/*
 * Copyright (C) 2000 Jeff Dike (jdike@karaya.com)
 * Licensed under the GPL
 */

/* 2001-09-28...2002-04-17
 * Partition stuff by James_McMechan@hotmail.com
 * old style ubd by setting UBD_SHIFT to 0
 * 2002-09-27...2002-10-18 massive tinkering for 2.5
 * partitions have changed in 2.5
 * 2003-01-29 more tinkering for 2.5.59-1
 * This should now address the sysfs problems and has
 * the symlink for devfs to allow for booting with
 * the common /dev/ubd/discX/... names rather than
 * only /dev/ubdN/discN this version also has lots of
 * clean ups preparing for ubd-many.
 * James McMechan
 */

#define UBD_SHIFT 4

#include "linux/kernel.h"
#include "linux/module.h"
#include "linux/blkdev.h"
#include "linux/ata.h"
#include "linux/hdreg.h"
#include "linux/init.h"
#include "linux/cdrom.h"
#include "linux/proc_fs.h"
#include "linux/seq_file.h"
#include "linux/ctype.h"
#include "linux/capability.h"
#include "linux/mm.h"
#include "linux/slab.h"
#include "linux/vmalloc.h"
#include "linux/mutex.h"
#include "linux/blkpg.h"
#include "linux/genhd.h"
#include "linux/spinlock.h"
#include "linux/platform_device.h"
#include "linux/scatterlist.h"
#include "asm/segment.h"
#include "asm/uaccess.h"
#include "asm/irq.h"
#include "asm/types.h"
#include "asm/tlbflush.h"
#include "mem_user.h"
#include "kern_util.h"
#include "kern.h"
#include "mconsole_kern.h"
#include "init.h"
#include "irq_user.h"
#include "irq_kern.h"
#include "ubd_user.h"
#include "os.h"
#include "mem.h"
#include "mem_kern.h"
#include "cow.h"

enum ubd_req { UBD_READ, UBD_WRITE };

struct io_thread_req {
        struct request *req;
        enum ubd_req op;
        int fds[2];
        unsigned long offsets[2];
        unsigned long long offset;
        unsigned long length;
        char *buffer;
        int sectorsize;
        unsigned long sector_mask;
        unsigned long long cow_offset;
        unsigned long bitmap_words[2];
        int error;
};

static inline int ubd_test_bit(__u64 bit, unsigned char *data)
{
        __u64 n;
        int bits, off;

        bits = sizeof(data[0]) * 8;
        n = bit / bits;
        off = bit % bits;
        return (data[n] & (1 << off)) != 0;
}

static inline void ubd_set_bit(__u64 bit, unsigned char *data)
{
        __u64 n;
        int bits, off;

        bits = sizeof(data[0]) * 8;
        n = bit / bits;
        off = bit % bits;
        data[n] |= (1 << off);
}
/*End stuff from ubd_user.h*/

#define DRIVER_NAME "uml-blkdev"

static DEFINE_MUTEX(ubd_lock);
static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */

static int ubd_open(struct block_device *bdev, fmode_t mode);
static int ubd_release(struct gendisk *disk, fmode_t mode);
static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
                     unsigned int cmd, unsigned long arg);
static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);

#define MAX_DEV (16)

static const struct block_device_operations ubd_blops = {
        .owner          = THIS_MODULE,
        .open           = ubd_open,
        .release        = ubd_release,
        .ioctl          = ubd_ioctl,
        .getgeo         = ubd_getgeo,
};

/* Protected by ubd_lock */
static int fake_major = UBD_MAJOR;
static struct gendisk *ubd_gendisk[MAX_DEV];
static struct gendisk *fake_gendisk[MAX_DEV];

#ifdef CONFIG_BLK_DEV_UBD_SYNC
#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
                                         .cl = 1 })
#else
#define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
                                         .cl = 1 })
#endif
static struct openflags global_openflags = OPEN_FLAGS;

struct cow {
        /* backing file name */
        char *file;
        /* backing file fd */
        int fd;
        unsigned long *bitmap;
        unsigned long bitmap_len;
        int bitmap_offset;
        int data_offset;
};

#define MAX_SG 64

struct ubd {
        struct list_head restart;
        /* name (and fd, below) of the file opened for writing, either the
         * backing or the cow file. */
        char *file;
        int count;
        int fd;
        __u64 size;
        struct openflags boot_openflags;
        struct openflags openflags;
        unsigned shared:1;
        unsigned no_cow:1;
        struct cow cow;
        struct platform_device pdev;
        struct request_queue *queue;
        spinlock_t lock;
        struct scatterlist sg[MAX_SG];
        struct request *request;
        int start_sg, end_sg;
        sector_t rq_pos;
};

#define DEFAULT_COW { \
        .file =                 NULL, \
        .fd =                   -1,     \
        .bitmap =               NULL, \
        .bitmap_offset =        0, \
        .data_offset =          0, \
}

