sysfs.c

   1 /*
   2  * sysfs - extract md related information from sysfs.  Part of:
   3  * mdadm - manage Linux "md" devices aka RAID arrays.
   4  *
   5  * Copyright (C) 2006 Neil Brown <neilb@suse.de>
   6  *
   7  *
   8  *    This program is free software; you can redistribute it and/or modify
   9  *    it under the terms of the GNU General Public License as published by
  10  *    the Free Software Foundation; either version 2 of the License, or
  11  *    (at your option) any later version.
  12  *
  13  *    This program is distributed in the hope that it will be useful,
  14  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  *    GNU General Public License for more details.
  17  *
  18  *    You should have received a copy of the GNU General Public License
  19  *    along with this program; if not, write to the Free Software
  20  *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  *
  22  *    Author: Neil Brown
  23  *    Email: <neilb@suse.de>
  24  */
  25
  26 #include        "mdadm.h"
  27 #include        <dirent.h>
  28 #include        <ctype.h>
  29
  30 int load_sys(char *path, char *buf)
  31 {
  32         int fd = open(path, O_RDONLY);
  33         int n;
  34         if (fd < 0)
  35                 return -1;
  36         n = read(fd, buf, 1024);
  37         close(fd);
  38         if (n <0 || n >= 1024)
  39                 return -1;
  40         buf[n] = 0;
  41         if (n && buf[n-1] == '\n')
  42                 buf[n-1] = 0;
  43         return 0;
  44 }
  45
  46 void sysfs_free(struct mdinfo *sra)
  47 {
  48         while (sra) {
  49                 struct mdinfo *sra2 = sra->next;
  50                 while (sra->devs) {
  51                         struct mdinfo *d = sra->devs;
  52                         sra->devs = d->next;
  53                         free(d);
  54                 }
  55                 free(sra);
  56                 sra = sra2;
  57         }
  58 }
  59
  60 int sysfs_open(int devnum, char *devname, char *attr)
  61 {
  62         char fname[50];
  63         int fd;
  64         char *mdname = devnum2devname(devnum);
  65
  66         if (!mdname)
  67                 return -1;
  68
  69         sprintf(fname, "/sys/block/%s/md/", mdname);
  70         if (devname) {
  71                 strcat(fname, devname);
  72                 strcat(fname, "/");
  73         }
  74         strcat(fname, attr);
  75         fd = open(fname, O_RDWR);
  76         if (fd < 0 && errno == EACCES)
  77                 fd = open(fname, O_RDONLY);
  78         free(mdname);
  79         return fd;
  80 }
  81
  82 void sysfs_init(struct mdinfo *mdi, int fd, int devnum)
  83 {
  84         mdi->sys_name[0] = 0;
  85         if (fd >= 0) {
  86                 mdu_version_t vers;
  87                 if (ioctl(fd, RAID_VERSION, &vers) != 0)
  88                         return;
  89                 devnum = fd2devnum(fd);
  90         }
  91         if (devnum == NoMdDev)
  92                 return;
  93         if (devnum >= 0)
  94                 sprintf(mdi->sys_name, "md%d", devnum);
  95         else
  96                 sprintf(mdi->sys_name, "md_d%d",
  97                         -1-devnum);
  98 }
  99
 100
 101 struct mdinfo *sysfs_read(int fd, int devnum, unsigned long options)
 102 {
 103         /* Longest possible name in sysfs, mounted at /sys, is
 104          *  /sys/block/md_dXXX/md/dev-XXXXX/block/dev
 105          *  /sys/block/md_dXXX/md/metadata_version
 106          * which is about 41 characters.  50 should do for now
 107          */
 108         char fname[50];
 109         char buf[1024];
 110         char *base;
 111         char *dbase;
 112         struct mdinfo *sra;
 113         struct mdinfo *dev;
 114         DIR *dir = NULL;
 115         struct dirent *de;
 116
 117         sra = malloc(sizeof(*sra));
 118         if (sra == NULL)
 119                 return sra;
 120         memset(sra, 0, sizeof(*sra));
 121         sysfs_init(sra, fd, devnum);
 122         if (sra->sys_name[0] == 0) {
 123                 free(sra);
 124                 return NULL;
 125         }
 126
 127         sprintf(fname, "/sys/block/%s/md/", sra->sys_name);
 128         base = fname + strlen(fname);
 129
 130         sra->devs = NULL;
 131         if (options & GET_VERSION) {
 132                 strcpy(base, "metadata_version");
 133                 if (load_sys(fname, buf))
 134                         goto abort;
 135                 if (strncmp(buf, "none", 4) == 0) {
 136                         sra->array.major_version =
 137                                 sra->array.minor_version = -1;
 138                         strcpy(sra->text_version, "");
 139                 } else if (strncmp(buf, "external:", 9) == 0) {
 140                         sra->array.major_version = -1;
