From: Thomas Schoebel-Theuer <tst@schoebel-theuer.de>
To: linux-kernel@vger.kernel.org, tst@schoebel-theuer.de
Subject: [RFC 17/31] mars: add new module xio_bio
Date: Thu, 31 Dec 2015 12:36:12 +0100
Message-Id: <1ad9cee560223010a88061c10e8d6d05aa6acb7f.1451558672.git.tst@schoebel-theuer.de>
In-Reply-To: <cover.1451558672.git.tst@schoebel-theuer.de>
References: <cover.1451558672.git.tst@schoebel-theuer.de>
In-Reply-To: <cover.1451558672.git.tst@schoebel-theuer.de>
References: <cover.1451558672.git.tst@schoebel-theuer.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 24827
Lines: 958

Signed-off-by: Thomas Schoebel-Theuer <tst@schoebel-theuer.de>
---
 drivers/staging/mars/xio_bricks/xio_bio.c | 845 ++++++++++++++++++++++++++++++
 include/linux/xio/xio_bio.h               |  85 +++
 2 files changed, 930 insertions(+)
 create mode 100644 drivers/staging/mars/xio_bricks/xio_bio.c
 create mode 100644 include/linux/xio/xio_bio.h

diff --git a/drivers/staging/mars/xio_bricks/xio_bio.c b/drivers/staging/mars/xio_bricks/xio_bio.c
new file mode 100644
index 0000000..ef18325
--- /dev/null
+++ b/drivers/staging/mars/xio_bricks/xio_bio.c
@@ -0,0 +1,845 @@
+/*
+ * 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.
+ */
+
+/*  Bio brick (interface to blkdev IO via kernel bios) */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/bio.h>
+
+#include <linux/xio/xio.h>
+#include <linux/brick/lib_timing.h>
+#include <linux/xio/lib_mapfree.h>
+
+#include <linux/xio/xio_bio.h>
+static struct timing_stats timings[2];
+
+struct threshold bio_submit_threshold = {
+	.thr_ban = &xio_global_ban,
+	.thr_parent = &global_io_threshold,
+	.thr_limit = BIO_SUBMIT_MAX_LATENCY,
+	.thr_factor = 100,
+	.thr_plus = 0,
+};
+
+struct threshold bio_io_threshold[2] = {
+	[0] = {
+		.thr_ban = &xio_global_ban,
+		.thr_parent = &global_io_threshold,
+		.thr_limit = BIO_IO_R_MAX_LATENCY,
+		.thr_factor = 10,
+		.thr_plus = 10000,
+	},
+	[1] = {
+		.thr_ban = &xio_global_ban,
+		.thr_parent = &global_io_threshold,
+		.thr_limit = BIO_IO_W_MAX_LATENCY,
+		.thr_factor = 10,
+		.thr_plus = 10000,
+	},
+};
+
+/************************ own type definitions ***********************/
+
+/************************ own helper functions ***********************/
+
+/* This is called from the kernel bio layer.
+ */
+static
+void bio_callback(struct bio *bio)
+{
+	struct bio_aio_aspect *aio_a = bio->bi_private;
+	struct bio_brick *brick;
+	unsigned long flags;
+
+	CHECK_PTR(aio_a, err);
+	CHECK_PTR(aio_a->output, err);
+	brick = aio_a->output->brick;
+	CHECK_PTR(brick, err);
+
+	aio_a->status_code = bio->bi_error;
+
+	spin_lock_irqsave(&brick->lock, flags);
+	list_del(&aio_a->io_head);
+	list_add_tail(&aio_a->io_head, &brick->completed_list);
+	atomic_inc(&brick->completed_count);
+	spin_unlock_irqrestore(&brick->lock, flags);
+
+	wake_up_interruptible(&brick->response_event);
+	goto out_return;
+err:
+	XIO_FAT("cannot handle bio callback\n");
+out_return:;
+}
+
+/* Map from kernel address/length to struct page (if not already known),
+ * check alignment constraints, create bio from it.
+ * Return the length (may be smaller than requested).
