[NET]: restructure sock_aio_{read,write} / sock_{readv,writev}

Mid-term I plan to restructure the file_operations so that we don't need
to have all these duplicate aio and vectored versions.  This patch is
a small step in that direction but also a worthwile cleanup on it's own:

(1) introduce a alloc_sock_iocb helper that encapsulates allocating a
    proper sock_iocb
(2) add do_sock_read and do_sock_write helpers for common read/write
    code
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/socket.c

@@ -640,154 +640,150 @@ static void sock_aio_dtor(struct kiocb *iocb)
 	kfree(iocb->private);
 }
 
-/*
- *	Read data from a socket. ubuf is a user mode pointer. We make sure the user
- *	area ubuf...ubuf+size-1 is writable before asking the protocol.
- */
-
-static ssize_t sock_aio_read(struct kiocb *iocb, char __user *ubuf,
-			 size_t size, loff_t pos)
+static ssize_t sock_sendpage(struct file *file, struct page *page,
+			     int offset, size_t size, loff_t *ppos, int more)
 {
-	struct sock_iocb *x, siocb;
 	struct socket *sock;
 	int flags;
 
-	if (pos != 0)
-		return -ESPIPE;
-	if (size==0)		/* Match SYS5 behaviour */
-		return 0;
+	sock = file->private_data;
 
-	if (is_sync_kiocb(iocb))
-		x = &siocb;
-	else {
-		x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL);
-		if (!x)
-			return -ENOMEM;
+	flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
+	if (more)
+		flags |= MSG_MORE;
+
+	return sock->ops->sendpage(sock, page, offset, size, flags);
+}
+
+static struct sock_iocb *alloc_sock_iocb(struct kiocb *iocb,
+		char __user *ubuf, size_t size, struct sock_iocb *siocb)
+{
+	if (!is_sync_kiocb(iocb)) {
+		siocb = kmalloc(sizeof(*siocb), GFP_KERNEL);
+		if (!siocb)
+			return NULL;
 		iocb->ki_dtor = sock_aio_dtor;
 	}
-	iocb->private = x;
-	x->kiocb = iocb;
-	sock = iocb->ki_filp->private_data; 
 
-	x->async_msg.msg_name = NULL;
-	x->async_msg.msg_namelen = 0;
-	x->async_msg.msg_iov = &x->async_iov;
-	x->async_msg.msg_iovlen = 1;
-	x->async_msg.msg_control = NULL;
-	x->async_msg.msg_controllen = 0;
-	x->async_iov.iov_base = ubuf;
-	x->async_iov.iov_len = size;
-	flags = !(iocb->ki_filp->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
+	siocb->kiocb = iocb;
+	siocb->async_iov.iov_base = ubuf;
+	siocb->async_iov.iov_len = size;
 
-	return __sock_recvmsg(iocb, sock, &x->async_msg, size, flags);
+	iocb->private = siocb;
+	return siocb;
 }
 
+static ssize_t do_sock_read(struct msghdr *msg, struct kiocb *iocb,
+		struct file *file, struct iovec *iov, unsigned long nr_segs)
+{
+	struct socket *sock = file->private_data;
+	size_t size = 0;
+	int i;
 
-/*
- *	Write data to a socket. We verify that the user area ubuf..ubuf+size-1
- *	is readable by the user process.
- */
+        for (i = 0 ; i < nr_segs ; i++)
+                size += iov[i].iov_len;
 
-static ssize_t sock_aio_write(struct kiocb *iocb, const char __user *ubuf,
-			  size_t size, loff_t pos)
+	msg->msg_name = NULL;
+	msg->msg_namelen = 0;
+	msg->msg_control = NULL;
+	msg->msg_controllen = 0;
+	msg->msg_iov = (struct iovec *) iov;
+	msg->msg_iovlen = nr_segs;
+	msg->msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
+
+	return __sock_recvmsg(iocb, sock, msg, size, msg->msg_flags);
+}
+
+static ssize_t sock_readv(struct file *file, const struct iovec *iov,
+			  unsigned long nr_segs, loff_t *ppos)
 {
-	struct sock_iocb *x, siocb;
-	struct socket *sock;
-	
+	struct kiocb iocb;
+	struct sock_iocb siocb;
+	struct msghdr msg;
+	int ret;
+
+        init_sync_kiocb(&iocb, NULL);
+	iocb.private = &siocb;
+
+	ret = do_sock_read(&msg, &iocb, file, (struct iovec *)iov, nr_segs);
+	if (-EIOCBQUEUED == ret)
+		ret = wait_on_sync_kiocb(&iocb);
+	return ret;
+}
+
+static ssize_t sock_aio_read(struct kiocb *iocb, char __user *ubuf,
+			 size_t count, loff_t pos)
+{
+	struct sock_iocb siocb, *x;
+
 	if (pos != 0)
 		return -ESPIPE;
-	if(size==0)		/* Match SYS5 behaviour */
+	if (count == 0)		/* Match SYS5 behaviour */
 		return 0;
 
