arch/um/drivers/ubd_kern.c

   1 /*
   2  * Copyright (C) 2000 Jeff Dike ([email protected])
   3  * Licensed under the GPL
   4  */
   5
   6 /* 2001-09-28...2002-04-17
   7  * Partition stuff by [email protected]
   8  * old style ubd by setting UBD_SHIFT to 0
   9  * 2002-09-27...2002-10-18 massive tinkering for 2.5
  10  * partitions have changed in 2.5
  11  * 2003-01-29 more tinkering for 2.5.59-1
  12  * This should now address the sysfs problems and has
  13  * the symlink for devfs to allow for booting with
  14  * the common /dev/ubd/discX/... names rather than
  15  * only /dev/ubdN/discN this version also has lots of
  16  * clean ups preparing for ubd-many.
  17  * James McMechan
  18  */
  19
  20 #define UBD_SHIFT 4
  21
  22 #include "linux/kernel.h"
  23 #include "linux/module.h"
  24 #include "linux/blkdev.h"
  25 #include "linux/ata.h"
  26 #include "linux/hdreg.h"
  27 #include "linux/init.h"
  28 #include "linux/cdrom.h"
  29 #include "linux/proc_fs.h"
  30 #include "linux/seq_file.h"
  31 #include "linux/ctype.h"
  32 #include "linux/capability.h"
  33 #include "linux/mm.h"
  34 #include "linux/slab.h"
  35 #include "linux/vmalloc.h"
  36 #include "linux/mutex.h"
  37 #include "linux/blkpg.h"
  38 #include "linux/genhd.h"
  39 #include "linux/spinlock.h"
  40 #include "linux/platform_device.h"
  41 #include "linux/scatterlist.h"
  42 #include "asm/segment.h"
  43 #include "asm/uaccess.h"
  44 #include "asm/irq.h"
  45 #include "asm/types.h"
  46 #include "asm/tlbflush.h"
  47 #include "mem_user.h"
  48 #include "kern_util.h"
  49 #include "kern.h"
  50 #include "mconsole_kern.h"
  51 #include "init.h"
  52 #include "irq_user.h"
  53 #include "irq_kern.h"
  54 #include "ubd_user.h"
  55 #include "os.h"
  56 #include "mem.h"
  57 #include "mem_kern.h"
  58 #include "cow.h"
  59
  60 enum ubd_req { UBD_READ, UBD_WRITE };
  61
  62 struct io_thread_req {
  63         struct request *req;
  64         enum ubd_req op;
  65         int fds[2];
  66         unsigned long offsets[2];
  67         unsigned long long offset;
  68         unsigned long length;
  69         char *buffer;
  70         int sectorsize;
  71         unsigned long sector_mask;
  72         unsigned long long cow_offset;
  73         unsigned long bitmap_words[2];
  74         int error;
  75 };
  76
  77 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
  78 {
  79         __u64 n;
  80         int bits, off;
  81
  82         bits = sizeof(data[0]) * 8;
  83         n = bit / bits;
  84         off = bit % bits;
  85         return (data[n] & (1 << off)) != 0;
  86 }
  87
  88 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
  89 {
  90         __u64 n;
  91         int bits, off;
  92
  93         bits = sizeof(data[0]) * 8;
  94         n = bit / bits;
  95         off = bit % bits;
  96         data[n] |= (1 << off);
  97 }
  98 /*End stuff from ubd_user.h*/
  99
 100 #define DRIVER_NAME "uml-blkdev"
 101
 102 static DEFINE_MUTEX(ubd_lock);
 103 static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */
 104
 105 static int ubd_open(struct block_device *bdev, fmode_t mode);
 106 static int ubd_release(struct gendisk *disk, fmode_t mode);
 107 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
 108                      unsigned int cmd, unsigned long arg);
 109 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
 110
 111 #define MAX_DEV (16)
 112
 113 static const struct block_device_operations ubd_blops = {
 114         .owner          = THIS_MODULE,
 115         .open           = ubd_open,
 116         .release        = ubd_release,
 117         .ioctl          = ubd_ioctl,
 118         .getgeo         = ubd_getgeo,
 119 };
 120
 121 /* Protected by ubd_lock */
 122 static int fake_major = UBD_MAJOR;
 123 static struct gendisk *ubd_gendisk[MAX_DEV];
 124 static struct gendisk *fake_gendisk[MAX_DEV];
 125
 126 #ifdef CONFIG_BLK_DEV_UBD_SYNC
 127 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
 128                                          .cl = 1 })
 129 #else
 130 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
 131                                          .cl = 1 })
 132 #endif
 133 static struct openflags global_openflags = OPEN_FLAGS;
 134
 135 struct cow {
 136         /* backing file name */
 137         char *file;
 138         /* backing file fd */
 139         int fd;
 140         unsigned long *bitmap;
 141         unsigned long bitmap_len;
 142         int bitmap_offset;
 143         int data_offset;
 144 };
 145
 146 #define MAX_SG 64
 147
 148 struct ubd {
 149         struct list_head restart;
 150         /* name (and fd, below) of the file opened for writing, either the
 151          * backing or the cow file. */
 152         char *file;
 153         int count;
 154         int fd;
 155         __u64 size;
 156         struct openflags boot_openflags;
 157         struct openflags openflags;
 158         unsigned shared:1;
 159         unsigned no_cow:1;
 160         struct cow cow;
 161         struct platform_device pdev;
 162         struct request_queue *queue;
 163         spinlock_t lock;
 164         struct scatterlist sg[MAX_SG];
 165         struct request *request;
 166         int start_sg, end_sg;
 167         sector_t rq_pos;
 168 };
 169
 170 #define DEFAULT_COW { \
 171         .file =                 NULL, \
 172         .fd =                   -1,     \
 173         .bitmap =               NULL, \
 174         .bitmap_offset =        0, \
 175         .data_offset =          0, \
 176 }
 177
 178 #define DEFAULT_UBD { \
 179         .file =                 NULL, \
 180         .count =                0, \
 181         .fd =                   -1, \
 182         .size =                 -1, \
 183         .boot_openflags =       OPEN_FLAGS, \
 184         .openflags =            OPEN_FLAGS, \
 185         .no_cow =               0, \
 186         .shared =               0, \
 187         .cow =                  DEFAULT_COW, \
 188         .lock =                 SPIN_LOCK_UNLOCKED,     \
 189         .request =              NULL, \
 190         .start_sg =             0, \
 191         .end_sg =               0, \
 192         .rq_pos =               0, \
 193 }
 194
 195 /* Protected by ubd_lock */
 196 static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };
 197
 198 /* Only changed by fake_ide_setup which is a setup */
 199 static int fake_ide = 0;
 200 static struct proc_dir_entry *proc_ide_root = NULL;
 201 static struct proc_dir_entry *proc_ide = NULL;
 202
 203 static void make_proc_ide(void)
 204 {
 205         proc_ide_root = proc_mkdir("ide", NULL);
 206         proc_ide = proc_mkdir("ide0", proc_ide_root);
 207 }
 208
 209 static int fake_ide_media_proc_show(struct seq_file *m, void *v)
 210 {
 211         seq_puts(m, "disk\n");
 212         return 0;
 213 }
 214
 215 static int fake_ide_media_proc_open(struct inode *inode, struct file *file)
 216 {
 217         return single_open(file, fake_ide_media_proc_show, NULL);
 218 }
 219
 220 static const struct file_operations fake_ide_media_proc_fops = {
 221         .owner          = THIS_MODULE,
 222         .open           = fake_ide_media_proc_open,
 223         .read           = seq_read,
 224         .llseek         = seq_lseek,
 225         .release        = single_release,
 226 };
 227
 228 static void make_ide_entries(const char *dev_name)
 229 {
 230         struct proc_dir_entry *dir, *ent;
 231         char name[64];
 232
 233         if(proc_ide_root == NULL) make_proc_ide();
 234
 235         dir = proc_mkdir(dev_name, proc_ide);
 236         if(!dir) return;
 237
 238         ent = proc_create("media", S_IRUGO, dir, &fake_ide_media_proc_fops);
 239         if(!ent) return;
 240         snprintf(name, sizeof(name), "ide0/%s", dev_name);
 241         proc_symlink(dev_name, proc_ide_root, name);
 242 }
 243
 244 static int fake_ide_setup(char *str)
 245 {
 246         fake_ide = 1;
 247         return 1;
 248 }
 249
 250 __setup("fake_ide", fake_ide_setup);
 251
 252 __uml_help(fake_ide_setup,
 253 "fake_ide\n"
 254 "    Create ide0 entries that map onto ubd devices.\n\n"
 255 );
 256
 257 static int parse_unit(char **ptr)
 258 {
 259         char *str = *ptr, *end;
 260         int n = -1;
 261
 262         if(isdigit(*str)) {
 263                 n = simple_strtoul(str, &end, 0);
 264                 if(end == str)
 265                         return -1;
 266                 *ptr = end;
 267         }
 268         else if (('a' <= *str) && (*str <= 'z')) {
 269                 n = *str - 'a';
 270                 str++;
 271                 *ptr = str;
 272         }
 273         return n;
 274 }
 275
 276 /* If *index_out == -1 at exit, the passed option was a general one;
 277  * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
 278  * should not be freed on exit.
 279  */
 280 static int ubd_setup_common(char *str, int *index_out, char **error_out)
 281 {
 282         struct ubd *ubd_dev;
 283         struct openflags flags = global_openflags;
 284         char *backing_file;
 285         int n, err = 0, i;
 286
 287         if(index_out) *index_out = -1;
 288         n = *str;
 289         if(n == '='){
 290                 char *end;
 291                 int major;
 292
 293                 str++;
 294                 if(!strcmp(str, "sync")){
 295                         global_openflags = of_sync(global_openflags);
 296                         goto out1;
 297                 }
 298
 299                 err = -EINVAL;
 300                 major = simple_strtoul(str, &end, 0);
 301                 if((*end != '\0') || (end == str)){
 302                         *error_out = "Didn't parse major number";
 303                         goto out1;
 304                 }
 305
 306                 mutex_lock(&ubd_lock);
 307                 if (fake_major != UBD_MAJOR) {
 308                         *error_out = "Can't assign a fake major twice";
 309                         goto out1;
 310                 }
 311
 312                 fake_major = major;
 313
 314                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
 315                        major);
 316                 err = 0;
 317         out1:
 318                 mutex_unlock(&ubd_lock);
 319                 return err;
 320         }
 321
 322         n = parse_unit(&str);
 323         if(n < 0){
 324                 *error_out = "Couldn't parse device number";
 325                 return -EINVAL;
 326         }
 327         if(n >= MAX_DEV){
 328                 *error_out = "Device number out of range";
 329                 return 1;
 330         }
 331
 332         err = -EBUSY;
 333         mutex_lock(&ubd_lock);
 334
 335         ubd_dev = &ubd_devs[n];
 336         if(ubd_dev->file != NULL){
 337                 *error_out = "Device is already configured";
 338                 goto out;
 339         }
 340
 341         if (index_out)
 342                 *index_out = n;
 343
 344         err = -EINVAL;
 345         for (i = 0; i < sizeof("rscd="); i++) {
 346                 switch (*str) {
 347                 case 'r':
 348                         flags.w = 0;
 349                         break;
 350                 case 's':
 351                         flags.s = 1;
 352                         break;
 353                 case 'd':
 354                         ubd_dev->no_cow = 1;
 355                         break;
 356                 case 'c':
 357                         ubd_dev->shared = 1;
 358                         break;
 359                 case '=':
 360                         str++;
 361                         goto break_loop;
 362                 default:
 363                         *error_out = "Expected '=' or flag letter "
 364                                 "(r, s, c, or d)";
 365                         goto out;
 366                 }
 367                 str++;
 368         }
 369
 370         if (*str == '=')
 371                 *error_out = "Too many flags specified";
 372         else
 373                 *error_out = "Missing '='";
 374         goto out;
 375
 376 break_loop:
 377         backing_file = strchr(str, ',');
 378
 379         if (backing_file == NULL)
 380                 backing_file = strchr(str, ':');
 381
 382         if(backing_file != NULL){
 383                 if(ubd_dev->no_cow){
 384                         *error_out = "Can't specify both 'd' and a cow file";
 385                         goto out;
 386                 }
 387                 else {
 388                         *backing_file = '\0';
 389                         backing_file++;
