zero-copy.6

实现linux平台下零拷贝技术的软件包。

+ssize_t sock_sendfile(struct file *file, loff_t *ppos, size_t count, read_actor_t actor, void *target);
 
 
 /*
@@ -136,7 +142,8 @@ static struct file_operations socket_fil
 	.fasync =	sock_fasync,
 	.readv =	sock_readv,
 	.writev =	sock_writev,
-	.sendpage =	sock_sendpage
+	.sendpage =	sock_sendpage,
+	.sendfile =	sock_sendfile,
 };
 
 /*
@@ -726,6 +733,395 @@ static ssize_t sock_aio_write(struct kio
 	return __sock_sendmsg(iocb, sock, &x->async_msg, size);
 }
 
+int zc_sock_alloc_data(struct zc_buf *zb)
+{
+	struct sock *sk = zb->priv;
+	unsigned long flags;
+	struct zc_page *zp;
+	int err = -ENODEV, need_wakeup = 0;
+	unsigned int towrite = zb->size;
+	struct sk_buff *skb = zb->skb;
+
+	if (!sk || !sk->zc_page_num || !skb)
+		goto out;
+
+	spin_lock_irqsave(&sk->zc_lock, flags);
+	if (!sk->zc_pages)
+		goto out_unlock;
+
+	BUG_ON(sk->zc_page_index + 1 > sk->zc_page_num);
+
+	need_wakeup = 1;
+	while (towrite) {
+		zp = &sk->zc_pages[sk->zc_page_index];
+		if (zp->size == zp->used || test_bit(ZC_PAGE_READY, &zp->flags)) {
+			set_bit(ZC_PAGE_READY, &zp->flags);
+
+			if (++sk->zc_page_index == sk->zc_page_num)
+				sk->zc_page_index = 0;
+
+			zp = &sk->zc_pages[sk->zc_page_index];
+			if (zp->size == zp->used || test_bit(ZC_PAGE_READY, &zp->flags))
+				break;
+		}
+		if (zp->size - zp->used < towrite && !zb->move_data)
+			break;
+
+		if (skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS) {
+			err = -ENOMEM;
+			break;
+		}
+		/*
+		 * Setup fragment with offset to point to the area where
+		 * we actually can write without overwriting old data.
+		 * Setup fragment size to be equal not to the real data size,
+		 * but size of the area where we actually can write data into.
+		 */
+		skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags, zp->page, zp->page_offset+zp->used, zp->size-zp->used);
+
+		printk("%s: [%1d.%1d] data=%p [%p], size=%4u, used=%4u, towrite=%4u, users=%u.\n", 
+				__func__, sk->zc_page_index, skb_shinfo(skb)->nr_frags-1,
+				zp->page, page_address(zp->page) + zp->page_offset, 
+				zp->size, zp->used, towrite, sk->zc_users);
+
+		if (zb->move_data) {
+			unsigned int sz = min(zp->size - zp->used, towrite);
+
+			err = zb->move_data(zb, sz);
+			if (err <= 0)
+				break;
+
+			if (zp->used + err == zp->size) {
+				printk("%s: [%1d.%1d] data=%p [%p], size=%4u, used=%4u, towrite=%4u, users=%u, page is ready.\n", 
+						__func__, sk->zc_page_index, skb_shinfo(skb)->nr_frags-1,
+						zp->page, page_address(zp->page) + zp->page_offset, 
+						zp->size, zp->used, towrite, sk->zc_users);
+				set_bit(ZC_PAGE_READY, &zp->flags);
+				if (++sk->zc_page_index == sk->zc_page_num)
+					sk->zc_page_index = 0;
+			}
+		} else 
+			err = zb->size;
+
+		skb->len	+= err;
+		skb->data_len	+= err;
+		skb->truesize	+= err;
+
+		towrite 	-= err;
+		zp->used 	+= err;
+
+		err = 0;
+	}
+
+	if (!err)
+		sk->zc_users += skb->data_len;
+
+out_unlock:
+	spin_unlock_irqrestore(&sk->zc_lock, flags);
+out:
+	if (need_wakeup)
+		wake_up(&sk->zc_data_ready);
+	return err;
+}
+
+int zc_sock_commit_data(struct zc_buf *zb)
+{
+	struct sock *sk = zb->priv;
+	unsigned long flags;
+	struct zc_page *zp;
+
+	spin_lock_irqsave(&sk->zc_lock, flags);
+
+	BUG_ON(sk->zc_page_index + 1 > sk->zc_page_num);
+
+	zp = &sk->zc_pages[sk->zc_page_index];
+
+	if (unlikely(zb->size != zp->size)) {
+		spin_unlock_irqrestore(&sk->zc_lock, flags);
+		return 1;
+	}
+
+	if (zp->used == zp->size) {
+		set_bit(ZC_PAGE_READY, &zp->flags);
+		if (++sk->zc_page_index == sk->zc_page_num)
+			sk->zc_page_index = 0;
+	}
+	spin_unlock_irqrestore(&sk->zc_lock, flags);
