[RFC 21/32] mars: add new module xio_copy

[Thomas Schoebel-Theuer]

Signed-off-by: Thomas Schoebel-Theuer <tst@xxxxxxxxxxxxxxxxxx>
---
 drivers/staging/mars/xio_bricks/xio_copy.c | 1005 ++++++++++++++++++++++++++++
 include/linux/xio/xio_copy.h               |  115 ++++
 2 files changed, 1120 insertions(+)
 create mode 100644 drivers/staging/mars/xio_bricks/xio_copy.c
 create mode 100644 include/linux/xio/xio_copy.h

diff --git a/drivers/staging/mars/xio_bricks/xio_copy.c b/drivers/staging/mars/xio_bricks/xio_copy.c
new file mode 100644
index 000000000000..56b60f2f837e
--- /dev/null
+++ b/drivers/staging/mars/xio_bricks/xio_copy.c
@@ -0,0 +1,1005 @@
+/*
+ * 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.
+ */
+
+/*  Copy brick (just for demonstration) */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+
+#include <linux/xio/xio.h>
+#include <linux/brick/lib_limiter.h>
+
+#ifndef READ
+#define READ				0
+#define WRITE				1
+#endif
+
+#define COPY_CHUNK			(PAGE_SIZE)
+#define NR_COPY_REQUESTS		(32 * 1024 * 1024 / COPY_CHUNK)
+
+#define STATES_PER_PAGE			(PAGE_SIZE / sizeof(struct copy_state))
+#define MAX_SUB_TABLES			(NR_COPY_REQUESTS / STATES_PER_PAGE + (NR_COPY_REQUESTS % STATES_PER_PAGE ? 1 : 0)\
+									\
+)
+#define MAX_COPY_REQUESTS		(PAGE_SIZE / sizeof(struct copy_state *) * STATES_PER_PAGE)
+
+#define GET_STATE(brick, index)						\
+	((brick)->st[(index) / STATES_PER_PAGE][(index) % STATES_PER_PAGE])
+
+/************************ own type definitions ***********************/
+
+#include <linux/xio/xio_copy.h>
+
+int xio_copy_overlap = 1;
+
+int xio_copy_read_prio = XIO_PRIO_NORMAL;
+
+int xio_copy_write_prio = XIO_PRIO_NORMAL;
+
+int xio_copy_read_max_fly;
+
+int xio_copy_write_max_fly;
+
+#define is_read_limited(brick)						\
+	(xio_copy_read_max_fly > 0 && atomic_read(&(brick)->copy_read_flight) >= xio_copy_read_max_fly)
+
+#define is_write_limited(brick)						\
+	(xio_copy_write_max_fly > 0 && atomic_read(&(brick)->copy_write_flight) >= xio_copy_write_max_fly)
+
+/************************ own helper functions ***********************/
+
+/* TODO:
+ * The clash logic is untested / alpha stage (Feb. 2011).
+ *
+ * For now, the output is never used, so this cannot do harm.
+ *
+ * In order to get the output really working / enterprise grade,
+ * some larger test effort should be invested.
+ */
+static inline
+void _clash(struct copy_brick *brick)
+{
+	brick->trigger = true;
+	set_bit(0, &brick->clash);
+	atomic_inc(&brick->total_clash_count);
+	wake_up_interruptible(&brick->event);
+}
+
+static inline
+int _clear_clash(struct copy_brick *brick)
+{
+	int old;
+
+	old = test_and_clear_bit(0, &brick->clash);
+	return old;
+}
+
+/* Current semantics:
+ *
+ * All writes are always going to the original input A. They are _not_
+ * replicated to B.
+ *
+ * In order to get B really uptodate, you have to replay the right
+ * transaction logs there (at the right time).
+ * [If you had no writes on A at all during the copy, of course
+ * this is not necessary]
+ *
+ * When utilize_mode is on, reads can utilize the already copied
+ * region from B, but only as long as this region has not been
+ * invalidated by writes (indicated by low_dirty).
+ *
+ * TODO: implement replicated writes, together with some transaction
+ * replay logic applying the transaction logs _only_ after
+ * crashes during inconsistency caused by partial replication of writes.