+ */
+static
+int make_bio(struct bio_brick *brick,
+	void *data,
+	int len,
+	loff_t pos,
+	struct bio_aio_aspect *private,
+	struct bio **_bio)
+{
+	unsigned long long sector;
+	int sector_offset;
+	int data_offset;
+	int page_offset;
+	int page_len;
+	int bvec_count;
+	int rest_len = len;
+	int result_len = 0;
+	int status;
+	int i;
+	struct bio *bio = NULL;
+	struct block_device *bdev;
+
+	status = -EINVAL;
+	CHECK_PTR(brick, out);
+	bdev = brick->bdev;
+	CHECK_PTR(bdev, out);
+
+	if (unlikely(rest_len <= 0)) {
+		XIO_ERR("bad bio len %d\n", rest_len);
+		goto out;
+	}
+
+	sector = pos >> 9;		       /*  TODO: make dynamic */
+	sector_offset = pos & ((1 << 9) - 1);  /*  TODO: make dynamic */
+	data_offset = ((unsigned long)data) & ((1 << 9) - 1);  /*  TODO: make dynamic */
+
+	if (unlikely(sector_offset > 0)) {
+		XIO_ERR("odd sector offset %d\n", sector_offset);
+		goto out;
+	}
+	if (unlikely(sector_offset != data_offset)) {
+		XIO_ERR("bad alignment: sector_offset %d != data_offset %d\n", sector_offset, data_offset);
+		goto out;
+	}
+	if (unlikely(rest_len & ((1 << 9) - 1))) {
+		XIO_ERR("odd length %d\n", rest_len);
+		goto out;
+	}
+
+	page_offset = ((unsigned long)data) & (PAGE_SIZE-1);
+	page_len = rest_len + page_offset;
+	bvec_count = (page_len - 1) / PAGE_SIZE + 1;
+	if (bvec_count > brick->bvec_max) {
+		bvec_count = brick->bvec_max;
+	} else if (unlikely(bvec_count <= 0)) {
+		XIO_WRN("bvec_count=%d\n", bvec_count);
+		bvec_count = 1;
+	}
+
+	bio = bio_alloc(GFP_BRICK, bvec_count);
+	status = -ENOMEM;
+
+	for (i = 0; i < bvec_count && rest_len > 0; i++) {
+		struct page *page;
+		int this_rest = PAGE_SIZE - page_offset;
+		int this_len = rest_len;
+
+		if (this_len > this_rest)
+			this_len = this_rest;
+
+		page = brick_iomap(data, &page_offset, &this_len);
+		if (unlikely(!page)) {
+			XIO_ERR("cannot iomap() kernel address %p\n", data);
+			status = -EINVAL;
+			goto out;
+		}
+
+		bio->bi_io_vec[i].bv_page = page;
+		bio->bi_io_vec[i].bv_len = this_len;
+		bio->bi_io_vec[i].bv_offset = page_offset;
+
+		data += this_len;
+		rest_len -= this_len;
+		result_len += this_len;
+		page_offset = 0;
+	}
+
+	if (unlikely(rest_len != 0)) {
+		XIO_ERR("computation of bvec_count %d was wrong, diff=%d\n", bvec_count, rest_len);
+		status = -EINVAL;
+		goto out;
+	}
+
+	bio->bi_vcnt = i;
+	bio->bi_iter.bi_idx = 0;
+	bio->bi_iter.bi_size = result_len;
+	bio->bi_iter.bi_sector = sector;
+	bio->bi_bdev = bdev;
+	bio->bi_private = private;
+	bio->bi_end_io = bio_callback;
+	bio->bi_rw = 0; /*  must be filled in later */
+	status = result_len;
+
+out:
+	if (unlikely(status < 0)) {
+		XIO_ERR("error %d\n", status);
+		if (bio) {
+			bio_put(bio);
+			bio = NULL;
+		}
+	}
+	*_bio = bio;
+	return status;
+}
+
+/***************** own brick * input * output operations *****************/
+
+#define PRIO_INDEX(aio) ((aio)->io_prio + 1)
+
+static int bio_get_info(struct bio_output *output, struct xio_info *info)
+{
