[RFC 19/32] mars: add new module xio_client

[Thomas Schoebel-Theuer]

Signed-off-by: Thomas Schoebel-Theuer <tst@xxxxxxxxxxxxxxxxxx>
---
 drivers/staging/mars/xio_bricks/xio_client.c | 1083 ++++++++++++++++++++++++++
 include/linux/xio/xio_client.h               |  105 +++
 2 files changed, 1188 insertions(+)
 create mode 100644 drivers/staging/mars/xio_bricks/xio_client.c
 create mode 100644 include/linux/xio/xio_client.h

diff --git a/drivers/staging/mars/xio_bricks/xio_client.c b/drivers/staging/mars/xio_bricks/xio_client.c
new file mode 100644
index 000000000000..209523378660
--- /dev/null
+++ b/drivers/staging/mars/xio_bricks/xio_client.c
@@ -0,0 +1,1083 @@
+/*
+ * MARS Long Distance Replication Software
+ *
+ * Copyright (C) 2010-2014 Thomas Schoebel-Theuer
+ * Copyright (C) 2011-2014 1&1 Internet AG
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/jiffies.h>
+
+#include <linux/xio/xio.h>
+
+/************************ own type definitions ***********************/
+
+#include <linux/xio/xio_client.h>
+
+#define CLIENT_HASH_MAX			(PAGE_SIZE / sizeof(struct list_head))
+
+int xio_client_abort = 10;
+
+int max_client_channels = 1;
+
+int max_client_bulk = 16;
+
+/************************ own helper functions ***********************/
+
+static int thread_count;
+
+static
+void _do_resubmit(struct client_channel *ch)
+{
+	struct client_output *output = ch->output;
+	unsigned long flags;
+
+	spin_lock_irqsave(&output->lock, flags);
+	if (!list_empty(&ch->wait_list)) {
+		struct list_head *first = ch->wait_list.next;
+		struct list_head *last = ch->wait_list.prev;
+		struct list_head *old_start = output->aio_list.next;
+
+#define list_connect __list_del /*  the original routine has a misleading name: in reality it is more general */
+		list_connect(&output->aio_list, first);
+		list_connect(last, old_start);
+		INIT_LIST_HEAD(&ch->wait_list);
+	}
+	spin_unlock_irqrestore(&output->lock, flags);
+}
+
+static
+void _kill_thread(struct client_threadinfo *ti, const char *name)
+{
+	struct task_struct *thread = ti->thread;
+
+	if (thread) {
+		XIO_DBG("stopping %s thread\n", name);
+		ti->thread = NULL;
+		brick_thread_stop(thread);
+	}
+}
+
+static
+void _kill_channel(struct client_channel *ch)
+{
+	XIO_DBG("channel = %p\n", ch);
+	if (xio_socket_is_alive(&ch->socket)) {
+		XIO_DBG("shutdown socket\n");
+		xio_shutdown_socket(&ch->socket);
+	}
+	_kill_thread(&ch->receiver, "receiver");
+	if (ch->is_open) {
+		XIO_DBG("close socket\n");
+		xio_put_socket(&ch->socket);
+	}
+	ch->recv_error = 0;
+	ch->is_used = false;
+	ch->is_open = false;
+	ch->is_connected = false;
+	/* Re-Submit any waiting requests
+	 */
+	_do_resubmit(ch);
+}
+
+static inline
+void _kill_all_channels(struct client_bundle *bundle)
+{
+	int i;
+
+	/*  first pass: shutdown in parallel without waiting */
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++) {
+		struct client_channel *ch = &bundle->channel[i];
+
+		if (xio_socket_is_alive(&ch->socket)) {
+			XIO_DBG("shutdown socket %d\n", i);
+			xio_shutdown_socket(&ch->socket);
+		}
+	}
+	/*  separate pass (may wait) */
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++)
+		_kill_channel(&bundle->channel[i]);
+}
+
+static int receiver_thread(void *data);
+
+static
+int _setup_channel(struct client_bundle *bundle, int ch_nr)
