Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1039 insertions, 0 deletions

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
new file mode 100644
index 000000000..735ee0ca4
--- /dev/null
+++ b/drivers/s390/block/dcssblk.c
@@ -0,0 +1,1039 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * dcssblk.c -- the S/390 block driver for dcss memory
+ *
+ * Authors: Carsten Otte, Stefan Weinhuber, Gerald Schaefer
+ */
+
+#define KMSG_COMPONENT "dcssblk"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/pfn_t.h>
+#include <linux/uio.h>
+#include <linux/dax.h>
+#include <asm/extmem.h>
+#include <asm/io.h>
+
+#define DCSSBLK_NAME "dcssblk"
+#define DCSSBLK_MINORS_PER_DISK 1
+#define DCSSBLK_PARM_LEN 400
+#define DCSS_BUS_ID_SIZE 20
+
+static int dcssblk_open(struct block_device *bdev, fmode_t mode);
+static void dcssblk_release(struct gendisk *disk, fmode_t mode);
+static void dcssblk_submit_bio(struct bio *bio);
+static long dcssblk_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+		long nr_pages, enum dax_access_mode mode, void **kaddr,
+		pfn_t *pfn);
+
+static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";
+
+static int dcssblk_major;
+static const struct block_device_operations dcssblk_devops = {
+	.owner   	= THIS_MODULE,
+	.submit_bio	= dcssblk_submit_bio,
+	.open    	= dcssblk_open,
+	.release 	= dcssblk_release,
+};
+
+static int dcssblk_dax_zero_page_range(struct dax_device *dax_dev,
+				       pgoff_t pgoff, size_t nr_pages)
+{
+	long rc;
+	void *kaddr;
+
+	rc = dax_direct_access(dax_dev, pgoff, nr_pages, DAX_ACCESS,
+			&kaddr, NULL);
+	if (rc < 0)
+		return rc;
+	memset(kaddr, 0, nr_pages << PAGE_SHIFT);
+	dax_flush(dax_dev, kaddr, nr_pages << PAGE_SHIFT);
+	return 0;
+}
+
+static const struct dax_operations dcssblk_dax_ops = {
+	.direct_access = dcssblk_dax_direct_access,
+	.zero_page_range = dcssblk_dax_zero_page_range,
+};
+
+struct dcssblk_dev_info {
+	struct list_head lh;
+	struct device dev;
+	char segment_name[DCSS_BUS_ID_SIZE];
+	atomic_t use_count;
+	struct gendisk *gd;
+	unsigned long start;
+	unsigned long end;
+	int segment_type;
+	unsigned char save_pending;
+	unsigned char is_shared;
+	int num_of_segments;
+	struct list_head seg_list;
+	struct dax_device *dax_dev;
+};
+
+struct segment_info {
+	struct list_head lh;
+	char segment_name[DCSS_BUS_ID_SIZE];
+	unsigned long start;
+	unsigned long end;
+	int segment_type;
+};
+
+static ssize_t dcssblk_add_store(struct device * dev, struct device_attribute *attr, const char * buf,
+				  size_t count);
+static ssize_t dcssblk_remove_store(struct device * dev, struct device_attribute *attr, const char * buf,
+				  size_t count);
+
+static DEVICE_ATTR(add, S_IWUSR, NULL, dcssblk_add_store);
+static DEVICE_ATTR(remove, S_IWUSR, NULL, dcssblk_remove_store);
+
+static struct device *dcssblk_root_dev;
+
+static LIST_HEAD(dcssblk_devices);
+static struct rw_semaphore dcssblk_devices_sem;
+
+/*
+ * release function for segment device.
+ */
+static void
+dcssblk_release_segment(struct device *dev)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry, *temp;
+
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+	list_for_each_entry_safe(entry, temp, &dev_info->seg_list, lh) {
+		list_del(&entry->lh);
+		kfree(entry);
+	}
+	kfree(dev_info);
+	module_put(THIS_MODULE);
+}
+
+/*
+ * get a minor number. needs to be called with
+ * down_write(&dcssblk_devices_sem) and the
+ * device needs to be enqueued before the semaphore is
+ * freed.