 141                         sra->array.minor_version = -2;
 142                         strcpy(sra->text_version, buf+9);
 143                 } else {
 144                         sscanf(buf, "%d.%d",
 145                                &sra->array.major_version,
 146                                &sra->array.minor_version);
 147                         strcpy(sra->text_version, buf);
 148                 }
 149         }
 150         if (options & GET_LEVEL) {
 151                 strcpy(base, "level");
 152                 if (load_sys(fname, buf))
 153                         goto abort;
 154                 sra->array.level = map_name(pers, buf);
 155         }
 156         if (options & GET_LAYOUT) {
 157                 strcpy(base, "layout");
 158                 if (load_sys(fname, buf))
 159                         goto abort;
 160                 sra->array.layout = strtoul(buf, NULL, 0);
 161         }
 162         if (options & GET_DISKS) {
 163                 strcpy(base, "raid_disks");
 164                 if (load_sys(fname, buf))
 165                         goto abort;
 166                 sra->array.raid_disks = strtoul(buf, NULL, 0);
 167         }
 168         if (options & GET_DEGRADED) {
 169                 strcpy(base, "degraded");
 170                 if (load_sys(fname, buf))
 171                         goto abort;
 172                 sra->array.failed_disks = strtoul(buf, NULL, 0);
 173         }
 174         if (options & GET_COMPONENT) {
 175                 strcpy(base, "component_size");
 176                 if (load_sys(fname, buf))
 177                         goto abort;
 178                 sra->component_size = strtoull(buf, NULL, 0);
 179                 /* sysfs reports "K", but we want sectors */
 180                 sra->component_size *= 2;
 181         }
 182         if (options & GET_CHUNK) {
 183                 strcpy(base, "chunk_size");
 184                 if (load_sys(fname, buf))
 185                         goto abort;
 186                 sra->array.chunk_size = strtoul(buf, NULL, 0);
 187         }
 188         if (options & GET_CACHE) {
 189                 strcpy(base, "stripe_cache_size");
 190                 if (load_sys(fname, buf))
 191                         goto abort;
 192                 sra->cache_size = strtoul(buf, NULL, 0);
 193         }
 194         if (options & GET_MISMATCH) {
 195                 strcpy(base, "mismatch_cnt");
 196                 if (load_sys(fname, buf))
 197                         goto abort;
 198                 sra->mismatch_cnt = strtoul(buf, NULL, 0);
 199         }
 200         if (options & GET_SAFEMODE) {
 201                 int scale = 1;
 202                 int dot = 0;
 203                 int i;
 204                 unsigned long msec;
 205                 size_t len;
 206
 207                 strcpy(base, "safe_mode_delay");
 208                 if (load_sys(fname, buf))
 209                         goto abort;
 210
 211                 /* remove a period, and count digits after it */
 212                 len = strlen(buf);
 213                 for (i = 0; i < len; i++) {
 214                         if (dot) {
 215                                 if (isdigit(buf[i])) {
 216                                         buf[i-1] = buf[i];
 217                                         scale *= 10;
 218                                 }
 219                                 buf[i] = 0;
 220                         } else if (buf[i] == '.') {
 221                                 dot=1;
 222                                 buf[i] = 0;
 223                         }
 224                 }
 225                 msec = strtoul(buf, NULL, 10);
 226                 msec = (msec * 1000) / scale;
 227                 sra->safe_mode_delay = msec;
 228         }
 229
 230         if (! (options & GET_DEVS))
 231                 return sra;
 232
 233         /* Get all the devices as well */
 234         *base = 0;
 235         dir = opendir(fname);
 236         if (!dir)
 237                 goto abort;
 238         sra->array.spare_disks = 0;
 239
 240         while ((de = readdir(dir)) != NULL) {
 241                 char *ep;
 242                 if (de->d_ino == 0 ||
 243                     strncmp(de->d_name, "dev-", 4) != 0)
 244                         continue;
 245                 strcpy(base, de->d_name);
 246                 dbase = base + strlen(base);
 247                 *dbase++ = '/';
 248
 249                 dev = malloc(sizeof(*dev));
 250                 if (!dev)
 251                         goto abort;
 252
 253                 /* Always get slot, major, minor */
 254                 strcpy(dbase, "slot");
 255                 if (load_sys(fname, buf)) {
 256                         /* hmm... unable to read 'slot' maybe the device
 257                          * is going away?