+ */
+static
+int _determine_input(struct copy_brick *brick, struct aio_object *aio)
+{
+	int rw;
+	int below;
+	int behind;
+	loff_t io_end;
+
+	if (!brick->utilize_mode || brick->low_dirty)
+		return INPUT_A_IO;
+
+	io_end = aio->io_pos + aio->io_len;
+	below = io_end <= brick->copy_start;
+	behind = !brick->copy_end || aio->io_pos >= brick->copy_end;
+	rw = aio->io_may_write | aio->io_rw;
+	if (rw) {
+		if (!behind) {
+			brick->low_dirty = true;
+			if (!below) {
+				_clash(brick);
+				wake_up_interruptible(&brick->event);
+			}
+		}
+		return INPUT_A_IO;
+	}
+
+	if (below)
+		return INPUT_B_IO;
+
+	return INPUT_A_IO;
+}
+
+#define GET_INDEX(pos)	  (((pos) / COPY_CHUNK) % NR_COPY_REQUESTS)
+#define GET_OFFSET(pos)   ((pos) % COPY_CHUNK)
+
+static
+void __clear_aio(struct copy_brick *brick, struct aio_object *aio, int queue)
+{
+	struct copy_input *input;
+
+	input = queue ? brick->inputs[INPUT_B_COPY] : brick->inputs[INPUT_A_COPY];
+	GENERIC_INPUT_CALL(input, aio_put, aio);
+}
+
+static
+void _clear_aio(struct copy_brick *brick, int index, int queue)
+{
+	struct copy_state *st = &GET_STATE(brick, index);
+	struct aio_object *aio = st->table[queue];
+
+	if (aio) {
+		if (unlikely(st->active[queue])) {
+			XIO_ERR("clearing active aio, index = %d queue = %d\n", index, queue);
+			st->active[queue] = false;
+		}
+		__clear_aio(brick, aio, queue);
+		st->table[queue] = NULL;
+	}
+}
+
+static
+void _clear_all_aio(struct copy_brick *brick)
+{
+	int i;
+
+	for (i = 0; i < NR_COPY_REQUESTS; i++) {
+		GET_STATE(brick, i).state = COPY_STATE_START;
+		_clear_aio(brick, i, 0);
+		_clear_aio(brick, i, 1);
+	}
+}
+
+static
+void _clear_state_table(struct copy_brick *brick)
+{
+	int i;
+
+	for (i = 0; i < MAX_SUB_TABLES; i++) {
+		struct copy_state *sub_table = brick->st[i];
+
+		memset(sub_table, 0, PAGE_SIZE);
+	}
+}
+
+static
+void copy_endio(struct generic_callback *cb)
+{
+	struct copy_aio_aspect *aio_a;
+	struct aio_object *aio;
+	struct copy_brick *brick;
+	struct copy_state *st;
+	int index;
+	int queue;
+	int error = 0;
+
+	LAST_CALLBACK(cb);
+	aio_a = cb->cb_private;
+	CHECK_PTR(aio_a, err);
+	aio = aio_a->object;
+	CHECK_PTR(aio, err);
+	brick = aio_a->brick;
+	CHECK_PTR(brick, err);
+
+	queue = aio_a->queue;
+	index = GET_INDEX(aio->io_pos);
+	st = &GET_STATE(brick, index);
+
+	if (unlikely(queue < 0 || queue >= 2)) {
+		XIO_ERR("bad queue %d\n", queue);
+		error = -EINVAL;
+		goto exit;
+	}
+	st->active[queue] = false;
+	if (unlikely(st->table[queue])) {
+		XIO_ERR("table corruption at %d %d (%p => %p)\n", index, queue, st->table[queue], aio);
+		error = -EEXIST;
+		goto exit;
+	}
+	if (unlikely(cb->cb_error < 0)) {
+		error = cb->cb_error;
+		__clear_aio(brick, aio, queue);
+		/* This is racy, but does no harm.
+		 * Worst case just produces more error output.
+		 */
+		if (!brick->copy_error_count++)
+			XIO_WRN("IO error %d on index %d, old state = %d\n", cb->cb_error, index, st->state);
+	} else {
+		if (unlikely(st->table[queue])) {
+			XIO_ERR("overwriting index %d, state = %d\n", index, st->state);
+			_clear_aio(brick, index, queue);
+		}
+		st->table[queue] = aio;
+	}
+
+exit:
+	if (unlikely(error < 0)) {
+		st->error = error;
+		_clash(brick);
+	}
+	if (aio->io_rw)
+		atomic_dec(&brick->copy_write_flight);
+	else
+		atomic_dec(&brick->copy_read_flight);
+	brick->trigger = true;
+	wake_up_interruptible(&brick->event);
+	goto out_return;
+err:
+	XIO_FAT("cannot handle callback\n");
+out_return:;
+}
+
+static
+int _make_aio(
+struct copy_brick *brick, int index, int queue, void *data, loff_t pos, loff_t end_pos, int rw, int cs_mode)
+{
+	struct aio_object *aio;
+	struct copy_aio_aspect *aio_a;
+	struct copy_input *input;
+	int offset;
+	int len;
+	int status = -EAGAIN;
+
+	if (brick->clash || end_pos <= 0)
+		goto done;
+
+	aio = copy_alloc_aio(brick);
+	status = -ENOMEM;
+
+	aio_a = copy_aio_get_aspect(brick, aio);
+	if (unlikely(!aio_a)) {
+		XIO_FAT("cannot get own apsect\n");
+		goto done;
+	}
+
+	aio_a->brick = brick;
+	aio_a->queue = queue;
+	aio->io_may_write = rw;
+	aio->io_rw = rw;
+	aio->io_data = data;
+	aio->io_pos = pos;
+	aio->io_cs_mode = cs_mode;
+	offset = GET_OFFSET(pos);
+	len = COPY_CHUNK - offset;
+	if (pos + len > end_pos)
+		len = end_pos - pos;
+	aio->io_len = len;
+	aio->io_prio = rw ?