+	struct bio_brick *brick = output->brick;
+	struct inode *inode;
+	int status = -ENOENT;
+
+	if (unlikely(!brick->mf ||
+		     !brick->mf->mf_filp ||
+		     !brick->mf->mf_filp->f_mapping)) {
+		goto done;
+	}
+	inode = brick->mf->mf_filp->f_mapping->host;
+	if (unlikely(!inode))
+		goto done;
+
+	info->tf_align = 512;
+	info->tf_min_size = 512;
+	brick->total_size = i_size_read(inode);
+	info->current_size = brick->total_size;
+	XIO_DBG("determined device size = %lld\n", info->current_size);
+	status = 0;
+
+done:
+	return status;
+}
+
+static int bio_io_get(struct bio_output *output, struct aio_object *aio)
+{
+	struct bio_aio_aspect *aio_a;
+	int status = -EINVAL;
+
+	CHECK_PTR(output, done);
+	CHECK_PTR(output->brick, done);
+
+	if (aio->obj_initialized) {
+		obj_get(aio);
+		return aio->io_len;
+	}
+
+	aio_a = bio_aio_get_aspect(output->brick, aio);
+	CHECK_PTR(aio_a, done);
+	aio_a->output = output;
+	aio_a->bio = NULL;
+
+	if (!aio->io_data) { /*  buffered IO. */
+		if (unlikely(aio->io_len <= 0))
+			goto done;
+		status = -ENOMEM;
+		aio->io_data = brick_block_alloc(aio->io_pos, (aio_a->alloc_len = aio->io_len));
+		aio_a->do_dealloc = true;
+	}
+
+	status = make_bio(output->brick, aio->io_data, aio->io_len, aio->io_pos, aio_a, &aio_a->bio);
+	if (unlikely(status < 0 || !aio_a->bio)) {
+		XIO_ERR("could not create bio, status = %d\n", status);
+		goto done;
+	}
+
+	if (unlikely(aio->io_prio < XIO_PRIO_HIGH))
+		aio->io_prio = XIO_PRIO_HIGH;
+	else if (unlikely(aio->io_prio > XIO_PRIO_LOW))
+		aio->io_prio = XIO_PRIO_LOW;
+
+	aio->io_len = status;
+	obj_get_first(aio);
+	status = 0;
+
+done:
+	return status;
+}
+
+static
+void _bio_io_put(struct bio_output *output, struct aio_object *aio)
+{
+	struct bio_aio_aspect *aio_a;
+
+	aio->io_total_size = output->brick->total_size;
+
+	aio_a = bio_aio_get_aspect(output->brick, aio);
+	CHECK_PTR(aio_a, err);
+
+	if (likely(aio_a->bio)) {
+		bio_put(aio_a->bio);
+		aio_a->bio = NULL;
+	}
+	if (aio_a->do_dealloc) {
+		brick_block_free(aio->io_data, aio_a->alloc_len);
+		aio->io_data = NULL;
+	}
+	obj_free(aio);
+
+	goto out_return;
+err:
+	XIO_FAT("cannot work\n");
+out_return:;
+}
+
+#define BIO_AIO_PUT(output, aio)					\
+	({								\
+		if (obj_put(aio)) {					\
+			_bio_io_put(output, aio);			\
+		}							\
+	})
+
+static
+void bio_io_put(struct bio_output *output, struct aio_object *aio)
+{
+	BIO_AIO_PUT(output, aio);
+}
+
+static
+void _bio_io_io(struct bio_output *output, struct aio_object *aio, bool cork)
+{
+	struct bio_brick *brick = output->brick;
+	struct bio_aio_aspect *aio_a = bio_aio_get_aspect(output->brick, aio);
+	struct bio *bio;
+	unsigned long long latency;
+	unsigned long flags;
+	int rw;
+	int status = -EINVAL;
+
+	CHECK_PTR(aio_a, err);
+	bio = aio_a->bio;
+	CHECK_PTR(bio, err);
+
+	obj_get(aio);
+	atomic_inc(&brick->fly_count[PRIO_INDEX(aio)]);
+
+	bio_get(bio);
+
+	rw = aio->io_rw & 1;
+	if (brick->do_noidle && !cork)
+		rw |= REQ_NOIDLE;
+	if (!aio->io_skip_sync) {