+{
+	struct client_channel *ch = &bundle->channel[ch_nr];
+	struct sockaddr_storage src_sockaddr;
+	struct sockaddr_storage dst_sockaddr;
+	int status;
+
+	ch->ch_nr = ch_nr;
+	if (unlikely(ch->receiver.thread)) {
+		XIO_WRN("receiver thread %d unexpectedly not dead\n", ch_nr);
+		_kill_thread(&ch->receiver, "receiver");
+	}
+
+	status = xio_create_sockaddr(&src_sockaddr, my_id());
+	if (unlikely(status < 0)) {
+		XIO_DBG("no src sockaddr, status = %d\n", status);
+		goto done;
+	}
+
+	status = xio_create_sockaddr(&dst_sockaddr, bundle->host);
+	if (unlikely(status < 0)) {
+		XIO_DBG("no dst sockaddr, status = %d\n", status);
+		goto done;
+	}
+
+	status = xio_create_socket(&ch->socket, &src_sockaddr, &dst_sockaddr, &device_tcp_params);
+	if (unlikely(status < 0)) {
+		XIO_DBG("no socket, status = %d\n", status);
+		goto really_done;
+	}
+	ch->socket.s_shutdown_on_err = true;
+	ch->socket.s_send_abort = xio_client_abort;
+	ch->socket.s_recv_abort = xio_client_abort;
+	ch->is_open = true;
+
+	ch->receiver.thread = brick_thread_create(
+	receiver_thread, ch, "xio_receiver%d.%d.%d", bundle->thread_count, ch_nr, ch->thread_count++);
+	if (unlikely(!ch->receiver.thread)) {
+		XIO_ERR("cannot start receiver thread %d, status = %d\n", ch_nr, status);
+		status = -ENOENT;
+		goto done;
+	}
+	ch->is_used = true;
+
+done:
+	if (status < 0) {
+		XIO_DBG(
+		"cannot connect channel %d to remote host '%s', retrying, status = %d\n",
+			 ch_nr,
+			 bundle->host ? bundle->host : "NULL",
+			 status);
+		_kill_channel(ch);
+	}
+
+really_done:
+	return status;
+}
+
+static
+void _kill_bundle(struct client_bundle *bundle)
+{
+	_kill_thread(&bundle->sender, "sender");
+	_kill_all_channels(bundle);
+}
+
+static
+void _maintain_bundle(struct client_bundle *bundle)
+{
+	int i;
+
+	/* Re-open _any_ failed channel, even old ones.
+	 * Reason: the number of channels might change during operation.
+	 */
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++) {
+		struct client_channel *ch = &bundle->channel[i];
+
+		if (!ch->is_used ||
+		    (!ch->recv_error && xio_socket_is_alive(&ch->socket)))
+			continue;
+
+		XIO_DBG("killing channel %d\n", i);
+		_kill_channel(ch);
+		/* Re-setup including connect optiona is done later.
+		 */
+	}
+}
+
+static
+struct client_channel *_get_channel(struct client_bundle *bundle, int min_channel, int max_channel)
+{
+	struct client_channel *res;
+	long best_space;
+	int best_channel;
+	int i;
+
+	if (unlikely(max_channel <= 0 || max_channel > MAX_CLIENT_CHANNELS))
+		max_channel = MAX_CLIENT_CHANNELS;
+	if (unlikely(min_channel < 0 || min_channel >= max_channel)) {
+		min_channel = max_channel - 1;
+		if (unlikely(min_channel < 0))
+			min_channel = 0;
+	}
+
+	/* Fast path.
+	 * Speculate that the next channel is already usable,
+	 * and that it has enough room.
+	 */
+	best_channel = bundle->old_channel + 1;
+	if (best_channel >= max_channel)
+		best_channel = min_channel;
+	res = &bundle->channel[best_channel];
+	if (res->is_connected && !res->recv_error && xio_socket_is_alive(&res->socket)) {
+		res->current_space = xio_socket_send_space_available(&res->socket);
+		if (res->current_space > (PAGE_SIZE + PAGE_SIZE / 4))
+			goto found;
+	}
+
+	/* Slow path. Do all the teady work.