#define DEFAULT_UBD { \
        .file =                 NULL, \
        .count =                0, \
        .fd =                   -1, \
        .size =                 -1, \
        .boot_openflags =       OPEN_FLAGS, \
        .openflags =            OPEN_FLAGS, \
        .no_cow =               0, \
        .shared =               0, \
        .cow =                  DEFAULT_COW, \
        .lock =                 SPIN_LOCK_UNLOCKED,     \
        .request =              NULL, \
        .start_sg =             0, \
        .end_sg =               0, \
        .rq_pos =               0, \
}

/* Protected by ubd_lock */
static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };

/* Only changed by fake_ide_setup which is a setup */
static int fake_ide = 0;
static struct proc_dir_entry *proc_ide_root = NULL;
static struct proc_dir_entry *proc_ide = NULL;

static void make_proc_ide(void)
{
        proc_ide_root = proc_mkdir("ide", NULL);
        proc_ide = proc_mkdir("ide0", proc_ide_root);
}

static int fake_ide_media_proc_show(struct seq_file *m, void *v)
{
        seq_puts(m, "disk\n");
        return 0;
}

static int fake_ide_media_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, fake_ide_media_proc_show, NULL);
}

static const struct file_operations fake_ide_media_proc_fops = {
        .owner          = THIS_MODULE,
        .open           = fake_ide_media_proc_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};

static void make_ide_entries(const char *dev_name)
{
        struct proc_dir_entry *dir, *ent;
        char name[64];

        if(proc_ide_root == NULL) make_proc_ide();

        dir = proc_mkdir(dev_name, proc_ide);
        if(!dir) return;

        ent = proc_create("media", S_IRUGO, dir, &fake_ide_media_proc_fops);
        if(!ent) return;
        snprintf(name, sizeof(name), "ide0/%s", dev_name);
        proc_symlink(dev_name, proc_ide_root, name);
}

static int fake_ide_setup(char *str)
{
        fake_ide = 1;
        return 1;
}

__setup("fake_ide", fake_ide_setup);

__uml_help(fake_ide_setup,
"fake_ide\n"
"    Create ide0 entries that map onto ubd devices.\n\n"
);

static int parse_unit(char **ptr)
{
        char *str = *ptr, *end;
        int n = -1;

        if(isdigit(*str)) {
                n = simple_strtoul(str, &end, 0);
                if(end == str)
                        return -1;
                *ptr = end;
        }
        else if (('a' <= *str) && (*str <= 'z')) {
                n = *str - 'a';
                str++;
                *ptr = str;
        }
        return n;
}

/* If *index_out == -1 at exit, the passed option was a general one;
 * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
 * should not be freed on exit.
 */
static int ubd_setup_common(char *str, int *index_out, char **error_out)
{
        struct ubd *ubd_dev;
        struct openflags flags = global_openflags;
        char *backing_file;
        int n, err = 0, i;

        if(index_out) *index_out = -1;
        n = *str;
        if(n == '='){
                char *end;
                int major;

                str++;
                if(!strcmp(str, "sync")){
                        global_openflags = of_sync(global_openflags);
                        goto out1;
                }

                err = -EINVAL;
                major = simple_strtoul(str, &end, 0);
                if((*end != '\0') || (end == str)){
                        *error_out = "Didn't parse major number";
                        goto out1;
                }

                mutex_lock(&ubd_lock);
                if (fake_major != UBD_MAJOR) {
                        *error_out = "Can't assign a fake major twice";
                        goto out1;
                }

                fake_major = major;

                printk(KERN_INFO "Setting extra ubd major number to %d\n",
                       major);
                err = 0;
        out1:
                mutex_unlock(&ubd_lock);
                return err;
        }

        n = parse_unit(&str);
        if(n < 0){
                *error_out = "Couldn't parse device number";
                return -EINVAL;
        }
        if(n >= MAX_DEV){
                *error_out = "Device number out of range";
                return 1;
        }

        err = -EBUSY;
        mutex_lock(&ubd_lock);

        ubd_dev = &ubd_devs[n];
        if(ubd_dev->file != NULL){
                *error_out = "Device is already configured";
                goto out;
        }

        if (index_out)
                *index_out = n;

        err = -EINVAL;
        for (i = 0; i < sizeof("rscd="); i++) {
                switch (*str) {
                case 'r':
                        flags.w = 0;
                        break;
                case 's':
                        flags.s = 1;
                        break;
                case 'd':
                        ubd_dev->no_cow = 1;
                        break;
                case 'c':
                        ubd_dev->shared = 1;
                        break;
                case '=':
                        str++;
                        goto break_loop;
                default:
                        *error_out = "Expected '=' or flag letter "
                                "(r, s, c, or d)";
                        goto out;
                }
                str++;
        }

        if (*str == '=')
                *error_out = "Too many flags specified";
        else
                *error_out = "Missing '='";
        goto out;