+		xio_copy_write_prio :
+		xio_copy_read_prio;
+	if (aio->io_prio < XIO_PRIO_HIGH || aio->io_prio > XIO_PRIO_LOW)
+		aio->io_prio = brick->io_prio;
+
+	SETUP_CALLBACK(aio, copy_endio, aio_a);
+
+	input = queue ? brick->inputs[INPUT_B_COPY] : brick->inputs[INPUT_A_COPY];
+	status = GENERIC_INPUT_CALL(input, aio_get, aio);
+	if (unlikely(status < 0)) {
+		XIO_ERR("status = %d\n", status);
+		obj_free(aio);
+		goto done;
+	}
+	if (unlikely(aio->io_len < len))
+		XIO_DBG("shorten len %d < %d\n", aio->io_len, len);
+	if (queue == 0) {
+		GET_STATE(brick, index).len = aio->io_len;
+	} else if (unlikely(aio->io_len < GET_STATE(brick, index).len)) {
+		XIO_DBG("shorten len %d < %d at index %d\n", aio->io_len, GET_STATE(brick, index).len, index);
+		GET_STATE(brick, index).len = aio->io_len;
+	}
+
+	GET_STATE(brick, index).active[queue] = true;
+	if (rw)
+		atomic_inc(&brick->copy_write_flight);
+	else
+		atomic_inc(&brick->copy_read_flight);
+	GENERIC_INPUT_CALL(input, aio_io, aio);
+
+done:
+	return status;
+}
+
+static
+void _update_percent(struct copy_brick *brick, bool force)
+{
+	if (force ||
+	    brick->copy_last > brick->copy_start + 8 * 1024 * 1024 ||
+	    time_is_before_jiffies(brick->last_jiffies + 5 * HZ) ||
+	    (brick->copy_last == brick->copy_end && brick->copy_end > 0)) {
+		brick->copy_start = brick->copy_last;
+		brick->last_jiffies = jiffies;
+		brick->power.percent_done = brick->copy_end > 0 ? brick->copy_start * 100 / brick->copy_end : 0;
+		XIO_INF(
+		"'%s' copied %lld / %lld bytes (%d%%)\n",
+		brick->brick_path,
+		brick->copy_last,
+		brick->copy_end,
+		brick->power.percent_done);
+	}
+}
+
+/* The heart of this brick.
+ * State transition function of the finite automaton.
+ * In case no progress is possible (e.g. preconditions not
+ * yet true), the state is left as is (idempotence property:
+ * calling this too often does no harm, just costs performance).
+ */
+static
+int _next_state(struct copy_brick *brick, int index, loff_t pos)
+{
+	struct aio_object *aio0;
+	struct aio_object *aio1;
+	struct copy_state *st;
+	char state;
+	char next_state;
+	bool do_restart = false;
+	int progress = 0;
+	int status;
+
+	st = &GET_STATE(brick, index);
+	next_state = st->state;
+
+restart:
+	state = next_state;
+
+	do_restart = false;
+
+	switch (state) {
+	case COPY_STATE_RESET:
+		/* This state is only entered after errors or
+		 * in restarting situations.
+		 */
+		_clear_aio(brick, index, 1);
+		_clear_aio(brick, index, 0);
+		next_state = COPY_STATE_START;
+		/* fallthrough */
+	case COPY_STATE_START:
+		/* This is the relgular starting state.
