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 <han...@stressinduktion.org>
Acked-by: Eric Dumazet <eduma...@google.com>
---
v2:
* replaced skb_queue_tail with the unlocked version, __skb_queue_tail (thanks,
Eric!)
* folded variable declaration and initialization (thanks, Cong!)
v3:
* unchanged
net/unix/af_unix.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 98 insertions(+), 1 deletion(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 941b3d2..7762c0b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -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 @@ out_err:
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)
{
--
2.1.0
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