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net: af_unix: implement stream sendpage support 

This patch implements sendpage support for AF_UNIX SOCK_STREAM
sockets. This is also required for a complete splice implementation.

The implementation is a bit tricky because we append to already existing
skbs and so have to hold unix_sk->readlock to protect the reading side
from either advancing UNIXCB.consumed or freeing the skb at the socket
receive tail.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Hannes Frederic Sowa 2015-05-21 16:59:59 +02:00 committed by David S. Miller
parent be12a1fe29
commit 869e7c6248
1 changed files with 98 additions and 1 deletions
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99
net/unix/af_unix.c
View File

@ -518,6 +518,8 @@ static int unix_ioctl(struct socket *, unsigned int, unsigned long);
static int unix_shutdown(struct socket *, int);
static int unix_stream_sendmsg(struct socket *, struct msghdr *, size_t);
static int unix_stream_recvmsg(struct socket *, struct msghdr *, size_t, int);
static ssize_t unix_stream_sendpage(struct socket *, struct page *, int offset,
size_t size, int flags);
static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);
static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);
static int unix_dgram_connect(struct socket *, struct sockaddr *,
@ -558,7 +560,7 @@ static const struct proto_ops unix_stream_ops = {
.sendmsg = unix_stream_sendmsg,
.recvmsg = unix_stream_recvmsg,
.mmap = sock_no_mmap,
.sendpage = sock_no_sendpage,
.sendpage = unix_stream_sendpage,
.set_peek_off = unix_set_peek_off,
};
@ -1720,6 +1722,101 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
return sent ? : err;
}
static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
int offset, size_t size, int flags)
{
int err = 0;
bool send_sigpipe = true;
struct sock *other, *sk = socket->sk;
struct sk_buff *skb, *newskb = NULL, *tail = NULL;
if (flags & MSG_OOB)
return -EOPNOTSUPP;
other = unix_peer(sk);
if (!other || sk->sk_state != TCP_ESTABLISHED)
return -ENOTCONN;
if (false) {
alloc_skb:
unix_state_unlock(other);
mutex_unlock(&unix_sk(other)->readlock);
newskb = sock_alloc_send_pskb(sk, 0, 0, flags & MSG_DONTWAIT,
&err, 0);
if (!newskb)
return err;
}
/* we must acquire readlock as we modify already present
* skbs in the sk_receive_queue and mess with skb->len
*/
err = mutex_lock_interruptible(&unix_sk(other)->readlock);
if (err) {
err = flags & MSG_DONTWAIT ? -EAGAIN : -ERESTARTSYS;
send_sigpipe = false;
goto err;
}
if (sk->sk_shutdown & SEND_SHUTDOWN) {
err = -EPIPE;
goto err_unlock;
}
unix_state_lock(other);
if (sock_flag(other, SOCK_DEAD) ||
other->sk_shutdown & RCV_SHUTDOWN) {
err = -EPIPE;
goto err_state_unlock;
}
skb = skb_peek_tail(&other->sk_receive_queue);
if (tail && tail == skb) {
skb = newskb;
} else if (!skb) {
if (newskb)
skb = newskb;
else
goto alloc_skb;
} else if (newskb) {
/* this is fast path, we don't necessarily need to
* call to kfree_skb even though with newskb == NULL
* this - does no harm
*/
consume_skb(newskb);
}
if (skb_append_pagefrags(skb, page, offset, size)) {
tail = skb;
goto alloc_skb;
}
skb->len += size;
skb->data_len += size;
skb->truesize += size;
atomic_add(size, &sk->sk_wmem_alloc);
if (newskb)
__skb_queue_tail(&other->sk_receive_queue, newskb);
unix_state_unlock(other);
mutex_unlock(&unix_sk(other)->readlock);
other->sk_data_ready(other);
return size;
err_state_unlock:
unix_state_unlock(other);
err_unlock:
mutex_unlock(&unix_sk(other)->readlock);
err:
kfree_skb(newskb);
if (send_sigpipe && !(flags & MSG_NOSIGNAL))
send_sig(SIGPIPE, current, 0);
return err;
}
static int unix_seqpacket_sendmsg(struct socket *sock, struct msghdr *msg,
size_t len)
{