+		 * It must be zero, automatically entered via memset()
+		 */
+		if (st->table[0] || st->table[1]) {
+			XIO_ERR("index %d not startable\n", index);
+			progress = -EPROTO;
+			goto idle;
+		}
+
+		_clear_aio(brick, index, 1);
+		_clear_aio(brick, index, 0);
+		st->writeout = false;
+		st->error = 0;
+
+		if (brick->is_aborting ||
+		    is_read_limited(brick))
+			goto idle;
+
+		status = _make_aio(brick, index, 0, NULL, pos, brick->copy_end, READ, brick->verify_mode ? 2 : 0);
+		if (unlikely(status < 0)) {
+			XIO_DBG("status = %d\n", status);
+			progress = status;
+			break;
+		}
+
+		next_state = COPY_STATE_READ1;
+		if (!brick->verify_mode)
+			break;
+
+		next_state = COPY_STATE_START2;
+		/* fallthrough */
+	case COPY_STATE_START2:
+		status = _make_aio(brick, index, 1, NULL, pos, brick->copy_end, READ, 2);
+		if (unlikely(status < 0)) {
+			XIO_DBG("status = %d\n", status);
+			progress = status;
+			break;
+		}
+		next_state = COPY_STATE_READ2;
+		/* fallthrough */
+	case COPY_STATE_READ2:
+		aio1 = st->table[1];
+		if (!aio1) { /*  idempotence: wait by unchanged state */
+			goto idle;
+		}
+		/* fallthrough = > wait for both aios to appear */
+	case COPY_STATE_READ1:
+	case COPY_STATE_READ3:
+		aio0 = st->table[0];
+		if (!aio0) { /*  idempotence: wait by unchanged state */
+			goto idle;
+		}
+		if (brick->copy_limiter) {
+			int amount = (aio0->io_len - 1) / 1024 + 1;
+
+			rate_limit_sleep(brick->copy_limiter, amount);
+		}
+		/*  on append mode: increase the end pointer dynamically */
+		if (brick->append_mode > 0 && aio0->io_total_size && aio0->io_total_size > brick->copy_end)
+			brick->copy_end = aio0->io_total_size;
+		/*  do verify (when applicable) */
+		aio1 = st->table[1];
+		if (aio1 && state != COPY_STATE_READ3) {
+			int len = aio0->io_len;
+			bool ok;
+
+			if (len != aio1->io_len) {
+				ok = false;
+			} else if (aio0->io_cs_mode) {
+				static unsigned char null[sizeof(aio0->io_checksum)];
+
+				ok = !memcmp(aio0->io_checksum, aio1->io_checksum, sizeof(aio0->io_checksum));
+				if (ok)
+					ok = memcmp(aio0->io_checksum, null, sizeof(aio0->io_checksum)) != 0;
+			} else if (!aio0->io_data || !aio1->io_data) {
+				ok = false;
+			} else {
+				ok = !memcmp(aio0->io_data, aio1->io_data, len);
+			}
+
+			_clear_aio(brick, index, 1);
+
+			if (ok)
+				brick->verify_ok_count++;
+			else
+				brick->verify_error_count++;
+
+			if (ok || !brick->repair_mode) {
+				/* skip start of writing, goto final treatment of writeout */
+				next_state = COPY_STATE_CLEANUP;
+				break;
+			}
+		}
+
+		if (aio0->io_cs_mode > 1) { /*	re-read, this time with data */
+			_clear_aio(brick, index, 0);
+			status = _make_aio(brick, index, 0, NULL, pos, brick->copy_end, READ, 0);
+			if (unlikely(status < 0)) {
+				XIO_DBG("status = %d\n", status);
+				progress = status;
+				next_state = COPY_STATE_RESET;
+				break;
+			}
+			next_state = COPY_STATE_READ3;
+			break;
+		}
+		next_state = COPY_STATE_WRITE;
+		/* fallthrough */
+	case COPY_STATE_WRITE:
+		if (is_write_limited(brick))
+			goto idle;
+		/* Obey ordering to get a strict "append" behaviour.
+		 * We assume that we don't need to wait for completion
+		 * of the previous write to avoid a sparse result file
+		 * under all circumstances, i.e. we only assure that
+		 * _starting_ the writes is in order.
+		 * This is only correct when all lower bricks obey the
+		 * order of io_io() operations.
+		 * Currenty, bio and aio are obeying this. Be careful when
+		 * implementing new IO bricks!
+		 */
+		if (st->prev >= 0 && !GET_STATE(brick, st->prev).writeout)
+			goto idle;
+		aio0 = st->table[0];
+		if (unlikely(!aio0 || !aio0->io_data)) {
+			XIO_ERR("src buffer for write does not exist, state %d at index %d\n", state, index);
+			progress = -EILSEQ;
+			break;
+		}
+		if (unlikely(brick->is_aborting)) {
+			progress = -EINTR;
+			break;
+		}
+		/* start writeout */
+		status = _make_aio(brick, index, 1, aio0->io_data, pos, pos + aio0->io_len, WRITE, 0);
+		if (unlikely(status < 0)) {
+			XIO_DBG("status = %d\n", status);
+			progress = status;
+			next_state = COPY_STATE_RESET;
+			break;
+		}
+		/* Attention! overlapped IO behind EOF could
+		 * lead to temporary inconsistent state of the
+		 * file, because the write order may be different from
+		 * strict O_APPEND behaviour.