+ */
+static int
+dcssblk_assign_free_minor(struct dcssblk_dev_info *dev_info)
+{
+	int minor, found;
+	struct dcssblk_dev_info *entry;
+
+	if (dev_info == NULL)
+		return -EINVAL;
+	for (minor = 0; minor < (1<<MINORBITS); minor++) {
+		found = 0;
+		// test if minor available
+		list_for_each_entry(entry, &dcssblk_devices, lh)
+			if (minor == entry->gd->first_minor)
+				found++;
+		if (!found) break; // got unused minor
+	}
+	if (found)
+		return -EBUSY;
+	dev_info->gd->first_minor = minor;
+	return 0;
+}
+
+/*
+ * get the struct dcssblk_dev_info from dcssblk_devices
+ * for the given name.
+ * down_read(&dcssblk_devices_sem) must be held.
+ */
+static struct dcssblk_dev_info *
+dcssblk_get_device_by_name(char *name)
+{
+	struct dcssblk_dev_info *entry;
+
+	list_for_each_entry(entry, &dcssblk_devices, lh) {
+		if (!strcmp(name, entry->segment_name)) {
+			return entry;
+		}
+	}
+	return NULL;
+}
+
+/*
+ * get the struct segment_info from seg_list
+ * for the given name.
+ * down_read(&dcssblk_devices_sem) must be held.
+ */
+static struct segment_info *
+dcssblk_get_segment_by_name(char *name)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry;
+
+	list_for_each_entry(dev_info, &dcssblk_devices, lh) {
+		list_for_each_entry(entry, &dev_info->seg_list, lh) {
+			if (!strcmp(name, entry->segment_name))
+				return entry;
+		}
+	}
+	return NULL;
+}
+
+/*
+ * get the highest address of the multi-segment block.
+ */
+static unsigned long
+dcssblk_find_highest_addr(struct dcssblk_dev_info *dev_info)
+{
+	unsigned long highest_addr;
+	struct segment_info *entry;
+
+	highest_addr = 0;
+	list_for_each_entry(entry, &dev_info->seg_list, lh) {
+		if (highest_addr < entry->end)
+			highest_addr = entry->end;
+	}
+	return highest_addr;
+}
+
+/*
+ * get the lowest address of the multi-segment block.
+ */
+static unsigned long
+dcssblk_find_lowest_addr(struct dcssblk_dev_info *dev_info)
+{
+	int set_first;
+	unsigned long lowest_addr;
+	struct segment_info *entry;
+
+	set_first = 0;
+	lowest_addr = 0;
+	list_for_each_entry(entry, &dev_info->seg_list, lh) {
+		if (set_first == 0) {
+			lowest_addr = entry->start;
+			set_first = 1;
+		} else {
+			if (lowest_addr > entry->start)
+				lowest_addr = entry->start;
+		}
+	}
+	return lowest_addr;
+}
+
+/*
+ * Check continuity of segments.
+ */
+static int
+dcssblk_is_continuous(struct dcssblk_dev_info *dev_info)
+{
+	int i, j, rc;
+	struct segment_info *sort_list, *entry, temp;
+
+	if (dev_info->num_of_segments <= 1)
+		return 0;
+
+	sort_list = kcalloc(dev_info->num_of_segments,
+			    sizeof(struct segment_info),
+			    GFP_KERNEL);
+	if (sort_list == NULL)
+		return -ENOMEM;
+	i = 0;
+	list_for_each_entry(entry, &dev_info->seg_list, lh) {
+		memcpy(&sort_list[i], entry, sizeof(struct segment_info));
+		i++;
+	}
+
+	/* sort segments */
+	for (i = 0; i < dev_info->num_of_segments; i++)
+		for (j = 0; j < dev_info->num_of_segments; j++)
+			if (sort_list[j].start > sort_list[i].start) {
+				memcpy(&temp, &sort_list[i],
+					sizeof(struct segment_info));
+				memcpy(&sort_list[i], &sort_list[j],
+					sizeof(struct segment_info));
+				memcpy(&sort_list[j], &temp,
+					sizeof(struct segment_info));
+			}
+
+	/* check continuity */
+	for (i = 0; i < dev_info->num_of_segments - 1; i++) {
+		if ((sort_list[i].end + 1) != sort_list[i+1].start) {
+			pr_err("Adjacent DCSSs %s and %s are not "
+			       "contiguous\n", sort_list[i].segment_name,
+			       sort_list[i+1].segment_name);
+			rc = -EINVAL;
+			goto out;
+		}
+		/* EN and EW are allowed in a block device */
+		if (sort_list[i].segment_type != sort_list[i+1].segment_type) {
+			if (!(sort_list[i].segment_type & SEGMENT_EXCLUSIVE) ||
+				(sort_list[i].segment_type == SEG_TYPE_ER) ||
+				!(sort_list[i+1].segment_type &
+				SEGMENT_EXCLUSIVE) ||
+				(sort_list[i+1].segment_type == SEG_TYPE_ER)) {
