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TOMOYO Linux Cross Reference
Linux/arch/um/drivers/ubd_kern.c

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  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 UBD_SHIFT 4
 21 
 22 #include <linux/module.h>
 23 #include <linux/init.h>
 24 #include <linux/blkdev.h>
 25 #include <linux/ata.h>
 26 #include <linux/hdreg.h>
 27 #include <linux/cdrom.h>
 28 #include <linux/proc_fs.h>
 29 #include <linux/seq_file.h>
 30 #include <linux/ctype.h>
 31 #include <linux/slab.h>
 32 #include <linux/vmalloc.h>
 33 #include <linux/platform_device.h>
 34 #include <linux/scatterlist.h>
 35 #include <asm/tlbflush.h>
 36 #include <kern_util.h>
 37 #include "mconsole_kern.h"
 38 #include <init.h>
 39 #include <irq_kern.h>
 40 #include "ubd.h"
 41 #include <os.h>
 42 #include "cow.h"
 43 
 44 enum ubd_req { UBD_READ, UBD_WRITE, UBD_FLUSH };
 45 
 46 struct io_thread_req {
 47         struct request *req;
 48         enum ubd_req op;
 49         int fds[2];
 50         unsigned long offsets[2];
 51         unsigned long long offset;
 52         unsigned long length;
 53         char *buffer;
 54         int sectorsize;
 55         unsigned long sector_mask;
 56         unsigned long long cow_offset;
 57         unsigned long bitmap_words[2];
 58         int error;
 59 };
 60 
 61 static inline int ubd_test_bit(__u64 bit, unsigned char *data)
 62 {
 63         __u64 n;
 64         int bits, off;
 65 
 66         bits = sizeof(data[0]) * 8;
 67         n = bit / bits;
 68         off = bit % bits;
 69         return (data[n] & (1 << off)) != 0;
 70 }
 71 
 72 static inline void ubd_set_bit(__u64 bit, unsigned char *data)
 73 {
 74         __u64 n;
 75         int bits, off;
 76 
 77         bits = sizeof(data[0]) * 8;
 78         n = bit / bits;
 79         off = bit % bits;
 80         data[n] |= (1 << off);
 81 }
 82 /*End stuff from ubd_user.h*/
 83 
 84 #define DRIVER_NAME "uml-blkdev"
 85 
 86 static DEFINE_MUTEX(ubd_lock);
 87 static DEFINE_MUTEX(ubd_mutex); /* replaces BKL, might not be needed */
 88 
 89 static int ubd_open(struct block_device *bdev, fmode_t mode);
 90 static void ubd_release(struct gendisk *disk, fmode_t mode);
 91 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
 92                      unsigned int cmd, unsigned long arg);
 93 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo);
 94 
 95 #define MAX_DEV (16)
 96 
 97 static const struct block_device_operations ubd_blops = {
 98         .owner          = THIS_MODULE,
 99         .open           = ubd_open,
100         .release        = ubd_release,
101         .ioctl          = ubd_ioctl,
102         .getgeo         = ubd_getgeo,
103 };
104 
105 /* Protected by ubd_lock */
106 static int fake_major = UBD_MAJOR;
107 static struct gendisk *ubd_gendisk[MAX_DEV];
108 static struct gendisk *fake_gendisk[MAX_DEV];
109 
110 #ifdef CONFIG_BLK_DEV_UBD_SYNC
111 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 1, .c = 0, \
112                                          .cl = 1 })
113 #else
114 #define OPEN_FLAGS ((struct openflags) { .r = 1, .w = 1, .s = 0, .c = 0, \
115                                          .cl = 1 })
116 #endif
117 static struct openflags global_openflags = OPEN_FLAGS;
118 
119 struct cow {
120         /* backing file name */
121         char *file;
122         /* backing file fd */
123         int fd;
124         unsigned long *bitmap;
125         unsigned long bitmap_len;
126         int bitmap_offset;
127         int data_offset;
128 };
129 
130 #define MAX_SG 64
131 
132 struct ubd {
133         struct list_head restart;
134         /* name (and fd, below) of the file opened for writing, either the
135          * backing or the cow file. */
136         char *file;
137         int count;
138         int fd;
139         __u64 size;
140         struct openflags boot_openflags;
141         struct openflags openflags;
142         unsigned shared:1;
143         unsigned no_cow:1;
144         struct cow cow;
145         struct platform_device pdev;
146         struct request_queue *queue;
147         spinlock_t lock;
148         struct scatterlist sg[MAX_SG];
149         struct request *request;
150         int start_sg, end_sg;
151         sector_t rq_pos;
152 };
153 
154 #define DEFAULT_COW { \
155         .file =                 NULL, \
156         .fd =                   -1,     \
157         .bitmap =               NULL, \
158         .bitmap_offset =        0, \
159         .data_offset =          0, \
160 }
161 
162 #define DEFAULT_UBD { \
163         .file =                 NULL, \
164         .count =                0, \
165         .fd =                   -1, \
166         .size =                 -1, \
167         .boot_openflags =       OPEN_FLAGS, \
168         .openflags =            OPEN_FLAGS, \
169         .no_cow =               0, \
170         .shared =               0, \
171         .cow =                  DEFAULT_COW, \
172         .lock =                 __SPIN_LOCK_UNLOCKED(ubd_devs.lock), \
173         .request =              NULL, \
174         .start_sg =             0, \
175         .end_sg =               0, \
176         .rq_pos =               0, \
177 }
178 
179 /* Protected by ubd_lock */
180 static struct ubd ubd_devs[MAX_DEV] = { [0 ... MAX_DEV - 1] = DEFAULT_UBD };
181 
182 /* Only changed by fake_ide_setup which is a setup */
183 static int fake_ide = 0;
184 static struct proc_dir_entry *proc_ide_root = NULL;
185 static struct proc_dir_entry *proc_ide = NULL;
186 
187 static void make_proc_ide(void)
188 {
189         proc_ide_root = proc_mkdir("ide", NULL);
190         proc_ide = proc_mkdir("ide0", proc_ide_root);
191 }
192 
193 static int fake_ide_media_proc_show(struct seq_file *m, void *v)
194 {
195         seq_puts(m, "disk\n");
196         return 0;
197 }
198 
199 static int fake_ide_media_proc_open(struct inode *inode, struct file *file)
200 {
201         return single_open(file, fake_ide_media_proc_show, NULL);
202 }
203 
204 static const struct file_operations fake_ide_media_proc_fops = {
205         .owner          = THIS_MODULE,
206         .open           = fake_ide_media_proc_open,
207         .read           = seq_read,