+		 */
+		if (xio_copy_overlap)
+			st->writeout = true;
+		next_state = COPY_STATE_WRITTEN;
+		/* fallthrough */
+	case COPY_STATE_WRITTEN:
+		aio1 = st->table[1];
+		if (!aio1) { /*  idempotence: wait by unchanged state */
+			goto idle;
+		}
+		st->writeout = true;
+		/* rechecking means to start over again.
+		 * ATTENTIION! this may lead to infinite request
+		 * submission loops, intentionally.
+		 * TODO: implement some timeout means.
+		 */
+		if (brick->recheck_mode && brick->repair_mode) {
+			next_state = COPY_STATE_RESET;
+			break;
+		}
+		next_state = COPY_STATE_CLEANUP;
+		/* fallthrough */
+	case COPY_STATE_CLEANUP:
+		_clear_aio(brick, index, 1);
+		_clear_aio(brick, index, 0);
+		next_state = COPY_STATE_FINISHED;
+		/* fallthrough */
+	case COPY_STATE_FINISHED:
+		/* Indicate successful completion by remaining in this state.
+		 * Restart of the finite automaton must be done externally.
+		 */
+		goto idle;
+	default:
+		XIO_ERR("illegal state %d at index %d\n", state, index);
+		_clash(brick);
+		progress = -EILSEQ;
+	}
+
+	do_restart = (state != next_state);
+
+idle:
+	if (unlikely(progress < 0)) {
+		if (st->error >= 0)
+			st->error = progress;
+		XIO_DBG("progress = %d\n", progress);
+		progress = 0;
+		_clash(brick);
+	} else if (do_restart) {
+		goto restart;
+	} else if (st->state != next_state) {
+		progress++;
+	}
+
+	/*  save the resulting state */
+	st->state = next_state;
+	return progress;
+}
+
+static
+int _run_copy(struct copy_brick *brick)
+{
+	int max;
+	loff_t pos;
+	loff_t limit = -1;
+
+	short prev;
+	int progress;
+
+	if (unlikely(_clear_clash(brick))) {
+		XIO_DBG("clash\n");
+		if (atomic_read(&brick->copy_read_flight) + atomic_read(&brick->copy_write_flight) > 0) {
+			/* wait until all pending copy IO has finished
+			 */
+			_clash(brick);
+			XIO_DBG("re-clash\n");
+			brick_msleep(100);
+			return 0;
+		}
+		_clear_all_aio(brick);
+		_clear_state_table(brick);
+	}
+
+	/* Do at most max iterations in the below loop
+	 */
+	max = NR_COPY_REQUESTS - atomic_read(&brick->io_flight) * 2;
+
+	prev = -1;
+	progress = 0;
+	for (
+	pos = brick->copy_last; pos < brick->copy_end || brick->append_mode > 1; pos = (
+	(pos / COPY_CHUNK) + 1) * COPY_CHUNK) {
+		int index = GET_INDEX(pos);
+		struct copy_state *st = &GET_STATE(brick, index);
+
+		if (max-- <= 0)
+			break;
+		st->prev = prev;
+		prev = index;
+		/*  call the finite state automaton */
+		if (!(st->active[0] | st->active[1])) {
+			progress += _next_state(brick, index, pos);
+			limit = pos;
+		}
+	}
+
+	/*  check the resulting state: can we advance the copy_last pointer? */
+	if (likely(progress && !brick->clash)) {
+		int count = 0;
+
+		for (pos = brick->copy_last; pos <= limit; pos = ((pos / COPY_CHUNK) + 1) * COPY_CHUNK) {
+			int index = GET_INDEX(pos);
+			struct copy_state *st = &GET_STATE(brick, index);
+
+			if (st->state != COPY_STATE_FINISHED)
+				break;
+			if (unlikely(st->error < 0)) {
+				/* check for fatal consistency errors */
+				if (st->error == -EMEDIUMTYPE) {
+					brick->copy_error = st->error;
+					brick->abort_mode = true;
+					XIO_WRN("Consistency is violated\n");
+				}
+				if (!brick->copy_error) {
+					brick->copy_error = st->error;
+					XIO_WRN("IO error = %d\n", st->error);
+				}
+				if (brick->abort_mode)
+					brick->is_aborting = true;
+				break;
+			}
+			/*  rollover */
+			st->state = COPY_STATE_START;
+			count += st->len;
+			/*  check contiguity */
+			if (unlikely(GET_OFFSET(pos) + st->len != COPY_CHUNK))
+				break;
+		}
+		if (count > 0) {
+			brick->copy_last += count;
+			get_lamport(&brick->copy_last_stamp);