+				pr_err("DCSS %s and DCSS %s have "
+				       "incompatible types\n",
+				       sort_list[i].segment_name,
+				       sort_list[i+1].segment_name);
+				rc = -EINVAL;
+				goto out;
+			}
+		}
+	}
+	rc = 0;
+out:
+	kfree(sort_list);
+	return rc;
+}
+
+/*
+ * Load a segment
+ */
+static int
+dcssblk_load_segment(char *name, struct segment_info **seg_info)
+{
+	int rc;
+
+	/* already loaded? */
+	down_read(&dcssblk_devices_sem);
+	*seg_info = dcssblk_get_segment_by_name(name);
+	up_read(&dcssblk_devices_sem);
+	if (*seg_info != NULL)
+		return -EEXIST;
+
+	/* get a struct segment_info */
+	*seg_info = kzalloc(sizeof(struct segment_info), GFP_KERNEL);
+	if (*seg_info == NULL)
+		return -ENOMEM;
+
+	strcpy((*seg_info)->segment_name, name);
+
+	/* load the segment */
+	rc = segment_load(name, SEGMENT_SHARED,
+			&(*seg_info)->start, &(*seg_info)->end);
+	if (rc < 0) {
+		segment_warning(rc, (*seg_info)->segment_name);
+		kfree(*seg_info);
+	} else {
+		INIT_LIST_HEAD(&(*seg_info)->lh);
+		(*seg_info)->segment_type = rc;
+	}
+	return rc;
+}
+
+/*
+ * device attribute for switching shared/nonshared (exclusive)
+ * operation (show + store)
+ */
+static ssize_t
+dcssblk_shared_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dcssblk_dev_info *dev_info;
+
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+	return sprintf(buf, dev_info->is_shared ? "1\n" : "0\n");
+}
+
+static ssize_t
+dcssblk_shared_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry, *temp;
+	int rc;
+
+	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0'))
+		return -EINVAL;
+	down_write(&dcssblk_devices_sem);
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+	if (atomic_read(&dev_info->use_count)) {
+		rc = -EBUSY;
+		goto out;
+	}
+	if (inbuf[0] == '1') {
+		/* reload segments in shared mode */
+		list_for_each_entry(entry, &dev_info->seg_list, lh) {
+			rc = segment_modify_shared(entry->segment_name,
+						SEGMENT_SHARED);
+			if (rc < 0) {
+				BUG_ON(rc == -EINVAL);
+				if (rc != -EAGAIN)
+					goto removeseg;
+			}
+		}
+		dev_info->is_shared = 1;
+		switch (dev_info->segment_type) {
+		case SEG_TYPE_SR:
+		case SEG_TYPE_ER:
+		case SEG_TYPE_SC:
+			set_disk_ro(dev_info->gd, 1);
+		}
+	} else if (inbuf[0] == '0') {
+		/* reload segments in exclusive mode */
+		if (dev_info->segment_type == SEG_TYPE_SC) {
+			pr_err("DCSS %s is of type SC and cannot be "
+			       "loaded as exclusive-writable\n",
+			       dev_info->segment_name);
+			rc = -EINVAL;
+			goto out;
+		}
+		list_for_each_entry(entry, &dev_info->seg_list, lh) {
+			rc = segment_modify_shared(entry->segment_name,
+						   SEGMENT_EXCLUSIVE);
+			if (rc < 0) {
+				BUG_ON(rc == -EINVAL);
+				if (rc != -EAGAIN)
+					goto removeseg;
+			}
+		}
+		dev_info->is_shared = 0;
+		set_disk_ro(dev_info->gd, 0);
+	} else {
+		rc = -EINVAL;
+		goto out;
+	}
+	rc = count;
+	goto out;
+
+removeseg:
+	pr_err("DCSS device %s is removed after a failed access mode "
+	       "change\n", dev_info->segment_name);
+	temp = entry;
+	list_for_each_entry(entry, &dev_info->seg_list, lh) {
+		if (entry != temp)
+			segment_unload(entry->segment_name);
+	}
+	list_del(&dev_info->lh);
+
+	dax_remove_host(dev_info->gd);
+	kill_dax(dev_info->dax_dev);
+	put_dax(dev_info->dax_dev);
+	del_gendisk(dev_info->gd);
+	put_disk(dev_info->gd);
+	up_write(&dcssblk_devices_sem);
+
+	if (device_remove_file_self(dev, attr)) {
+		device_unregister(dev);
+		put_device(dev);
+	}
+	return rc;
+out:
+	up_write(&dcssblk_devices_sem);
+	return rc;
+}
+static DEVICE_ATTR(shared, S_IWUSR | S_IRUSR, dcssblk_shared_show,
+		   dcssblk_shared_store);
+
+/*
+ * device attribute for save operation on current copy
+ * of the segment. If the segment is busy, saving will
+ * become pending until it gets released, which can be
+ * undone by storing a non-true value to this entry.
