Merge branch 'af_unix_sendpage'

Hannes Frederic Sowa says:

====================
net: af_unix: zerocopy stream bits

This series implements zerocopy support for AF_UNIX SOCK_STREAM sockets.

Changelog in the specific patches. Thanks to all the reviewers!
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 271 insertions, 52 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f3fe9bd9e672..9bac0e6f8dfa 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1870,15 +1870,39 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
 	return false;
 }
 
+ssize_t skb_socket_splice(struct sock *sk,
+			  struct pipe_inode_info *pipe,
+			  struct splice_pipe_desc *spd)
+{
+	int ret;
+
+	/* Drop the socket lock, otherwise we have reverse
+	 * locking dependencies between sk_lock and i_mutex
+	 * here as compared to sendfile(). We enter here
+	 * with the socket lock held, and splice_to_pipe() will
+	 * grab the pipe inode lock. For sendfile() emulation,
+	 * we call into ->sendpage() with the i_mutex lock held
+	 * and networking will grab the socket lock.
+	 */
+	release_sock(sk);
+	ret = splice_to_pipe(pipe, spd);
+	lock_sock(sk);
+
+	return ret;
+}
+
 /*
  * Map data from the skb to a pipe. Should handle both the linear part,
  * the fragments, and the frag list. It does NOT handle frag lists within
  * the frag list, if such a thing exists. We'd probably need to recurse to
  * handle that cleanly.
  */
-int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
+int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		    struct pipe_inode_info *pipe, unsigned int tlen,
-		    unsigned int flags)
+		    unsigned int flags,
+		    ssize_t (*splice_cb)(struct sock *,
+					 struct pipe_inode_info *,
+					 struct splice_pipe_desc *))
 {
 	struct partial_page partial[MAX_SKB_FRAGS];
 	struct page *pages[MAX_SKB_FRAGS];
@@ -1891,7 +1915,6 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
 		.spd_release = sock_spd_release,
 	};
 	struct sk_buff *frag_iter;
-	struct sock *sk = skb->sk;
 	int ret = 0;
 
 	/*
@@ -1914,23 +1937,12 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
 	}
 
 done:
-	if (spd.nr_pages) {
-		/*
-		 * Drop the socket lock, otherwise we have reverse
-		 * locking dependencies between sk_lock and i_mutex
-		 * here as compared to sendfile(). We enter here
-		 * with the socket lock held, and splice_to_pipe() will
-		 * grab the pipe inode lock. For sendfile() emulation,
-		 * we call into ->sendpage() with the i_mutex lock held
-		 * and networking will grab the socket lock.
-		 */
-		release_sock(sk);
-		ret = splice_to_pipe(pipe, &spd);
-		lock_sock(sk);
-	}
+	if (spd.nr_pages)
+		ret = splice_cb(sk, pipe, &spd);
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(skb_splice_bits);
 
 /**
  *	skb_store_bits - store bits from kernel buffer to skb
@@ -2915,6 +2927,24 @@ int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
 }
 EXPORT_SYMBOL(skb_append_datato_frags);
 
+int skb_append_pagefrags(struct sk_buff *skb, struct page *page,
+			 int offset, size_t size)
+{
+	int i = skb_shinfo(skb)->nr_frags;
+
+	if (skb_can_coalesce(skb, i, page, offset)) {
+		skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], size);
+	} else if (i < MAX_SKB_FRAGS) {
+		get_page(page);
+		skb_fill_page_desc(skb, i, page, offset, size);
+	} else {
+		return -EMSGSIZE;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(skb_append_pagefrags);
+
 /**
  *	skb_pull_rcsum - pull skb and update receive checksum
  *	@skb: buffer to update
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 8d91b922fcfe..451b009dae75 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1233,11 +1233,9 @@ ssize_t	ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
 	}
 
 	while (size > 0) {
-		int i;
-
-		if (skb_is_gso(skb))
+		if (skb_is_gso(skb)) {
 			len = size;
-		else {
+		} else {
 
 			/* Check if the remaining data fits into current packet. */
 			len = mtu - skb->len;
@@ -1289,15 +1287,10 @@ ssize_t	ip_append_page(struct sock *sk, struct flowi4 *fl4, struct page *page,
 			continue;
 		}
 