+	 */
+	_maintain_bundle(bundle);
+
+	res = NULL;
+	best_space = -1;
+	best_channel = -1;
+	for (i = min_channel; i < max_channel; i++) {
+		struct client_channel *ch = &bundle->channel[i];
+		long this_space;
+
+		/*  create new channels when necessary */
+		if (unlikely(!ch->is_open)) {
+			int status;
+
+			/*  only create one new channel at a time */
+			status = _setup_channel(bundle, i);
+			XIO_DBG("setup channel %d status=%d\n", i, status);
+			if (unlikely(status < 0))
+				continue;
+
+			this_space = xio_socket_send_space_available(&ch->socket);
+			ch->current_space = this_space;
+			/* Always prefer the newly opened channel */
+			res = ch;
+			best_channel = i;
+			break;
+		}
+
+		/*  select the best usable channel */
+		this_space = xio_socket_send_space_available(&ch->socket);
+		ch->current_space = this_space;
+		if (this_space > best_space) {
+			best_space = this_space;
+			best_channel = i;
+			res = ch;
+		}
+	}
+
+	if (unlikely(!res)) {
+		XIO_WRN(
+		"cannot setup communication channel '%s' @%s\n",
+			 bundle->path,
+			 bundle->host);
+		goto done;
+	}
+
+	/*  send initial connect command */
+	if (unlikely(!res->is_connected)) {
+		struct xio_cmd cmd = {
+			.cmd_code = CMD_CONNECT,
+			.cmd_str1 = bundle->path,
+		};
+		int status;
+
+		if (strstr(bundle->path, "/replay-"))
+			cmd.cmd_code = CMD_CONNECT_LOGGER;
+
+		status = xio_send_struct(&res->socket, &cmd, xio_cmd_meta);
+		XIO_DBG("send CMD_CONNECT status = %d\n", status);
+		if (unlikely(status < 0)) {
+			XIO_WRN(
+			"connect '%s' @%s on channel %d failed, status = %d\n",
+				 bundle->path,
+				 bundle->host,
+				 best_channel,
+				 status);
+			_kill_channel(res);
+			res = NULL;
+			goto done;
+		}
+		res->is_connected = true;
+	}
+
+found:
+	bundle->old_channel = best_channel;
+
+done:
+	return res;
+}
+
+static
+int _request_info(struct client_channel *ch)
+{
+	struct xio_cmd cmd = {
+		.cmd_code = CMD_GETINFO,
+	};
+	int status;
+
+	status = xio_send_struct(&ch->socket, &cmd, xio_cmd_meta);
+	XIO_DBG("send CMD_GETINFO status = %d\n", status);
+	if (unlikely(status < 0))
+		XIO_DBG("send of getinfo failed, status = %d\n", status);
+	return status;
+}
+
+static int sender_thread(void *data);
+
+static
+int _setup_bundle(struct client_bundle *bundle, const char *str)
+{
+	int status = -ENOMEM;
+
+	_kill_bundle(bundle);
+	brick_string_free(bundle->path);
+
+	bundle->path = brick_strdup(str);
+
+	status = -EINVAL;
+	bundle->host = strchr(bundle->path, '@');
+	if (unlikely(!bundle->host)) {
+		brick_string_free(bundle->path);
+		bundle->path = NULL;
+		XIO_ERR("parameter string '%s' contains no remote specifier with '@'-syntax\n", str);
+		goto done;
+	}
+	*bundle->host++ = '\0';
+
+	bundle->thread_count = thread_count++;
+	bundle->sender.thread = brick_thread_create(sender_thread, bundle, "xio_sender%d", bundle->thread_count);
+	if (unlikely(!bundle->sender.thread)) {
+		XIO_ERR(
+		"cannot start sender thread for '%s' @%s\n",
+			 bundle->path,
+			 bundle->host);
+		status = -ENOENT;
+		goto done;
+	}
+
+	status = 0;
+
+done:
+	XIO_DBG("status = %d\n", status);
+	return status;
+}
+
+/***************** own brick * input * output operations *****************/
+
+static int client_get_info(struct client_output *output, struct xio_info *info)
+{
+	int status;
+
+	output->get_info = true;
+	wake_up_interruptible_all(&output->bundle.sender_event);
+
+	wait_event_interruptible_timeout(output->info_event, output->got_info, 20 * HZ);
+	status = -ETIME;
+	if (output->got_info && info) {
+		output->got_info = false;
+		memcpy(info, &output->info, sizeof(*info));
+		status = 0;
+	}
+
+	return status;
+}
+
+static int client_io_get(struct client_output *output, struct aio_object *aio)
+{
+	int maxlen;
+
+	if (aio->obj_initialized) {
+		obj_get(aio);
+		return aio->io_len;
+	}
+
+	/* Limit transfers to page boundaries.
+	 * Currently, this is more restrictive than necessary.
+	 * TODO: improve performance by doing better when possible.
+	 * This needs help from the server in some efficient way.