 258                          */
 259                         strcpy(dbase, "block");
 260                         if (readlink(fname, buf, sizeof(buf)) < 0 &&
 261                             errno != ENAMETOOLONG) {
 262                                 /* ...yup device is gone */
 263                                 free(dev);
 264                                 continue;
 265                         } else {
 266                                 /* slot is unreadable but 'block' link
 267                                  * still intact... something bad is happening
 268                                  * so abort
 269                                  */
 270                                 free(dev);
 271                                 goto abort;
 272                         }
 273
 274                 }
 275                 strcpy(dev->sys_name, de->d_name);
 276                 dev->disk.raid_disk = strtoul(buf, &ep, 10);
 277                 if (*ep) dev->disk.raid_disk = -1;
 278
 279                 strcpy(dbase, "block/dev");
 280                 if (load_sys(fname, buf)) {
 281                         free(dev);
 282                         if (options & SKIP_GONE_DEVS)
 283                                 continue;
 284                         else
 285                                 goto abort;
 286                 }
 287                 sscanf(buf, "%d:%d", &dev->disk.major, &dev->disk.minor);
 288
 289                 /* special case check for block devices that can go 'offline' */
 290                 if (options & SKIP_GONE_DEVS) {
 291                         strcpy(dbase, "block/device/state");
 292                         if (load_sys(fname, buf) == 0 &&
 293                             strncmp(buf, "offline", 7) == 0) {
 294                                 free(dev);
 295                                 continue;
 296                         }
 297                 }
 298
 299                 /* finally add this disk to the array */
 300                 dev->next = sra->devs;
 301                 sra->devs = dev;
 302
 303                 if (options & GET_OFFSET) {
 304                         strcpy(dbase, "offset");
 305                         if (load_sys(fname, buf))
 306                                 goto abort;
 307                         dev->data_offset = strtoull(buf, NULL, 0);
 308                 }
 309                 if (options & GET_SIZE) {
 310                         strcpy(dbase, "size");
 311                         if (load_sys(fname, buf))
 312                                 goto abort;
 313                         dev->component_size = strtoull(buf, NULL, 0) * 2;
 314                 }
 315                 if (options & GET_STATE) {
 316                         dev->disk.state = 0;
 317                         strcpy(dbase, "state");
 318                         if (load_sys(fname, buf))
 319                                 goto abort;
 320                         if (strstr(buf, "in_sync"))
 321                                 dev->disk.state |= (1<<MD_DISK_SYNC);
 322                         if (strstr(buf, "faulty"))
 323                                 dev->disk.state |= (1<<MD_DISK_FAULTY);
 324                         if (dev->disk.state == 0)
 325                                 sra->array.spare_disks++;
 326                 }
 327                 if (options & GET_ERROR) {
 328                         strcpy(buf, "errors");
 329                         if (load_sys(fname, buf))
 330                                 goto abort;
 331                         dev->errors = strtoul(buf, NULL, 0);
 332                 }
 333         }
 334         closedir(dir);
 335         return sra;
 336
 337  abort:
 338         if (dir)
 339                 closedir(dir);
 340         sysfs_free(sra);
 341         return NULL;
 342 }
 343
 344 int sysfs_attr_match(const char *attr, const char *str)
 345 {
 346         /* See if attr, read from a sysfs file, matches
 347          * str.  They must either be the same, or attr can
 348          * have a trailing newline or comma
 349          */
 350         while (*attr && *str && *attr == *str) {
 351                 attr++;
 352                 str++;
 353         }
 354
 355         if (*str || (*attr && *attr != ',' && *attr != '\n'))
 356                 return 0;
 357         return 1;
 358 }
 359
 360 int sysfs_match_word(const char *word, char **list)
 361 {
 362         int n;
 363         for (n=0; list[n]; n++)
 364                 if (sysfs_attr_match(word, list[n]))
 365                         break;
 366         return n;
 367 }
 368
 369 unsigned long long get_component_size(int fd)
 370 {
 371         /* Find out the component size of the array.