+		if (brick->do_sync)
+			rw |= REQ_SYNC;
+	}
+
+	aio_a->start_stamp = cpu_clock(raw_smp_processor_id());
+	spin_lock_irqsave(&brick->lock, flags);
+	list_add_tail(&aio_a->io_head, &brick->submitted_list[rw & 1]);
+	spin_unlock_irqrestore(&brick->lock, flags);
+
+	bio->bi_rw = rw;
+	latency = TIME_STATS(
+		&timings[rw & 1],
+		submit_bio(rw, bio)
+		);
+
+	threshold_check(&bio_submit_threshold, latency);
+
+	status = 0;
+#ifdef BIO_EOPNOTSUPP /* missing since b25de9d6da49b1a8760a89672283128aa8c78345 */
+	if (unlikely(bio_flagged(bio, BIO_EOPNOTSUPP)))
+		status = -EOPNOTSUPP;
+#endif
+
+	if (likely(status >= 0))
+		goto done;
+
+	bio_put(bio);
+	atomic_dec(&brick->fly_count[PRIO_INDEX(aio)]);
+
+err:
+	XIO_ERR("IO error %d\n", status);
+	CHECKED_CALLBACK(aio, status, done);
+	atomic_dec(&xio_global_io_flying);
+
+done:;
+}
+
+static
+void bio_io_io(struct bio_output *output, struct aio_object *aio)
+{
+	CHECK_PTR(aio, fatal);
+
+	obj_get(aio);
+	atomic_inc(&xio_global_io_flying);
+
+	if (aio->io_prio == XIO_PRIO_LOW ||
+	    (aio->io_prio == XIO_PRIO_NORMAL && aio->io_rw)) {
+		struct bio_aio_aspect *aio_a = bio_aio_get_aspect(output->brick, aio);
+		struct bio_brick *brick = output->brick;
+		unsigned long flags;
+
+		spin_lock_irqsave(&brick->lock, flags);
+		list_add_tail(&aio_a->io_head, &brick->queue_list[PRIO_INDEX(aio)]);
+		atomic_inc(&brick->queue_count[PRIO_INDEX(aio)]);
+		spin_unlock_irqrestore(&brick->lock, flags);
+		brick->submitted = true;
+
+		wake_up_interruptible(&brick->submit_event);
+		goto out_return;
+	}
+
+	/*  realtime IO: start immediately */
+	_bio_io_io(output, aio, false);
+	BIO_AIO_PUT(output, aio);
+	goto out_return;
+fatal:
+	XIO_FAT("cannot handle aio %p on output %p\n", aio, output);
+out_return:;
+}
+
+static
+int bio_response_thread(void *data)
+{
+	struct bio_brick *brick = data;
+
+	XIO_INF("bio response thread has started on '%s'.\n", brick->brick_path);
+
+	for (;;) {
+		LIST_HEAD(tmp_list);
+		unsigned long flags;
+		int thr_limit;
+		int sleeptime;
+		int count;
+		int i;
+
+		thr_limit = bio_io_threshold[0].thr_limit;
+		if (bio_io_threshold[1].thr_limit < thr_limit)
+			thr_limit = bio_io_threshold[1].thr_limit;
+
+		sleeptime = HZ / 10;
+		if (thr_limit > 0) {
+			sleeptime = thr_limit / (1000000 * 2 / HZ);
+			if (unlikely(sleeptime < 2))
+				sleeptime = 2;
+		}
+
+		wait_event_interruptible_timeout(
+			brick->response_event,
+			atomic_read(&brick->completed_count) > 0,
+			sleeptime);
+
+		spin_lock_irqsave(&brick->lock, flags);
+		list_replace_init(&brick->completed_list, &tmp_list);
+		spin_unlock_irqrestore(&brick->lock, flags);
+
+		count = 0;
+		for (;;) {
+			struct list_head *tmp;
+			struct bio_aio_aspect *aio_a;
+			struct aio_object *aio;
+			unsigned long long latency;
+			int code;
+
+			if (list_empty(&tmp_list)) {
+				if (brick_thread_should_stop() &&
+				    atomic_read(&brick->fly_count[0]) +
+				    atomic_read(&brick->fly_count[1]) +
