git.oblomov.eu Git - linux-2.6/blob - arch/um/drivers/ubd_kern.c

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