208         .llseek         = seq_lseek,
209         .release        = single_release,
210 };
211 
212 static void make_ide_entries(const char *dev_name)
213 {
214         struct proc_dir_entry *dir, *ent;
215         char name[64];
216 
217         if(proc_ide_root == NULL) make_proc_ide();
218 
219         dir = proc_mkdir(dev_name, proc_ide);
220         if(!dir) return;
221 
222         ent = proc_create("media", S_IRUGO, dir, &fake_ide_media_proc_fops);
223         if(!ent) return;
224         snprintf(name, sizeof(name), "ide0/%s", dev_name);
225         proc_symlink(dev_name, proc_ide_root, name);
226 }
227 
228 static int fake_ide_setup(char *str)
229 {
230         fake_ide = 1;
231         return 1;
232 }
233 
234 __setup("fake_ide", fake_ide_setup);
235 
236 __uml_help(fake_ide_setup,
237 "fake_ide\n"
238 "    Create ide0 entries that map onto ubd devices.\n\n"
239 );
240 
241 static int parse_unit(char **ptr)
242 {
243         char *str = *ptr, *end;
244         int n = -1;
245 
246         if(isdigit(*str)) {
247                 n = simple_strtoul(str, &end, 0);
248                 if(end == str)
249                         return -1;
250                 *ptr = end;
251         }
252         else if (('a' <= *str) && (*str <= 'z')) {
253                 n = *str - 'a';
254                 str++;
255                 *ptr = str;
256         }
257         return n;
258 }
259 
260 /* If *index_out == -1 at exit, the passed option was a general one;
261  * otherwise, the str pointer is used (and owned) inside ubd_devs array, so it
262  * should not be freed on exit.
263  */
264 static int ubd_setup_common(char *str, int *index_out, char **error_out)
265 {
266         struct ubd *ubd_dev;
267         struct openflags flags = global_openflags;
268         char *backing_file;
269         int n, err = 0, i;
270 
271         if(index_out) *index_out = -1;
272         n = *str;
273         if(n == '='){
274                 char *end;
275                 int major;
276 
277                 str++;
278                 if(!strcmp(str, "sync")){
279                         global_openflags = of_sync(global_openflags);
280                         goto out1;
281                 }
282 
283                 err = -EINVAL;
284                 major = simple_strtoul(str, &end, 0);
285                 if((*end != '\0') || (end == str)){
286                         *error_out = "Didn't parse major number";
287                         goto out1;
288                 }
289 
290                 mutex_lock(&ubd_lock);
291                 if (fake_major != UBD_MAJOR) {
292                         *error_out = "Can't assign a fake major twice";
293                         goto out1;
294                 }
295 
296                 fake_major = major;
297 
298                 printk(KERN_INFO "Setting extra ubd major number to %d\n",
299                        major);
300                 err = 0;
301         out1:
302                 mutex_unlock(&ubd_lock);
303                 return err;
304         }
305 
306         n = parse_unit(&str);
307         if(n < 0){
308                 *error_out = "Couldn't parse device number";
309                 return -EINVAL;
310         }
311         if(n >= MAX_DEV){
312                 *error_out = "Device number out of range";
313                 return 1;
314         }
315 
316         err = -EBUSY;
317         mutex_lock(&ubd_lock);
318 
319         ubd_dev = &ubd_devs[n];
320         if(ubd_dev->file != NULL){
321                 *error_out = "Device is already configured";
322                 goto out;
323         }
324 
325         if (index_out)
326                 *index_out = n;
327 
328         err = -EINVAL;
329         for (i = 0; i < sizeof("rscd="); i++) {
330                 switch (*str) {
331                 case 'r':
332                         flags.w = 0;
333                         break;
334                 case 's':
335                         flags.s = 1;
336                         break;
337                 case 'd':
338                         ubd_dev->no_cow = 1;
339                         break;
340                 case 'c':
341                         ubd_dev->shared = 1;
342                         break;
343                 case '=':
344                         str++;
345                         goto break_loop;
346                 default:
347                         *error_out = "Expected '=' or flag letter "
348                                 "(r, s, c, or d)";
349                         goto out;
350                 }
351                 str++;
352         }
353 
354         if (*str == '=')
355                 *error_out = "Too many flags specified";
356         else
357                 *error_out = "Missing '='";
358         goto out;
359 
360 break_loop:
361         backing_file = strchr(str, ',');
362 
363         if (backing_file == NULL)
364                 backing_file = strchr(str, ':');
365 
366         if(backing_file != NULL){
367                 if(ubd_dev->no_cow){
368                         *error_out = "Can't specify both 'd' and a cow file";
369                         goto out;
370                 }
371                 else {
372                         *backing_file = '\0';
373                         backing_file++;
374                 }
375         }
376         err = 0;
377         ubd_dev->file = str;
378         ubd_dev->cow.file = backing_file;
379         ubd_dev->boot_openflags = flags;
380 out:
381         mutex_unlock(&ubd_lock);
382         return err;
383 }
384 
385 static int ubd_setup(char *str)
386 {
387         char *error;
388         int err;
389 
390         err = ubd_setup_common(str, NULL, &error);
391         if(err)
392                 printk(KERN_ERR "Failed to initialize device with \"%s\" : "
393                        "%s\n", str, error);
394         return 1;
395 }
396 
397 __setup("ubd", ubd_setup);
398 __uml_help(ubd_setup,
399 "ubd<n><flags>=<filename>[(:|,)<filename2>]\n"
400 "    This is used to associate a device with a file in the underlying\n"
401 "    filesystem. When specifying two filenames, the first one is the\n"
402 "    COW name and the second is the backing file name. As separator you can\n"
