lib/sysfs.c

   1 /*
   2  * No copyright is claimed.  This code is in the public domain; do with
   3  * it what you wish.
   4  *
   5  * Written by Karel Zak <kzak@redhat.com>
   6  */
   7 #include <ctype.h>
   8 #include <libgen.h>
   9 #include <fcntl.h>
  10 #include <sys/stat.h>
  11 #include <unistd.h>
  12
  13 #include "c.h"
  14 #include "pathnames.h"
  15 #include "sysfs.h"
  16 #include "fileutils.h"
  17 #include "all-io.h"
  18
  19 char *sysfs_devno_attribute_path(dev_t devno, char *buf,
  20                                  size_t bufsiz, const char *attr)
  21 {
  22         int len;
  23
  24         if (attr)
  25                 len = snprintf(buf, bufsiz, _PATH_SYS_DEVBLOCK "/%d:%d/%s",
  26                         major(devno), minor(devno), attr);
  27         else
  28                 len = snprintf(buf, bufsiz, _PATH_SYS_DEVBLOCK "/%d:%d",
  29                         major(devno), minor(devno));
  30
  31         return (len < 0 || (size_t) len >= bufsiz) ? NULL : buf;
  32 }
  33
  34 int sysfs_devno_has_attribute(dev_t devno, const char *attr)
  35 {
  36         char path[PATH_MAX];
  37         struct stat info;
  38
  39         if (!sysfs_devno_attribute_path(devno, path, sizeof(path), attr))
  40                 return 0;
  41         if (stat(path, &info) == 0)
  42                 return 1;
  43         return 0;
  44 }
  45
  46 char *sysfs_devno_path(dev_t devno, char *buf, size_t bufsiz)
  47 {
  48         return sysfs_devno_attribute_path(devno, buf, bufsiz, NULL);
  49 }
  50
  51 dev_t sysfs_devname_to_devno(const char *name, const char *parent)
  52 {
  53         char buf[PATH_MAX], *path = NULL;
  54         dev_t dev = 0;
  55
  56         if (strncmp("/dev/", name, 5) == 0) {
  57                 /*
  58                  * Read from /dev
  59                  */
  60                 struct stat st;
  61
  62                 if (stat(name, &st) == 0)
  63                         dev = st.st_rdev;
  64                 else
  65                         name += 5;      /* unaccesible, or not node in /dev */
  66         }
  67
  68         if (!dev && parent && strncmp("dm-", name, 3)) {
  69                 /*
  70                  * Create path to /sys/block/<parent>/<name>/dev
  71                  */
  72                 char *_name = strdup(name), *_parent = strdup(parent);
  73                 int len;
  74
  75                 if (!_name || !_parent) {
  76                         free(_name);
  77                         free(_parent);
  78                         return 0;
  79                 }
  80                 sysfs_devname_dev_to_sys(_name);
  81                 sysfs_devname_dev_to_sys(_parent);
  82
  83                 len = snprintf(buf, sizeof(buf),
  84                                 _PATH_SYS_BLOCK "/%s/%s/dev", _parent, _name);
  85                 free(_name);
  86                 free(_parent);
  87                 if (len < 0 || (size_t) len >= sizeof(buf))
  88                         return 0;
  89                 path = buf;
  90
  91         } else if (!dev) {
  92                 /*
  93                  * Create path to /sys/block/<sysname>/dev
  94                  */
  95                 char *_name = strdup(name);
  96                 int len;
  97
  98                 if (!_name)
  99                         return 0;
 100
 101                 sysfs_devname_dev_to_sys(_name);
 102                 len = snprintf(buf, sizeof(buf),
 103                                 _PATH_SYS_BLOCK "/%s/dev", _name);
 104                 free(_name);
 105                 if (len < 0 || (size_t) len >= sizeof(buf))
 106                         return 0;
 107                 path = buf;
 108         }
 109
 110         if (path) {
 111                 /*
 112                  * read devno from sysfs
 113                  */
 114                 FILE *f;
 115                 int maj = 0, min = 0;
 116
 117                 f = fopen(path, "r" UL_CLOEXECSTR);
 118                 if (!f)
 119                         return 0;
 120
 121                 if (fscanf(f, "%d:%d", &maj, &min) == 2)
 122                         dev = makedev(maj, min);
 123                 fclose(f);
 124         }
 125         return dev;
 126 }
 127
 128 /*
 129  * Returns devname (e.g. "/dev/sda1") for the given devno.
 130  *
 131  * Please, use more robust blkid_devno_to_devname() in your applications.