+			_update_percent(brick, false);
+		}
+	}
+	return progress;
+}
+
+static
+bool _is_done(struct copy_brick *brick)
+{
+	if (brick_thread_should_stop())
+		brick->is_aborting = true;
+	return brick->is_aborting &&
+		atomic_read(&brick->copy_read_flight) + atomic_read(&brick->copy_write_flight) <= 0;
+}
+
+static int _copy_thread(void *data)
+{
+	struct copy_brick *brick = data;
+	int rounds = 0;
+
+	XIO_DBG("--------------- copy_thread %p starting\n", brick);
+	brick->copy_error = 0;
+	brick->copy_error_count = 0;
+	brick->verify_ok_count = 0;
+	brick->verify_error_count = 0;
+
+	_update_percent(brick, true);
+
+	xio_set_power_on_led((void *)brick, true);
+	brick->trigger = true;
+
+	while (!_is_done(brick)) {
+		loff_t old_start = brick->copy_start;
+		loff_t old_end = brick->copy_end;
+		int progress = 0;
+
+		if (old_end > 0) {
+			progress = _run_copy(brick);
+			if (!progress || ++rounds > 1000)
+				rounds = 0;
+		}
+
+		wait_event_interruptible_timeout(
+		brick->event,
+						 progress > 0 ||
+						 brick->trigger ||
+						 brick->copy_start != old_start ||
+						 brick->copy_end != old_end ||
+						 _is_done(brick),
+						 1 * HZ);
+		brick->trigger = false;
+	}
+
+	/* check for fatal consistency errors */
+	if (brick->copy_error == -EMEDIUMTYPE) {
+		/* reset the whole area */
+		brick->copy_start = 0;
+		brick->copy_last = 0;
+		XIO_WRN("resetting the full copy area\n");
+	}
+	_update_percent(brick, true);
+
+	XIO_DBG(
+	"--------------- copy_thread terminating (%d read requests / %d write requests flying, copy_start = %lld copy_end = %lld)\n",
+		 atomic_read(&brick->copy_read_flight),
+		 atomic_read(&brick->copy_write_flight),
+		 brick->copy_start,
+		 brick->copy_end);
+
+	_clear_all_aio(brick);
+	xio_set_power_off_led((void *)brick, true);
+	XIO_DBG("--------------- copy_thread done.\n");
+	return 0;
+}
+
+/***************** own brick * input * output operations *****************/
+
+static int copy_get_info(struct copy_output *output, struct xio_info *info)
+{
+	struct copy_input *input = output->brick->inputs[INPUT_B_IO];
+
+	return GENERIC_INPUT_CALL(input, xio_get_info, info);
+}
+
+static int copy_io_get(struct copy_output *output, struct aio_object *aio)
+{
+	struct copy_input *input;
+	int index;
+	int status;
+
+	index = _determine_input(output->brick, aio);
+	input = output->brick->inputs[index];
+	status = GENERIC_INPUT_CALL(input, aio_get, aio);
+	if (status >= 0)
+		atomic_inc(&output->brick->io_flight);
+	return status;
+}
+
+static void copy_io_put(struct copy_output *output, struct aio_object *aio)
+{
+	struct copy_input *input;
+	int index;
+
+	index = _determine_input(output->brick, aio);
+	input = output->brick->inputs[index];
+	GENERIC_INPUT_CALL(input, aio_put, aio);
+	if (atomic_dec_and_test(&output->brick->io_flight)) {
+		output->brick->trigger = true;
+		wake_up_interruptible(&output->brick->event);
+	}
+}
+
+static void copy_io_io(struct copy_output *output, struct aio_object *aio)
+{
+	struct copy_input *input;
+	int index;
+
+	index = _determine_input(output->brick, aio);
+	input = output->brick->inputs[index];
+	GENERIC_INPUT_CALL(input, aio_io, aio);
+}
+
+static int copy_switch(struct copy_brick *brick)
+{
+	static int version;
+
+	XIO_DBG("power.button = %d\n", brick->power.button);
+	if (brick->power.button) {
+		if (brick->power.on_led)
+			goto done;
+		xio_set_power_off_led((void *)brick, false);
+		brick->is_aborting = false;
+		if (!brick->thread) {
+			brick->copy_last = brick->copy_start;
+			get_lamport(&brick->copy_last_stamp);
+			brick->thread = brick_thread_create(_copy_thread, brick, "xio_copy%d", version++);