403 "    use either a ':' or a ',': the first one allows writing things like;\n"
404 "       ubd0=~/Uml/root_cow:~/Uml/root_backing_file\n"
405 "    while with a ',' the shell would not expand the 2nd '~'.\n"
406 "    When using only one filename, UML will detect whether to treat it like\n"
407 "    a COW file or a backing file. To override this detection, add the 'd'\n"
408 "    flag:\n"
409 "       ubd0d=BackingFile\n"
410 "    Usually, there is a filesystem in the file, but \n"
411 "    that's not required. Swap devices containing swap files can be\n"
412 "    specified like this. Also, a file which doesn't contain a\n"
413 "    filesystem can have its contents read in the virtual \n"
414 "    machine by running 'dd' on the device. <n> must be in the range\n"
415 "    0 to 7. Appending an 'r' to the number will cause that device\n"
416 "    to be mounted read-only. For example ubd1r=./ext_fs. Appending\n"
417 "    an 's' will cause data to be written to disk on the host immediately.\n"
418 "    'c' will cause the device to be treated as being shared between multiple\n"
419 "    UMLs and file locking will be turned off - this is appropriate for a\n"
420 "    cluster filesystem and inappropriate at almost all other times.\n\n"
421 );
422 
423 static int udb_setup(char *str)
424 {
425         printk("udb%s specified on command line is almost certainly a ubd -> "
426                "udb TYPO\n", str);
427         return 1;
428 }
429 
430 __setup("udb", udb_setup);
431 __uml_help(udb_setup,
432 "udb\n"
433 "    This option is here solely to catch ubd -> udb typos, which can be\n"
434 "    to impossible to catch visually unless you specifically look for\n"
435 "    them.  The only result of any option starting with 'udb' is an error\n"
436 "    in the boot output.\n\n"
437 );
438 
439 static void do_ubd_request(struct request_queue * q);
440 
441 /* Only changed by ubd_init, which is an initcall. */
442 static int thread_fd = -1;
443 static LIST_HEAD(restart);
444 
445 /* XXX - move this inside ubd_intr. */
446 /* Called without dev->lock held, and only in interrupt context. */
447 static void ubd_handler(void)
448 {
449         struct io_thread_req *req;
450         struct ubd *ubd;
451         struct list_head *list, *next_ele;
452         unsigned long flags;
453         int n;
454 
455         while(1){
456                 n = os_read_file(thread_fd, &req,
457                                  sizeof(struct io_thread_req *));
458                 if(n != sizeof(req)){
459                         if(n == -EAGAIN)
460                                 break;
461                         printk(KERN_ERR "spurious interrupt in ubd_handler, "
462                                "err = %d\n", -n);
463                         return;
464                 }
465 
466                 blk_end_request(req->req, 0, req->length);
467                 kfree(req);
468         }
469         reactivate_fd(thread_fd, UBD_IRQ);
470 
471         list_for_each_safe(list, next_ele, &restart){
472                 ubd = container_of(list, struct ubd, restart);
473                 list_del_init(&ubd->restart);
474                 spin_lock_irqsave(&ubd->lock, flags);
475                 do_ubd_request(ubd->queue);
476                 spin_unlock_irqrestore(&ubd->lock, flags);
477         }
478 }
479 
480 static irqreturn_t ubd_intr(int irq, void *dev)
481 {
482         ubd_handler();
483         return IRQ_HANDLED;
484 }
485 
486 /* Only changed by ubd_init, which is an initcall. */
487 static int io_pid = -1;
488 
489 static void kill_io_thread(void)
490 {
491         if(io_pid != -1)
492                 os_kill_process(io_pid, 1);
493 }
494 
495 __uml_exitcall(kill_io_thread);
496 
497 static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
498 {
499         char *file;
500         int fd;
501         int err;
502 
503         __u32 version;
504         __u32 align;
505         char *backing_file;
506         time_t mtime;
507         unsigned long long size;
508         int sector_size;
509         int bitmap_offset;
510 
511         if (ubd_dev->file && ubd_dev->cow.file) {
512                 file = ubd_dev->cow.file;
513 
514                 goto out;
515         }
516 
517         fd = os_open_file(ubd_dev->file, of_read(OPENFLAGS()), 0);
518         if (fd < 0)
519                 return fd;
520 
521         err = read_cow_header(file_reader, &fd, &version, &backing_file, \
522                 &mtime, &size, &sector_size, &align, &bitmap_offset);
523         os_close_file(fd);
524 
525         if(err == -EINVAL)
526                 file = ubd_dev->file;
527         else
528                 file = backing_file;
529 
530 out:
531         return os_file_size(file, size_out);
532 }
533 
534 static int read_cow_bitmap(int fd, void *buf, int offset, int len)
535 {
536         int err;
537 
538         err = os_pread_file(fd, buf, len, offset);
539         if (err < 0)
540                 return err;
541 
542         return 0;
543 }
544 
545 static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
546 {
547         unsigned long modtime;
548         unsigned long long actual;
549         int err;
550 
551         err = os_file_modtime(file, &modtime);
552         if (err < 0) {
553                 printk(KERN_ERR "Failed to get modification time of backing "
554                        "file \"%s\", err = %d\n", file, -err);
555                 return err;
556         }
557 
558         err = os_file_size(file, &actual);
559         if (err < 0) {
560                 printk(KERN_ERR "Failed to get size of backing file \"%s\", "
561                        "err = %d\n", file, -err);
562                 return err;
563         }
564 
565         if (actual != size) {
566                 /*__u64 can be a long on AMD64 and with %lu GCC complains; so
567                  * the typecast.*/
568                 printk(KERN_ERR "Size mismatch (%llu vs %llu) of COW header "
569                        "vs backing file\n", (unsigned long long) size, actual);
570                 return -EINVAL;
571         }
572         if (modtime != mtime) {
573                 printk(KERN_ERR "mtime mismatch (%ld vs %ld) of COW header vs "