 132  */
 133 char *sysfs_devno_to_devpath(dev_t devno, char *buf, size_t bufsiz)
 134 {
 135         struct sysfs_cxt cxt;
 136         char *name;
 137         size_t sz;
 138         struct stat st;
 139
 140         if (sysfs_init(&cxt, devno, NULL))
 141                 return NULL;
 142
 143         name = sysfs_get_devname(&cxt, buf, bufsiz);
 144         sysfs_deinit(&cxt);
 145
 146         if (!name)
 147                 return NULL;
 148
 149         sz = strlen(name);
 150
 151         if (sz + sizeof("/dev/") > bufsiz)
 152                 return NULL;
 153
 154         /* create the final "/dev/<name>" string */
 155         memmove(buf + 5, name, sz + 1);
 156         memcpy(buf, "/dev/", 5);
 157
 158         if (!stat(buf, &st) && S_ISBLK(st.st_mode) && st.st_rdev == devno)
 159                 return buf;
 160
 161         return NULL;
 162 }
 163
 164 int sysfs_init(struct sysfs_cxt *cxt, dev_t devno, struct sysfs_cxt *parent)
 165 {
 166         char path[PATH_MAX];
 167         int fd, rc;
 168
 169         memset(cxt, 0, sizeof(*cxt));
 170         cxt->dir_fd = -1;
 171
 172         if (!sysfs_devno_path(devno, path, sizeof(path)))
 173                 goto err;
 174
 175         fd = open(path, O_RDONLY|O_CLOEXEC);
 176         if (fd < 0)
 177                 goto err;
 178         cxt->dir_fd = fd;
 179
 180         cxt->dir_path = strdup(path);
 181         if (!cxt->dir_path)
 182                 goto err;
 183         cxt->devno = devno;
 184         cxt->parent = parent;
 185         return 0;
 186 err:
 187         rc = errno > 0 ? -errno : -1;
 188         sysfs_deinit(cxt);
 189         return rc;
 190 }
 191
 192 void sysfs_deinit(struct sysfs_cxt *cxt)
 193 {
 194         if (!cxt)
 195                 return;
 196
 197         if (cxt->dir_fd >= 0)
 198                close(cxt->dir_fd);
 199         free(cxt->dir_path);
 200
 201         memset(cxt, 0, sizeof(*cxt));
 202
 203         cxt->dir_fd = -1;
 204 }
 205
 206 int sysfs_stat(struct sysfs_cxt *cxt, const char *attr, struct stat *st)
 207 {
 208         int rc = fstatat(cxt->dir_fd, attr, st, 0);
 209
 210         if (rc != 0 && errno == ENOENT &&
 211             strncmp(attr, "queue/", 6) == 0 && cxt->parent) {
 212
 213                 /* Exception for "queue/<attr>". These attributes are available
 214                  * for parental devices only
 215                  */
 216                 return fstatat(cxt->parent->dir_fd, attr, st, 0);
 217         }
 218         return rc;
 219 }
 220
 221 int sysfs_has_attribute(struct sysfs_cxt *cxt, const char *attr)
 222 {
 223         struct stat st;
 224
 225         return sysfs_stat(cxt, attr, &st) == 0;
 226 }
 227
 228 static int sysfs_open(struct sysfs_cxt *cxt, const char *attr, int flags)
 229 {
 230         int fd = openat(cxt->dir_fd, attr, flags);
 231
 232         if (fd == -1 && errno == ENOENT &&
 233             strncmp(attr, "queue/", 6) == 0 && cxt->parent) {
 234
 235                 /* Exception for "queue/<attr>". These attributes are available
 236                  * for parental devices only
 237                  */
 238                 fd = openat(cxt->parent->dir_fd, attr, flags);
 239         }
 240         return fd;
 241 }
 242
 243 ssize_t sysfs_readlink(struct sysfs_cxt *cxt, const char *attr,
 244                    char *buf, size_t bufsiz)
 245 {
 246         if (!cxt->dir_path)
 247                 return -1;
 248
 249         if (attr)
 250                 return readlinkat(cxt->dir_fd, attr, buf, bufsiz);
 251
 252         /* read /sys/dev/block/<maj:min> link */
 253         return readlink(cxt->dir_path, buf, bufsiz);
 254 }
 255
 256 DIR *sysfs_opendir(struct sysfs_cxt *cxt, const char *attr)
 257 {
 258         DIR *dir;
 259         int fd = -1;
 260
 261         if (attr)
 262                 fd = sysfs_open(cxt, attr, O_RDONLY|O_CLOEXEC);
 263
 264         else if (cxt->dir_fd >= 0)
 265                 /* request to open root of device in sysfs (/sys/block/<dev>)
 266                  * -- we cannot use cxt->sysfs_fd directly, because closedir()
 267                  * will close this our persistent file descriptor.