+	 */
+	maxlen = PAGE_SIZE - (aio->io_pos & (PAGE_SIZE - 1));
+	if (aio->io_len > maxlen)
+		aio->io_len = maxlen;
+
+	if (!aio->io_data) { /*  buffered IO */
+		struct client_aio_aspect *aio_a = client_aio_get_aspect(output->brick, aio);
+
+		if (!aio_a)
+			return -EILSEQ;
+
+		aio->io_data = brick_block_alloc(aio->io_pos, (aio_a->alloc_len = aio->io_len));
+
+		aio_a->do_dealloc = true;
+		aio->io_flags = 0;
+	}
+
+	obj_get_first(aio);
+	return 0;
+}
+
+static void client_io_put(struct client_output *output, struct aio_object *aio)
+{
+	struct client_aio_aspect *aio_a;
+
+	if (!obj_put(aio))
+		goto out_return;
+	aio_a = client_aio_get_aspect(output->brick, aio);
+	if (aio_a && aio_a->do_dealloc)
+		brick_block_free(aio->io_data, aio_a->alloc_len);
+	obj_free(aio);
+out_return:;
+}
+
+static
+void _hash_insert(struct client_output *output, struct client_aio_aspect *aio_a)
+{
+	struct aio_object *aio = aio_a->object;
+	unsigned long flags;
+	int hash_index;
+
+	spin_lock_irqsave(&output->lock, flags);
+	list_del(&aio_a->io_head);
+	list_add_tail(&aio_a->io_head, &output->aio_list);
+	list_del(&aio_a->hash_head);
+	aio->io_id = ++output->last_id;
+	hash_index = aio->io_id % CLIENT_HASH_MAX;
+	list_add_tail(&aio_a->hash_head, &output->hash_table[hash_index]);
+	spin_unlock_irqrestore(&output->lock, flags);
+}
+
+static void client_io_io(struct client_output *output, struct aio_object *aio)
+{
+	struct client_aio_aspect *aio_a;
+	int error = -EINVAL;
+
+	aio_a = client_aio_get_aspect(output->brick, aio);
+	if (unlikely(!aio_a))
+		goto error;
+
+	while (output->brick->max_flying > 0 && atomic_read(&output->fly_count) > output->brick->max_flying)
+		brick_msleep(1000 * 2 / HZ);
+
+	if (!output->brick->power.on_led)
+		XIO_ERR("IO submission on dead instance\n");
+
+	atomic_inc(&xio_global_io_flying);
+	atomic_inc(&output->fly_count);
+	obj_get(aio);
+
+	aio_a->submit_jiffies = jiffies;
+	_hash_insert(output, aio_a);
+
+	wake_up_interruptible_all(&output->bundle.sender_event);
+
+	goto out_return;
+error:
+	XIO_ERR("IO error = %d\n", error);
+	SIMPLE_CALLBACK(aio, error);
+	client_io_put(output, aio);
+out_return:;
+}
+
+static
+int receiver_thread(void *data)
+{
+	struct client_channel *ch = data;
+	struct client_output *output = ch->output;
+	int status = 0;
+
+	while (!brick_thread_should_stop()) {
+		struct xio_cmd cmd = {};
+		struct list_head *tmp;
+		struct client_aio_aspect *aio_a = NULL;
+		struct aio_object *aio = NULL;
+		unsigned long flags;
+
+		if (ch->recv_error) {
+			/* The protocol may be out of sync.
+			 * Consume some data to avoid distributed deadlocks.
+			 */
+			(void)xio_recv_raw(&ch->socket, &cmd, 0, sizeof(cmd));
+			brick_msleep(100);
+			status = ch->recv_error;
+			continue;
+		}
+
+		status = xio_recv_struct(&ch->socket, &cmd, xio_cmd_meta);
+		if (status <= 0) {
+			if (!xio_socket_is_alive(&ch->socket)) {
+				XIO_DBG("socket is dead\n");
+				brick_msleep(1000);
+				continue;
+			}
+			goto done;
+		}
+
+		switch (cmd.cmd_code & CMD_FLAG_MASK) {
+		case CMD_NOTIFY:
+			local_trigger();
+			break;
+		case CMD_CONNECT:
+			if (cmd.cmd_int1 < 0) {
+				status = cmd.cmd_int1;
+				XIO_ERR(
+				"remote brick connect '%s' @%s failed, remote status = %d\n",
+					 output->bundle.path,
+					 output->bundle.host,
+					 status);
+				goto done;
+			}
+			break;
+		case CMD_CB:
+		{
+			int hash_index = cmd.cmd_int1 % CLIENT_HASH_MAX;
+
+			spin_lock_irqsave(&output->lock, flags);
+			for (
+			tmp = output->hash_table[hash_index].next; tmp != &output->hash_table[hash_index]; tmp = tmp->next) {
+				struct aio_object *tmp_aio;
+
+				aio_a = container_of(tmp, struct client_aio_aspect, hash_head);
+				tmp_aio = aio_a->object;
+				CHECK_PTR(tmp_aio, err);
+				if (tmp_aio->io_id != cmd.cmd_int1)
+					continue;
+				aio = tmp_aio;
+				list_del_init(&aio_a->hash_head);
+				list_del_init(&aio_a->io_head);
+				break;
+
+err:
+				spin_unlock_irqrestore(&output->lock, flags);
+				status = -EBADR;
+				goto done;
+			}
+			spin_unlock_irqrestore(&output->lock, flags);
+
+			if (unlikely(!aio)) {
+				XIO_WRN(