+			if (brick->thread) {
+				brick->trigger = true;
+			} else {
+				xio_set_power_off_led((void *)brick, true);
+				XIO_ERR("could not start copy thread\n");
+			}
+		}
+	} else {
+		if (brick->power.off_led)
+			goto done;
+		xio_set_power_on_led((void *)brick, false);
+		if (brick->thread) {
+			XIO_INF("stopping thread...\n");
+			brick_thread_stop(brick->thread);
+		}
+	}
+done:
+	return 0;
+}
+
+/*************** informational * statistics **************/
+
+static
+char *copy_statistics(struct copy_brick *brick, int verbose)
+{
+	char *res = brick_string_alloc(1024);
+
+	snprintf(
+	res, 1024,
+		 "copy_start = %lld copy_last = %lld copy_end = %lld copy_error = %d copy_error_count = %d verify_ok_count = %d verify_error_count = %d low_dirty = %d is_aborting = %d clash = %lu | total clash_count = %d | io_flight = %d copy_read_flight = %d copy_write_flight = %d\n",
+		 brick->copy_start,
+		 brick->copy_last,
+		 brick->copy_end,
+		 brick->copy_error,
+		 brick->copy_error_count,
+		 brick->verify_ok_count,
+		 brick->verify_error_count,
+		 brick->low_dirty,
+		 brick->is_aborting,
+		 brick->clash,
+		 atomic_read(&brick->total_clash_count),
+		 atomic_read(&brick->io_flight),
+		 atomic_read(&brick->copy_read_flight),
+		 atomic_read(&brick->copy_write_flight));
+
+	return res;
+}
+
+static
+void copy_reset_statistics(struct copy_brick *brick)
+{
+	atomic_set(&brick->total_clash_count, 0);
+}
+
+/*************** object * aspect constructors * destructors **************/
+
+static int copy_aio_aspect_init_fn(struct generic_aspect *_ini)
+{
+	struct copy_aio_aspect *ini = (void *)_ini;
+
+	(void)ini;
+	return 0;
+}
+
+static void copy_aio_aspect_exit_fn(struct generic_aspect *_ini)
+{
+	struct copy_aio_aspect *ini = (void *)_ini;
+
+	(void)ini;
+}
+
+XIO_MAKE_STATICS(copy);
+
+/********************* brick constructors * destructors *******************/
+
+static
+void _free_pages(struct copy_brick *brick)
+{
+	int i;
+
+	for (i = 0; i < MAX_SUB_TABLES; i++) {
+		struct copy_state *sub_table = brick->st[i];
+
+		if (!sub_table)
+			continue;
+
+		brick_block_free(sub_table, PAGE_SIZE);
+	}
+	brick_block_free(brick->st, PAGE_SIZE);
+}
+
+static int copy_brick_construct(struct copy_brick *brick)
+{
+	int i;
+
+	brick->st = brick_block_alloc(0, PAGE_SIZE);
+	memset(brick->st, 0, PAGE_SIZE);
+
+	for (i = 0; i < MAX_SUB_TABLES; i++) {
+		struct copy_state *sub_table;
+
+		/*  this should be usually optimized away as dead code */
+		if (unlikely(i >= MAX_SUB_TABLES)) {
+			XIO_ERR("sorry, subtable index %d is too large.\n", i);
+			_free_pages(brick);
+			return -EINVAL;
+		}
+
+		sub_table = brick_block_alloc(0, PAGE_SIZE);
+		brick->st[i] = sub_table;
+		memset(sub_table, 0, PAGE_SIZE);
+	}
+
+	init_waitqueue_head(&brick->event);
+	sema_init(&brick->mutex, 1);
+	return 0;
+}
+
+static int copy_brick_destruct(struct copy_brick *brick)
+{
+	_free_pages(brick);
+	return 0;
+}
+
+static int copy_output_construct(struct copy_output *output)
+{
+	return 0;
+}
+
+static int copy_output_destruct(struct copy_output *output)
+{
+	return 0;
+}
+
+/************************ static structs ***********************/
+
+static struct copy_brick_ops copy_brick_ops = {
+	.brick_switch = copy_switch,
+	.brick_statistics = copy_statistics,
+	.reset_statistics = copy_reset_statistics,
+};
+
+static struct copy_output_ops copy_output_ops = {
+	.xio_get_info = copy_get_info,
+	.aio_get = copy_io_get,
+	.aio_put = copy_io_put,
+	.aio_io = copy_io_io,
+};
+
+const struct copy_input_type copy_input_type = {
+	.type_name = "copy_input",