 390                 }
 391         }
 392         err = 0;
 393         ubd_dev->file = str;
 394         ubd_dev->cow.file = backing_file;
 395         ubd_dev->boot_openflags = flags;
 396 out:
 397         mutex_unlock(&ubd_lock);
 398         return err;
 399 }
 400
 401 static int ubd_setup(char *str)
 402 {
 403         char *error;
 404         int err;
 405
 406         err = ubd_setup_common(str, NULL, &error);
 407         if(err)
 408                 printk(KERN_ERR "Failed to initialize device with \"%s\" : "
 409                        "%s\n", str, error);
 410         return 1;
 411 }
 412
 413 __setup("ubd", ubd_setup);
 414 __uml_help(ubd_setup,
 415 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
 416 "    This is used to associate a device with a file in the underlying\n"
 417 "    filesystem. When specifying two filenames, the first one is the\n"
 418 "    COW name and the second is the backing file name. As separator you can\n"
 419 "    use either a ':' or a ',': the first one allows writing things like;\n"
 420 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
 421 "    while with a ',' the shell would not expand the 2nd '~'.\n"
 422 "    When using only one filename, UML will detect whether to treat it like\n"
 423 "    a COW file or a backing file. To override this detection, add the 'd'\n"
 424 "    flag:\n"
 425 "       ubd0d=BackingFile\n"
 426 "    Usually, there is a filesystem in the file, but \n"
 427 "    that's not required. Swap devices containing swap files can be\n"
 428 "    specified like this. Also, a file which doesn't contain a\n"
 429 "    filesystem can have its contents read in the virtual \n"
 430 "    machine by running 'dd' on the device. <n> must be in the range\n"
 431 "    0 to 7. Appending an 'r' to the number will cause that device\n"
 432 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
 433 "    an 's' will cause data to be written to disk on the host immediately.\n"
 434 "    'c' will cause the device to be treated as being shared between multiple\n"
 435 "    UMLs and file locking will be turned off - this is appropriate for a\n"
 436 "    cluster filesystem and inappropriate at almost all other times.\n\n"
 437 );
 438
 439 static int udb_setup(char *str)
 440 {
 441         printk("udb%s specified on command line is almost certainly a ubd -> "
 442                "udb TYPO\n", str);
 443         return 1;
 444 }
 445
 446 __setup("udb", udb_setup);
 447 __uml_help(udb_setup,
 448 "udb\n"
 449 "    This option is here solely to catch ubd -> udb typos, which can be\n"
 450 "    to impossible to catch visually unless you specifically look for\n"
 451 "    them.  The only result of any option starting with 'udb' is an error\n"
 452 "    in the boot output.\n\n"
 453 );
 454
 455 static void do_ubd_request(struct request_queue * q);
 456
 457 /* Only changed by ubd_init, which is an initcall. */
 458 static int thread_fd = -1;
 459 static LIST_HEAD(restart);
 460
 461 /* XXX - move this inside ubd_intr. */
 462 /* Called without dev->lock held, and only in interrupt context. */
 463 static void ubd_handler(void)
 464 {
 465         struct io_thread_req *req;
 466         struct ubd *ubd;
 467         struct list_head *list, *next_ele;
 468         unsigned long flags;
 469         int n;
 470
 471         while(1){
 472                 n = os_read_file(thread_fd, &req,
 473                                  sizeof(struct io_thread_req *));
 474                 if(n != sizeof(req)){
 475                         if(n == -EAGAIN)
 476                                 break;
 477                         printk(KERN_ERR "spurious interrupt in ubd_handler, "
 478                                "err = %d\n", -n);
 479                         return;
 480                 }
 481
 482                 blk_end_request(req->req, 0, req->length);
 483                 kfree(req);
 484         }
 485         reactivate_fd(thread_fd, UBD_IRQ);
 486
 487         list_for_each_safe(list, next_ele, &restart){
 488                 ubd = container_of(list, struct ubd, restart);
 489                 list_del_init(&ubd->restart);
 490                 spin_lock_irqsave(&ubd->lock, flags);
 491                 do_ubd_request(ubd->queue);
 492                 spin_unlock_irqrestore(&ubd->lock, flags);
 493         }
 494 }
 495
 496 static irqreturn_t ubd_intr(int irq, void *dev)
 497 {
 498         ubd_handler();
 499         return IRQ_HANDLED;
 500 }
 501
 502 /* Only changed by ubd_init, which is an initcall. */
 503 static int io_pid = -1;
 504
 505 static void kill_io_thread(void)
 506 {
 507         if(io_pid != -1)
 508                 os_kill_process(io_pid, 1);
 509 }
 510
 511 __uml_exitcall(kill_io_thread);
 512
 513 static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
 514 {
 515         char *file;
 516
 517         file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
 518         return os_file_size(file, size_out);
 519 }
 520
 521 static int read_cow_bitmap(int fd, void *buf, int offset, int len)
 522 {
 523         int err;
 524
 525         err = os_seek_file(fd, offset);
 526         if (err < 0)
 527                 return err;
 528
 529         err = os_read_file(fd, buf, len);
 530         if (err < 0)
 531                 return err;
 532
 533         return 0;
 534 }
 535
 536 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
 537 {
 538         unsigned long modtime;
 539         unsigned long long actual;
 540         int err;
 541
 542         err = os_file_modtime(file, &modtime);
 543         if (err < 0) {
 544                 printk(KERN_ERR "Failed to get modification time of backing "
 545                        "file \"%s\", err = %d\n", file, -err);
 546                 return err;
 547         }
 548
 549         err = os_file_size(file, &actual);
 550         if (err < 0) {
 551                 printk(KERN_ERR "Failed to get size of backing file \"%s\", "
 552                        "err = %d\n", file, -err);
 553                 return err;
 554         }
 555
 556         if (actual != size) {
 557                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
 558                  * the typecast.*/
 559                 printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