break_loop:
        backing_file = strchr(str, ',');

        if (backing_file == NULL)
                backing_file = strchr(str, ':');

        if(backing_file != NULL){
                if(ubd_dev->no_cow){
                        *error_out = "Can't specify both 'd' and a cow file";
                        goto out;
                }
                else {
                        *backing_file = '\0';
                        backing_file++;
                }
        }
        err = 0;
        ubd_dev->file = str;
        ubd_dev->cow.file = backing_file;
        ubd_dev->boot_openflags = flags;
out:
        mutex_unlock(&ubd_lock);
        return err;
}

static int ubd_setup(char *str)
{
        char *error;
        int err;

        err = ubd_setup_common(str, NULL, &error);
        if(err)
                printk(KERN_ERR "Failed to initialize device with \"%s\" : "
                       "%s\n", str, error);
        return 1;
}

__setup("ubd", ubd_setup);
__uml_help(ubd_setup,
"ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
"    This is used to associate a device with a file in the underlying\n"
"    filesystem. When specifying two filenames, the first one is the\n"
"    COW name and the second is the backing file name. As separator you can\n"
"    use either a ':' or a ',': the first one allows writing things like;\n"
"       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
"    while with a ',' the shell would not expand the 2nd '~'.\n"
"    When using only one filename, UML will detect whether to treat it like\n"
"    a COW file or a backing file. To override this detection, add the 'd'\n"
"    flag:\n"
"       ubd0d=BackingFile\n"
"    Usually, there is a filesystem in the file, but \n"
"    that's not required. Swap devices containing swap files can be\n"
"    specified like this. Also, a file which doesn't contain a\n"
"    filesystem can have its contents read in the virtual \n"
"    machine by running 'dd' on the device. <n> must be in the range\n"
"    0 to 7. Appending an 'r' to the number will cause that device\n"
"    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
"    an 's' will cause data to be written to disk on the host immediately.\n"
"    'c' will cause the device to be treated as being shared between multiple\n"
"    UMLs and file locking will be turned off - this is appropriate for a\n"
"    cluster filesystem and inappropriate at almost all other times.\n\n"
);

static int udb_setup(char *str)
{
        printk("udb%s specified on command line is almost certainly a ubd -> "
               "udb TYPO\n", str);
        return 1;
}

__setup("udb", udb_setup);
__uml_help(udb_setup,
"udb\n"
"    This option is here solely to catch ubd -> udb typos, which can be\n"
"    to impossible to catch visually unless you specifically look for\n"
"    them.  The only result of any option starting with 'udb' is an error\n"
"    in the boot output.\n\n"
);

static void do_ubd_request(struct request_queue * q);

/* Only changed by ubd_init, which is an initcall. */
static int thread_fd = -1;
static LIST_HEAD(restart);

/* XXX - move this inside ubd_intr. */
/* Called without dev->lock held, and only in interrupt context. */
static void ubd_handler(void)
{
        struct io_thread_req *req;
        struct ubd *ubd;
        struct list_head *list, *next_ele;
        unsigned long flags;
        int n;

        while(1){
                n = os_read_file(thread_fd, &req,
                                 sizeof(struct io_thread_req *));
                if(n != sizeof(req)){
                        if(n == -EAGAIN)
                                break;
                        printk(KERN_ERR "spurious interrupt in ubd_handler, "
                               "err = %d\n", -n);
                        return;
                }

                blk_end_request(req->req, 0, req->length);
                kfree(req);
        }
        reactivate_fd(thread_fd, UBD_IRQ);

        list_for_each_safe(list, next_ele, &restart){
                ubd = container_of(list, struct ubd, restart);
                list_del_init(&ubd->restart);
                spin_lock_irqsave(&ubd->lock, flags);
                do_ubd_request(ubd->queue);
                spin_unlock_irqrestore(&ubd->lock, flags);
        }
}

static irqreturn_t ubd_intr(int irq, void *dev)
{
        ubd_handler();
        return IRQ_HANDLED;
}

/* Only changed by ubd_init, which is an initcall. */
static int io_pid = -1;

static void kill_io_thread(void)
{
        if(io_pid != -1)
                os_kill_process(io_pid, 1);
}