574                        "backing file\n", mtime, modtime);
575                 return -EINVAL;
576         }
577         return 0;
578 }
579 
580 static int path_requires_switch(char *from_cmdline, char *from_cow, char *cow)
581 {
582         struct uml_stat buf1, buf2;
583         int err;
584 
585         if (from_cmdline == NULL)
586                 return 0;
587         if (!strcmp(from_cmdline, from_cow))
588                 return 0;
589 
590         err = os_stat_file(from_cmdline, &buf1);
591         if (err < 0) {
592                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cmdline,
593                        -err);
594                 return 0;
595         }
596         err = os_stat_file(from_cow, &buf2);
597         if (err < 0) {
598                 printk(KERN_ERR "Couldn't stat '%s', err = %d\n", from_cow,
599                        -err);
600                 return 1;
601         }
602         if ((buf1.ust_dev == buf2.ust_dev) && (buf1.ust_ino == buf2.ust_ino))
603                 return 0;
604 
605         printk(KERN_ERR "Backing file mismatch - \"%s\" requested, "
606                "\"%s\" specified in COW header of \"%s\"\n",
607                from_cmdline, from_cow, cow);
608         return 1;
609 }
610 
611 static int open_ubd_file(char *file, struct openflags *openflags, int shared,
612                   char **backing_file_out, int *bitmap_offset_out,
613                   unsigned long *bitmap_len_out, int *data_offset_out,
614                   int *create_cow_out)
615 {
616         time_t mtime;
617         unsigned long long size;
618         __u32 version, align;
619         char *backing_file;
620         int fd, err, sectorsize, asked_switch, mode = 0644;
621 
622         fd = os_open_file(file, *openflags, mode);
623         if (fd < 0) {
624                 if ((fd == -ENOENT) && (create_cow_out != NULL))
625                         *create_cow_out = 1;
626                 if (!openflags->w ||
627                     ((fd != -EROFS) && (fd != -EACCES)))
628                         return fd;
629                 openflags->w = 0;
630                 fd = os_open_file(file, *openflags, mode);
631                 if (fd < 0)
632                         return fd;
633         }
634 
635         if (shared)
636                 printk(KERN_INFO "Not locking \"%s\" on the host\n", file);
637         else {
638                 err = os_lock_file(fd, openflags->w);
639                 if (err < 0) {
640                         printk(KERN_ERR "Failed to lock '%s', err = %d\n",
641                                file, -err);
642                         goto out_close;
643                 }
644         }
645 
646         /* Successful return case! */
647         if (backing_file_out == NULL)
648                 return fd;
649 
650         err = read_cow_header(file_reader, &fd, &version, &backing_file, &mtime,
651                               &size, &sectorsize, &align, bitmap_offset_out);
652         if (err && (*backing_file_out != NULL)) {
653                 printk(KERN_ERR "Failed to read COW header from COW file "
654                        "\"%s\", errno = %d\n", file, -err);
655                 goto out_close;
656         }
657         if (err)
658                 return fd;
659 
660         asked_switch = path_requires_switch(*backing_file_out, backing_file,
661                                             file);
662 
663         /* Allow switching only if no mismatch. */
664         if (asked_switch && !backing_file_mismatch(*backing_file_out, size,
665                                                    mtime)) {
666                 printk(KERN_ERR "Switching backing file to '%s'\n",
667                        *backing_file_out);
668                 err = write_cow_header(file, fd, *backing_file_out,
669                                        sectorsize, align, &size);
670                 if (err) {
671                         printk(KERN_ERR "Switch failed, errno = %d\n", -err);
672                         goto out_close;
673                 }
674         } else {
675                 *backing_file_out = backing_file;
676                 err = backing_file_mismatch(*backing_file_out, size, mtime);
677                 if (err)
678                         goto out_close;
679         }
680 
681         cow_sizes(version, size, sectorsize, align, *bitmap_offset_out,
682                   bitmap_len_out, data_offset_out);
683 
684         return fd;
685  out_close:
686         os_close_file(fd);
687         return err;
688 }
689 
690 static int create_cow_file(char *cow_file, char *backing_file,
691                     struct openflags flags,
692                     int sectorsize, int alignment, int *bitmap_offset_out,
693                     unsigned long *bitmap_len_out, int *data_offset_out)
694 {
695         int err, fd;
696 
697         flags.c = 1;
698         fd = open_ubd_file(cow_file, &flags, 0, NULL, NULL, NULL, NULL, NULL);
699         if (fd < 0) {
700                 err = fd;
701                 printk(KERN_ERR "Open of COW file '%s' failed, errno = %d\n",
702                        cow_file, -err);
703                 goto out;
704         }
705 
706         err = init_cow_file(fd, cow_file, backing_file, sectorsize, alignment,
707                             bitmap_offset_out, bitmap_len_out,
708                             data_offset_out);
709         if (!err)
710                 return fd;
711         os_close_file(fd);
712  out:
713         return err;
714 }
715 
716 static void ubd_close_dev(struct ubd *ubd_dev)
717 {
718         os_close_file(ubd_dev->fd);
719         if(ubd_dev->cow.file == NULL)
720                 return;
721 
722         os_close_file(ubd_dev->cow.fd);
723         vfree(ubd_dev->cow.bitmap);
724         ubd_dev->cow.bitmap = NULL;
725 }
726 
727 static int ubd_open_dev(struct ubd *ubd_dev)
728 {
729         struct openflags flags;
730         char **back_ptr;
731         int err, create_cow, *create_ptr;
732         int fd;
733 
734         ubd_dev->openflags = ubd_dev->boot_openflags;
735         create_cow = 0;
736         create_ptr = (ubd_dev->cow.file != NULL) ? &create_cow : NULL;
