
> + if (n != sizeof(gso))
> return -EFAULT;
>
> if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
> @@ -1050,7 +1052,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
>
> if (gso.hdr_len > len)
> return -EINVAL;
> - offset += tun->vnet_hdr_sz;
> + iov_iter_advance(from, tun->vnet_hdr_sz);
tun->vnet_hdr_sz - sizeof(gso)
> }
>
> if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
> @@ -1063,6 +1065,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> good_linear = SKB_MAX_HEAD(align);
>
> if (msg_control) {
> + struct iov_iter i = *from;
Blank line needed after a declaration.
> /* There are 256 bytes to be copied in skb, so there is
> * enough room for skb expand head in case it is used.
> * The rest of the buffer is mapped from userspace.
> @@ -1071,7 +1074,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> if (copylen > good_linear)
> copylen = good_linear;
> linear = copylen;
> - if (iov_pages(iv, offset + copylen, count) <= MAX_SKB_FRAGS)
> + iov_iter_advance(&i, copylen);
> + if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
Again, the maxpages argument should be MAX_SKB_FRAGS + 1.
> zerocopy = true;
> }
>
> @@ -1091,9 +1095,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
> }
>
> if (zerocopy)
> - err = zerocopy_sg_from_iovec(skb, iv, offset, count);
> + err = zerocopy_sg_from_iter(skb, from);
> else {
> - err = skb_copy_datagram_from_iovec(skb, 0, iv, offset, len);
> + err = skb_copy_datagram_from_iter(skb, 0, from, len);
[...]
Again len is equal to iov_iter_count(from), so I think that parameter is
redundant.
Ben.
--
Ben Hutchings
Absolutum obsoletum. (If it works, it's out of date.) - Stafford Beer
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