+				    atomic_read(&brick->fly_count[2]) <= 0)
+					goto done;
+				break;
+			}
+
+			tmp = tmp_list.next;
+			list_del_init(tmp);
+			atomic_dec(&brick->completed_count);
+
+			aio_a = container_of(tmp, struct bio_aio_aspect, io_head);
+			aio = aio_a->object;
+
+			latency = cpu_clock(raw_smp_processor_id()) - aio_a->start_stamp;
+			threshold_check(&bio_io_threshold[aio->io_rw & 1], latency);
+
+			code = aio_a->status_code;
+
+			if (code < 0) {
+				XIO_ERR("IO error %d\n", code);
+			} else {
+				aio_checksum(aio);
+				aio->io_flags |= AIO_UPTODATE;
+			}
+
+			SIMPLE_CALLBACK(aio, code);
+
+			atomic_dec(&brick->fly_count[PRIO_INDEX(aio)]);
+			atomic_inc(&brick->total_completed_count[PRIO_INDEX(aio)]);
+			count++;
+
+			if (likely(aio_a->bio))
+				bio_put(aio_a->bio);
+			BIO_AIO_PUT(aio_a->output, aio);
+
+			atomic_dec(&xio_global_io_flying);
+		}
+
+		/* Try to detect slow requests as early as possible,
+		 * even before they have completed.
+		 */
+		for (i = 0; i < 2; i++) {
+			unsigned long long eldest = 0;
+
+			spin_lock_irqsave(&brick->lock, flags);
+			if (!list_empty(&brick->submitted_list[i])) {
+				struct bio_aio_aspect *aio_a;
+
+				aio_a = container_of(brick->submitted_list[i].next, struct bio_aio_aspect, io_head);
+				eldest = aio_a->start_stamp;
+			}
+			spin_unlock_irqrestore(&brick->lock, flags);
+
+			if (eldest)
+				threshold_check(&bio_io_threshold[i], cpu_clock(raw_smp_processor_id()) - eldest);
+		}
+
+		if (count) {
+			brick->submitted = true;
+			wake_up_interruptible(&brick->submit_event);
+		}
+	}
+done:
+	XIO_INF("bio response thread has stopped.\n");
+	return 0;
+}
+
+static
+bool _bg_should_run(struct bio_brick *brick)
+{
+	return (atomic_read(&brick->queue_count[2]) > 0 &&
+		atomic_read(&brick->fly_count[0]) + atomic_read(&brick->fly_count[1]) <= brick->bg_threshold &&
+		(brick->bg_maxfly <= 0 || atomic_read(&brick->fly_count[2]) < brick->bg_maxfly));
+}
+
+static
+int bio_submit_thread(void *data)
+{
+	struct bio_brick *brick = data;
+
+	XIO_INF("bio submit thread has started on '%s'.\n", brick->brick_path);
+
+	while (!brick_thread_should_stop()) {
+		int prio;
+
+		wait_event_interruptible_timeout(
+			brick->submit_event,
+			brick->submitted,
+			HZ / 2);
+
+		brick->submitted = false;
+
+		for (prio = 0; prio < XIO_PRIO_NR; prio++) {
+			LIST_HEAD(tmp_list);
+			unsigned long flags;
+
+			if (prio == XIO_PRIO_NR-1 && !_bg_should_run(brick))
+				break;
+
+			spin_lock_irqsave(&brick->lock, flags);
+			list_replace_init(&brick->queue_list[prio], &tmp_list);
+			spin_unlock_irqrestore(&brick->lock, flags);
+
+			while (!list_empty(&tmp_list)) {
+				struct list_head *tmp = tmp_list.next;
+				struct bio_aio_aspect *aio_a;
+				struct aio_object *aio;
+				bool cork;
+
+				list_del_init(tmp);
+
+				aio_a = container_of(tmp, struct bio_aio_aspect, io_head);
+				aio = aio_a->object;
+				if (unlikely(!aio)) {
+					XIO_ERR("invalid aio\n");
+					continue;
+				}
+