 560                        "vs backing file\n", (unsigned long long) size, actual);
 561                 return -EINVAL;
 562         }
 563         if (modtime != mtime) {
 564                 printk(KERN_ERR "mtime mismatch (%ld vs %ld) of COW header vs "
 565                        "backing file\n", mtime, modtime);
 566                 return -EINVAL;
 567         }
 568         return 0;
 569 }
 570
 571 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
 572 {
 573         struct uml_stat buf1, buf2;
 574         int err;
 575
 576         if (from_cmdline == NULL)
 577                 return 0;
 578         if (!strcmp(from_cmdline, from_cow))
 579                 return 0;
 580
 581         err = os_stat_file(from_cmdline, &buf1);
 582         if (err < 0) {
 583                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
 584                        -err);
 585                 return 0;
 586         }
 587         err = os_stat_file(from_cow, &buf2);
 588         if (err < 0) {
 589                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
 590                        -err);
 591                 return 1;
 592         }
 593         if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
 594                 return 0;
 595
 596         printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
 597                "\"%s\" specified in COW header of \"%s\"\n",
 598                from_cmdline, from_cow, cow);
 599         return 1;
 600 }
 601
 602 static int open_ubd_file(char *file, struct openflags *openflags, int shared,
 603                   char **backing_file_out, int *bitmap_offset_out,
 604                   unsigned long *bitmap_len_out, int *data_offset_out,
 605                   int *create_cow_out)
 606 {
 607         time_t mtime;
 608         unsigned long long size;
 609         __u32 version, align;
 610         char *backing_file;
 611         int fd, err, sectorsize, asked_switch, mode = 0644;
 612
 613         fd = os_open_file(file, *openflags, mode);
 614         if (fd < 0) {
 615                 if ((fd == -ENOENT) && (create_cow_out != NULL))
 616                         *create_cow_out = 1;
 617                 if (!openflags->w ||
 618                     ((fd != -EROFS) && (fd != -EACCES)))
 619                         return fd;
 620                 openflags->w = 0;
 621                 fd = os_open_file(file, *openflags, mode);
 622                 if (fd < 0)
 623                         return fd;
 624         }
 625
 626         if (shared)
 627                 printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
 628         else {
 629                 err = os_lock_file(fd, openflags->w);
 630                 if (err < 0) {
 631                         printk(KERN_ERR "Failed to lock '%s', err = %d\n",
 632                                file, -err);
 633                         goto out_close;
 634                 }
 635         }
 636
 637         /* Successful return case! */
 638         if (backing_file_out == NULL)
 639                 return fd;
 640
 641         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
 642                               &size, &sectorsize, &align, bitmap_offset_out);
 643         if (err && (*backing_file_out != NULL)) {
 644                 printk(KERN_ERR "Failed to read COW header from COW file "
 645                        "\"%s\", errno = %d\n", file, -err);
 646                 goto out_close;
 647         }
 648         if (err)
 649                 return fd;
 650
 651         asked_switch = path_requires_switch(*backing_file_out, backing_file,
 652                                             file);
 653
 654         /* Allow switching only if no mismatch. */
 655         if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
 656                                                    mtime)) {
 657                 printk(KERN_ERR "Switching backing file to '%s'\n",
 658                        *backing_file_out);
 659                 err = write_cow_header(file, fd, *backing_file_out,
 660                                        sectorsize, align, &size);
 661                 if (err) {
 662                         printk(KERN_ERR "Switch failed, errno = %d\n", -err);
 663                         goto out_close;
 664                 }
 665         } else {
 666                 *backing_file_out = backing_file;
 667                 err = backing_file_mismatch(*backing_file_out, size, mtime);
 668                 if (err)
 669                         goto out_close;
 670         }
 671
 672         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
 673                   bitmap_len_out, data_offset_out);
 674
 675         return fd;
 676  out_close:
 677         os_close_file(fd);
 678         return err;
 679 }
 680
 681 static int create_cow_file(char *cow_file, char *backing_file,
 682                     struct openflags flags,
 683                     int sectorsize, int alignment, int *bitmap_offset_out,
 684                     unsigned long *bitmap_len_out, int *data_offset_out)
 685 {
 686         int err, fd;
 687
 688         flags.c = 1;
 689         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
 690         if (fd < 0) {
 691                 err = fd;
 692                 printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
 693                        cow_file, -err);
 694                 goto out;
 695         }
 696
 697         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
 698                             bitmap_offset_out, bitmap_len_out,
 699                             data_offset_out);
 700         if (!err)
 701                 return fd;
 702         os_close_file(fd);
 703  out:
 704         return err;
 705 }
 706
 707 static void ubd_close_dev(struct ubd *ubd_dev)
 708 {
 709         os_close_file(ubd_dev->fd);
 710         if(ubd_dev->cow.file == NULL)
 711                 return;
 712
 713         os_close_file(ubd_dev->cow.fd);
 714         vfree(ubd_dev->cow.bitmap);
 715         ubd_dev->cow.bitmap = NULL;
 716 }
 717
 718 static int ubd_open_dev(struct ubd *ubd_dev)
 719 {
 720         struct openflags flags;
 721         char **back_ptr;
 722         int err, create_cow, *create_ptr;
 723         int fd;
 724
