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ubd_kern.c

/*
 * 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 MAJOR_NR UBD_MAJOR
#define UBD_SHIFT 4

#include "linux/kernel.h"
#include "linux/module.h"
#include "linux/blkdev.h"
#include "linux/hdreg.h"
#include "linux/init.h"
#include "linux/cdrom.h"
#include "linux/proc_fs.h"
#include "linux/ctype.h"
#include "linux/capability.h"
#include "linux/mm.h"
#include "linux/vmalloc.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;
};

extern 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);
extern 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);
extern int read_cow_bitmap(int fd, void *buf, int offset, int len);
extern void do_io(struct io_thread_req *req);

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 int ubd_open(struct inode * inode, struct file * filp);
static int ubd_release(struct inode * inode, struct file * file);
static int ubd_ioctl(struct inode * inode, struct file * file,
                 unsigned int cmd, unsigned long arg);
static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);

#define MAX_DEV (16)

static 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 = MAJOR_NR;
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;
};

#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, \
}

/* Protected by ubd_lock */
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 proc_ide_read_media(char *page, char **start, off_t off, int count,
                         int *eof, void *data)
{
      int len;

      strcpy(page, "disk\n");
      len = strlen("disk\n");
      len -= off;
      if (len < count){
            *eof = 1;
            if (len <= 0) return 0;
      }
      else len = count;
      *start = page + off;
      return len;
}

static void make_ide_entries(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 = create_proc_entry("media", S_IFREG|S_IRUGO, dir);
      if(!ent) return;
      ent->data = NULL;
      ent->read_proc = proc_ide_read_media;
      ent->write_proc = NULL;
      sprintf(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 != MAJOR_NR){
                  *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\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 int fakehd_set = 0;
static int fakehd(char *str)
{
      printk(KERN_INFO "fakehd : Changing ubd name to \"hd\".\n");
      fakehd_set = 1;
      return 1;
}

__setup("fakehd", fakehd);
__uml_help(fakehd,
"fakehd\n"
"    Change the ubd device name to \"hd\".\n\n"
);

static void do_ubd_request(struct request_queue * q);

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

static void ubd_end_request(struct request *req, int bytes, int uptodate)
{
      if (!end_that_request_first(req, uptodate, bytes >> 9)) {
            struct ubd *dev = req->rq_disk->private_data;
            unsigned long flags;

            add_disk_randomness(req->rq_disk);
            spin_lock_irqsave(&dev->lock, flags);
            end_that_request_last(req, uptodate);
            spin_unlock_irqrestore(&dev->lock, flags);
      }
}

/* Callable only from interrupt context - otherwise you need to do
 * spin_lock_irq()/spin_lock_irqsave() */
static inline void ubd_finish(struct request *req, int bytes)
{
      if(bytes < 0){
            ubd_end_request(req, 0, 0);
            return;
      }
      ubd_end_request(req, bytes, 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 request *rq;
      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;
            }

            rq = req->req;
            rq->nr_sectors -= req->length >> 9;
            if(rq->nr_sectors == 0)
                  ubd_finish(rq, rq->hard_nr_sectors << 9);
            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;

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 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_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->driver_data;

      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 == MAJOR_NR)
            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 == MAJOR_NR) {
            ubd_devs[unit].pdev.id   = unit;
            ubd_devs[unit].pdev.name = DRIVER_NAME;
            ubd_devs[unit].pdev.dev.release = ubd_device_release;
            ubd_devs[unit].pdev.dev.driver_data = &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_hw_segments(ubd_dev->queue, MAX_SG);
      err = ubd_disk_register(MAJOR_NR, ubd_dev->size, n, &ubd_gendisk[n]);
      if(err){
            *error_out = "Failed to register device";
            goto out_cleanup;
      }

      if(fake_major != MAJOR_NR)
            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 and also the fakehd_set 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(MAJOR_NR, "ubd"))
            return -1;

      if (fake_major != MAJOR_NR) {
            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 inode *inode, struct file *filp)
{
      struct gendisk *disk = inode->i_bdev->bd_disk;
      struct ubd *ubd_dev = disk->private_data;
      int err = 0;

      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((filp->f_mode & FMODE_WRITE) && !ubd_dev->openflags.w){
              if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
              err = -EROFS;
      }*/
 out:
      return err;
}

static int ubd_release(struct inode * inode, struct file * file)
{
      struct gendisk *disk = inode->i_bdev->bd_disk;
      struct ubd *ubd_dev = disk->private_data;

      if(--ubd_dev->count == 0)
            ubd_close_dev(ubd_dev);
      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 == ((bitmap_len + sizeof(unsigned long) - 1) /
                     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, last_sectors;

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

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

            req = dev->request;
            last_sectors = 0;
            while(dev->start_sg < dev->end_sg){
                  struct scatterlist *sg = &dev->sg[dev->start_sg];

                  req->sector += last_sectors;
                  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) req->sector << 9,
                              sg->offset, sg->length, sg_page(sg));

                  last_sectors = sg->length >> 9;
                  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->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 inode * inode, struct file * file,
                 unsigned int cmd, unsigned long arg)
{
      struct ubd *ubd_dev = inode->i_bdev->bd_disk->private_data;
      struct hd_driveid ubd_id = {
            .cyls       = 0,
            .heads            = 128,
            .sectors    = 32,
      };

      switch (cmd) {
            struct cdrom_volctrl volume;
      case HDIO_GET_IDENTITY:
            ubd_id.cyls = ubd_dev->size / (128 * 32 * 512);
            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 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("Couldn't stat '%s', err = %d\n", from_cmdline, -err);
            return 0;
      }
      err = os_stat_file(from_cow, &buf2);
      if(err < 0){
            printk("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("Backing file mismatch - \"%s\" requested,\n"
             "\"%s\" specified in COW header of \"%s\"\n",
             from_cmdline, from_cow, cow);
      return 1;
}

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("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("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("Size mismatch (%llu vs %llu) of COW header vs backing "
                   "file\n", (unsigned long long) size, actual);
            return -EINVAL;
      }
      if(modtime != mtime){
            printk("mtime mismatch (%ld vs %ld) of COW header vs backing "
                   "file\n", mtime, modtime);
            return -EINVAL;
      }
      return 0;
}

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;
}

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("Not locking \"%s\" on the host\n", file);
      else {
            err = os_lock_file(fd, openflags->w);
            if(err < 0){
                  printk("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("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("Switching backing file to '%s'\n", *backing_file_out);
            err = write_cow_header(file, fd, *backing_file_out,
                               sectorsize, align, &size);
            if (err) {
                  printk("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;
}

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("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 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;
}

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;
}

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