__uml_exitcall(kill_io_thread);

static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
{
        char *file;

        file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
        return os_file_size(file, size_out);
}

static int read_cow_bitmap(int fd, void *buf, int offset, int len)
{
        int err;

        err = os_seek_file(fd, offset);
        if (err < 0)
                return err;

        err = os_read_file(fd, buf, len);
        if (err < 0)
                return err;

        return 0;
}

static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
{
        unsigned long modtime;
        unsigned long long actual;
        int err;

        err = os_file_modtime(file, &modtime);
        if (err < 0) {
                printk(KERN_ERR "Failed to get modification time of backing "
                       "file \"%s\", err = %d\n", file, -err);
                return err;
        }

        err = os_file_size(file, &actual);
        if (err < 0) {
                printk(KERN_ERR "Failed to get size of backing file \"%s\", "
                       "err = %d\n", file, -err);
                return err;
        }

        if (actual != size) {
                /*__u64 can be a long on AMD64 and with %lu GCC complains; so
                 * the typecast.*/
                printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
                       "vs backing file\n", (unsigned long long) size, actual);
                return -EINVAL;
        }
        if (modtime != mtime) {
                printk(KERN_ERR "mtime mismatch (%ld vs %ld) of COW header vs "
                       "backing file\n", mtime, modtime);
                return -EINVAL;
        }
        return 0;
}

static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
{
        struct uml_stat buf1, buf2;
        int err;

        if (from_cmdline == NULL)
                return 0;
        if (!strcmp(from_cmdline, from_cow))
                return 0;

        err = os_stat_file(from_cmdline, &buf1);
        if (err < 0) {
                printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
                       -err);
                return 0;
        }
        err = os_stat_file(from_cow, &buf2);
        if (err < 0) {
                printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
                       -err);
                return 1;
        }
        if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
                return 0;

        printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
               "\"%s\" specified in COW header of \"%s\"\n",
               from_cmdline, from_cow, cow);
        return 1;
}

static int open_ubd_file(char *file, struct openflags *openflags, int shared,
                  char **backing_file_out, int *bitmap_offset_out,
                  unsigned long *bitmap_len_out, int *data_offset_out,
                  int *create_cow_out)
{
        time_t mtime;
        unsigned long long size;
        __u32 version, align;
        char *backing_file;
        int fd, err, sectorsize, asked_switch, mode = 0644;

        fd = os_open_file(file, *openflags, mode);
        if (fd < 0) {
                if ((fd == -ENOENT) && (create_cow_out != NULL))
                        *create_cow_out = 1;
                if (!openflags->w ||
                    ((fd != -EROFS) && (fd != -EACCES)))
                        return fd;
                openflags->w = 0;
                fd = os_open_file(file, *openflags, mode);
                if (fd < 0)
                        return fd;
        }

        if (shared)
                printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
        else {
                err = os_lock_file(fd, openflags->w);
                if (err < 0) {
                        printk(KERN_ERR "Failed to lock '%s', err = %d\n",
                               file, -err);
                        goto out_close;
                }
        }

        /* Successful return case! */
        if (backing_file_out == NULL)
                return fd;

        err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
                              &size, &sectorsize, &align, bitmap_offset_out);
        if (err && (*backing_file_out != NULL)) {
                printk(KERN_ERR "Failed to read COW header from COW file "
                       "\"%s\", errno = %d\n", file, -err);
                goto out_close;
        }
        if (err)
                return fd;

        asked_switch = path_requires_switch(*backing_file_out, backing_file,
                                            file);

        /* Allow switching only if no mismatch. */
        if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
                                                   mtime)) {
                printk(KERN_ERR "Switching backing file to '%s'\n",
                       *backing_file_out);
                err = write_cow_header(file, fd, *backing_file_out,
                                       sectorsize, align, &size);
                if (err) {
                        printk(KERN_ERR "Switch failed, errno = %d\n", -err);
                        goto out_close;
                }
        } else {
                *backing_file_out = backing_file;
                err = backing_file_mismatch(*backing_file_out, size, mtime);
                if (err)
                        goto out_close;
        }

        cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
                  bitmap_len_out, data_offset_out);

        return fd;
 out_close:
        os_close_file(fd);
        return err;
}

static int create_cow_file(char *cow_file, char *backing_file,
                    struct openflags flags,
                    int sectorsize, int alignment, int *bitmap_offset_out,
                    unsigned long *bitmap_len_out, int *data_offset_out)
{
        int err, fd;

        flags.c = 1;
        fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
        if (fd < 0) {
                err = fd;
                printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
                       cow_file, -err);
                goto out;
        }

        err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
                            bitmap_offset_out, bitmap_len_out,
                            data_offset_out);
        if (!err)
                return fd;
        os_close_file(fd);
 out:
        return err;
}

static void ubd_close_dev(struct ubd *ubd_dev)
{
        os_close_file(ubd_dev->fd);
        if(ubd_dev->cow.file == NULL)
                return;

        os_close_file(ubd_dev->cow.fd);
        vfree(ubd_dev->cow.bitmap);
        ubd_dev->cow.bitmap = NULL;
}

static int ubd_open_dev(struct ubd *ubd_dev)
{
        struct openflags flags;
        char **back_ptr;
        int err, create_cow, *create_ptr;
        int fd;

        ubd_dev->openflags = ubd_dev->boot_openflags;
        create_cow = 0;
        create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
        back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;

        fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
                                back_ptr, &ubd_dev->cow.bitmap_offset,
                                &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
                                create_ptr);