 725         ubd_dev->openflags = ubd_dev->boot_openflags;
 726         create_cow = 0;
 727         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
 728         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
 729
 730         fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
 731                                 back_ptr, &ubd_dev->cow.bitmap_offset,
 732                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
 733                                 create_ptr);
 734
 735         if((fd == -ENOENT) && create_cow){
 736                 fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
 737                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
 738                                           &ubd_dev->cow.bitmap_offset,
 739                                           &ubd_dev->cow.bitmap_len,
 740                                           &ubd_dev->cow.data_offset);
 741                 if(fd >= 0){
 742                         printk(KERN_INFO "Creating \"%s\" as COW file for "
 743                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
 744                 }
 745         }
 746
 747         if(fd < 0){
 748                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
 749                        -fd);
 750                 return fd;
 751         }
 752         ubd_dev->fd = fd;
 753
 754         if(ubd_dev->cow.file != NULL){
 755                 blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));
 756
 757                 err = -ENOMEM;
 758                 ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
 759                 if(ubd_dev->cow.bitmap == NULL){
 760                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
 761                         goto error;
 762                 }
 763                 flush_tlb_kernel_vm();
 764
 765                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
 766                                       ubd_dev->cow.bitmap_offset,
 767                                       ubd_dev->cow.bitmap_len);
 768                 if(err < 0)
 769                         goto error;
 770
 771                 flags = ubd_dev->openflags;
 772                 flags.w = 0;
 773                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
 774                                     NULL, NULL, NULL, NULL);
 775                 if(err < 0) goto error;
 776                 ubd_dev->cow.fd = err;
 777         }
 778         return 0;
 779  error:
 780         os_close_file(ubd_dev->fd);
 781         return err;
 782 }
 783
 784 static void ubd_device_release(struct device *dev)
 785 {
 786         struct ubd *ubd_dev = dev_get_drvdata(dev);
 787
 788         blk_cleanup_queue(ubd_dev->queue);
 789         *ubd_dev = ((struct ubd) DEFAULT_UBD);
 790 }
 791
 792 static int ubd_disk_register(int major, u64 size, int unit,
 793                              struct gendisk **disk_out)
 794 {
 795         struct gendisk *disk;
 796
 797         disk = alloc_disk(1 << UBD_SHIFT);
 798         if(disk == NULL)
 799                 return -ENOMEM;
 800
 801         disk->major = major;
 802         disk->first_minor = unit << UBD_SHIFT;
 803         disk->fops = &ubd_blops;
 804         set_capacity(disk, size / 512);
 805         if (major == UBD_MAJOR)
 806                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
 807         else
 808                 sprintf(disk->disk_name, "ubd_fake%d", unit);
 809
 810         /* sysfs register (not for ide fake devices) */
 811         if (major == UBD_MAJOR) {
 812                 ubd_devs[unit].pdev.id   = unit;
 813                 ubd_devs[unit].pdev.name = DRIVER_NAME;
 814                 ubd_devs[unit].pdev.dev.release = ubd_device_release;
 815                 dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
 816                 platform_device_register(&ubd_devs[unit].pdev);
 817                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
 818         }
 819
 820         disk->private_data = &ubd_devs[unit];
 821         disk->queue = ubd_devs[unit].queue;
 822         add_disk(disk);
 823
 824         *disk_out = disk;
 825         return 0;
 826 }
 827
 828 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
 829
 830 static int ubd_add(int n, char **error_out)
 831 {
 832         struct ubd *ubd_dev = &ubd_devs[n];
 833         int err = 0;
 834
 835         if(ubd_dev->file == NULL)
 836                 goto out;
 837
 838         err = ubd_file_size(ubd_dev, &ubd_dev->size);
 839         if(err < 0){
 840                 *error_out = "Couldn't determine size of device's file";
 841                 goto out;
 842         }
 843
 844         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 845
 846         INIT_LIST_HEAD(&ubd_dev->restart);
 847         sg_init_table(ubd_dev->sg, MAX_SG);
 848
 849         err = -ENOMEM;
 850         ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
 851         if (ubd_dev->queue == NULL) {
 852                 *error_out = "Failed to initialize device queue";
 853                 goto out;
 854         }
 855         ubd_dev->queue->queuedata = ubd_dev;
 856
 857         blk_queue_max_segments(ubd_dev->queue, MAX_SG);
 858         err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, &ubd_gendisk[n]);
 859         if(err){
 860                 *error_out = "Failed to register device";
 861                 goto out_cleanup;
 862         }
 863
 864         if (fake_major != UBD_MAJOR)
 865                 ubd_disk_register(fake_major, ubd_dev->size, n,
 866                                   &fake_gendisk[n]);
 867
 868         /*
 869          * Perhaps this should also be under the "if (fake_major)" above
 870          * using the fake_disk->disk_name
 871          */
 872         if (fake_ide)
 873                 make_ide_entries(ubd_gendisk[n]->disk_name);
 874
 875         err = 0;
 876 out:
 877         return err;
 878
 879 out_cleanup:
 880         blk_cleanup_queue(ubd_dev->queue);
 881         goto out;
 882 }
 883
 884 static int ubd_config(char *str, char **error_out)
 885 {
 886         int n, ret;
 887
 888         /* This string is possibly broken up and stored, so it's only
 889          * freed if ubd_setup_common fails, or if only general options
 890          * were set.