-	if (is_sync_kiocb(iocb))
-		x = &siocb;
-	else {
-		x = kmalloc(sizeof(struct sock_iocb), GFP_KERNEL);
-		if (!x)
-			return -ENOMEM;
-		iocb->ki_dtor = sock_aio_dtor;
-	}
-	iocb->private = x;
-	x->kiocb = iocb;
-	sock = iocb->ki_filp->private_data; 
-
-	x->async_msg.msg_name = NULL;
-	x->async_msg.msg_namelen = 0;
-	x->async_msg.msg_iov = &x->async_iov;
-	x->async_msg.msg_iovlen = 1;
-	x->async_msg.msg_control = NULL;
-	x->async_msg.msg_controllen = 0;
-	x->async_msg.msg_flags = !(iocb->ki_filp->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
-	if (sock->type == SOCK_SEQPACKET)
-		x->async_msg.msg_flags |= MSG_EOR;
-	x->async_iov.iov_base = (void __user *)ubuf;
-	x->async_iov.iov_len = size;
-	
-	return __sock_sendmsg(iocb, sock, &x->async_msg, size);
+	x = alloc_sock_iocb(iocb, ubuf, count, &siocb);
+	if (!x)
+		return -ENOMEM;
+	return do_sock_read(&x->async_msg, iocb, iocb->ki_filp,
+			&x->async_iov, 1);
 }
 
-static ssize_t sock_sendpage(struct file *file, struct page *page,
-			     int offset, size_t size, loff_t *ppos, int more)
+static ssize_t do_sock_write(struct msghdr *msg, struct kiocb *iocb,
+		struct file *file, struct iovec *iov, unsigned long nr_segs)
 {
-	struct socket *sock;
-	int flags;
+	struct socket *sock = file->private_data;
+	size_t size = 0;
+	int i;
 
-	sock = file->private_data;
+        for (i = 0 ; i < nr_segs ; i++)
+                size += iov[i].iov_len;
 
-	flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
-	if (more)
-		flags |= MSG_MORE;
+	msg->msg_name = NULL;
+	msg->msg_namelen = 0;
+	msg->msg_control = NULL;
+	msg->msg_controllen = 0;
+	msg->msg_iov = (struct iovec *) iov;
+	msg->msg_iovlen = nr_segs;
+	msg->msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
+	if (sock->type == SOCK_SEQPACKET)
+		msg->msg_flags |= MSG_EOR;
 
-	return sock->ops->sendpage(sock, page, offset, size, flags);
+	return __sock_sendmsg(iocb, sock, msg, size);
 }
 
-static int sock_readv_writev(int type,
-			     struct file * file, const struct iovec * iov,
-			     long count, size_t size)
+static ssize_t sock_writev(struct file *file, const struct iovec *iov,
+			   unsigned long nr_segs, loff_t *ppos)
 {
 	struct msghdr msg;
-	struct socket *sock;
+	struct kiocb iocb;
+	struct sock_iocb siocb;
+	int ret;
 
-	sock = file->private_data;
+	init_sync_kiocb(&iocb, NULL);
+	iocb.private = &siocb;
 
-	msg.msg_name = NULL;
-	msg.msg_namelen = 0;
-	msg.msg_control = NULL;
-	msg.msg_controllen = 0;
-	msg.msg_iov = (struct iovec *) iov;
-	msg.msg_iovlen = count;
-	msg.msg_flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
+	ret = do_sock_write(&msg, &iocb, file, (struct iovec *)iov, nr_segs);
+	if (-EIOCBQUEUED == ret)
+		ret = wait_on_sync_kiocb(&iocb);
+	return ret;
+}
 
-	/* read() does a VERIFY_WRITE */
-	if (type == VERIFY_WRITE)
-		return sock_recvmsg(sock, &msg, size, msg.msg_flags);
+static ssize_t sock_aio_write(struct kiocb *iocb, const char __user *ubuf,
+			  size_t count, loff_t pos)
+{
+	struct sock_iocb siocb, *x;
 
-	if (sock->type == SOCK_SEQPACKET)
-		msg.msg_flags |= MSG_EOR;
+	if (pos != 0)
+		return -ESPIPE;
+	if (count == 0)		/* Match SYS5 behaviour */
+		return 0;
 
-	return sock_sendmsg(sock, &msg, size);
-}
+	x = alloc_sock_iocb(iocb, (void __user *)ubuf, count, &siocb);
+	if (!x)
+		return -ENOMEM;
 
-static ssize_t sock_readv(struct file *file, const struct iovec *vector,
-			  unsigned long count, loff_t *ppos)
-{
-	size_t tot_len = 0;
-	int i;
-        for (i = 0 ; i < count ; i++)
-                tot_len += vector[i].iov_len;
-	return sock_readv_writev(VERIFY_WRITE,
-				 file, vector, count, tot_len);
-}
-	
-static ssize_t sock_writev(struct file *file, const struct iovec *vector,
-			   unsigned long count, loff_t *ppos)
-{
-	size_t tot_len = 0;
-	int i;
-        for (i = 0 ; i < count ; i++)
-                tot_len += vector[i].iov_len;
-	return sock_readv_writev(VERIFY_READ,
-				 file, vector, count, tot_len);
+	return do_sock_write(&x->async_msg, iocb, iocb->ki_filp,
+			&x->async_iov, 1);
 }