 268                  */
 269                 fd = dup_fd_cloexec(cxt->dir_fd, STDERR_FILENO + 1);
 270
 271         if (fd < 0)
 272                 return NULL;
 273
 274         dir = fdopendir(fd);
 275         if (!dir) {
 276                 close(fd);
 277                 return NULL;
 278         }
 279         if (!attr)
 280                  rewinddir(dir);
 281         return dir;
 282 }
 283
 284
 285 static FILE *sysfs_fopen(struct sysfs_cxt *cxt, const char *attr)
 286 {
 287         int fd = sysfs_open(cxt, attr, O_RDONLY|O_CLOEXEC);
 288
 289         return fd < 0 ? NULL : fdopen(fd, "r" UL_CLOEXECSTR);
 290 }
 291
 292
 293 static struct dirent *xreaddir(DIR *dp)
 294 {
 295         struct dirent *d;
 296
 297         while ((d = readdir(dp))) {
 298                 if (!strcmp(d->d_name, ".") ||
 299                     !strcmp(d->d_name, ".."))
 300                         continue;
 301
 302                 /* blacklist here? */
 303                 break;
 304         }
 305         return d;
 306 }
 307
 308 int sysfs_is_partition_dirent(DIR *dir, struct dirent *d, const char *parent_name)
 309 {
 310         char path[256];
 311
 312 #ifdef _DIRENT_HAVE_D_TYPE
 313         if (d->d_type != DT_DIR &&
 314             d->d_type != DT_LNK &&
 315             d->d_type != DT_UNKNOWN)
 316                 return 0;
 317 #endif
 318         if (parent_name) {
 319                 const char *p = parent_name;
 320                 size_t len;
 321
 322                 /* /dev/sda --> "sda" */
 323                 if (*parent_name == '/') {
 324                         p = strrchr(parent_name, '/');
 325                         if (!p)
 326                                 return 0;
 327                         p++;
 328                 }
 329
 330                 len = strlen(p);
 331                 if (strlen(d->d_name) <= len)
 332                         return 0;
 333
 334                 /* partitions subdir name is
 335                  *      "<parent>[:digit:]" or "<parent>p[:digit:]"
 336                  */
 337                 return strncmp(p, d->d_name, len) == 0 &&
 338                        ((*(d->d_name + len) == 'p' && isdigit(*(d->d_name + len + 1)))
 339                         || isdigit(*(d->d_name + len)));
 340         }
 341
 342         /* Cannot use /partition file, not supported on old sysfs */
 343         snprintf(path, sizeof(path), "%s/start", d->d_name);
 344
 345         return faccessat(dirfd(dir), path, R_OK, 0) == 0;
 346 }
 347
 348 /*
 349  * Converts @partno (partition number) to devno of the partition.
 350  * The @cxt handles wholedisk device.
 351  *
 352  * Note that this code does not expect any special format of the
 353  * partitions devnames.
 354  */
 355 dev_t sysfs_partno_to_devno(struct sysfs_cxt *cxt, int partno)
 356 {
 357         DIR *dir;
 358         struct dirent *d;
 359         char path[256];
 360         dev_t devno = 0;
 361
 362         dir = sysfs_opendir(cxt, NULL);
 363         if (!dir)
 364                 return 0;
 365
 366         while ((d = xreaddir(dir))) {
 367                 int n, maj, min;
 368
 369                 if (!sysfs_is_partition_dirent(dir, d, NULL))
 370                         continue;
 371
 372                 snprintf(path, sizeof(path), "%s/partition", d->d_name);
 373                 if (sysfs_read_int(cxt, path, &n))
 374                         continue;
 375
 376                 if (n == partno) {
 377                         snprintf(path, sizeof(path), "%s/dev", d->d_name);
 378                         if (sysfs_scanf(cxt, path, "%d:%d", &maj, &min) == 2)
 379                                 devno = makedev(maj, min);
 380                         break;
 381                 }
 382         }
 383
 384         closedir(dir);
 385         return devno;
 386 }
 387
 388
 389 int sysfs_scanf(struct sysfs_cxt *cxt,  const char *attr, const char *fmt, ...)