 891          */
 892         str = kstrdup(str, GFP_KERNEL);
 893         if (str == NULL) {
 894                 *error_out = "Failed to allocate memory";
 895                 return -ENOMEM;
 896         }
 897
 898         ret = ubd_setup_common(str, &n, error_out);
 899         if (ret)
 900                 goto err_free;
 901
 902         if (n == -1) {
 903                 ret = 0;
 904                 goto err_free;
 905         }
 906
 907         mutex_lock(&ubd_lock);
 908         ret = ubd_add(n, error_out);
 909         if (ret)
 910                 ubd_devs[n].file = NULL;
 911         mutex_unlock(&ubd_lock);
 912
 913 out:
 914         return ret;
 915
 916 err_free:
 917         kfree(str);
 918         goto out;
 919 }
 920
 921 static int ubd_get_config(char *name, char *str, int size, char **error_out)
 922 {
 923         struct ubd *ubd_dev;
 924         int n, len = 0;
 925
 926         n = parse_unit(&name);
 927         if((n >= MAX_DEV) || (n < 0)){
 928                 *error_out = "ubd_get_config : device number out of range";
 929                 return -1;
 930         }
 931
 932         ubd_dev = &ubd_devs[n];
 933         mutex_lock(&ubd_lock);
 934
 935         if(ubd_dev->file == NULL){
 936                 CONFIG_CHUNK(str, size, len, "", 1);
 937                 goto out;
 938         }
 939
 940         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
 941
 942         if(ubd_dev->cow.file != NULL){
 943                 CONFIG_CHUNK(str, size, len, ",", 0);
 944                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
 945         }
 946         else CONFIG_CHUNK(str, size, len, "", 1);
 947
 948  out:
 949         mutex_unlock(&ubd_lock);
 950         return len;
 951 }
 952
 953 static int ubd_id(char **str, int *start_out, int *end_out)
 954 {
 955         int n;
 956
 957         n = parse_unit(str);
 958         *start_out = 0;
 959         *end_out = MAX_DEV - 1;
 960         return n;
 961 }
 962
 963 static int ubd_remove(int n, char **error_out)
 964 {
 965         struct gendisk *disk = ubd_gendisk[n];
 966         struct ubd *ubd_dev;
 967         int err = -ENODEV;
 968
 969         mutex_lock(&ubd_lock);
 970
 971         ubd_dev = &ubd_devs[n];
 972
 973         if(ubd_dev->file == NULL)
 974                 goto out;
 975
 976         /* you cannot remove a open disk */
 977         err = -EBUSY;
 978         if(ubd_dev->count > 0)
 979                 goto out;
 980
 981         ubd_gendisk[n] = NULL;
 982         if(disk != NULL){
 983                 del_gendisk(disk);
 984                 put_disk(disk);
 985         }
 986
 987         if(fake_gendisk[n] != NULL){
 988                 del_gendisk(fake_gendisk[n]);
 989                 put_disk(fake_gendisk[n]);
 990                 fake_gendisk[n] = NULL;
 991         }
 992
 993         err = 0;
 994         platform_device_unregister(&ubd_dev->pdev);
 995 out:
 996         mutex_unlock(&ubd_lock);
 997         return err;
 998 }
 999
1000 /* All these are called by mconsole in process context and without
1001  * ubd-specific locks.  The structure itself is const except for .list.
1002  */
1003 static struct mc_device ubd_mc = {
1004         .list           = LIST_HEAD_INIT(ubd_mc.list),
1005         .name           = "ubd",
1006         .config         = ubd_config,
1007         .get_config     = ubd_get_config,
1008         .id             = ubd_id,
1009         .remove         = ubd_remove,
1010 };
1011
1012 static int __init ubd_mc_init(void)
1013 {
1014         mconsole_register_dev(&ubd_mc);
1015         return 0;
1016 }
1017
1018 __initcall(ubd_mc_init);
1019
1020 static int __init ubd0_init(void)
1021 {
1022         struct ubd *ubd_dev = &ubd_devs[0];
1023
1024         mutex_lock(&ubd_lock);
1025         if(ubd_dev->file == NULL)
1026                 ubd_dev->file = "root_fs";
1027         mutex_unlock(&ubd_lock);
1028
1029         return 0;
1030 }
1031
1032 __initcall(ubd0_init);
1033
1034 /* Used in ubd_init, which is an initcall */
1035 static struct platform_driver ubd_driver = {
1036         .driver = {
1037                 .name  = DRIVER_NAME,
1038         },
1039 };
1040
1041 static int __init ubd_init(void)
1042 {
1043         char *error;
1044         int i, err;
1045
1046         if (register_blkdev(UBD_MAJOR, "ubd"))
1047                 return -1;
1048
1049         if (fake_major != UBD_MAJOR) {
1050                 char name[sizeof("ubd_nnn\0")];
1051
1052                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
1053                 if (register_blkdev(fake_major, "ubd"))
1054                         return -1;
1055         }
1056         platform_driver_register(&ubd_driver);
1057         mutex_lock(&ubd_lock);
1058         for (i = 0; i < MAX_DEV; i++){
1059                 err = ubd_add(i, &error);
1060                 if(err)
1061                         printk(KERN_ERR "Failed to initialize ubd device %d :"
1062                                "%s\n", i, error);
1063         }
1064         mutex_unlock(&ubd_lock);
1065         return 0;
1066 }
1067
1068 late_initcall(ubd_init);
1069
1070 static int __init ubd_driver_init(void){
1071         unsigned long stack;
1072         int err;
1073
1074         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
1075         if(global_openflags.s){
1076                 printk(KERN_INFO "ubd: Synchronous mode\n");
1077                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
1078                  * enough. So use anyway the io thread. */
1079         }
1080         stack = alloc_stack(0, 0);
1081         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
1082                                  &thread_fd);
1083         if(io_pid < 0){
1084                 printk(KERN_ERR
1085                        "ubd : Failed to start I/O thread (errno = %d) - "
1086                        "falling back to synchronous I/O\n", -io_pid);
1087                 io_pid = -1;
1088                 return 0;
1089         }
1090         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
1091                              IRQF_DISABLED, "ubd", ubd_devs);
1092         if(err != 0)
1093                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
1094         return 0;
1095 }
1096
1097 device_initcall(ubd_driver_init);
1098
1099 static int ubd_open(struct block_device *bdev, fmode_t mode)
1100 {
1101         struct gendisk *disk = bdev->bd_disk;
1102         struct ubd *ubd_dev = disk->private_data;
1103         int err = 0;
1104
1105         mutex_lock(&ubd_mutex);
1106         if(ubd_dev->count == 0){
1107                 err = ubd_open_dev(ubd_dev);
1108                 if(err){
1109                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
1110                                disk->disk_name, ubd_dev->file, -err);