+
+	wake_up(&sk->zc_data_ready);
+
+	return 0;
+}
+
+extern struct page * __grab_cache_page(struct address_space *mapping, unsigned long index,
+			struct page **cached_page, struct pagevec *lru_pvec);
+
+static int commit_page(struct zc_page *zp, struct file *file, struct address_space *mapping)
+{
+	int err;
+	struct address_space_operations *a_ops = mapping->a_ops;
+
+	flush_dcache_page(zp->page);
+	err = a_ops->commit_write(file, zp->page, zp->page_offset, zp->page_offset+zp->used);
+	unlock_page(zp->page);
+	mark_page_accessed(zp->page);
+	page_cache_release(zp->page);
+	if (zp->cached_page) {
+		page_cache_release(zp->cached_page);
+		zp->cached_page = NULL;
+	}
+
+	printk("%s: zp=%p, page=%p, page_offset=%u, used=%u, size=%u has been committed: err=%d.\n", 
+			__func__, zp, zp->page, zp->page_offset, zp->used, zp->size, err);
+
+	if (err < 0)
+		goto err_out_exit;
+
+	balance_dirty_pages_ratelimited(mapping);
+
+err_out_exit:
+	return err;
+}
+
+static int prepare_page(struct zc_page *zp, struct file *file, struct address_space *mapping, 
+		loff_t *ppos, loff_t count, struct pagevec *lru_pvec)
+{
+	unsigned long index;
+	unsigned long page_offset;
+	unsigned long bytes;
+	struct address_space_operations *a_ops = mapping->a_ops;
+	loff_t pos_allocated = *ppos;
+	int err = 0;
+
+	page_offset = (pos_allocated & (PAGE_CACHE_SIZE -1));
+	index = pos_allocated >> PAGE_CACHE_SHIFT;
+	bytes = PAGE_CACHE_SIZE - page_offset;
+	if (bytes > count)
+		bytes = count;
+
+	zp->page = __grab_cache_page(mapping, index, &zp->cached_page, lru_pvec);
+	if (!zp->page) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	err = a_ops->prepare_write(file, zp->page, page_offset, page_offset+bytes);
+	if (unlikely(err)) {
+		unlock_page(zp->page);
+		page_cache_release(zp->page);
+		goto err_out_exit;
+	}
+
+	zp->page_offset = page_offset;
+	zp->size = bytes;
+	zp->used = 0;
+	clear_bit(ZC_PAGE_READY, &zp->flags);
+
+	printk("%s: zp=%p, page=%p, page_offset=%u, used=%u, size=%u has been prepared: err=%d.\n", 
+			__func__, zp, zp->page, zp->page_offset, zp->used, zp->size, err);
+
+	pos_allocated += bytes;
+
+	*ppos = pos_allocated;
+
+err_out_exit:
+	return err;
+}
+
+/*
+ * This should process all socket's related stuff,
+ * for example emit TCP ACKs...
+ * Since zero-copy skb can only have valid header,
+ * this should process that header at skb->data.
+ * skb_copy_datagram_iovec() is changed to not even touch
+ * zero-copied skb.
+ */
+
+static u8 message_buf[PAGE_SIZE];
+
+int receive_message(struct socket *sock, unsigned int ack_size)
+{
+	struct msghdr msg;
+	struct kvec iov;
+	int err;
+	
+	sock->sk->sk_allocation |= GFP_NOIO;
+	iov.iov_base = message_buf;
+	iov.iov_len = min(ack_size, sizeof(message_buf));
+	msg.msg_name = NULL;
+	msg.msg_namelen = 0;
+	msg.msg_control = NULL;
+	msg.msg_controllen = 0;
+	msg.msg_namelen = 0;
+	msg.msg_flags = MSG_NOSIGNAL | MSG_DONTWAIT;
+	
+	err = kernel_recvmsg(sock, &msg, &iov, 1, iov.iov_len, msg.msg_flags);
+
+	printk("%s: kernel_recvmsg returned %d, ack_size=%u.\n", __func__, err, ack_size);
+	
+	return err;
+}
+
+ssize_t sock_sendfile(struct file *in_file, loff_t *ppos, size_t count, read_actor_t actor, void *target)
+{
+	struct socket *sock;
+	struct sock *sk;
+	int err = 0;
+	size_t written = 0;
+	struct file *file = target;
+	struct address_space *mapping = file->f_mapping;
+	struct inode *inode = mapping->host;
+	loff_t pos, pos_allocated;
+	struct pagevec lru_pvec;
+	unsigned long flags;
+	int pnum_max = 16, i;
+	unsigned int zc_page_index, ack_size;
+	struct zc_page *zc_pages, *zp;
+
+	if (!count)
+		return 0;
+
+	pos = pos_allocated = *ppos;