737         back_ptr = ubd_dev->no_cow ? NULL : &ubd_dev->cow.file;
738 
739         fd = open_ubd_file(ubd_dev->file, &ubd_dev->openflags, ubd_dev->shared,
740                                 back_ptr, &ubd_dev->cow.bitmap_offset,
741                                 &ubd_dev->cow.bitmap_len, &ubd_dev->cow.data_offset,
742                                 create_ptr);
743 
744         if((fd == -ENOENT) && create_cow){
745                 fd = create_cow_file(ubd_dev->file, ubd_dev->cow.file,
746                                           ubd_dev->openflags, 1 << 9, PAGE_SIZE,
747                                           &ubd_dev->cow.bitmap_offset,
748                                           &ubd_dev->cow.bitmap_len,
749                                           &ubd_dev->cow.data_offset);
750                 if(fd >= 0){
751                         printk(KERN_INFO "Creating \"%s\" as COW file for "
752                                "\"%s\"\n", ubd_dev->file, ubd_dev->cow.file);
753                 }
754         }
755 
756         if(fd < 0){
757                 printk("Failed to open '%s', errno = %d\n", ubd_dev->file,
758                        -fd);
759                 return fd;
760         }
761         ubd_dev->fd = fd;
762 
763         if(ubd_dev->cow.file != NULL){
764                 blk_queue_max_hw_sectors(ubd_dev->queue, 8 * sizeof(long));
765 
766                 err = -ENOMEM;
767                 ubd_dev->cow.bitmap = vmalloc(ubd_dev->cow.bitmap_len);
768                 if(ubd_dev->cow.bitmap == NULL){
769                         printk(KERN_ERR "Failed to vmalloc COW bitmap\n");
770                         goto error;
771                 }
772                 flush_tlb_kernel_vm();
773 
774                 err = read_cow_bitmap(ubd_dev->fd, ubd_dev->cow.bitmap,
775                                       ubd_dev->cow.bitmap_offset,
776                                       ubd_dev->cow.bitmap_len);
777                 if(err < 0)
778                         goto error;
779 
780                 flags = ubd_dev->openflags;
781                 flags.w = 0;
782                 err = open_ubd_file(ubd_dev->cow.file, &flags, ubd_dev->shared, NULL,
783                                     NULL, NULL, NULL, NULL);
784                 if(err < 0) goto error;
785                 ubd_dev->cow.fd = err;
786         }
787         return 0;
788  error:
789         os_close_file(ubd_dev->fd);
790         return err;
791 }
792 
793 static void ubd_device_release(struct device *dev)
794 {
795         struct ubd *ubd_dev = dev_get_drvdata(dev);
796 
797         blk_cleanup_queue(ubd_dev->queue);
798         *ubd_dev = ((struct ubd) DEFAULT_UBD);
799 }
800 
801 static int ubd_disk_register(int major, u64 size, int unit,
802                              struct gendisk **disk_out)
803 {
804         struct gendisk *disk;
805 
806         disk = alloc_disk(1 << UBD_SHIFT);
807         if(disk == NULL)
808                 return -ENOMEM;
809 
810         disk->major = major;
811         disk->first_minor = unit << UBD_SHIFT;
812         disk->fops = &ubd_blops;
813         set_capacity(disk, size / 512);
814         if (major == UBD_MAJOR)
815                 sprintf(disk->disk_name, "ubd%c", 'a' + unit);
816         else
817                 sprintf(disk->disk_name, "ubd_fake%d", unit);
818 
819         /* sysfs register (not for ide fake devices) */
820         if (major == UBD_MAJOR) {
821                 ubd_devs[unit].pdev.id   = unit;
822                 ubd_devs[unit].pdev.name = DRIVER_NAME;
823                 ubd_devs[unit].pdev.dev.release = ubd_device_release;
824                 dev_set_drvdata(&ubd_devs[unit].pdev.dev, &ubd_devs[unit]);
825                 platform_device_register(&ubd_devs[unit].pdev);
826                 disk->driverfs_dev = &ubd_devs[unit].pdev.dev;
827         }
828 
829         disk->private_data = &ubd_devs[unit];
830         disk->queue = ubd_devs[unit].queue;
831         add_disk(disk);
832 
833         *disk_out = disk;
834         return 0;
835 }
836 
837 #define ROUND_BLOCK(n) ((n + ((1 << 9) - 1)) & (-1 << 9))
838 
839 static int ubd_add(int n, char **error_out)
840 {
841         struct ubd *ubd_dev = &ubd_devs[n];
842         int err = 0;
843 
844         if(ubd_dev->file == NULL)
845                 goto out;
846 
847         err = ubd_file_size(ubd_dev, &ubd_dev->size);
848         if(err < 0){
849                 *error_out = "Couldn't determine size of device's file";
850                 goto out;
851         }
852 
853         ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
854 
855         INIT_LIST_HEAD(&ubd_dev->restart);
856         sg_init_table(ubd_dev->sg, MAX_SG);
857 
858         err = -ENOMEM;
859         ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
860         if (ubd_dev->queue == NULL) {
861                 *error_out = "Failed to initialize device queue";
862                 goto out;
863         }
864         ubd_dev->queue->queuedata = ubd_dev;
865         blk_queue_write_cache(ubd_dev->queue, true, false);
866 
867         blk_queue_max_segments(ubd_dev->queue, MAX_SG);
868         err = ubd_disk_register(UBD_MAJOR, ubd_dev->size, n, &ubd_gendisk[n]);
869         if(err){
870                 *error_out = "Failed to register device";
871                 goto out_cleanup;
872         }
873 
874         if (fake_major != UBD_MAJOR)
875                 ubd_disk_register(fake_major, ubd_dev->size, n,
876                                   &fake_gendisk[n]);
877 
878         /*
879          * Perhaps this should also be under the "if (fake_major)" above
880          * using the fake_disk->disk_name
881          */
882         if (fake_ide)
883                 make_ide_entries(ubd_gendisk[n]->disk_name);
884 
885         err = 0;
886 out:
887         return err;
888 
889 out_cleanup:
890         blk_cleanup_queue(ubd_dev->queue);
891         goto out;
892 }
893 
894 static int ubd_config(char *str, char **error_out)
895 {
896         int n, ret;
897 
898         /* This string is possibly broken up and stored, so it's only
899          * freed if ubd_setup_common fails, or if only general options
900          * were set.