+				"got unknown callback id %d on '%s' @%s\n",
+					 cmd.cmd_int1,
+					 output->bundle.path,
+					 output->bundle.host);
+				/*  try to consume the corresponding payload */
+				aio = client_alloc_aio(output->brick);
+				status = xio_recv_cb(&ch->socket, aio, &cmd);
+				obj_free(aio);
+				goto done;
+			}
+
+			status = xio_recv_cb(&ch->socket, aio, &cmd);
+			if (unlikely(status < 0)) {
+				XIO_WRN(
+				"interrupted data transfer during callback on '%s' @%s, status = %d\n",
+					 output->bundle.path,
+					 output->bundle.host,
+					 status);
+				_hash_insert(output, aio_a);
+				goto done;
+			}
+
+			if (aio->_object_cb.cb_error < 0)
+				XIO_DBG("ERROR %d\n", aio->_object_cb.cb_error);
+			SIMPLE_CALLBACK(aio, aio->_object_cb.cb_error);
+
+			client_io_put(output, aio);
+
+			atomic_dec(&output->fly_count);
+			atomic_dec(&xio_global_io_flying);
+			break;
+		}
+		case CMD_GETINFO:
+			status = xio_recv_struct(&ch->socket, &output->info, xio_info_meta);
+			if (status < 0) {
+				XIO_WRN(
+				"got bad info from remote '%s' @%s, status = %d\n",
+					 output->bundle.path,
+					 output->bundle.host,
+					 status);
+				goto done;
+			}
+			output->got_info = true;
+			wake_up_interruptible_all(&output->info_event);
+			break;
+		default:
+			XIO_ERR(
+			"got bad command %d from remote '%s' @%s, terminating.\n",
+				 cmd.cmd_code,
+				 output->bundle.path,
+				 output->bundle.host);
+			status = -EBADR;
+			goto done;
+		}
+done:
+		brick_string_free(cmd.cmd_str1);
+		if (unlikely(status < 0)) {
+			if (!ch->recv_error) {
+				XIO_DBG("signalling recv_error = %d\n", status);
+				ch->recv_error = status;
+			}
+			brick_msleep(100);
+		}
+		/*  wake up sender in any case */
+		wake_up_interruptible_all(&output->bundle.sender_event);
+	}
+
+	if (unlikely(status < 0)) {
+		XIO_WRN(
+		"receiver thread '%s' @%s terminated with status = %d\n",
+			 output->bundle.path,
+			 output->bundle.host,
+			 status);
+	}
+
+	xio_shutdown_socket(&ch->socket);
+	return status;
+}
+
+static
+void _do_timeout(struct client_output *output, struct list_head *anchor, int *rounds, bool force)
+{
+	struct client_brick *brick = output->brick;
+	struct list_head *tmp;
+	struct list_head *next;
+	LIST_HEAD(tmp_list);
+	long io_timeout = brick->power.io_timeout;
+	unsigned long flags;
+
+	if (list_empty(anchor))
+		goto out_return;
+	/* When io_timeout is 0, use the global default.
+	 * When io_timeout is negative, no timeout will occur.
+	 * Exeception: when the brick is forcefully shutting down.
+	 */
+	if (!io_timeout)
+		io_timeout = global_net_io_timeout;
+
+	if (!xio_net_is_alive || !brick->power.button)
+		force = true;
+
+	if (!force && io_timeout <= 0)
+		goto out_return;
+	io_timeout *= HZ;
+
+	spin_lock_irqsave(&output->lock, flags);
+	for (tmp = anchor->next, next = tmp->next; tmp != anchor; tmp = next, next = tmp->next) {
+		struct client_aio_aspect *aio_a;
+
+		aio_a = container_of(tmp, struct client_aio_aspect, io_head);
+
+		if (!force &&
+		    !time_is_before_jiffies(aio_a->submit_jiffies + io_timeout)) {
+			continue;
+		}
+
+		list_del_init(&aio_a->hash_head);
+		list_del_init(&aio_a->io_head);
+		list_add_tail(&aio_a->tmp_head, &tmp_list);
+	}
+	spin_unlock_irqrestore(&output->lock, flags);
+
+	while (!list_empty(&tmp_list)) {
+		struct client_aio_aspect *aio_a;
+		struct aio_object *aio;
+
+		tmp = tmp_list.next;
+		list_del_init(tmp);
+		aio_a = container_of(tmp, struct client_aio_aspect, tmp_head);
+		aio = aio_a->object;
+
+		if (unlikely(!(*rounds)++)) {
+			XIO_WRN(
+			"'%s' @%s timeout after %ld: signalling IO error at pos = %lld len = %d\n",
+				 output->bundle.path,
+				 output->bundle.host,
+				 io_timeout,
+				 aio->io_pos,
+				 aio->io_len);
+		}
+
+		atomic_inc(&output->timeout_count);
+
+		SIMPLE_CALLBACK(aio, -ESTALE);
+
+		client_io_put(output, aio);
+
+		atomic_dec(&output->fly_count);
+		atomic_dec(&xio_global_io_flying);
+	}
+out_return:;
+}
+
+static
+void _do_timeout_all(struct client_output *output, bool force)
+{
+	int rounds = 0;
+	int i;
+
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++) {
