ubd_kern.c

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/*
 * Copyright (C) 2000 Jeff Dike ([email protected])
 * Licensed under the GPL
 */

/* 2001-09-28...2002-04-17
 * Partition stuff by [email protected]
 * 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/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/ata.h>
#include <linux/hdreg.h>
#include <linux/cdrom.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/ctype.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/platform_device.h>
#include <linux/scatterlist.h>
#include <asm/tlbflush.h>
#include <kern_util.h>
#include "mconsole_kern.h"
#include <init.h>
#include <irq_kern.h>
#include "ubd.h"
#include <os.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(ubd_devs.lock), \
    .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;
    int fd;
    int err;

    __u32 version;
    __u32 align;
    char *backing_file;
    time_t mtime;
    unsigned long long size;
    int sector_size;
    int bitmap_offset;

    if (ubd_dev->file && ubd_dev->cow.file) {
        file = ubd_dev->cow.file;

        goto out;
    }

    fd = os_open_file(ubd_dev->file, of_read(OPENFLAGS()), 0);
    if (fd < 0)
        return fd;

    err = read_cow_header(file_reader, &fd, &version, &backing_file, \
        &mtime, &size, &sector_size, &align, &bitmap_offset);
    os_close_file(fd);

    if(err == -EINVAL)
        file = ubd_dev->file;
    else
        file = backing_file;

out:
    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,
                 0, "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;
}