+ * (show + store)
+ */
+static ssize_t
+dcssblk_save_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct dcssblk_dev_info *dev_info;
+
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+	return sprintf(buf, dev_info->save_pending ? "1\n" : "0\n");
+}
+
+static ssize_t
+dcssblk_save_store(struct device *dev, struct device_attribute *attr, const char *inbuf, size_t count)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry;
+
+	if ((count > 1) && (inbuf[1] != '\n') && (inbuf[1] != '\0'))
+		return -EINVAL;
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+
+	down_write(&dcssblk_devices_sem);
+	if (inbuf[0] == '1') {
+		if (atomic_read(&dev_info->use_count) == 0) {
+			// device is idle => we save immediately
+			pr_info("All DCSSs that map to device %s are "
+				"saved\n", dev_info->segment_name);
+			list_for_each_entry(entry, &dev_info->seg_list, lh) {
+				if (entry->segment_type == SEG_TYPE_EN ||
+				    entry->segment_type == SEG_TYPE_SN)
+					pr_warn("DCSS %s is of type SN or EN"
+						" and cannot be saved\n",
+						entry->segment_name);
+				else
+					segment_save(entry->segment_name);
+			}
+		}  else {
+			// device is busy => we save it when it becomes
+			// idle in dcssblk_release
+			pr_info("Device %s is in use, its DCSSs will be "
+				"saved when it becomes idle\n",
+				dev_info->segment_name);
+			dev_info->save_pending = 1;
+		}
+	} else if (inbuf[0] == '0') {
+		if (dev_info->save_pending) {
+			// device is busy & the user wants to undo his save
+			// request
+			dev_info->save_pending = 0;
+			pr_info("A pending save request for device %s "
+				"has been canceled\n",
+				dev_info->segment_name);
+		}
+	} else {
+		up_write(&dcssblk_devices_sem);
+		return -EINVAL;
+	}
+	up_write(&dcssblk_devices_sem);
+	return count;
+}
+static DEVICE_ATTR(save, S_IWUSR | S_IRUSR, dcssblk_save_show,
+		   dcssblk_save_store);
+
+/*
+ * device attribute for showing all segments in a device
+ */
+static ssize_t
+dcssblk_seglist_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	int i;
+
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry;
+
+	down_read(&dcssblk_devices_sem);
+	dev_info = container_of(dev, struct dcssblk_dev_info, dev);
+	i = 0;
+	buf[0] = '\0';
+	list_for_each_entry(entry, &dev_info->seg_list, lh) {
+		strcpy(&buf[i], entry->segment_name);
+		i += strlen(entry->segment_name);
+		buf[i] = '\n';
+		i++;
+	}
+	up_read(&dcssblk_devices_sem);
+	return i;
+}
+static DEVICE_ATTR(seglist, S_IRUSR, dcssblk_seglist_show, NULL);
+
+static struct attribute *dcssblk_dev_attrs[] = {
+	&dev_attr_shared.attr,
+	&dev_attr_save.attr,
+	&dev_attr_seglist.attr,
+	NULL,
+};
+static struct attribute_group dcssblk_dev_attr_group = {
+	.attrs = dcssblk_dev_attrs,
+};
+static const struct attribute_group *dcssblk_dev_attr_groups[] = {
+	&dcssblk_dev_attr_group,
+	NULL,
+};
+
+/*
+ * device attribute for adding devices
+ */
+static ssize_t
+dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	int rc, i, j, num_of_segments;
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *seg_info, *temp;
+	char *local_buf;
+	unsigned long seg_byte_size;
+
+	dev_info = NULL;
+	seg_info = NULL;
+	if (dev != dcssblk_root_dev) {
+		rc = -EINVAL;
+		goto out_nobuf;
+	}
+	if ((count < 1) || (buf[0] == '\0') || (buf[0] == '\n')) {
+		rc = -ENAMETOOLONG;
+		goto out_nobuf;
+	}
+
+	local_buf = kmalloc(count + 1, GFP_KERNEL);
+	if (local_buf == NULL) {
+		rc = -ENOMEM;
+		goto out_nobuf;
+	}
+
+	/*
+	 * parse input
+	 */
+	num_of_segments = 0;
+	for (i = 0; (i < count && (buf[i] != '\0') && (buf[i] != '\n')); i++) {
+		for (j = i; j < count &&
+			(buf[j] != ':') &&
+			(buf[j] != '\0') &&
+			(buf[j] != '\n'); j++) {
+			local_buf[j-i] = toupper(buf[j]);
+		}
+		local_buf[j-i] = '\0';
+		if (((j - i) == 0) || ((j - i) > 8)) {
+			rc = -ENAMETOOLONG;
+			goto seg_list_del;
+		}
+
+		rc = dcssblk_load_segment(local_buf, &seg_info);
+		if (rc < 0)
+			goto seg_list_del;
+		/*
+		 * get a struct dcssblk_dev_info
+		 */
+		if (num_of_segments == 0) {
+			dev_info = kzalloc(sizeof(struct dcssblk_dev_info),
+					GFP_KERNEL);
+			if (dev_info == NULL) {
+				rc = -ENOMEM;
+				goto out;
+			}
+			strcpy(dev_info->segment_name, local_buf);
+			dev_info->segment_type = seg_info->segment_type;
+			INIT_LIST_HEAD(&dev_info->seg_list);
+		}
+		list_add_tail(&seg_info->lh, &dev_info->seg_list);
+		num_of_segments++;
+		i = j;
+
+		if ((buf[j] == '\0') || (buf[j] == '\n'))
+			break;
+	}
+
+	/* no trailing colon at the end of the input */
+	if ((i > 0) && (buf[i-1] == ':')) {
+		rc = -ENAMETOOLONG;
+		goto seg_list_del;
+	}
+	strscpy(local_buf, buf, i + 1);
+	dev_info->num_of_segments = num_of_segments;
+	rc = dcssblk_is_continuous(dev_info);
+	if (rc < 0)
+		goto seg_list_del;
+
+	dev_info->start = dcssblk_find_lowest_addr(dev_info);
+	dev_info->end = dcssblk_find_highest_addr(dev_info);
+
+	dev_set_name(&dev_info->dev, "%s", dev_info->segment_name);
+	dev_info->dev.release = dcssblk_release_segment;
+	dev_info->dev.groups = dcssblk_dev_attr_groups;
+	INIT_LIST_HEAD(&dev_info->lh);
+	dev_info->gd = blk_alloc_disk(NUMA_NO_NODE);
+	if (dev_info->gd == NULL) {
+		rc = -ENOMEM;
+		goto seg_list_del;
+	}
+	dev_info->gd->major = dcssblk_major;
+	dev_info->gd->minors = DCSSBLK_MINORS_PER_DISK;
+	dev_info->gd->fops = &dcssblk_devops;
+	dev_info->gd->private_data = dev_info;
+	dev_info->gd->flags |= GENHD_FL_NO_PART;
+	blk_queue_logical_block_size(dev_info->gd->queue, 4096);
+	blk_queue_flag_set(QUEUE_FLAG_DAX, dev_info->gd->queue);
+
+	seg_byte_size = (dev_info->end - dev_info->start + 1);
+	set_capacity(dev_info->gd, seg_byte_size >> 9); // size in sectors
+	pr_info("Loaded %s with total size %lu bytes and capacity %lu "
+		"sectors\n", local_buf, seg_byte_size, seg_byte_size >> 9);
+
+	dev_info->save_pending = 0;
+	dev_info->is_shared = 1;
+	dev_info->dev.parent = dcssblk_root_dev;
+
+	/*