+		struct client_channel *ch = &output->bundle.channel[i];
+
+		if (!ch->is_used)
+			continue;
+		_do_timeout(output, &ch->wait_list, &rounds, force);
+	}
+	_do_timeout(output, &output->aio_list, &rounds, force);
+	if (unlikely(rounds > 0)) {
+		XIO_WRN(
+		"'%s' @%s had %d timeouts, force = %d\n",
+			 output->bundle.path,
+			 output->bundle.host,
+			 rounds,
+			 force);
+	}
+}
+
+static int sender_thread(void *data)
+{
+	struct client_bundle *bundle = data;
+	struct client_output *output = container_of(bundle, struct client_output, bundle);
+	struct client_brick *brick = output->brick;
+	struct client_channel *ch = NULL;
+	bool do_timeout = false;
+	int ch_skip = max_client_bulk;
+	int status = -ESHUTDOWN;
+	unsigned long flags;
+
+	while (!brick_thread_should_stop()) {
+		struct list_head *tmp = NULL;
+		struct client_aio_aspect *aio_a;
+		struct aio_object *aio;
+		int min_nr;
+		int max_nr;
+
+		/*  timeouting is a rather expensive operation, don't do it too often */
+		if (do_timeout) {
+			do_timeout = false;
+			_maintain_bundle(&output->bundle);
+			_do_timeout_all(output, false);
+		}
+
+		wait_event_interruptible_timeout(
+		output->bundle.sender_event,
+						 !list_empty(&output->aio_list) ||
+						 output->get_info,
+						 2 * HZ);
+
+		if (output->get_info) {
+			ch = _get_channel(bundle, 0, 1);
+			if (unlikely(!ch)) {
+				do_timeout = true;
+				brick_msleep(1000);
+				continue;
+			}
+			status = _request_info(ch);
+			if (unlikely(status < 0)) {
+				XIO_WRN(
+				"cannot send info request '%s' @%s, status = %d\n",
+					 output->bundle.path,
+					 output->bundle.host,
+					 status);
+				do_timeout = true;
+				brick_msleep(1000);
+				continue;
+			}
+			output->get_info = false;
+		}
+
+		/* Grab the next aio from the queue
+		 */
+		spin_lock_irqsave(&output->lock, flags);
+		tmp = output->aio_list.next;
+		if (tmp == &output->aio_list) {
+			spin_unlock_irqrestore(&output->lock, flags);
+			XIO_DBG("empty %d %d\n", output->get_info, brick_thread_should_stop());
+			do_timeout = true;
+			continue;
+		}
+		list_del_init(tmp);
+		/*  notice: hash_head remains in its list! */
+		spin_unlock_irqrestore(&output->lock, flags);
+
+		aio_a = container_of(tmp, struct client_aio_aspect, io_head);
+		aio = aio_a->object;
+
+		if (brick->limit_mode) {
+			int amount = 0;
+
+			if (aio->io_cs_mode < 2)
+				amount = (aio->io_len - 1) / 1024 + 1;
+			rate_limit_sleep(&client_limiter, amount);
+		}
+
+		/*  try to spread reads over multiple channels.... */
+		min_nr = 0;
+		max_nr = max_client_channels;
+		if (!aio->io_rw) {
+			/* optionally separate reads from writes */
+			if (brick->separate_reads && max_nr > 1)
+				min_nr = 1;
+		} else if (!brick->allow_permuting_writes) {
+			max_nr = 1;
+		}
+		if (!ch || ch->recv_error ||
+		    !xio_socket_is_alive(&ch->socket))
+			do_timeout = true;
+		if (do_timeout || ch->ch_nr >= max_nr || --ch_skip < 0) {
+			ch = _get_channel(bundle, min_nr, max_nr);
+			if (unlikely(!ch)) {
+				/*  notice: this will re-assign hash_head without harm */
+				_hash_insert(output, aio_a);
+				brick_msleep(1000);
+				continue;
+			}
+			/* estimate: add some headroom for overhead */
+			ch_skip = ch->current_space / PAGE_SIZE +
+				ch->current_space / (PAGE_SIZE * 8);
+			if (ch_skip > max_client_bulk)
+				ch_skip = max_client_bulk;
+		}
+
+		spin_lock_irqsave(&output->lock, flags);
+		list_add(tmp, &ch->wait_list);
+		/*  notice: hash_head is already there! */
+		spin_unlock_irqrestore(&output->lock, flags);
+
+		status = xio_send_aio(&ch->socket, aio);
+		if (unlikely(status < 0)) {
+			_hash_insert(output, aio_a);
+			do_timeout = true;
+			ch = NULL;
+			/*  retry submission on next occasion.. */
+			XIO_WRN(
+			"aio send '%s' @%s failed, status = %d\n",
+				 output->bundle.path,
+				 output->bundle.host,
+				 status);
+
+			brick_msleep(100);
+			continue;
+		}
+	}
+
+	if (unlikely(status < 0)) {
+		XIO_WRN(
+		"sender thread '%s' @%s terminated with status = %d\n",
+			 output->bundle.path,
+			 output->bundle.host,
+			 status);
+	}
+
+	_kill_all_channels(bundle);
+
+	/* Signal error on all pending IO requests.