901          */
902         str = kstrdup(str, GFP_KERNEL);
903         if (str == NULL) {
904                 *error_out = "Failed to allocate memory";
905                 return -ENOMEM;
906         }
907 
908         ret = ubd_setup_common(str, &n, error_out);
909         if (ret)
910                 goto err_free;
911 
912         if (n == -1) {
913                 ret = 0;
914                 goto err_free;
915         }
916 
917         mutex_lock(&ubd_lock);
918         ret = ubd_add(n, error_out);
919         if (ret)
920                 ubd_devs[n].file = NULL;
921         mutex_unlock(&ubd_lock);
922 
923 out:
924         return ret;
925 
926 err_free:
927         kfree(str);
928         goto out;
929 }
930 
931 static int ubd_get_config(char *name, char *str, int size, char **error_out)
932 {
933         struct ubd *ubd_dev;
934         int n, len = 0;
935 
936         n = parse_unit(&name);
937         if((n >= MAX_DEV) || (n < 0)){
938                 *error_out = "ubd_get_config : device number out of range";
939                 return -1;
940         }
941 
942         ubd_dev = &ubd_devs[n];
943         mutex_lock(&ubd_lock);
944 
945         if(ubd_dev->file == NULL){
946                 CONFIG_CHUNK(str, size, len, "", 1);
947                 goto out;
948         }
949 
950         CONFIG_CHUNK(str, size, len, ubd_dev->file, 0);
951 
952         if(ubd_dev->cow.file != NULL){
953                 CONFIG_CHUNK(str, size, len, ",", 0);
954                 CONFIG_CHUNK(str, size, len, ubd_dev->cow.file, 1);
955         }
956         else CONFIG_CHUNK(str, size, len, "", 1);
957 
958  out:
959         mutex_unlock(&ubd_lock);
960         return len;
961 }
962 
963 static int ubd_id(char **str, int *start_out, int *end_out)
964 {
965         int n;
966 
967         n = parse_unit(str);
968         *start_out = 0;
969         *end_out = MAX_DEV - 1;
970         return n;
971 }
972 
973 static int ubd_remove(int n, char **error_out)
974 {
975         struct gendisk *disk = ubd_gendisk[n];
976         struct ubd *ubd_dev;
977         int err = -ENODEV;
978 
979         mutex_lock(&ubd_lock);
980 
981         ubd_dev = &ubd_devs[n];
982 
983         if(ubd_dev->file == NULL)
984                 goto out;
985 
986         /* you cannot remove a open disk */
987         err = -EBUSY;
988         if(ubd_dev->count > 0)
989                 goto out;
990 
991         ubd_gendisk[n] = NULL;
992         if(disk != NULL){
993                 del_gendisk(disk);
994                 put_disk(disk);
995         }
996 
997         if(fake_gendisk[n] != NULL){
998                 del_gendisk(fake_gendisk[n]);
999                 put_disk(fake_gendisk[n]);
1000                 fake_gendisk[n] = NULL;
1001         }
1002 
1003         err = 0;
1004         platform_device_unregister(&ubd_dev->pdev);
1005 out:
1006         mutex_unlock(&ubd_lock);
1007         return err;
1008 }
1009 
1010 /* All these are called by mconsole in process context and without
1011  * ubd-specific locks.  The structure itself is const except for .list.
1012  */
1013 static struct mc_device ubd_mc = {
1014         .list           = LIST_HEAD_INIT(ubd_mc.list),
1015         .name           = "ubd",
1016         .config         = ubd_config,
1017         .get_config     = ubd_get_config,
1018         .id             = ubd_id,
1019         .remove         = ubd_remove,
1020 };
1021 
1022 static int __init ubd_mc_init(void)
1023 {
1024         mconsole_register_dev(&ubd_mc);
1025         return 0;
1026 }
1027 
1028 __initcall(ubd_mc_init);
1029 
1030 static int __init ubd0_init(void)
1031 {
1032         struct ubd *ubd_dev = &ubd_devs[0];
1033 
1034         mutex_lock(&ubd_lock);
1035         if(ubd_dev->file == NULL)
1036                 ubd_dev->file = "root_fs";
1037         mutex_unlock(&ubd_lock);
1038 
1039         return 0;
1040 }
1041 
1042 __initcall(ubd0_init);
1043 
1044 /* Used in ubd_init, which is an initcall */
1045 static struct platform_driver ubd_driver = {
1046         .driver = {
1047                 .name  = DRIVER_NAME,
1048         },
1049 };
1050 
1051 static int __init ubd_init(void)
1052 {
1053         char *error;
1054         int i, err;
1055 
1056         if (register_blkdev(UBD_MAJOR, "ubd"))
1057                 return -1;
1058 
1059         if (fake_major != UBD_MAJOR) {
1060                 char name[sizeof("ubd_nnn\0")];
1061 
1062                 snprintf(name, sizeof(name), "ubd_%d", fake_major);
1063                 if (register_blkdev(fake_major, "ubd"))
1064                         return -1;
1065         }
1066         platform_driver_register(&ubd_driver);
1067         mutex_lock(&ubd_lock);
1068         for (i = 0; i < MAX_DEV; i++){
1069                 err = ubd_add(i, &error);
1070                 if(err)
1071                         printk(KERN_ERR "Failed to initialize ubd device %d :"
1072                                "%s\n", i, error);
1073         }
1074         mutex_unlock(&ubd_lock);
1075         return 0;
1076 }
1077 
1078 late_initcall(ubd_init);
1079 
1080 static int __init ubd_driver_init(void){
1081         unsigned long stack;
1082         int err;
1083 
1084         /* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
1085         if(global_openflags.s){
1086                 printk(KERN_INFO "ubd: Synchronous mode\n");
1087                 /* Letting ubd=sync be like using ubd#s= instead of ubd#= is
1088                  * enough. So use anyway the io thread. */
1089         }
1090         stack = alloc_stack(0, 0);
1091         io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *),
1092                                  &thread_fd);
1093         if(io_pid < 0){
1094                 printk(KERN_ERR
1095                        "ubd : Failed to start I/O thread (errno = %d) - "
1096                        "falling back to synchronous I/O\n", -io_pid);
1097                 io_pid = -1;
1098                 return 0;
1099         }
1100         err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
1101                              0, "ubd", ubd_devs);
1102         if(err != 0)
1103                 printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
1104         return 0;
1105 }
1106 
1107 device_initcall(ubd_driver_init);
1108 
1109 static int ubd_open(struct block_device *bdev, fmode_t mode)
1110 {
1111         struct gendisk *disk = bdev->bd_disk;
1112         struct ubd *ubd_dev = disk->private_data;
1113         int err = 0;
1114 
1115         mutex_lock(&ubd_mutex);
1116         if(ubd_dev->count == 0){
1117                 err = ubd_open_dev(ubd_dev);
1118                 if(err){
1119                         printk(KERN_ERR "%s: Can't open \"%s\": errno = %d\n",
1120                                disk->disk_name, ubd_dev->file, -err);
1121                         goto out;
1122                 }
1123         }
1124         ubd_dev->count++;
1125         set_disk_ro(disk, !ubd_dev->openflags.w);
1126 
1127         /* This should no more be needed. And it didn't work anyway to exclude
1128          * read-write remounting of filesystems.*/
1129         /*if((mode & FMODE_WRITE) && !ubd_dev->openflags.w){
1130                 if(--ubd_dev->count == 0) ubd_close_dev(ubd_dev);
1131                 err = -EROFS;
1132         }*/
1133 out:
1134         mutex_unlock(&ubd_mutex);
1135         return err;
1136 }
1137 
1138 static void ubd_release(struct gendisk *disk, fmode_t mode)
1139 {
1140         struct ubd *ubd_dev = disk->private_data;
1141 
1142         mutex_lock(&ubd_mutex);
1143         if(--ubd_dev->count == 0)
1144                 ubd_close_dev(ubd_dev);
1145         mutex_unlock(&ubd_mutex);
1146 }
1147 
1148 static void cowify_bitmap(__u64 io_offset, int length, unsigned long *cow_mask,
1149                           __u64 *cow_offset, unsigned long *bitmap,
1150                           __u64 bitmap_offset, unsigned long *bitmap_words,
1151                           __u64 bitmap_len)
1152 {
1153         __u64 sector = io_offset >> 9;
1154         int i, update_bitmap = 0;
1155 
1156         for(i = 0; i < length >> 9; i++){
1157                 if(cow_mask != NULL)
1158                         ubd_set_bit(i, (unsigned char *) cow_mask);
1159                 if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1160                         continue;
1161 
1162                 update_bitmap = 1;
1163                 ubd_set_bit(sector + i, (unsigned char *) bitmap);
1164         }
1165 
1166         if(!update_bitmap)
1167                 return;
1168 
1169         *cow_offset = sector / (sizeof(unsigned long) * 8);
1170 
1171         /* This takes care of the case where we're exactly at the end of the
1172          * device, and *cow_offset + 1 is off the end.  So, just back it up
1173          * by one word.  Thanks to Lynn Kerby for the fix and James McMechan
1174          * for the original diagnosis.