+	 *get minor, add to list
+	 */
+	down_write(&dcssblk_devices_sem);
+	if (dcssblk_get_segment_by_name(local_buf)) {
+		rc = -EEXIST;
+		goto release_gd;
+	}
+	rc = dcssblk_assign_free_minor(dev_info);
+	if (rc)
+		goto release_gd;
+	sprintf(dev_info->gd->disk_name, "dcssblk%d",
+		dev_info->gd->first_minor);
+	list_add_tail(&dev_info->lh, &dcssblk_devices);
+
+	if (!try_module_get(THIS_MODULE)) {
+		rc = -ENODEV;
+		goto dev_list_del;
+	}
+	/*
+	 * register the device
+	 */
+	rc = device_register(&dev_info->dev);
+	if (rc)
+		goto put_dev;
+
+	dev_info->dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops);
+	if (IS_ERR(dev_info->dax_dev)) {
+		rc = PTR_ERR(dev_info->dax_dev);
+		dev_info->dax_dev = NULL;
+		goto put_dev;
+	}
+	set_dax_synchronous(dev_info->dax_dev);
+	rc = dax_add_host(dev_info->dax_dev, dev_info->gd);
+	if (rc)
+		goto out_dax;
+
+	get_device(&dev_info->dev);
+	rc = device_add_disk(&dev_info->dev, dev_info->gd, NULL);
+	if (rc)
+		goto out_dax_host;
+
+	switch (dev_info->segment_type) {
+		case SEG_TYPE_SR:
+		case SEG_TYPE_ER:
+		case SEG_TYPE_SC:
+			set_disk_ro(dev_info->gd,1);
+			break;
+		default:
+			set_disk_ro(dev_info->gd,0);
+			break;
+	}
+	up_write(&dcssblk_devices_sem);
+	rc = count;
+	goto out;
+
+out_dax_host:
+	put_device(&dev_info->dev);
+	dax_remove_host(dev_info->gd);
+out_dax:
+	kill_dax(dev_info->dax_dev);
+	put_dax(dev_info->dax_dev);
+put_dev:
+	list_del(&dev_info->lh);
+	put_disk(dev_info->gd);
+	list_for_each_entry(seg_info, &dev_info->seg_list, lh) {
+		segment_unload(seg_info->segment_name);
+	}
+	put_device(&dev_info->dev);
+	up_write(&dcssblk_devices_sem);
+	goto out;
+dev_list_del:
+	list_del(&dev_info->lh);
+release_gd:
+	put_disk(dev_info->gd);
+	up_write(&dcssblk_devices_sem);
+seg_list_del:
+	if (dev_info == NULL)
+		goto out;
+	list_for_each_entry_safe(seg_info, temp, &dev_info->seg_list, lh) {
+		list_del(&seg_info->lh);
+		segment_unload(seg_info->segment_name);
+		kfree(seg_info);
+	}
+	kfree(dev_info);
+out:
+	kfree(local_buf);
+out_nobuf:
+	return rc;
+}
+
+/*
+ * device attribute for removing devices
+ */
+static ssize_t
+dcssblk_remove_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct segment_info *entry;
+	int rc, i;
+	char *local_buf;
+
+	if (dev != dcssblk_root_dev) {
+		return -EINVAL;
+	}
+	local_buf = kmalloc(count + 1, GFP_KERNEL);
+	if (local_buf == NULL) {
+		return -ENOMEM;
+	}
+	/*
+	 * parse input
+	 */
+	for (i = 0; (i < count && (*(buf+i)!='\0') && (*(buf+i)!='\n')); i++) {
+		local_buf[i] = toupper(buf[i]);
+	}
+	local_buf[i] = '\0';
+	if ((i == 0) || (i > 8)) {
+		rc = -ENAMETOOLONG;
+		goto out_buf;
+	}
+
+	down_write(&dcssblk_devices_sem);
+	dev_info = dcssblk_get_device_by_name(local_buf);
+	if (dev_info == NULL) {
+		up_write(&dcssblk_devices_sem);
+		pr_warn("Device %s cannot be removed because it is not a known device\n",
+			local_buf);
+		rc = -ENODEV;
+		goto out_buf;
+	}
+	if (atomic_read(&dev_info->use_count) != 0) {