        if((fd == -ENOENT) && create_cow){
                fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
                                          ubd_dev->openflags, 1 << 9, PAGE_SIZE,
                                          &ubd_dev->cow.bitmap_offset,
                                          &ubd_dev->cow.bitmap_len,
                                          &ubd_dev->cow.data_offset);
                if(fd >= 0){
                        printk(KERN_INFO "Creating \"%s\" as COW file for "
                               "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
                }
        }

        if(fd < 0){
                printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
                       -fd);
                return fd;
        }
        ubd_dev->fd = fd;

        if(ubd_dev->cow.file != NULL){
                blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));

                err = -ENOMEM;
                ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
                if(ubd_dev->cow.bitmap == NULL){
                        printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
                        goto error;
                }
                flush_tlb_kernel_vm();

                err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
                                      ubd_dev->cow.bitmap_offset,
                                      ubd_dev->cow.bitmap_len);
                if(err < 0)
                        goto error;

                flags = ubd_dev->openflags;
                flags.w = 0;
                err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
                                    NULL, NULL, NULL, NULL);
                if(err < 0) goto error;
                ubd_dev->cow.fd = err;
        }
        return 0;
 error:
        os_close_file(ubd_dev->fd);
        return err;
}

static void ubd_device_release(struct device *dev)
{
        struct ubd *ubd_dev = dev_get_drvdata(dev);

        blk_cleanup_queue(ubd_dev->queue);
        *ubd_dev = ((struct ubd) DEFAULT_UBD);
}

static int ubd_disk_register(int major, u64 size, int unit,
                             struct gendisk **disk_out)
{
        struct gendisk *disk;

        disk = alloc_disk(1 << UBD_SHIFT);
        if(disk == NULL)
                return -ENOMEM;

        disk->major = major;
        disk->first_minor = unit << UBD_SHIFT;
        disk->fops = &ubd_blops;
        set_capacity(disk, size / 512);
        if (major == UBD_MAJOR)
                sprintf(disk->disk_name, "ubd%c", 'a' + unit);
        else
                sprintf(disk->disk_name, "ubd_fake%d", unit);

        /* sysfs register (not for ide fake devices) */
        if (major == UBD_MAJOR) {
                ubd_devs[unit].pdev.id   = unit;
                ubd_devs[unit].pdev.name = DRIVER_NAME;
                ubd_devs[unit].pdev.dev.release = ubd_device_release;
                dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
                platform_device_register(&ubd_devs[unit].pdev);
                disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
        }

        disk->private_data = &ubd_devs[unit];
        disk->queue = ubd_devs[unit].queue;
        add_disk(disk);

        *disk_out = disk;
        return 0;
}

#define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))

static int ubd_add(int n, char **error_out)
{
        struct ubd *ubd_dev = &ubd_devs[n];
        int err = 0;

        if(ubd_dev->file == NULL)
                goto out;

        err = ubd_file_size(ubd_dev, &ubd_dev->size);
        if(err < 0){
                *error_out = "Couldn't determine size of device's file";
                goto out;
        }

        ubd_dev->size = ROUND_BLOCK(ubd_dev->size);

        INIT_LIST_HEAD(&ubd_dev->restart);
        sg_init_table(ubd_dev->sg, MAX_SG);

        err = -ENOMEM;
        ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
        if (ubd_dev->queue == NULL) {
                *error_out = "Failed to initialize device queue";
                goto out;
        }
        ubd_dev->queue->queuedata = ubd_dev;

        blk_queue_max_segments(ubd_dev->queue, MAX_SG);
        err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, &ubd_gendisk[n]);
        if(err){
                *error_out = "Failed to register device";
                goto out_cleanup;
        }

        if (fake_major != UBD_MAJOR)
                ubd_disk_register(fake_major, ubd_dev->size, n,
                                  &fake_gendisk[n]);

        /*
         * Perhaps this should also be under the "if (fake_major)" above
         * using the fake_disk->disk_name
         */
        if (fake_ide)
                make_ide_entries(ubd_gendisk[n]->disk_name);

        err = 0;
out:
        return err;

out_cleanup:
        blk_cleanup_queue(ubd_dev->queue);
        goto out;
}

static int ubd_config(char *str, char **error_out)
{
        int n, ret;

        /* This string is possibly broken up and stored, so it's only
         * freed if ubd_setup_common fails, or if only general options
         * were set.
         */
        str = kstrdup(str, GFP_KERNEL);
        if (str == NULL) {
                *error_out = "Failed to allocate memory";
                return -ENOMEM;
        }

        ret = ubd_setup_common(str, &n, error_out);
        if (ret)
                goto err_free;

        if (n == -1) {
                ret = 0;
                goto err_free;
        }

        mutex_lock(&ubd_lock);
        ret = ubd_add(n, error_out);
        if (ret)
                ubd_devs[n].file = NULL;
        mutex_unlock(&ubd_lock);

out:
        return ret;

err_free:
        kfree(str);
        goto out;
}

static int ubd_get_config(char *name, char *str, int size, char **error_out)
{
        struct ubd *ubd_dev;
        int n, len = 0;

        n = parse_unit(&name);
        if((n >= MAX_DEV) || (n < 0)){
                *error_out = "ubd_get_config : device number out of range";
                return -1;
        }

        ubd_dev = &ubd_devs[n];
        mutex_lock(&ubd_lock);

        if(ubd_dev->file == NULL){
                CONFIG_CHUNK(str, size, len, "", 1);
                goto out;
        }

        CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);

        if(ubd_dev->cow.file != NULL){
                CONFIG_CHUNK(str, size, len, ",", 0);
                CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
        }
        else CONFIG_CHUNK(str, size, len, "", 1);

 out:
        mutex_unlock(&ubd_lock);
        return len;
}

static int ubd_id(char **str, int *start_out, int *end_out)
{
        int n;

        n = parse_unit(str);
        *start_out = 0;
        *end_out = MAX_DEV - 1;
        return n;
}

static int ubd_remove(int n, char **error_out)
{
        struct gendisk *disk = ubd_gendisk[n];
        struct ubd *ubd_dev;
        int err = -ENODEV;

        mutex_lock(&ubd_lock);

        ubd_dev = &ubd_devs[n];

        if(ubd_dev->file == NULL)
                goto out;

        /* you cannot remove a open disk */
        err = -EBUSY;
        if(ubd_dev->count > 0)
                goto out;

        ubd_gendisk[n] = NULL;
        if(disk != NULL){
                del_gendisk(disk);
                put_disk(disk);
        }

        if(fake_gendisk[n] != NULL){
                del_gendisk(fake_gendisk[n]);
                put_disk(fake_gendisk[n]);
                fake_gendisk[n] = NULL;
        }

        err = 0;
        platform_device_unregister(&ubd_dev->pdev);
out:
        mutex_unlock(&ubd_lock);
        return err;
}

/* All these are called by mconsole in process context and without

 * ubd-specific locks.  The structure itself is const except for .list.
 */
static struct mc_device ubd_mc = {
        .list           = LIST_HEAD_INIT(ubd_mc.list),
        .name           = "ubd",
        .config         = ubd_config,
        .get_config     = ubd_get_config,
        .id             = ubd_id,
        .remove         = ubd_remove,
};

static int __init ubd_mc_init(void)
{
        mconsole_register_dev(&ubd_mc);
        return 0;
}

__initcall(ubd_mc_init);

static int __init ubd0_init(void)
{
        struct ubd *ubd_dev = &ubd_devs[0];

        mutex_lock(&ubd_lock);
        if(ubd_dev->file == NULL)
                ubd_dev->file = "root_fs";
        mutex_unlock(&ubd_lock);

        return 0;
}

__initcall(ubd0_init);

/* Used in ubd_init, which is an initcall */
static struct platform_driver ubd_driver = {
        .driver = {
                .name  = DRIVER_NAME,
        },
};

static int __init ubd_init(void)
{
        char *error;
        int i, err;

        if (register_blkdev(UBD_MAJOR, "ubd"))
                return -1;

        if (fake_major != UBD_MAJOR) {
                char name[sizeof("ubd_nnn\0")];

                snprintf(name, sizeof(name), "ubd_%d", fake_major);
                if (register_blkdev(fake_major, "ubd"))
                        return -1;
        }
        platform_driver_register(&ubd_driver);
        mutex_lock(&ubd_lock);
        for (i = 0; i < MAX_DEV; i++){
                err = ubd_add(i, &error);
                if(err)
                        printk(KERN_ERR "Failed to initialize ubd device %d :"
                               "%s\n", i, error);
        }
        mutex_unlock(&ubd_lock);
        return 0;
}

late_initcall(ubd_init);

static int __init ubd_driver_init(void){
        unsigned long stack;
        int err;

        /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
        if(global_openflags.s){
                printk(KERN_INFO "ubd: Synchronous mode\n");
                /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
                 * enough. So use anyway the io thread. */
        }
        stack = alloc_stack(0, 0);
        io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
                                 &thread_fd);
        if(io_pid < 0){
                printk(KERN_ERR
                       "ubd : Failed to start I/O thread (errno = %d) - "
                       "falling back to synchronous I/O\n", -io_pid);
                io_pid = -1;
                return 0;
        }
        err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
                             IRQF_DISABLED, "ubd", ubd_devs);
        if(err != 0)
                printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
        return 0;
}

device_initcall(ubd_driver_init);

static int ubd_open(struct block_device *bdev, fmode_t mode)
{
        struct gendisk *disk = bdev->bd_disk;
        struct ubd *ubd_dev = disk->private_data;
        int err = 0;

        mutex_lock(&ubd_mutex);
        if(ubd_dev->count == 0){
                err = ubd_open_dev(ubd_dev);
                if(err){
                        printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
                               disk->disk_name, ubd_dev->file, -err);
                        goto out;
                }
        }
        ubd_dev->count++;
        set_disk_ro(disk, !ubd_dev->openflags.w);