+				atomic_dec(&brick->queue_count[PRIO_INDEX(aio)]);
+				cork = atomic_read(&brick->queue_count[PRIO_INDEX(aio)]) > 0;
+
+				_bio_io_io(aio_a->output, aio, cork);
+
+				BIO_AIO_PUT(aio_a->output, aio);
+			}
+		}
+	}
+
+	XIO_INF("bio submit thread has stopped.\n");
+	return 0;
+}
+
+static int bio_switch(struct bio_brick *brick)
+{
+	int status = 0;
+
+	if (brick->power.button) {
+		if (brick->power.on_led)
+			goto done;
+
+		xio_set_power_off_led((void *)brick, false);
+
+		if (!brick->bdev) {
+			static int index;
+			const char *path = brick->brick_path;
+			int flags = O_RDWR | O_EXCL | O_LARGEFILE;
+			struct address_space *mapping;
+			struct inode *inode = NULL;
+			struct request_queue *q;
+
+			brick->mf = mapfree_get(path, flags);
+			if (unlikely(!brick->mf || !brick->mf->mf_filp)) {
+				status = -ENOENT;
+				XIO_ERR("cannot open file '%s'\n", path);
+				goto done;
+			}
+			mapfree_pages(brick->mf, -1);
+			mapping = brick->mf->mf_filp->f_mapping;
+			if (likely(mapping))
+				inode = mapping->host;
+			if (unlikely(!mapping || !inode)) {
+				XIO_ERR("internal problem with '%s'\n", path);
+				status = -EINVAL;
+				goto done;
+			}
+			if (unlikely(!S_ISBLK(inode->i_mode) || !inode->i_bdev)) {
+				XIO_ERR("sorry, '%s' is not a block device\n", path);
+				status = -ENODEV;
+				goto done;
+			}
+
+			mapping_set_gfp_mask(mapping, mapping_gfp_mask(mapping) & ~(__GFP_IO | __GFP_FS));
+
+			q = bdev_get_queue(inode->i_bdev);
+			if (unlikely(!q)) {
+				XIO_ERR("internal queue '%s' does not exist\n", path);
+				status = -EINVAL;
+				goto done;
+			}
+
+			XIO_INF("'%s' ra_pages OLD=%lu NEW=%d\n",
+				path,
+				q->backing_dev_info.ra_pages,
+				brick->ra_pages);
+			q->backing_dev_info.ra_pages = brick->ra_pages;
+
+			brick->bvec_max = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
+			if (brick->bvec_max > BIO_MAX_PAGES)
+				brick->bvec_max = BIO_MAX_PAGES;
+			else if (brick->bvec_max <= 1)
+				brick->bvec_max = 1;
+			brick->total_size = i_size_read(inode);
+			XIO_INF("'%s' size=%lld bvec_max=%d\n",
+				 path, brick->total_size, brick->bvec_max);
+
+			brick->response_thread = brick_thread_create(bio_response_thread,
+				brick,
+				"xio_bio_r%d",
+				index);
+			brick->submit_thread = brick_thread_create(bio_submit_thread, brick, "xio_bio_s%d", index);
+			status = -ENOMEM;
+			if (likely(brick->submit_thread && brick->response_thread)) {
+				brick->bdev = inode->i_bdev;
+				brick->mode_ptr = &brick->mf->mf_mode;
+				index++;
+				status = 0;
+			}
+		}
+	}
+
+	xio_set_power_on_led((void *)brick, brick->power.button && brick->bdev != NULL);
+
+done:
+	if (status < 0 || !brick->power.button) {
+		if (brick->submit_thread) {
+			brick_thread_stop(brick->submit_thread);
+			brick->submit_thread = NULL;
+		}
+		if (brick->response_thread) {
+			brick_thread_stop(brick->response_thread);
+			brick->response_thread = NULL;
+		}
+		if (brick->mf) {
+			mapfree_put(brick->mf);