+		up_write(&dcssblk_devices_sem);
+		pr_warn("Device %s cannot be removed while it is in use\n",
+			local_buf);
+		rc = -EBUSY;
+		goto out_buf;
+	}
+
+	list_del(&dev_info->lh);
+	dax_remove_host(dev_info->gd);
+	kill_dax(dev_info->dax_dev);
+	put_dax(dev_info->dax_dev);
+	del_gendisk(dev_info->gd);
+	put_disk(dev_info->gd);
+
+	/* unload all related segments */
+	list_for_each_entry(entry, &dev_info->seg_list, lh)
+		segment_unload(entry->segment_name);
+
+	up_write(&dcssblk_devices_sem);
+
+	device_unregister(&dev_info->dev);
+	put_device(&dev_info->dev);
+
+	rc = count;
+out_buf:
+	kfree(local_buf);
+	return rc;
+}
+
+static int
+dcssblk_open(struct block_device *bdev, fmode_t mode)
+{
+	struct dcssblk_dev_info *dev_info;
+	int rc;
+
+	dev_info = bdev->bd_disk->private_data;
+	if (NULL == dev_info) {
+		rc = -ENODEV;
+		goto out;
+	}
+	atomic_inc(&dev_info->use_count);
+	rc = 0;
+out:
+	return rc;
+}
+
+static void
+dcssblk_release(struct gendisk *disk, fmode_t mode)
+{
+	struct dcssblk_dev_info *dev_info = disk->private_data;
+	struct segment_info *entry;
+
+	if (!dev_info) {
+		WARN_ON(1);
+		return;
+	}
+	down_write(&dcssblk_devices_sem);
+	if (atomic_dec_and_test(&dev_info->use_count)
+	    && (dev_info->save_pending)) {
+		pr_info("Device %s has become idle and is being saved "
+			"now\n", dev_info->segment_name);
+		list_for_each_entry(entry, &dev_info->seg_list, lh) {
+			if (entry->segment_type == SEG_TYPE_EN ||
+			    entry->segment_type == SEG_TYPE_SN)
+				pr_warn("DCSS %s is of type SN or EN and cannot"
+					" be saved\n", entry->segment_name);
+			else
+				segment_save(entry->segment_name);
+		}
+		dev_info->save_pending = 0;
+	}
+	up_write(&dcssblk_devices_sem);
+}
+
+static void
+dcssblk_submit_bio(struct bio *bio)
+{
+	struct dcssblk_dev_info *dev_info;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+	unsigned long index;
+	unsigned long page_addr;
+	unsigned long source_addr;
+	unsigned long bytes_done;
+
+	bio = bio_split_to_limits(bio);
+	if (!bio)
+		return;
+
+	bytes_done = 0;
+	dev_info = bio->bi_bdev->bd_disk->private_data;
+	if (dev_info == NULL)
+		goto fail;
+	if ((bio->bi_iter.bi_sector & 7) != 0 ||
+	    (bio->bi_iter.bi_size & 4095) != 0)
+		/* Request is not page-aligned. */
+		goto fail;
+	/* verify data transfer direction */
+	if (dev_info->is_shared) {
+		switch (dev_info->segment_type) {
+		case SEG_TYPE_SR:
+		case SEG_TYPE_ER:
+		case SEG_TYPE_SC:
+			/* cannot write to these segments */
+			if (bio_data_dir(bio) == WRITE) {
+				pr_warn("Writing to %s failed because it is a read-only device\n",
+					dev_name(&dev_info->dev));
+				goto fail;
+			}
+		}
+	}
+
+	index = (bio->bi_iter.bi_sector >> 3);
+	bio_for_each_segment(bvec, bio, iter) {
+		page_addr = (unsigned long)bvec_virt(&bvec);
+		source_addr = dev_info->start + (index<<12) + bytes_done;
+		if (unlikely((page_addr & 4095) != 0) || (bvec.bv_len & 4095) != 0)
+			// More paranoia.