1111                         goto out;
1112                 }
1113         }
1114         ubd_dev->count++;
1115         set_disk_ro(disk, !ubd_dev->openflags.w);
1116
1117         /* This should no more be needed. And it didn't work anyway to exclude
1118          * read-write remounting of filesystems.*/
1119         /*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
1120                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
1121                 err = -EROFS;
1122         }*/
1123 out:
1124         mutex_unlock(&ubd_mutex);
1125         return err;
1126 }
1127
1128 static int ubd_release(struct gendisk *disk, fmode_t mode)
1129 {
1130         struct ubd *ubd_dev = disk->private_data;
1131
1132         mutex_lock(&ubd_mutex);
1133         if(--ubd_dev->count == 0)
1134                 ubd_close_dev(ubd_dev);
1135         mutex_unlock(&ubd_mutex);
1136         return 0;
1137 }
1138
1139 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
1140                           __u64 *cow_offset, unsigned long *bitmap,
1141                           __u64 bitmap_offset, unsigned long *bitmap_words,
1142                           __u64 bitmap_len)
1143 {
1144         __u64 sector = io_offset >> 9;
1145         int i, update_bitmap = 0;
1146
1147         for(i = 0; i < length >> 9; i++){
1148                 if(cow_mask != NULL)
1149                         ubd_set_bit(i, (unsigned char *) cow_mask);
1150                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1151                         continue;
1152
1153                 update_bitmap = 1;
1154                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
1155         }
1156
1157         if(!update_bitmap)
1158                 return;
1159
1160         *cow_offset = sector / (sizeof(unsigned long) * 8);
1161
1162         /* This takes care of the case where we're exactly at the end of the
1163          * device, and *cow_offset + 1 is off the end.  So, just back it up
1164          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
1165          * for the original diagnosis.
1166          */
1167         if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
1168                                          sizeof(unsigned long)) - 1))
1169                 (*cow_offset)--;
1170
1171         bitmap_words[0] = bitmap[*cow_offset];
1172         bitmap_words[1] = bitmap[*cow_offset + 1];
1173
1174         *cow_offset *= sizeof(unsigned long);
1175         *cow_offset += bitmap_offset;
1176 }
1177
1178 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
1179                        __u64 bitmap_offset, __u64 bitmap_len)
1180 {
1181         __u64 sector = req->offset >> 9;
1182         int i;
1183
1184         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
1185                 panic("Operation too long");
1186
1187         if(req->op == UBD_READ) {
1188                 for(i = 0; i < req->length >> 9; i++){
1189                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1190                                 ubd_set_bit(i, (unsigned char *)
1191                                             &req->sector_mask);
1192                 }
1193         }
1194         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
1195                            &req->cow_offset, bitmap, bitmap_offset,
1196                            req->bitmap_words, bitmap_len);
1197 }
1198
1199 /* Called with dev->lock held */
1200 static void prepare_request(struct request *req, struct io_thread_req *io_req,
1201                             unsigned long long offset, int page_offset,
1202                             int len, struct page *page)
1203 {
1204         struct gendisk *disk = req->rq_disk;
1205         struct ubd *ubd_dev = disk->private_data;
1206
1207         io_req->req = req;
1208         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
1209                 ubd_dev->fd;
1210         io_req->fds[1] = ubd_dev->fd;
1211         io_req->cow_offset = -1;
1212         io_req->offset = offset;
1213         io_req->length = len;
1214         io_req->error = 0;
1215         io_req->sector_mask = 0;
1216
1217         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1218         io_req->offsets[0] = 0;
1219         io_req->offsets[1] = ubd_dev->cow.data_offset;
1220         io_req->buffer = page_address(page) + page_offset;
1221         io_req->sectorsize = 1 << 9;
1222
1223         if(ubd_dev->cow.file != NULL)
1224                 cowify_req(io_req, ubd_dev->cow.bitmap,
1225                            ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);
1226
1227 }
1228
1229 /* Called with dev->lock held */
1230 static void do_ubd_request(struct request_queue *q)
1231 {
1232         struct io_thread_req *io_req;
1233         struct request *req;
1234         int n;
1235
1236         while(1){
1237                 struct ubd *dev = q->queuedata;
1238                 if(dev->end_sg == 0){
1239                         struct request *req = blk_fetch_request(q);
1240                         if(req == NULL)
1241                                 return;
1242
1243                         dev->request = req;
1244                         dev->rq_pos = blk_rq_pos(req);
1245                         dev->start_sg = 0;
1246                         dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
1247                 }
1248
1249                 req = dev->request;
1250                 while(dev->start_sg < dev->end_sg){
1251                         struct scatterlist *sg = &dev->sg[dev->start_sg];
1252
1253                         io_req = kmalloc(sizeof(struct io_thread_req),
1254                                          GFP_ATOMIC);
1255                         if(io_req == NULL){
1256                                 if(list_empty(&dev->restart))
1257                                         list_add(&dev->restart, &restart);
1258                                 return;
1259                         }
1260                         prepare_request(req, io_req,
1261                                         (unsigned long long)dev->rq_pos << 9,
1262                                         sg->offset, sg->length, sg_page(sg));
1263
1264                         n = os_write_file(thread_fd, &io_req,
1265                                           sizeof(struct io_thread_req *));
1266                         if(n != sizeof(struct io_thread_req *)){
1267                                 if(n != -EAGAIN)
1268                                         printk("write to io thread failed, "
1269                                                "errno = %d\n", -n);
1270                                 else if(list_empty(&dev->restart))
1271                                         list_add(&dev->restart, &restart);