        /* This should no more be needed. And it didn't work anyway to exclude
         * read-write remounting of filesystems.*/
        /*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
                if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
                err = -EROFS;
        }*/
out:
        mutex_unlock(&ubd_mutex);
        return err;
}

static int ubd_release(struct gendisk *disk, fmode_t mode)
{
        struct ubd *ubd_dev = disk->private_data;

        mutex_lock(&ubd_mutex);
        if(--ubd_dev->count == 0)
                ubd_close_dev(ubd_dev);
        mutex_unlock(&ubd_mutex);
        return 0;
}

static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
                          __u64 *cow_offset, unsigned long *bitmap,
                          __u64 bitmap_offset, unsigned long *bitmap_words,
                          __u64 bitmap_len)
{
        __u64 sector = io_offset >> 9;
        int i, update_bitmap = 0;

        for(i = 0; i < length >> 9; i++){
                if(cow_mask != NULL)
                        ubd_set_bit(i, (unsigned char *) cow_mask);
                if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
                        continue;

                update_bitmap = 1;
                ubd_set_bit(sector + i, (unsigned char *) bitmap);
        }

        if(!update_bitmap)
                return;

        *cow_offset = sector / (sizeof(unsigned long) * 8);

        /* This takes care of the case where we're exactly at the end of the
         * device, and *cow_offset + 1 is off the end.  So, just back it up
         * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
         * for the original diagnosis.
         */
        if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
                                         sizeof(unsigned long)) - 1))
                (*cow_offset)--;

        bitmap_words[0] = bitmap[*cow_offset];
        bitmap_words[1] = bitmap[*cow_offset + 1];

        *cow_offset *= sizeof(unsigned long);
        *cow_offset += bitmap_offset;
}

static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
                       __u64 bitmap_offset, __u64 bitmap_len)
{
        __u64 sector = req->offset >> 9;
        int i;

        if(req->length > (sizeof(req->sector_mask) * 8) << 9)
                panic("Operation too long");

        if(req->op == UBD_READ) {
                for(i = 0; i < req->length >> 9; i++){
                        if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
                                ubd_set_bit(i, (unsigned char *)
                                            &req->sector_mask);
                }
        }
        else cowify_bitmap(req->offset, req->length, &req->sector_mask,
                           &req->cow_offset, bitmap, bitmap_offset,
                           req->bitmap_words, bitmap_len);
}

/* Called with dev->lock held */
static void prepare_request(struct request *req, struct io_thread_req *io_req,
                            unsigned long long offset, int page_offset,
                            int len, struct page *page)
{
        struct gendisk *disk = req->rq_disk;
        struct ubd *ubd_dev = disk->private_data;

        io_req->req = req;
        io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
                ubd_dev->fd;
        io_req->fds[1] = ubd_dev->fd;
        io_req->cow_offset = -1;
        io_req->offset = offset;
        io_req->length = len;
        io_req->error = 0;
        io_req->sector_mask = 0;

        io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
        io_req->offsets[0] = 0;
        io_req->offsets[1] = ubd_dev->cow.data_offset;
        io_req->buffer = page_address(page) + page_offset;
        io_req->sectorsize = 1 << 9;

        if(ubd_dev->cow.file != NULL)
                cowify_req(io_req, ubd_dev->cow.bitmap,
                           ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);

}

/* Called with dev->lock held */
static void do_ubd_request(struct request_queue *q)
{
        struct io_thread_req *io_req;
        struct request *req;
        int n;

        while(1){
                struct ubd *dev = q->queuedata;
                if(dev->end_sg == 0){
                        struct request *req = blk_fetch_request(q);
                        if(req == NULL)
                                return;

                        dev->request = req;
                        dev->rq_pos = blk_rq_pos(req);
                        dev->start_sg = 0;
                        dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
                }

                req = dev->request;
                while(dev->start_sg < dev->end_sg){
                        struct scatterlist *sg = &dev->sg[dev->start_sg];

                        io_req = kmalloc(sizeof(struct io_thread_req),
                                         GFP_ATOMIC);
                        if(io_req == NULL){
                                if(list_empty(&dev->restart))
                                        list_add(&dev->restart, &restart);
                                return;
                        }
                        prepare_request(req, io_req,
                                        (unsigned long long)dev->rq_pos << 9,
                                        sg->offset, sg->length, sg_page(sg));

                        n = os_write_file(thread_fd, &io_req,
                                          sizeof(struct io_thread_req *));
                        if(n != sizeof(struct io_thread_req *)){
                                if(n != -EAGAIN)
                                        printk("write to io thread failed, "
                                               "errno = %d\n", -n);
                                else if(list_empty(&dev->restart))
                                        list_add(&dev->restart, &restart);
                                kfree(io_req);
                                return;
                        }