+	 * We have no other chance (except probably delaying
+	 * this until destruction which is probably not what
+	 * we want).
+	 */
+	_do_timeout_all(output, true);
+	wake_up_interruptible_all(&output->bundle.sender_event);
+	XIO_DBG("sender terminated\n");
+	return status;
+}
+
+static int client_switch(struct client_brick *brick)
+{
+	struct client_output *output = brick->outputs[0];
+	int status = 0;
+
+	if (brick->power.button) {
+		if (brick->power.on_led)
+			goto done;
+		xio_set_power_off_led((void *)brick, false);
+		status = _setup_bundle(&output->bundle, brick->brick_name);
+		if (likely(status >= 0)) {
+			output->get_info = true;
+			brick->connection_state = 1;
+			xio_set_power_on_led((void *)brick, true);
+		}
+	} else {
+		if (brick->power.off_led)
+			goto done;
+		xio_set_power_on_led((void *)brick, false);
+		_kill_bundle(&output->bundle);
+		_do_timeout_all(output, true);
+		output->got_info = false;
+		brick->connection_state = 0;
+		xio_set_power_off_led((void *)brick, !output->bundle.sender.thread);
+	}
+done:
+	return status;
+}
+
+/*************** informational * statistics **************/
+
+static
+char *client_statistics(struct client_brick *brick, int verbose)
+{
+	struct client_output *output = brick->outputs[0];
+	char *res = brick_string_alloc(1024);
+	int socket_count = 0;
+	int i;
+
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++) {
+		struct client_channel *ch = &output->bundle.channel[i];
+
+		if (xio_socket_is_alive(&ch->socket))
+			socket_count++;
+	}
+	snprintf(
+	res, 1024,
+		 "socket_count = %d max_flying = %d io_timeout = %d | timeout_count = %d fly_count = %d\n",
+		 socket_count,
+		 brick->max_flying,
+		 brick->power.io_timeout,
+		 atomic_read(&output->timeout_count),
+		 atomic_read(&output->fly_count));
+
+	return res;
+}
+
+static
+void client_reset_statistics(struct client_brick *brick)
+{
+	struct client_output *output = brick->outputs[0];
+
+	atomic_set(&output->timeout_count, 0);
+}
+
+/*************** object * aspect constructors * destructors **************/
+
+static int client_aio_aspect_init_fn(struct generic_aspect *_ini)
+{
+	struct client_aio_aspect *ini = (void *)_ini;
+
+	INIT_LIST_HEAD(&ini->io_head);
+	INIT_LIST_HEAD(&ini->hash_head);
+	INIT_LIST_HEAD(&ini->tmp_head);
+	return 0;
+}
+
+static void client_aio_aspect_exit_fn(struct generic_aspect *_ini)
+{
+	struct client_aio_aspect *ini = (void *)_ini;
+
+	CHECK_HEAD_EMPTY(&ini->io_head);
+	CHECK_HEAD_EMPTY(&ini->hash_head);
+}
+
+XIO_MAKE_STATICS(client);
+
+/********************* brick constructors * destructors *******************/
+
+static int client_brick_construct(struct client_brick *brick)
+{
+	return 0;
+}
+
+static int client_output_construct(struct client_output *output)
+{
+	int i;
+
+	output->hash_table = brick_block_alloc(0, PAGE_SIZE);
+
+	for (i = 0; i < CLIENT_HASH_MAX; i++)
+		INIT_LIST_HEAD(&output->hash_table[i]);
+
+	for (i = 0; i < MAX_CLIENT_CHANNELS; i++) {
+		struct client_channel *ch = &output->bundle.channel[i];
+
+		ch->output = output;
+		INIT_LIST_HEAD(&ch->wait_list);
+	}
+
+	init_waitqueue_head(&output->bundle.sender_event);
+
+	spin_lock_init(&output->lock);
+	INIT_LIST_HEAD(&output->aio_list);
+	init_waitqueue_head(&output->info_event);
+	return 0;
+}
+
+static int client_output_destruct(struct client_output *output)
+{
+	brick_string_free(output->bundle.path);
+	output->bundle.path = NULL;
+	brick_block_free(output->hash_table, PAGE_SIZE);
+	return 0;
+}
+
+/************************ static structs ***********************/
+
+static struct client_brick_ops client_brick_ops = {
+	.brick_switch = client_switch,
+	.brick_statistics = client_statistics,
+	.reset_statistics = client_reset_statistics,
+};
+
+static struct client_output_ops client_output_ops = {
+	.xio_get_info = client_get_info,