+			goto fail;
+		if (bio_data_dir(bio) == READ) {
+			memcpy((void*)page_addr, (void*)source_addr,
+				bvec.bv_len);
+		} else {
+			memcpy((void*)source_addr, (void*)page_addr,
+				bvec.bv_len);
+		}
+		bytes_done += bvec.bv_len;
+	}
+	bio_endio(bio);
+	return;
+fail:
+	bio_io_error(bio);
+}
+
+static long
+__dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff,
+		long nr_pages, void **kaddr, pfn_t *pfn)
+{
+	resource_size_t offset = pgoff * PAGE_SIZE;
+	unsigned long dev_sz;
+
+	dev_sz = dev_info->end - dev_info->start + 1;
+	if (kaddr)
+		*kaddr = (void *) dev_info->start + offset;
+	if (pfn)
+		*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
+				PFN_DEV|PFN_SPECIAL);
+
+	return (dev_sz - offset) / PAGE_SIZE;
+}
+
+static long
+dcssblk_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+		long nr_pages, enum dax_access_mode mode, void **kaddr,
+		pfn_t *pfn)
+{
+	struct dcssblk_dev_info *dev_info = dax_get_private(dax_dev);
+
+	return __dcssblk_direct_access(dev_info, pgoff, nr_pages, kaddr, pfn);
+}
+
+static void
+dcssblk_check_params(void)
+{
+	int rc, i, j, k;
+	char buf[DCSSBLK_PARM_LEN + 1];
+	struct dcssblk_dev_info *dev_info;
+
+	for (i = 0; (i < DCSSBLK_PARM_LEN) && (dcssblk_segments[i] != '\0');
+	     i++) {
+		for (j = i; (j < DCSSBLK_PARM_LEN) &&
+			    (dcssblk_segments[j] != ',')  &&
+			    (dcssblk_segments[j] != '\0') &&
+			    (dcssblk_segments[j] != '('); j++)
+		{
+			buf[j-i] = dcssblk_segments[j];
+		}
+		buf[j-i] = '\0';
+		rc = dcssblk_add_store(dcssblk_root_dev, NULL, buf, j-i);
+		if ((rc >= 0) && (dcssblk_segments[j] == '(')) {
+			for (k = 0; (buf[k] != ':') && (buf[k] != '\0'); k++)
+				buf[k] = toupper(buf[k]);
+			buf[k] = '\0';
+			if (!strncmp(&dcssblk_segments[j], "(local)", 7)) {
+				down_read(&dcssblk_devices_sem);
+				dev_info = dcssblk_get_device_by_name(buf);
+				up_read(&dcssblk_devices_sem);
+				if (dev_info)
+					dcssblk_shared_store(&dev_info->dev,
+							     NULL, "0\n", 2);
+			}
+		}
+		while ((dcssblk_segments[j] != ',') &&
+		       (dcssblk_segments[j] != '\0'))
+		{
+			j++;
+		}
+		if (dcssblk_segments[j] == '\0')
+			break;
+		i = j;
+	}
+}
+
+/*
+ * The init/exit functions.
+ */
+static void __exit
+dcssblk_exit(void)
+{
+	root_device_unregister(dcssblk_root_dev);
+	unregister_blkdev(dcssblk_major, DCSSBLK_NAME);
+}
+
+static int __init
+dcssblk_init(void)
+{
+	int rc;
+
+	dcssblk_root_dev = root_device_register("dcssblk");
+	if (IS_ERR(dcssblk_root_dev))
+		return PTR_ERR(dcssblk_root_dev);
+	rc = device_create_file(dcssblk_root_dev, &dev_attr_add);
+	if (rc)
+		goto out_root;
+	rc = device_create_file(dcssblk_root_dev, &dev_attr_remove);
+	if (rc)
+		goto out_root;
+	rc = register_blkdev(0, DCSSBLK_NAME);
+	if (rc < 0)
+		goto out_root;
+	dcssblk_major = rc;
+	init_rwsem(&dcssblk_devices_sem);
+
+	dcssblk_check_params();
+	return 0;
+
+out_root:
+	root_device_unregister(dcssblk_root_dev);
+
+	return rc;
+}
+
+module_init(dcssblk_init);
+module_exit(dcssblk_exit);
+
+module_param_string(segments, dcssblk_segments, DCSSBLK_PARM_LEN, 0444);
+MODULE_PARM_DESC(segments, "Name of DCSS segment(s) to be loaded, "
+		 "comma-separated list, names in each set separated "
+		 "by commas are separated by colons, each set contains "
+		 "names of contiguous segments and each name max. 8 chars.\n"
+		 "Adding \"(local)\" to the end of each set equals echoing 0 "
+		 "to /sys/devices/dcssblk/<device name>/shared after loading "
+		 "the contiguous segments - \n"
+		 "e.g. segments=\"mydcss1,mydcss2:mydcss3,mydcss4(local)\"");
+
+MODULE_LICENSE("GPL");