1175          */
1176         if (*cow_offset == (DIV_ROUND_UP(bitmap_len,
1177                                          sizeof(unsigned long)) - 1))
1178                 (*cow_offset)--;
1179 
1180         bitmap_words[0] = bitmap[*cow_offset];
1181         bitmap_words[1] = bitmap[*cow_offset + 1];
1182 
1183         *cow_offset *= sizeof(unsigned long);
1184         *cow_offset += bitmap_offset;
1185 }
1186 
1187 static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
1188                        __u64 bitmap_offset, __u64 bitmap_len)
1189 {
1190         __u64 sector = req->offset >> 9;
1191         int i;
1192 
1193         if(req->length > (sizeof(req->sector_mask) * 8) << 9)
1194                 panic("Operation too long");
1195 
1196         if(req->op == UBD_READ) {
1197                 for(i = 0; i < req->length >> 9; i++){
1198                         if(ubd_test_bit(sector + i, (unsigned char *) bitmap))
1199                                 ubd_set_bit(i, (unsigned char *)
1200                                             &req->sector_mask);
1201                 }
1202         }
1203         else cowify_bitmap(req->offset, req->length, &req->sector_mask,
1204                            &req->cow_offset, bitmap, bitmap_offset,
1205                            req->bitmap_words, bitmap_len);
1206 }
1207 
1208 /* Called with dev->lock held */
1209 static void prepare_request(struct request *req, struct io_thread_req *io_req,
1210                             unsigned long long offset, int page_offset,
1211                             int len, struct page *page)
1212 {
1213         struct gendisk *disk = req->rq_disk;
1214         struct ubd *ubd_dev = disk->private_data;
1215 
1216         io_req->req = req;
1217         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
1218                 ubd_dev->fd;
1219         io_req->fds[1] = ubd_dev->fd;
1220         io_req->cow_offset = -1;
1221         io_req->offset = offset;
1222         io_req->length = len;
1223         io_req->error = 0;
1224         io_req->sector_mask = 0;
1225 
1226         io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
1227         io_req->offsets[0] = 0;
1228         io_req->offsets[1] = ubd_dev->cow.data_offset;
1229         io_req->buffer = page_address(page) + page_offset;
1230         io_req->sectorsize = 1 << 9;
1231 
1232         if(ubd_dev->cow.file != NULL)
1233                 cowify_req(io_req, ubd_dev->cow.bitmap,
1234                            ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);
1235 
1236 }
1237 
1238 /* Called with dev->lock held */
1239 static void prepare_flush_request(struct request *req,
1240                                   struct io_thread_req *io_req)
1241 {
1242         struct gendisk *disk = req->rq_disk;
1243         struct ubd *ubd_dev = disk->private_data;
1244 
1245         io_req->req = req;
1246         io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
1247                 ubd_dev->fd;
1248         io_req->op = UBD_FLUSH;
1249 }
1250 
1251 static bool submit_request(struct io_thread_req *io_req, struct ubd *dev)
1252 {
1253         int n = os_write_file(thread_fd, &io_req,
1254                              sizeof(io_req));
1255         if (n != sizeof(io_req)) {
1256                 if (n != -EAGAIN)
1257                         printk("write to io thread failed, "
1258                                "errno = %d\n", -n);
1259                 else if (list_empty(&dev->restart))
1260                         list_add(&dev->restart, &restart);
1261 
1262                 kfree(io_req);
1263                 return false;
1264         }
1265         return true;
1266 }
1267 
1268 /* Called with dev->lock held */
1269 static void do_ubd_request(struct request_queue *q)
1270 {
1271         struct io_thread_req *io_req;
1272         struct request *req;
1273 
1274         while(1){
1275                 struct ubd *dev = q->queuedata;
1276                 if(dev->request == NULL){
1277                         struct request *req = blk_fetch_request(q);
1278                         if(req == NULL)
1279                                 return;
1280 
1281                         dev->request = req;
1282                         dev->rq_pos = blk_rq_pos(req);
1283                         dev->start_sg = 0;
1284                         dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
1285                 }
1286 
1287                 req = dev->request;
1288 
1289                 if (req->cmd_flags & REQ_FLUSH) {
1290                         io_req = kmalloc(sizeof(struct io_thread_req),
1291                                          GFP_ATOMIC);
1292                         if (io_req == NULL) {
1293                                 if (list_empty(&dev->restart))
1294                                         list_add(&dev->restart, &restart);
1295                                 return;
1296                         }
1297                         prepare_flush_request(req, io_req);
1298                         if (submit_request(io_req, dev) == false)
1299                                 return;
1300                 }
1301 
1302                 while(dev->start_sg < dev->end_sg){
1303                         struct scatterlist *sg = &dev->sg[dev->start_sg];
1304 
1305                         io_req = kmalloc(sizeof(struct io_thread_req),
1306                                          GFP_ATOMIC);
1307                         if(io_req == NULL){
1308                                 if(list_empty(&dev->restart))
1309                                         list_add(&dev->restart, &restart);
1310                                 return;
1311                         }
1312                         prepare_request(req, io_req,
1313                                         (unsigned long long)dev->rq_pos << 9,
1314                                         sg->offset, sg->length, sg_page(sg));
1315 
1316                         if (submit_request(io_req, dev) == false)
1317                                 return;
1318 
1319                         dev->rq_pos += sg->length >> 9;
1320                         dev->start_sg++;
1321                 }
1322                 dev->end_sg = 0;
1323                 dev->request = NULL;
1324         }
1325 }
1326 
1327 static int ubd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
1328 {
1329         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1330 