+	.aio_get = client_io_get,
+	.aio_put = client_io_put,
+	.aio_io = client_io_io,
+};
+
+const struct client_input_type client_input_type = {
+	.type_name = "client_input",
+	.input_size = sizeof(struct client_input),
+};
+
+static const struct client_input_type *client_input_types[] = {
+	&client_input_type,
+};
+
+const struct client_output_type client_output_type = {
+	.type_name = "client_output",
+	.output_size = sizeof(struct client_output),
+	.master_ops = &client_output_ops,
+	.output_construct = &client_output_construct,
+	.output_destruct = &client_output_destruct,
+};
+
+static const struct client_output_type *client_output_types[] = {
+	&client_output_type,
+};
+
+const struct client_brick_type client_brick_type = {
+	.type_name = "client_brick",
+	.brick_size = sizeof(struct client_brick),
+	.max_inputs = 0,
+	.max_outputs = 1,
+	.master_ops = &client_brick_ops,
+	.aspect_types = client_aspect_types,
+	.default_input_types = client_input_types,
+	.default_output_types = client_output_types,
+	.brick_construct = &client_brick_construct,
+};
+
+/***************** module init stuff ************************/
+
+struct rate_limiter client_limiter = {
+	/* Let all be zero */
+};
+
+int global_net_io_timeout = 30;
+
+module_param_named(net_io_timeout, global_net_io_timeout, int, 0);
+
+int __init init_xio_client(void)
+{
+	XIO_INF("init_client()\n");
+	_client_brick_type = (void *)&client_brick_type;
+	return client_register_brick_type();
+}
+
+void exit_xio_client(void)
+{
+	XIO_INF("exit_client()\n");
+	client_unregister_brick_type();
+}
diff --git a/include/linux/xio/xio_client.h b/include/linux/xio/xio_client.h
new file mode 100644
index 000000000000..5accb4898adc
--- /dev/null
+++ b/include/linux/xio/xio_client.h
@@ -0,0 +1,105 @@
+/*
+ * MARS Long Distance Replication Software
+ *
+ * Copyright (C) 2010-2014 Thomas Schoebel-Theuer
+ * Copyright (C) 2011-2014 1&1 Internet AG
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef XIO_CLIENT_H
+#define XIO_CLIENT_H
+
+#include <linux/xio/xio_net.h>
+#include <linux/brick/lib_limiter.h>
+
+extern struct rate_limiter client_limiter;
+extern int global_net_io_timeout;
+extern int xio_client_abort;
+extern int max_client_channels;
+extern int max_client_bulk;
+
+#define MAX_CLIENT_CHANNELS		4
+
+struct client_aio_aspect {
+	GENERIC_ASPECT(aio);
+	struct list_head io_head;
+	struct list_head hash_head;
+	struct list_head tmp_head;
+	unsigned long submit_jiffies;
+	int alloc_len;
+	bool do_dealloc;
+};
+
+struct client_brick {
+	XIO_BRICK(client);
+	/*  tunables */
+	int max_flying; /*  limit on parallelism */
+	bool limit_mode;
+	bool allow_permuting_writes;
+	bool separate_reads;
+
+	/*  readonly from outside */
+	int connection_state; /*  0 = switched off, 1 = not connected, 2 = connected */
+};
+
+struct client_input {
+	XIO_INPUT(client);
+};
+
+struct client_threadinfo {
+	struct task_struct *thread;
+};
+
+struct client_channel {
+	struct xio_socket socket;
+	struct client_threadinfo receiver;
+	struct list_head wait_list;
+	struct client_output *output;
+	long current_space;
+	int thread_count;
+	int recv_error;
+	int ch_nr;
+	bool is_used;
+	bool is_open;
+	bool is_connected;
+};
+
+struct client_bundle {
+	char *host;
+	char *path;
+	int thread_count;
+	int old_channel;
+
+	wait_queue_head_t sender_event;
+	struct client_threadinfo sender;
+	struct client_channel channel[MAX_CLIENT_CHANNELS];
+};
+
+struct client_output {
+	XIO_OUTPUT(client);
+	atomic_t fly_count;
+	atomic_t timeout_count;
+	spinlock_t lock;
+	struct list_head aio_list;
+	int  last_id;
+	struct client_bundle bundle;
+	struct xio_info info;
+
+	wait_queue_head_t info_event;
+	bool get_info;
+	bool got_info;
+	struct list_head *hash_table;
+};
+
+XIO_TYPES(client);
+
+#endif
-- 
2.11.0