 372          * We cannot trust GET_ARRAY_INFO ioctl as it's
 373          * size field is only 32bits.
 374          * So look in /sys/block/mdXXX/md/component_size
 375          *
 376          * This returns in units of sectors.
 377          */
 378         struct stat stb;
 379         char fname[50];
 380         int n;
 381         if (fstat(fd, &stb)) return 0;
 382         if (major(stb.st_rdev) != get_mdp_major())
 383                 sprintf(fname, "/sys/block/md%d/md/component_size",
 384                         (int)minor(stb.st_rdev));
 385         else
 386                 sprintf(fname, "/sys/block/md_d%d/md/component_size",
 387                         (int)minor(stb.st_rdev)>>MdpMinorShift);
 388         fd = open(fname, O_RDONLY);
 389         if (fd < 0)
 390                 return 0;
 391         n = read(fd, fname, sizeof(fname));
 392         close(fd);
 393         if (n == sizeof(fname))
 394                 return 0;
 395         fname[n] = 0;
 396         return strtoull(fname, NULL, 10) * 2;
 397 }
 398
 399 int sysfs_set_str(struct mdinfo *sra, struct mdinfo *dev,
 400                   char *name, char *val)
 401 {
 402         char fname[50];
 403         int n;
 404         int fd;
 405
 406         sprintf(fname, "/sys/block/%s/md/%s/%s",
 407                 sra->sys_name, dev?dev->sys_name:"", name);
 408         fd = open(fname, O_WRONLY);
 409         if (fd < 0)
 410                 return -1;
 411         n = write(fd, val, strlen(val));
 412         close(fd);
 413         if (n != strlen(val)) {
 414                 dprintf(Name ": failed to write '%s' to '%s' (%s)\n",
 415                         val, fname, strerror(errno));
 416                 return -1;
 417         }
 418         return 0;
 419 }
 420
 421 int sysfs_set_num(struct mdinfo *sra, struct mdinfo *dev,
 422                   char *name, unsigned long long val)
 423 {
 424         char valstr[50];
 425         sprintf(valstr, "%llu", val);
 426         return sysfs_set_str(sra, dev, name, valstr);
 427 }
 428
 429 int sysfs_uevent(struct mdinfo *sra, char *event)
 430 {
 431         char fname[50];
 432         int n;
 433         int fd;
 434
 435         sprintf(fname, "/sys/block/%s/uevent",
 436                 sra->sys_name);
 437         fd = open(fname, O_WRONLY);
 438         if (fd < 0)
 439                 return -1;
 440         n = write(fd, event, strlen(event));
 441         close(fd);
 442         return 0;
 443 }
 444
 445 int sysfs_get_ll(struct mdinfo *sra, struct mdinfo *dev,
 446                        char *name, unsigned long long *val)
 447 {
 448         char fname[50];
 449         char buf[50];
 450         int n;
 451         int fd;
 452         char *ep;
 453         sprintf(fname, "/sys/block/%s/md/%s/%s",
 454                 sra->sys_name, dev?dev->sys_name:"", name);
 455         fd = open(fname, O_RDONLY);
 456         if (fd < 0)
 457                 return -1;
 458         n = read(fd, buf, sizeof(buf));
 459         close(fd);
 460         if (n <= 0)
 461                 return -1;
 462         buf[n] = 0;
 463         *val = strtoull(buf, &ep, 0);
 464         if (ep == buf || (*ep != 0 && *ep != '\n' && *ep != ' '))
 465                 return -1;
 466         return 0;
 467 }
 468
 469 int sysfs_set_safemode(struct mdinfo *sra, unsigned long ms)
 470 {
 471         unsigned long sec;
 472         unsigned long msec;
 473         char delay[30];
 474
 475         sec = ms / 1000;
 476         msec = ms % 1000;
 477
 478         sprintf(delay, "%ld.%03ld\n", sec, msec);
 479         /*             this '\n' ^ needed for kernels older than 2.6.28 */
 480         return sysfs_set_str(sra, NULL, "safe_mode_delay", delay);
 481 }
 482
 483 int sysfs_set_array(struct mdinfo *info, int vers)
 484 {
 485         int rv = 0;
 486         char ver[100];
 487
 488         ver[0] = 0;
 489         if (info->array.major_version == -1 &&
 490             info->array.minor_version == -2) {
 491                 strcat(strcpy(ver, "external:"), info->text_version);
 492
 493                 if ((vers % 100) < 2 ||
 494                     sysfs_set_str(info, NULL, "metadata_version",
 495                                   ver) < 0) {