+	.input_size = sizeof(struct copy_input),
+};
+
+static const struct copy_input_type *copy_input_types[] = {
+	&copy_input_type,
+	&copy_input_type,
+	&copy_input_type,
+	&copy_input_type,
+};
+
+const struct copy_output_type copy_output_type = {
+	.type_name = "copy_output",
+	.output_size = sizeof(struct copy_output),
+	.master_ops = &copy_output_ops,
+	.output_construct = &copy_output_construct,
+	.output_destruct = &copy_output_destruct,
+};
+
+static const struct copy_output_type *copy_output_types[] = {
+	&copy_output_type,
+};
+
+const struct copy_brick_type copy_brick_type = {
+	.type_name = "copy_brick",
+	.brick_size = sizeof(struct copy_brick),
+	.max_inputs = 4,
+	.max_outputs = 1,
+	.master_ops = &copy_brick_ops,
+	.aspect_types = copy_aspect_types,
+	.default_input_types = copy_input_types,
+	.default_output_types = copy_output_types,
+	.brick_construct = &copy_brick_construct,
+	.brick_destruct = &copy_brick_destruct,
+};
+
+/***************** module init stuff ************************/
+
+int __init init_xio_copy(void)
+{
+	XIO_INF("init_copy()\n");
+	return copy_register_brick_type();
+}
+
+void exit_xio_copy(void)
+{
+	XIO_INF("exit_copy()\n");
+	copy_unregister_brick_type();
+}
diff --git a/include/linux/xio/xio_copy.h b/include/linux/xio/xio_copy.h
new file mode 100644
index 000000000000..f92e898419f1
--- /dev/null
+++ b/include/linux/xio/xio_copy.h
@@ -0,0 +1,115 @@
+/*
+ * 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_COPY_H
+#define XIO_COPY_H
+
+#include <linux/wait.h>
+#include <linux/semaphore.h>
+
+#define INPUT_A_IO			0
+#define INPUT_A_COPY			1
+#define INPUT_B_IO			2
+#define INPUT_B_COPY			3
+
+extern int xio_copy_overlap;
+extern int xio_copy_read_prio;
+extern int xio_copy_write_prio;
+extern int xio_copy_read_max_fly;
+extern int xio_copy_write_max_fly;
+
+enum {
+	COPY_STATE_RESET = -1,
+	COPY_STATE_START = 0, /*  don't change this, it _must_ be zero */
+	COPY_STATE_START2,
+	COPY_STATE_READ1,
+	COPY_STATE_READ2,
+	COPY_STATE_READ3,
+	COPY_STATE_WRITE,
+	COPY_STATE_WRITTEN,
+	COPY_STATE_CLEANUP,
+	COPY_STATE_FINISHED,
+};
+
+struct copy_state {
+	struct aio_object *table[2];
+	bool active[2];
+	char state;
+	bool writeout;
+
+	short prev;
+	short len;
+	short error;
+};
+
+struct copy_aio_aspect {
+	GENERIC_ASPECT(aio);
+	struct copy_brick *brick;
+	int queue;
+};
+
+struct copy_brick {
+	XIO_BRICK(copy);
+	/*  parameters */
+	struct rate_limiter *copy_limiter;
+	loff_t copy_start;
+
+	loff_t copy_end; /*  stop working if == 0 */
+	int io_prio;
+
+	int append_mode; /*  1 = passively, 2 = actively */
+	bool verify_mode; /*  0 = copy, 1 = checksum+compare */
+	bool repair_mode; /*  whether to repair in case of verify errors */
+	bool recheck_mode; /*  whether to re-check after repairs (costs performance) */
+	bool utilize_mode; /*  utilize already copied data */
+	bool abort_mode;  /*  abort on IO error (default is retry forever) */
+	/*  readonly from outside */
+	loff_t copy_last; /*  current working position */
+	struct timespec copy_last_stamp;
+	int copy_error;
+	int copy_error_count;
+	int verify_ok_count;
+	int verify_error_count;
+	bool low_dirty;
+	bool is_aborting;
+
+	/*  internal */
+	bool trigger;
+	unsigned long clash;
+	atomic_t total_clash_count;
+	atomic_t io_flight;
+	atomic_t copy_read_flight;
+	atomic_t copy_write_flight;
+	unsigned long last_jiffies;
+
+	wait_queue_head_t event;
+	struct semaphore mutex;
+	struct task_struct *thread;
+	struct copy_state **st;
+};
+
+struct copy_input {
+	XIO_INPUT(copy);
+};
+
+struct copy_output {
+	XIO_OUTPUT(copy);
+};
+
+XIO_TYPES(copy);
+
+#endif
-- 
2.11.0