[mirror_ubuntu-artful-kernel.git] / drivers / s390 / block / dcssblk.c

/*
 * 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/platform_device.h>
#include <linux/pfn_t.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 blk_qc_t dcssblk_make_request(struct request_queue *q,
                                                struct bio *bio);
static long dcssblk_direct_access(struct block_device *bdev, sector_t secnum,
                         void __pmem **kaddr, pfn_t *pfn, long size);

static char dcssblk_segments[DCSSBLK_PARM_LEN] = "\0";

static int dcssblk_major;
static const struct block_device_operations dcssblk_devops = {
        .owner          = THIS_MODULE,
        .open           = dcssblk_open,
        .release        = dcssblk_release,
        .direct_access  = dcssblk_direct_access,
};

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;
        struct request_queue *dcssblk_queue;
        int num_of_segments;
        struct list_head seg_list;
};

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 = kzalloc(
                        sizeof(struct segment_info) * dev_info->num_of_segments,
                        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);

        del_gendisk(dev_info->gd);
        blk_cleanup_queue(dev_info->dcssblk_queue);
        dev_info->gd->queue = NULL;
        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;
        }
        strlcpy(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 = alloc_disk(DCSSBLK_MINORS_PER_DISK);
        if (dev_info->gd == NULL) {
                rc = -ENOMEM;
                goto seg_list_del;
        }
        dev_info->gd->major = dcssblk_major;
        dev_info->gd->fops = &dcssblk_devops;
        dev_info->dcssblk_queue = blk_alloc_queue(GFP_KERNEL);
        dev_info->gd->queue = dev_info->dcssblk_queue;
        dev_info->gd->private_data = dev_info;
        dev_info->gd->driverfs_dev = &dev_info->dev;
        blk_queue_make_request(dev_info->dcssblk_queue, dcssblk_make_request);
        blk_queue_logical_block_size(dev_info->dcssblk_queue, 4096);

        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;

        get_device(&dev_info->dev);
        add_disk(dev_info->gd);

        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;

put_dev:
        list_del(&dev_info->lh);
        blk_cleanup_queue(dev_info->dcssblk_queue);
        dev_info->gd->queue = NULL;
        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:
        blk_cleanup_queue(dev_info->dcssblk_queue);
        dev_info->gd->queue = NULL;
        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);
        del_gendisk(dev_info->gd);
        blk_cleanup_queue(dev_info->dcssblk_queue);
        dev_info->gd->queue = NULL;
        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);
        bdev->bd_block_size = 4096;
        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 blk_qc_t
dcssblk_make_request(struct request_queue *q, 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;

        blk_queue_split(q, &bio, q->bio_split);

        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;
        if (bio_end_sector(bio) > get_capacity(bio->bi_bdev->bd_disk)) {
                /* Request beyond end of DCSS segment. */
                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)
                        page_address(bvec.bv_page) + bvec.bv_offset;
                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 BLK_QC_T_NONE;
fail:
        bio_io_error(bio);
        return BLK_QC_T_NONE;
}

static long
dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
                        void __pmem **kaddr, pfn_t *pfn, long size)
{
        struct dcssblk_dev_info *dev_info;
        unsigned long offset, dev_sz;

        dev_info = bdev->bd_disk->private_data;
        if (!dev_info)
                return -ENODEV;
        dev_sz = dev_info->end - dev_info->start;
        offset = secnum * 512;
        *kaddr = (void __pmem *) (dev_info->start + offset);
        *pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);

        return dev_sz - offset;
}

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;
        }
}

/*
 * Suspend / Resume
 */
static int dcssblk_freeze(struct device *dev)
{
        struct dcssblk_dev_info *dev_info;
        int rc = 0;

        list_for_each_entry(dev_info, &dcssblk_devices, lh) {
                switch (dev_info->segment_type) {
                        case SEG_TYPE_SR:
                        case SEG_TYPE_ER:
                        case SEG_TYPE_SC:
                                if (!dev_info->is_shared)
                                        rc = -EINVAL;
                                break;
                        default:
                                rc = -EINVAL;
                                break;
                }
                if (rc)
                        break;
        }
        if (rc)
                pr_err("Suspending the system failed because DCSS device %s "
                       "is writable\n",
                       dev_info->segment_name);
        return rc;
}

static int dcssblk_restore(struct device *dev)
{
        struct dcssblk_dev_info *dev_info;
        struct segment_info *entry;
        unsigned long start, end;
        int rc = 0;

        list_for_each_entry(dev_info, &dcssblk_devices, lh) {
                list_for_each_entry(entry, &dev_info->seg_list, lh) {
                        segment_unload(entry->segment_name);
                        rc = segment_load(entry->segment_name, SEGMENT_SHARED,
                                          &start, &end);
                        if (rc < 0) {
// TODO in_use check ?
                                segment_warning(rc, entry->segment_name);
                                goto out_panic;
                        }
                        if (start != entry->start || end != entry->end) {
                                pr_err("The address range of DCSS %s changed "
                                       "while the system was suspended\n",
                                       entry->segment_name);
                                goto out_panic;
                        }
                }
        }
        return 0;
out_panic:
        panic("fatal dcssblk resume error\n");
}

static int dcssblk_thaw(struct device *dev)
{
        return 0;
}

static const struct dev_pm_ops dcssblk_pm_ops = {
        .freeze         = dcssblk_freeze,
        .thaw           = dcssblk_thaw,
        .restore        = dcssblk_restore,
};

static struct platform_driver dcssblk_pdrv = {
        .driver = {
                .name   = "dcssblk",
                .pm     = &dcssblk_pm_ops,
        },
};

static struct platform_device *dcssblk_pdev;


/*
 * The init/exit functions.
 */
static void __exit
dcssblk_exit(void)
{
        platform_device_unregister(dcssblk_pdev);
        platform_driver_unregister(&dcssblk_pdrv);
        root_device_unregister(dcssblk_root_dev);
        unregister_blkdev(dcssblk_major, DCSSBLK_NAME);
}

static int __init
dcssblk_init(void)
{
        int rc;

        rc = platform_driver_register(&dcssblk_pdrv);
        if (rc)
                return rc;

        dcssblk_pdev = platform_device_register_simple("dcssblk", -1, NULL,
                                                        0);
        if (IS_ERR(dcssblk_pdev)) {
                rc = PTR_ERR(dcssblk_pdev);
                goto out_pdrv;
        }

        dcssblk_root_dev = root_device_register("dcssblk");
        if (IS_ERR(dcssblk_root_dev)) {
                rc = PTR_ERR(dcssblk_root_dev);
                goto out_pdev;
        }
        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);
out_pdev:
        platform_device_unregister(dcssblk_pdev);
out_pdrv:
        platform_driver_unregister(&dcssblk_pdrv);
        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");