+			brick->mf = NULL;
+		}
+		brick->mode_ptr = NULL;
+		brick->bdev = NULL;
+		if (!brick->power.button) {
+			xio_set_power_off_led((void *)brick, true);
+			brick->total_size = 0;
+		}
+	}
+	return status;
+}
+
+/*************** informational * statistics **************/
+
+static noinline
+char *bio_statistics(struct bio_brick *brick, int verbose)
+{
+	char *res = brick_string_alloc(4096);
+	int pos = 0;
+
+	pos += report_timing(&timings[0], res + pos, 4096 - pos);
+	pos += report_timing(&timings[1], res + pos, 4096 - pos);
+
+	snprintf(res + pos, 4096 - pos,
+		 "total completed[0] = %d completed[1] = %d completed[2] = %d | queued[0] = %d queued[1] = %d queued[2] = %d flying[0] = %d flying[1] = %d flying[2] = %d completing = %d\n",
+		 atomic_read(&brick->total_completed_count[0]),
+		 atomic_read(&brick->total_completed_count[1]),
+		 atomic_read(&brick->total_completed_count[2]),
+		 atomic_read(&brick->fly_count[0]),
+		 atomic_read(&brick->queue_count[0]),
+		 atomic_read(&brick->queue_count[1]),
+		 atomic_read(&brick->queue_count[2]),
+		 atomic_read(&brick->fly_count[1]),
+		 atomic_read(&brick->fly_count[2]),
+		 atomic_read(&brick->completed_count));
+
+	return res;
+}
+
+static noinline
+void bio_reset_statistics(struct bio_brick *brick)
+{
+	atomic_set(&brick->total_completed_count[0], 0);
+	atomic_set(&brick->total_completed_count[1], 0);
+	atomic_set(&brick->total_completed_count[2], 0);
+}
+
+/*************** object * aspect constructors * destructors **************/
+
+static int bio_aio_aspect_init_fn(struct generic_aspect *_ini)
+{
+	struct bio_aio_aspect *ini = (void *)_ini;
+
+	INIT_LIST_HEAD(&ini->io_head);
+	return 0;
+}
+
+static void bio_aio_aspect_exit_fn(struct generic_aspect *_ini)
+{
+	struct bio_aio_aspect *ini = (void *)_ini;
+
+	(void)ini;
+}
+
+XIO_MAKE_STATICS(bio);
+
+/********************* brick constructors * destructors *******************/
+
+static int bio_brick_construct(struct bio_brick *brick)
+{
+	spin_lock_init(&brick->lock);
+	INIT_LIST_HEAD(&brick->queue_list[0]);
+	INIT_LIST_HEAD(&brick->queue_list[1]);
+	INIT_LIST_HEAD(&brick->queue_list[2]);
+	INIT_LIST_HEAD(&brick->submitted_list[0]);
+	INIT_LIST_HEAD(&brick->submitted_list[1]);
+	INIT_LIST_HEAD(&brick->completed_list);
+	init_waitqueue_head(&brick->submit_event);
+	init_waitqueue_head(&brick->response_event);
+	return 0;
+}
+
+static int bio_brick_destruct(struct bio_brick *brick)
+{
+	return 0;
+}
+
+static int bio_output_construct(struct bio_output *output)
+{
+	return 0;
+}
+
+static int bio_output_destruct(struct bio_output *output)
+{
+	return 0;
+}
+
+/************************ static structs ***********************/
+
+static struct bio_brick_ops bio_brick_ops = {
+	.brick_switch = bio_switch,
+	.brick_statistics = bio_statistics,
+	.reset_statistics = bio_reset_statistics,
+};
+
+static struct bio_output_ops bio_output_ops = {
+	.xio_get_info = bio_get_info,
+	.aio_get = bio_io_get,
+	.aio_put = bio_io_put,
+	.aio_io = bio_io_io,