                        dev->rq_pos += sg->length >> 9;
                        dev->start_sg++;
                }
                dev->end_sg = 0;
                dev->request = NULL;
        }
}

static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
        struct ubd *ubd_dev = bdev->bd_disk->private_data;

        geo->heads = 128;
        geo->sectors = 32;
        geo->cylinders = ubd_dev->size / (128 * 32 * 512);
        return 0;
}

static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
                     unsigned int cmd, unsigned long arg)
{
        struct ubd *ubd_dev = bdev->bd_disk->private_data;
        u16 ubd_id[ATA_ID_WORDS];

        switch (cmd) {
                struct cdrom_volctrl volume;
        case HDIO_GET_IDENTITY:
                memset(&ubd_id, 0, ATA_ID_WORDS * 2);
                ubd_id[ATA_ID_CYLS]     = ubd_dev->size / (128 * 32 * 512);
                ubd_id[ATA_ID_HEADS]    = 128;
                ubd_id[ATA_ID_SECTORS]  = 32;
                if(copy_to_user((char __user *) arg, (char *) &ubd_id,
                                 sizeof(ubd_id)))
                        return -EFAULT;
                return 0;

        case CDROMVOLREAD:
                if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
                        return -EFAULT;
                volume.channel0 = 255;
                volume.channel1 = 255;
                volume.channel2 = 255;
                volume.channel3 = 255;
                if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
                        return -EFAULT;
                return 0;
        }
        return -EINVAL;
}

static int update_bitmap(struct io_thread_req *req)
{
        int n;

        if(req->cow_offset == -1)
                return 0;

        n = os_seek_file(req->fds[1], req->cow_offset);
        if(n < 0){
                printk("do_io - bitmap lseek failed : err = %d\n", -n);
                return 1;
        }

        n = os_write_file(req->fds[1], &req->bitmap_words,
                          sizeof(req->bitmap_words));
        if(n != sizeof(req->bitmap_words)){
                printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
                       req->fds[1]);
                return 1;
        }

        return 0;
}

static void do_io(struct io_thread_req *req)
{
        char *buf;
        unsigned long len;
        int n, nsectors, start, end, bit;
        int err;
        __u64 off;

        nsectors = req->length / req->sectorsize;
        start = 0;
        do {
                bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
                end = start;
                while((end < nsectors) &&
                      (ubd_test_bit(end, (unsigned char *)
                                    &req->sector_mask) == bit))
                        end++;

                off = req->offset + req->offsets[bit] +
                        start * req->sectorsize;
                len = (end - start) * req->sectorsize;
                buf = &req->buffer[start * req->sectorsize];

                err = os_seek_file(req->fds[bit], off);
                if(err < 0){
                        printk("do_io - lseek failed : err = %d\n", -err);
                        req->error = 1;
                        return;
                }
                if(req->op == UBD_READ){
                        n = 0;
                        do {
                                buf = &buf[n];
                                len -= n;
                                n = os_read_file(req->fds[bit], buf, len);
                                if (n < 0) {
                                        printk("do_io - read failed, err = %d "
                                               "fd = %d\n", -n, req->fds[bit]);
                                        req->error = 1;
                                        return;
                                }
                        } while((n < len) && (n != 0));
                        if (n < len) memset(&buf[n], 0, len - n);
                } else {
                        n = os_write_file(req->fds[bit], buf, len);
                        if(n != len){
                                printk("do_io - write failed err = %d "
                                       "fd = %d\n", -n, req->fds[bit]);
                                req->error = 1;
                                return;
                        }
                }

                start = end;
        } while(start < nsectors);

        req->error = update_bitmap(req);
}

/* Changed in start_io_thread, which is serialized by being called only
 * from ubd_init, which is an initcall.
 */
int kernel_fd = -1;

/* Only changed by the io thread. XXX: currently unused. */
static int io_count = 0;

int io_thread(void *arg)
{
        struct io_thread_req *req;
        int n;

        ignore_sigwinch_sig();
        while(1){
                n = os_read_file(kernel_fd, &req,
                                 sizeof(struct io_thread_req *));
                if(n != sizeof(struct io_thread_req *)){
                        if(n < 0)
                                printk("io_thread - read failed, fd = %d, "
                                       "err = %d\n", kernel_fd, -n);
                        else {
                                printk("io_thread - short read, fd = %d, "
                                       "length = %d\n", kernel_fd, n);
                        }
                        continue;
                }
                io_count++;
                do_io(req);
                n = os_write_file(kernel_fd, &req,
                                  sizeof(struct io_thread_req *));
                if(n != sizeof(struct io_thread_req *))
                        printk("io_thread - write failed, fd = %d, err = %d\n",
                               kernel_fd, -n);
        }

        return 0;
}