 496                         fprintf(stderr, Name ": This kernel does not "
 497                                 "support external metadata.\n");
 498                         return 1;
 499                 }
 500         }
 501         if (info->array.level < 0)
 502                 return 0; /* FIXME */
 503         rv |= sysfs_set_str(info, NULL, "level",
 504                             map_num(pers, info->array.level));
 505         rv |= sysfs_set_num(info, NULL, "raid_disks", info->array.raid_disks);
 506         rv |= sysfs_set_num(info, NULL, "chunk_size", info->array.chunk_size);
 507         rv |= sysfs_set_num(info, NULL, "layout", info->array.layout);
 508         rv |= sysfs_set_num(info, NULL, "component_size", info->component_size/2);
 509         if (info->custom_array_size) {
 510                 int rc;
 511
 512                 rc = sysfs_set_num(info, NULL, "array_size",
 513                                    info->custom_array_size/2);
 514                 if (rc && errno == ENOENT) {
 515                         fprintf(stderr, Name ": This kernel does not "
 516                                 "have the md/array_size attribute, "
 517                                 "the array may be larger than expected\n");
 518                         rc = 0;
 519                 }
 520                 rv |= rc;
 521         }
 522
 523         if (info->array.level > 0)
 524                 rv |= sysfs_set_num(info, NULL, "resync_start", info->resync_start);
 525         return rv;
 526 }
 527
 528 int sysfs_add_disk(struct mdinfo *sra, struct mdinfo *sd)
 529 {
 530         char dv[100];
 531         char nm[100];
 532         char *dname;
 533         int rv;
 534
 535         sprintf(dv, "%d:%d", sd->disk.major, sd->disk.minor);
 536         rv = sysfs_set_str(sra, NULL, "new_dev", dv);
 537         if (rv)
 538                 return rv;
 539
 540         memset(nm, 0, sizeof(nm));
 541         sprintf(dv, "/sys/dev/block/%d:%d", sd->disk.major, sd->disk.minor);
 542         rv = readlink(dv, nm, sizeof(nm));
 543         if (rv <= 0)
 544                 return -1;
 545         nm[rv] = '\0';
 546         dname = strrchr(nm, '/');
 547         if (dname) dname++;
 548         strcpy(sd->sys_name, "dev-");
 549         strcpy(sd->sys_name+4, dname);
 550
 551         rv = sysfs_set_num(sra, sd, "offset", sd->data_offset);
 552         rv |= sysfs_set_num(sra, sd, "size", (sd->component_size+1) / 2);
 553         if (sra->array.level != LEVEL_CONTAINER) {
 554                 rv |= sysfs_set_num(sra, sd, "slot", sd->disk.raid_disk);
 555 //              rv |= sysfs_set_str(sra, sd, "state", "in_sync");
 556         }
 557         return rv;
 558 }
 559
 560 #if 0
 561 int sysfs_disk_to_sg(int fd)
 562 {
 563         /* from an open block device, try find and open its corresponding
 564          * scsi_generic interface
 565          */
 566         struct stat st;
 567         char path[256];
 568         char sg_path[256];
 569         char sg_major_minor[8];
 570         char *c;
 571         DIR *dir;
 572         struct dirent *de;
 573         int major, minor, rv;
 574
 575         if (fstat(fd, &st))
 576                 return -1;
 577
 578         snprintf(path, sizeof(path), "/sys/dev/block/%d:%d/device",
 579                  major(st.st_rdev), minor(st.st_rdev));
 580
 581         dir = opendir(path);
 582         if (!dir)
 583                 return -1;
 584
 585         de = readdir(dir);
 586         while (de) {
 587                 if (strncmp("scsi_generic:", de->d_name,
 588                             strlen("scsi_generic:")) == 0)
 589                         break;
 590                 de = readdir(dir);
 591         }
 592         closedir(dir);
 593
 594         if (!de)
 595                 return -1;
 596
 597         snprintf(sg_path, sizeof(sg_path), "%s/%s/dev", path, de->d_name);
 598         fd = open(sg_path, O_RDONLY);
 599         if (fd < 0)
 600                 return fd;
 601
 602         rv = read(fd, sg_major_minor, sizeof(sg_major_minor));
 603         close(fd);
 604         if (rv < 0)
 605                 return -1;
 606         else
 607                 sg_major_minor[rv - 1] = '\0';
 608