1331         geo->heads = 128;
1332         geo->sectors = 32;
1333         geo->cylinders = ubd_dev->size / (128 * 32 * 512);
1334         return 0;
1335 }
1336 
1337 static int ubd_ioctl(struct block_device *bdev, fmode_t mode,
1338                      unsigned int cmd, unsigned long arg)
1339 {
1340         struct ubd *ubd_dev = bdev->bd_disk->private_data;
1341         u16 ubd_id[ATA_ID_WORDS];
1342 
1343         switch (cmd) {
1344                 struct cdrom_volctrl volume;
1345         case HDIO_GET_IDENTITY:
1346                 memset(&ubd_id, 0, ATA_ID_WORDS * 2);
1347                 ubd_id[ATA_ID_CYLS]     = ubd_dev->size / (128 * 32 * 512);
1348                 ubd_id[ATA_ID_HEADS]    = 128;
1349                 ubd_id[ATA_ID_SECTORS]  = 32;
1350                 if(copy_to_user((char __user *) arg, (char *) &ubd_id,
1351                                  sizeof(ubd_id)))
1352                         return -EFAULT;
1353                 return 0;
1354 
1355         case CDROMVOLREAD:
1356                 if(copy_from_user(&volume, (char __user *) arg, sizeof(volume)))
1357                         return -EFAULT;
1358                 volume.channel0 = 255;
1359                 volume.channel1 = 255;
1360                 volume.channel2 = 255;
1361                 volume.channel3 = 255;
1362                 if(copy_to_user((char __user *) arg, &volume, sizeof(volume)))
1363                         return -EFAULT;
1364                 return 0;
1365         }
1366         return -EINVAL;
1367 }
1368 
1369 static int update_bitmap(struct io_thread_req *req)
1370 {
1371         int n;
1372 
1373         if(req->cow_offset == -1)
1374                 return 0;
1375 
1376         n = os_pwrite_file(req->fds[1], &req->bitmap_words,
1377                           sizeof(req->bitmap_words), req->cow_offset);
1378         if(n != sizeof(req->bitmap_words)){
1379                 printk("do_io - bitmap update failed, err = %d fd = %d\n", -n,
1380                        req->fds[1]);
1381                 return 1;
1382         }
1383 
1384         return 0;
1385 }
1386 
1387 static void do_io(struct io_thread_req *req)
1388 {
1389         char *buf;
1390         unsigned long len;
1391         int n, nsectors, start, end, bit;
1392         __u64 off;
1393 
1394         if (req->op == UBD_FLUSH) {
1395                 /* fds[0] is always either the rw image or our cow file */
1396                 n = os_sync_file(req->fds[0]);
1397                 if (n != 0) {
1398                         printk("do_io - sync failed err = %d "
1399                                "fd = %d\n", -n, req->fds[0]);
1400                         req->error = 1;
1401                 }
1402                 return;
1403         }
1404 
1405         nsectors = req->length / req->sectorsize;
1406         start = 0;
1407         do {
1408                 bit = ubd_test_bit(start, (unsigned char *) &req->sector_mask);
1409                 end = start;
1410                 while((end < nsectors) &&
1411                       (ubd_test_bit(end, (unsigned char *)
1412                                     &req->sector_mask) == bit))
1413                         end++;
1414 
1415                 off = req->offset + req->offsets[bit] +
1416                         start * req->sectorsize;
1417                 len = (end - start) * req->sectorsize;
1418                 buf = &req->buffer[start * req->sectorsize];
1419 
1420                 if(req->op == UBD_READ){
1421                         n = 0;
1422                         do {
1423                                 buf = &buf[n];
1424                                 len -= n;
1425                                 n = os_pread_file(req->fds[bit], buf, len, off);
1426                                 if (n < 0) {
1427                                         printk("do_io - read failed, err = %d "
1428                                                "fd = %d\n", -n, req->fds[bit]);
1429                                         req->error = 1;
1430                                         return;
1431                                 }
1432                         } while((n < len) && (n != 0));
1433                         if (n < len) memset(&buf[n], 0, len - n);
1434                 } else {
1435                         n = os_pwrite_file(req->fds[bit], buf, len, off);
1436                         if(n != len){
1437                                 printk("do_io - write failed err = %d "
1438                                        "fd = %d\n", -n, req->fds[bit]);
1439                                 req->error = 1;
1440                                 return;
1441                         }
1442                 }
1443 
1444                 start = end;
1445         } while(start < nsectors);
1446 
1447         req->error = update_bitmap(req);
1448 }
1449 
1450 /* Changed in start_io_thread, which is serialized by being called only
1451  * from ubd_init, which is an initcall.
1452  */
1453 int kernel_fd = -1;
1454 
1455 /* Only changed by the io thread. XXX: currently unused. */
1456 static int io_count = 0;
1457 
1458 int io_thread(void *arg)
1459 {
1460         struct io_thread_req *req;
1461         int n;
1462 
1463         os_fix_helper_signals();
1464 
1465         while(1){
1466                 n = os_read_file(kernel_fd, &req,
1467                                  sizeof(struct io_thread_req *));
1468                 if(n != sizeof(struct io_thread_req *)){
1469                         if(n < 0)
1470                                 printk("io_thread - read failed, fd = %d, "
1471                                        "err = %d\n", kernel_fd, -n);
1472                         else {
1473                                 printk("io_thread - short read, fd = %d, "
1474                                        "length = %d\n", kernel_fd, n);
1475                         }
1476                         continue;
1477                 }
1478                 io_count++;
1479                 do_io(req);
1480                 n = os_write_file(kernel_fd, &req,
1481                                   sizeof(struct io_thread_req *));
1482                 if(n != sizeof(struct io_thread_req *))
1483                         printk("io_thread - write failed, fd = %d, err = %d\n",
1484                                kernel_fd, -n);
1485         }
1486 
1487         return 0;
1488 }
1489 

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