+};
+
+const struct bio_input_type bio_input_type = {
+	.type_name = "bio_input",
+	.input_size = sizeof(struct bio_input),
+};
+
+static const struct bio_input_type *bio_input_types[] = {
+	&bio_input_type,
+};
+
+const struct bio_output_type bio_output_type = {
+	.type_name = "bio_output",
+	.output_size = sizeof(struct bio_output),
+	.master_ops = &bio_output_ops,
+	.output_construct = &bio_output_construct,
+	.output_destruct = &bio_output_destruct,
+};
+
+static const struct bio_output_type *bio_output_types[] = {
+	&bio_output_type,
+};
+
+const struct bio_brick_type bio_brick_type = {
+	.type_name = "bio_brick",
+	.brick_size = sizeof(struct bio_brick),
+	.max_inputs = 0,
+	.max_outputs = 1,
+	.master_ops = &bio_brick_ops,
+	.aspect_types = bio_aspect_types,
+	.default_input_types = bio_input_types,
+	.default_output_types = bio_output_types,
+	.brick_construct = &bio_brick_construct,
+	.brick_destruct = &bio_brick_destruct,
+};
+
+/***************** module init stuff ************************/
+
+int __init init_xio_bio(void)
+{
+	XIO_INF("init_bio()\n");
+	_bio_brick_type = (void *)&bio_brick_type;
+	return bio_register_brick_type();
+}
+
+void exit_xio_bio(void)
+{
+	XIO_INF("exit_bio()\n");
+	bio_unregister_brick_type();
+}
diff --git a/include/linux/xio/xio_bio.h b/include/linux/xio/xio_bio.h
new file mode 100644
index 0000000..a0d98be
--- /dev/null
+++ b/include/linux/xio/xio_bio.h
@@ -0,0 +1,85 @@
+/*
+ * 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_BIO_H
+#define XIO_BIO_H
+
+#define BIO_SUBMIT_MAX_LATENCY		250 /*	250 us */
+#define BIO_IO_R_MAX_LATENCY		40000 /*   40 ms */
+#define BIO_IO_W_MAX_LATENCY		100000 /*  100 ms */
+
+extern struct threshold bio_submit_threshold;
+extern struct threshold bio_io_threshold[2];
+
+#include <linux/blkdev.h>
+
+struct bio_aio_aspect {
+	GENERIC_ASPECT(aio);
+	struct list_head io_head;
+	struct bio *bio;
+	struct bio_output *output;
+	unsigned long long start_stamp;
+	int status_code;
+	int hash_pos;
+	int alloc_len;
+	bool do_dealloc;
+};
+
+struct bio_brick {
+	XIO_BRICK(bio);
+	/*  tunables */
+	int ra_pages;
+	int bg_threshold;
+	int bg_maxfly;
+	bool do_noidle;
+	bool do_sync;
+	bool do_unplug;
+
+	/*  readonly */
+	loff_t total_size;
+	atomic_t fly_count[XIO_PRIO_NR];
+	atomic_t queue_count[XIO_PRIO_NR];
+	atomic_t completed_count;
+	atomic_t total_completed_count[XIO_PRIO_NR];
+
+	/*  private */
+	spinlock_t lock;
+	struct list_head queue_list[XIO_PRIO_NR];
+	struct list_head submitted_list[2];
+	struct list_head completed_list;
+
+	wait_queue_head_t submit_event;
+	wait_queue_head_t response_event;
+	struct mapfree_info *mf;
+	struct block_device *bdev;
+	struct task_struct *submit_thread;
+	struct task_struct *response_thread;
+	int bvec_max;
+	bool submitted;
+};
+
+struct bio_input {
+	XIO_INPUT(bio);
+};
+
+struct bio_output {
+	XIO_OUTPUT(bio);
+};
+
+XIO_TYPES(bio);
+
+#endif
-- 
2.6.4

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