 609         c = strchr(sg_major_minor, ':');
 610         *c = '\0';
 611         c++;
 612         major = strtol(sg_major_minor, NULL, 10);
 613         minor = strtol(c, NULL, 10);
 614         snprintf(path, sizeof(path), "/dev/.tmp.md.%d:%d:%d",
 615                  (int) getpid(), major, minor);
 616         if (mknod(path, S_IFCHR|0600, makedev(major, minor))==0) {
 617                         fd = open(path, O_RDONLY);
 618                         unlink(path);
 619                         return fd;
 620         }
 621
 622         return -1;
 623 }
 624 #endif
 625
 626 int sysfs_disk_to_scsi_id(int fd, __u32 *id)
 627 {
 628         /* from an open block device, try to retrieve it scsi_id */
 629         struct stat st;
 630         char path[256];
 631         char *c1, *c2;
 632         DIR *dir;
 633         struct dirent *de;
 634
 635         if (fstat(fd, &st))
 636                 return 1;
 637
 638         snprintf(path, sizeof(path), "/sys/dev/block/%d:%d/device",
 639                  major(st.st_rdev), minor(st.st_rdev));
 640
 641         dir = opendir(path);
 642         if (!dir)
 643                 return 1;
 644
 645         de = readdir(dir);
 646         while (de) {
 647                 if (strncmp("scsi_disk:", de->d_name,
 648                             strlen("scsi_disk:")) == 0)
 649                         break;
 650                 de = readdir(dir);
 651         }
 652         closedir(dir);
 653
 654         if (!de)
 655                 return 1;
 656
 657         c1 = strchr(de->d_name, ':');
 658         c1++;
 659         c2 = strchr(c1, ':');
 660         *c2 = '\0';
 661         *id = strtol(c1, NULL, 10) << 24; /* host */
 662         c1 = c2 + 1;
 663         c2 = strchr(c1, ':');
 664         *c2 = '\0';
 665         *id |= strtol(c1, NULL, 10) << 16; /* channel */
 666         c1 = c2 + 1;
 667         c2 = strchr(c1, ':');
 668         *c2 = '\0';
 669         *id |= strtol(c1, NULL, 10) << 8; /* lun */
 670         c1 = c2 + 1;
 671         *id |= strtol(c1, NULL, 10); /* id */
 672
 673         return 0;
 674 }
 675
 676
 677 int sysfs_unique_holder(int devnum, long rdev)
 678 {
 679         /* Check that devnum is a holder of rdev,
 680          * and is the only holder.
 681          * we should be locked against races by
 682          * an O_EXCL on devnum
 683          */
 684         DIR *dir;
 685         struct dirent *de;
 686         char dirname[100];
 687         char l;
 688         int found = 0;
 689         sprintf(dirname, "/sys/dev/block/%d:%d/holders",
 690                 major(rdev), minor(rdev));
 691         dir = opendir(dirname);
 692         errno = ENOENT;
 693         if (!dir)
 694                 return 0;
 695         l = strlen(dirname);
 696         while ((de = readdir(dir)) != NULL) {
 697                 char buf[10];
 698                 int n;
 699                 int mj, mn;
 700                 char c;
 701                 int fd;
 702
 703                 if (de->d_ino == 0)
 704                         continue;
 705                 if (de->d_name[0] == '.')
 706                         continue;
 707                 strcpy(dirname+l, "/");
 708                 strcat(dirname+l, de->d_name);
 709                 strcat(dirname+l, "/dev");
 710                 fd = open(dirname, O_RDONLY);
 711                 if (fd < 0) {
 712                         errno = ENOENT;
 713                         break;
 714                 }
 715                 n = read(fd, buf, sizeof(buf)-1);
 716                 close(fd);
 717                 buf[n] = 0;
 718                 if (sscanf(buf, "%d:%d%c", &mj, &mn, &c) != 3 ||
 719                     c != '\n') {
 720                         errno = ENOENT;
 721                         break;
 722                 }
 723                 if (mj != MD_MAJOR)
 724                         mn = -1-(mn>>6);
 725
 726                 if (devnum != mn) {
 727                         errno = EEXIST;
 728                         break;
 729                 }
 730                 found = 1;
 731         }
 732         closedir(dir);
 733         if (de)
 734                 return 0;
 735         else
 736                 return found;
 737 }