+	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
+	if (err)
+		goto err_out_exit;
+
+	sock = SOCKET_I(in_file->f_dentry->d_inode);
+
+	if (!sock || !sock->sk) {
+		err = -ENODEV;
+		goto err_out_exit;
+	}
+	sk = sock->sk;
+
+	pnum_max = ((count >> PAGE_CACHE_SHIFT) > pnum_max)?pnum_max:(count >> PAGE_CACHE_SHIFT);
+	zc_pages = kzalloc(sizeof(struct zc_page) * pnum_max, GFP_KERNEL);
+	if (!zc_pages) {
+		err = -ENOMEM;
+		goto err_out_exit;
+	}
+
+	pagevec_init(&lru_pvec, 0);
+	
+	err = 0;
+	for (i=0; i<pnum_max; ++i) {
+		zp = &zc_pages[i];
+		
+		err = prepare_page(zp, file, mapping, &pos_allocated, count, &lru_pvec);
+		if (unlikely(err))
+			goto err_out_release_pages;
+	}
+
+	zc_page_index = 0;
+	
+	spin_lock_irqsave(&sk->zc_lock, flags);
+	sk->zc_pages 		= zc_pages;
+	sk->zc_page_num 	= pnum_max;
+	sk->zc_page_index 	= zc_page_index;
+	sk->zc_alloc_data	= &zc_sock_alloc_data;
+	sk->zc_commit_data	= &zc_sock_commit_data;
+	spin_unlock_irqrestore(&sk->zc_lock, flags);
+
+	printk("%s: sk=%p, %d pages have been set up.\n", __func__, sk, pnum_max);
+
+	while (count) {
+		struct zc_page *zp;
+
+		interruptible_sleep_on_timeout(&sk->zc_data_ready, 5*HZ);
+
+		printk("%s: wakeup: zc_page_index=%d, sk->zc_page_index=%d, sk->sk_state=%d.\n", 
+				__func__, zc_page_index, sk->zc_page_index, sk->sk_state);
+
+		ack_size = 0;
+		for (i=0; i<pnum_max; ++i) {
+			zp = &zc_pages[i];
+
+			if (test_bit(ZC_PAGE_READY, &zp->flags)) {
+				printk("%s: checking page %p [%d]: page=%p, flags=%08lx, page_offset=%08x, size=%08x, used=%08x, written=%zx.\n", 
+						__func__, zp, i, zp->page, zp->flags, zp->page_offset, zp->size, zp->used, written);
+
+				err = commit_page(zp, file, mapping);
+				if (err)
+					goto err_out_release_all_pages;
+
+				count -= zp->used;
+				written += zp->used;
+				pos += zp->used;
+
+				if (++zc_page_index >= pnum_max)
+					zc_page_index = 0;
+
+				ack_size += zp->used;
+
+				err = prepare_page(zp, file, mapping, &pos_allocated, count, &lru_pvec);
+			}
+		}
+
+		while (ack_size) {
+			err = receive_message(sock, ack_size);
+			if (err > 0) {
+				spin_lock_irqsave(&sk->zc_lock, flags);
+				sk->zc_users -= err;
+				spin_unlock_irqrestore(&sk->zc_lock, flags);
+				ack_size -= err;
+			} else
+				break;
+		}
+
+		if (signal_pending(current))
+			break;
+	}
+
+	pagevec_lru_add(&lru_pvec);
+
+	*ppos = pos;
+	err = written;
+
+err_out_release_all_pages:
+	i = pnum_max;
+err_out_release_pages:
+	spin_lock_irqsave(&sk->zc_lock, flags);
+	sk->zc_pages 		= NULL;
+	sk->zc_page_num 	= 0;
+	sk->zc_page_index 	= 0;
+	sk->zc_alloc_data	= NULL;
+	sk->zc_commit_data	= NULL;
+	spin_unlock_irqrestore(&sk->zc_lock, flags);
+
+	/*
+	 * No new skbs can contribute data into VFS cache after this 
+	 * condition, so we only must care about those which are 
+	 * in socket queue already or will be inserted there after
+	 * allocation, but allocation itself will always fail
+	 * due to above locked changes.
+	 */
+
+	for (--i; i>=0; --i)
+		commit_page(&zc_pages[i], file, mapping);
+
+	while (sk->zc_users) {
+		struct sk_buff *skb;
+		
+		interruptible_sleep_on_timeout(&sk->zc_data_ready, 5*HZ);
+		
+		printk("%s: going to flush receive queue: sk->zc_users=%u.\n",
+				__func__, sk->zc_users);
+
+		while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+			sk->zc_users -= skb->data_len;
+			kfree_skb(skb);
+		}
+	}
+
+	printk("%s: flushed: sk->zc_users=%u.\n", __func__, sk->zc_users);
+
+	kfree(zc_pages);
+
+err_out_exit:
+
+	return err;
+}
+
 static ssize_t sock_sendpage(struct file *file, struct page *page,
 			     int offset, size_t size, loff_t *ppos, int more)
 {