-		i = skb_shinfo(skb)->nr_frags;
 		if (len > size)
 			len = size;
-		if (skb_can_coalesce(skb, i, page, offset)) {
-			skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
-		} else if (i < MAX_SKB_FRAGS) {
-			get_page(page);
-			skb_fill_page_desc(skb, i, page, offset, len);
-		} else {
+
+		if (skb_append_pagefrags(skb, page, offset, len)) {
 			err = -EMSGSIZE;
 			goto error;
 		}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 90afcec3f427..65f791f74845 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -695,8 +695,9 @@ static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
 	struct tcp_splice_state *tss = rd_desc->arg.data;
 	int ret;
 
-	ret = skb_splice_bits(skb, offset, tss->pipe, min(rd_desc->count, len),
-			      tss->flags);
+	ret = skb_splice_bits(skb, skb->sk, offset, tss->pipe,
+			      min(rd_desc->count, len), tss->flags,
+			      skb_socket_splice);
 	if (ret > 0)
 		rd_desc->count -= ret;
 	return ret;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 941b3d26e3bf..b8c44076c776 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -518,6 +518,11 @@ 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 ssize_t unix_stream_splice_read(struct socket *,  loff_t *ppos,
+				       struct pipe_inode_info *, size_t size,
+				       unsigned 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 +563,8 @@ 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,
+	.splice_read =	unix_stream_splice_read,
 	.set_peek_off =	unix_set_peek_off,
 };
 
@@ -1720,6 +1726,101 @@ 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)
 {
@@ -1860,8 +1961,9 @@ out:
  *	Sleep until more data has arrived. But check for races..
  */
 static long unix_stream_data_wait(struct sock *sk, long timeo,
-				  struct sk_buff *last)
+				  struct sk_buff *last, unsigned int last_len)
 {
+	struct sk_buff *tail;
 	DEFINE_WAIT(wait);
 
 	unix_state_lock(sk);
@@ -1869,7 +1971,9 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,
 	for (;;) {
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 
-		if (skb_peek_tail(&sk->sk_receive_queue) != last ||
+		tail = skb_peek_tail(&sk->sk_receive_queue);
+		if (tail != last ||
+		    (tail && tail->len != last_len) ||
 		    sk->sk_err ||
 		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
 		    signal_pending(current) ||
@@ -1893,38 +1997,50 @@ static unsigned int unix_skb_len(const struct sk_buff *skb)
 	return skb->len - UNIXCB(skb).consumed;
 }
 
-static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
-			       size_t size, int flags)
+struct unix_stream_read_state {
+	int (*recv_actor)(struct sk_buff *, int, int,
+			  struct unix_stream_read_state *);
+	struct socket *socket;
+	struct msghdr *msg;
+	struct pipe_inode_info *pipe;
+	size_t size;
+	int flags;
+	unsigned int splice_flags;
+};
+
+static int unix_stream_read_generic(struct unix_stream_read_state *state)
 {
 	struct scm_cookie scm;
+	struct socket *sock = state->socket;
 	struct sock *sk = sock->sk;
 	struct unix_sock *u = unix_sk(sk);
-	DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, msg->msg_name);
 	int copied = 0;
+	int flags = state->flags;
 	int noblock = flags & MSG_DONTWAIT;
-	int check_creds = 0;
+	bool check_creds = false;
 	int target;
 	int err = 0;
 	long timeo;
 	int skip;
+	size_t size = state->size;
+	unsigned int last_len;
 
 	err = -EINVAL;
 	if (sk->sk_state != TCP_ESTABLISHED)
 		goto out;
 
 	err = -EOPNOTSUPP;
-	if (flags&MSG_OOB)
+	if (flags & MSG_OOB)
 		goto out;
 
-	target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
+	target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
 	timeo = sock_rcvtimeo(sk, noblock);
 
+	memset(&scm, 0, sizeof(scm));
+
 	/* Lock the socket to prevent queue disordering
 	 * while sleeps in memcpy_tomsg
 	 */
-
-	memset(&scm, 0, sizeof(scm));
-
 	err = mutex_lock_interruptible(&u->readlock);
 	if (unlikely(err)) {
 		/* recvmsg() in non blocking mode is supposed to return -EAGAIN
@@ -1940,6 +2056,7 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
 
 		unix_state_lock(sk);
 		last = skb = skb_peek(&sk->sk_receive_queue);
+		last_len = last ? last->len : 0;
 again:
 		if (skb == NULL) {
 			unix_sk(sk)->recursion_level = 0;
@@ -1962,16 +2079,17 @@ again:
 				break;
 			mutex_unlock(&u->readlock);
 