1272                                 kfree(io_req);
1273                                 return;
1274                         }
1275
1276                         dev->rq_pos += sg->length >> 9;
1277                         dev->start_sg++;
1278                 }
1279                 dev->end_sg = 0;
1280                 dev->request = NULL;
1281         }
1282 }
1283
1284 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1285 {
1286         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1287
1288         geo->heads = 128;
1289         geo->sectors = 32;
1290         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1291         return 0;
1292 }
1293
1294 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
1295                      unsigned int cmd, unsigned long arg)
1296 {
1297         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1298         u16 ubd_id[ATA_ID_WORDS];
1299
1300         switch (cmd) {
1301                 struct cdrom_volctrl volume;
1302         case HDIO_GET_IDENTITY:
1303                 memset(&ubd_id, 0, ATA_ID_WORDS * 2);
1304                 ubd_id[ATA_ID_CYLS]     = ubd_dev->size / (128 * 32 * 512);
1305                 ubd_id[ATA_ID_HEADS]    = 128;
1306                 ubd_id[ATA_ID_SECTORS]  = 32;
1307                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1308                                  sizeof(ubd_id)))
1309                         return -EFAULT;
1310                 return 0;
1311
1312         case CDROMVOLREAD:
1313                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1314                         return -EFAULT;
1315                 volume.channel0 = 255;
1316                 volume.channel1 = 255;
1317                 volume.channel2 = 255;
1318                 volume.channel3 = 255;
1319                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1320                         return -EFAULT;
1321                 return 0;
1322         }
1323         return -EINVAL;
1324 }
1325
1326 static int update_bitmap(struct io_thread_req *req)
1327 {
1328         int n;
1329
1330         if(req->cow_offset == -1)
1331                 return 0;
1332
1333         n = os_seek_file(req->fds[1], req->cow_offset);
1334         if(n < 0){
1335                 printk("do_io - bitmap lseek failed : err = %d\n", -n);
1336                 return 1;
1337         }
1338
1339         n = os_write_file(req->fds[1], &req->bitmap_words,
1340                           sizeof(req->bitmap_words));
1341         if(n != sizeof(req->bitmap_words)){
1342                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1343                        req->fds[1]);
1344                 return 1;
1345         }
1346
1347         return 0;
1348 }
1349
1350 static void do_io(struct io_thread_req *req)
1351 {
1352         char *buf;
1353         unsigned long len;
1354         int n, nsectors, start, end, bit;
1355         int err;
1356         __u64 off;
1357
1358         nsectors = req->length / req->sectorsize;
1359         start = 0;
1360         do {
1361                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1362                 end = start;
1363                 while((end < nsectors) &&
1364                       (ubd_test_bit(end, (unsigned char *)
1365                                     &req->sector_mask) == bit))
1366                         end++;
1367
1368                 off = req->offset + req->offsets[bit] +
1369                         start * req->sectorsize;
1370                 len = (end - start) * req->sectorsize;
1371                 buf = &req->buffer[start * req->sectorsize];
1372
1373                 err = os_seek_file(req->fds[bit], off);
1374                 if(err < 0){
1375                         printk("do_io - lseek failed : err = %d\n", -err);
1376                         req->error = 1;
1377                         return;
1378                 }
1379                 if(req->op == UBD_READ){
1380                         n = 0;
1381                         do {
1382                                 buf = &buf[n];
1383                                 len -= n;
1384                                 n = os_read_file(req->fds[bit], buf, len);
1385                                 if (n < 0) {
1386                                         printk("do_io - read failed, err = %d "
1387                                                "fd = %d\n", -n, req->fds[bit]);
1388                                         req->error = 1;
1389                                         return;
1390                                 }
1391                         } while((n < len) && (n != 0));
1392                         if (n < len) memset(&buf[n], 0, len - n);
1393                 } else {
1394                         n = os_write_file(req->fds[bit], buf, len);
1395                         if(n != len){
1396                                 printk("do_io - write failed err = %d "
1397                                        "fd = %d\n", -n, req->fds[bit]);
1398                                 req->error = 1;
1399                                 return;
1400                         }
1401                 }
1402
1403                 start = end;
1404         } while(start < nsectors);
1405
1406         req->error = update_bitmap(req);
1407 }
1408
1409 /* Changed in start_io_thread, which is serialized by being called only
1410  * from ubd_init, which is an initcall.
1411  */
1412 int kernel_fd = -1;
1413
1414 /* Only changed by the io thread. XXX: currently unused. */
1415 static int io_count = 0;
1416
1417 int io_thread(void *arg)
1418 {
1419         struct io_thread_req *req;
1420         int n;
1421
1422         ignore_sigwinch_sig();
1423         while(1){
1424                 n = os_read_file(kernel_fd, &req,
1425                                  sizeof(struct io_thread_req *));
1426                 if(n != sizeof(struct io_thread_req *)){
1427                         if(n < 0)
1428                                 printk("io_thread - read failed, fd = %d, "
1429                                        "err = %d\n", kernel_fd, -n);
1430                         else {
1431                                 printk("io_thread - short read, fd = %d, "
1432                                        "length = %d\n", kernel_fd, n);
1433                         }
1434                         continue;
1435                 }
1436                 io_count++;
1437                 do_io(req);
1438                 n = os_write_file(kernel_fd, &req,
1439                                   sizeof(struct io_thread_req *));
1440                 if(n != sizeof(struct io_thread_req *))
1441                         printk("io_thread - write failed, fd = %d, err = %d\n",
1442                                kernel_fd, -n);
1443         }
1444
1445         return 0;
1446 }