-			timeo = unix_stream_data_wait(sk, timeo, last);
+			timeo = unix_stream_data_wait(sk, timeo, last,
+						      last_len);
 
-			if (signal_pending(current)
-			    ||  mutex_lock_interruptible(&u->readlock)) {
+			if (signal_pending(current) ||
+			    mutex_lock_interruptible(&u->readlock)) {
 				err = sock_intr_errno(timeo);
 				goto out;
 			}
 
 			continue;
- unlock:
+unlock:
 			unix_state_unlock(sk);
 			break;
 		}
@@ -1980,6 +2098,7 @@ again:
 		while (skip >= unix_skb_len(skb)) {
 			skip -= unix_skb_len(skb);
 			last = skb;
+			last_len = skb->len;
 			skb = skb_peek_next(skb, &sk->sk_receive_queue);
 			if (!skb)
 				goto again;
@@ -1996,18 +2115,20 @@ again:
 		} else if (test_bit(SOCK_PASSCRED, &sock->flags)) {
 			/* Copy credentials */
 			scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
-			check_creds = 1;
+			check_creds = true;
 		}
 
 		/* Copy address just once */
-		if (sunaddr) {
-			unix_copy_addr(msg, skb->sk);
+		if (state->msg && state->msg->msg_name) {
+			DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr,
+					 state->msg->msg_name);
+			unix_copy_addr(state->msg, skb->sk);
 			sunaddr = NULL;
 		}
 
 		chunk = min_t(unsigned int, unix_skb_len(skb) - skip, size);
-		if (skb_copy_datagram_msg(skb, UNIXCB(skb).consumed + skip,
-					  msg, chunk)) {
+		chunk = state->recv_actor(skb, skip, chunk, state);
+		if (chunk < 0) {
 			if (copied == 0)
 				copied = -EFAULT;
 			break;
@@ -2045,11 +2166,85 @@ again:
 	} while (size);
 
 	mutex_unlock(&u->readlock);
-	scm_recv(sock, msg, &scm, flags);
+	if (state->msg)
+		scm_recv(sock, state->msg, &scm, flags);
+	else
+		scm_destroy(&scm);
 out:
 	return copied ? : err;
 }
 
+static int unix_stream_read_actor(struct sk_buff *skb,
+				  int skip, int chunk,
+				  struct unix_stream_read_state *state)
+{
+	int ret;
+
+	ret = skb_copy_datagram_msg(skb, UNIXCB(skb).consumed + skip,
+				    state->msg, chunk);
+	return ret ?: chunk;
+}
+
+static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
+			       size_t size, int flags)
+{
+	struct unix_stream_read_state state = {
+		.recv_actor = unix_stream_read_actor,
+		.socket = sock,
+		.msg = msg,
+		.size = size,
+		.flags = flags
+	};
+
+	return unix_stream_read_generic(&state);
+}
+
+static ssize_t skb_unix_socket_splice(struct sock *sk,
+				      struct pipe_inode_info *pipe,
+				      struct splice_pipe_desc *spd)
+{
+	int ret;
+	struct unix_sock *u = unix_sk(sk);
+
+	mutex_unlock(&u->readlock);
+	ret = splice_to_pipe(pipe, spd);
+	mutex_lock(&u->readlock);
+
+	return ret;
+}
+
+static int unix_stream_splice_actor(struct sk_buff *skb,
+				    int skip, int chunk,
+				    struct unix_stream_read_state *state)
+{
+	return skb_splice_bits(skb, state->socket->sk,
+			       UNIXCB(skb).consumed + skip,
+			       state->pipe, chunk, state->splice_flags,
+			       skb_unix_socket_splice);
+}
+
+static ssize_t unix_stream_splice_read(struct socket *sock,  loff_t *ppos,
+				       struct pipe_inode_info *pipe,
+				       size_t size, unsigned int flags)
+{
+	struct unix_stream_read_state state = {
+		.recv_actor = unix_stream_splice_actor,
+		.socket = sock,
+		.pipe = pipe,
+		.size = size,
+		.splice_flags = flags,
+	};
+
+	if (unlikely(*ppos))
+		return -ESPIPE;
+
+	if (sock->file->f_flags & O_NONBLOCK ||
+	    flags & SPLICE_F_NONBLOCK)
+		state.flags = MSG_DONTWAIT;
+
+	return unix_stream_read_generic(&state);
+}
+
 static int unix_shutdown(struct socket *sock, int mode)
 {
 	struct sock *sk = sock->sk;