 390 {
 391         FILE *f = sysfs_fopen(cxt, attr);
 392         va_list ap;
 393         int rc;
 394
 395         if (!f)
 396                 return -EINVAL;
 397         va_start(ap, fmt);
 398         rc = vfscanf(f, fmt, ap);
 399         va_end(ap);
 400
 401         fclose(f);
 402         return rc;
 403 }
 404
 405
 406 int sysfs_read_s64(struct sysfs_cxt *cxt, const char *attr, int64_t *res)
 407 {
 408         int64_t x = 0;
 409
 410         if (sysfs_scanf(cxt, attr, "%"SCNd64, &x) == 1) {
 411                 if (res)
 412                         *res = x;
 413                 return 0;
 414         }
 415         return -1;
 416 }
 417
 418 int sysfs_read_u64(struct sysfs_cxt *cxt, const char *attr, uint64_t *res)
 419 {
 420         uint64_t x = 0;
 421
 422         if (sysfs_scanf(cxt, attr, "%"SCNu64, &x) == 1) {
 423                 if (res)
 424                         *res = x;
 425                 return 0;
 426         }
 427         return -1;
 428 }
 429
 430 int sysfs_read_int(struct sysfs_cxt *cxt, const char *attr, int *res)
 431 {
 432         int x = 0;
 433
 434         if (sysfs_scanf(cxt, attr, "%d", &x) == 1) {
 435                 if (res)
 436                         *res = x;
 437                 return 0;
 438         }
 439         return -1;
 440 }
 441
 442 int sysfs_write_string(struct sysfs_cxt *cxt, const char *attr, const char *str)
 443 {
 444         int fd = sysfs_open(cxt, attr, O_WRONLY|O_CLOEXEC);
 445         int rc, errsv;
 446
 447         if (fd < 0)
 448                 return -errno;
 449         rc = write_all(fd, str, strlen(str));
 450
 451         errsv = errno;
 452         close(fd);
 453         errno = errsv;
 454         return rc;
 455 }
 456
 457 int sysfs_write_u64(struct sysfs_cxt *cxt, const char *attr, uint64_t num)
 458 {
 459         char buf[sizeof(stringify_value(ULLONG_MAX))];
 460         int fd, rc = 0, len, errsv;
 461
 462         fd = sysfs_open(cxt, attr, O_WRONLY|O_CLOEXEC);
 463         if (fd < 0)
 464                 return -errno;
 465
 466         len = snprintf(buf, sizeof(buf), "%" PRIu64, num);
 467         if (len < 0 || (size_t) len >= sizeof(buf))
 468                 rc = len < 0 ? -errno : -E2BIG;
 469         else
 470                 rc = write_all(fd, buf, len);
 471
 472         errsv = errno;
 473         close(fd);
 474         errno = errsv;
 475         return rc;
 476 }
 477
 478 char *sysfs_strdup(struct sysfs_cxt *cxt, const char *attr)
 479 {
 480         char buf[BUFSIZ];
 481         return sysfs_scanf(cxt, attr, "%1023[^\n]", buf) == 1 ?
 482                                                 strdup(buf) : NULL;
 483 }
 484
 485
 486 int sysfs_count_dirents(struct sysfs_cxt *cxt, const char *attr)
 487 {
 488         DIR *dir;
 489         int r = 0;
 490
 491         if (!(dir = sysfs_opendir(cxt, attr)))
 492                 return 0;
 493
 494         while (xreaddir(dir)) r++;
 495
 496         closedir(dir);
 497         return r;
 498 }
 499
 500 int sysfs_count_partitions(struct sysfs_cxt *cxt, const char *devname)
 501 {
 502         DIR *dir;
 503         struct dirent *d;
 504         int r = 0;
 505
 506         if (!(dir = sysfs_opendir(cxt, NULL)))
 507                 return 0;
 508
 509         while ((d = xreaddir(dir))) {
 510                 if (sysfs_is_partition_dirent(dir, d, devname))
 511                         r++;
 512         }
 513
 514         closedir(dir);
 515         return r;
 516 }
 517
 518 /*
 519  * Returns slave name if there is only one slave, otherwise returns NULL.
 520  * The result should be deallocated by free().
 521  */
 522 char *sysfs_get_slave(struct sysfs_cxt *cxt)
 523 {
 524         DIR *dir;
 525         struct dirent *d;
 526         char *name = NULL;
 527
 528         if (!(dir = sysfs_opendir(cxt, "slaves")))
 529                 return NULL;
 530
 531         while ((d = xreaddir(dir))) {
 532                 if (name)
 533                         goto err;       /* more slaves */
 534
 535                 name = strdup(d->d_name);
 536         }
 537
 538         closedir(dir);
 539         return name;
 540 err:
 541         free(name);
 542         closedir(dir);
 543         return NULL;
 544 }
 545
 546 char *sysfs_get_devname(struct sysfs_cxt *cxt, char *buf, size_t bufsiz)
 547 {
 548         char linkpath[PATH_MAX];
 549         char *name;
 550         ssize_t sz;
 551
 552         sz = sysfs_readlink(cxt, NULL, linkpath, sizeof(linkpath) - 1);
 553         if (sz < 0)
 554                 return NULL;
 555         linkpath[sz] = '\0';
 556
 557         name = strrchr(linkpath, '/');
 558         if (!name)
 559                 return NULL;
 560
 561         name++;
 562         sz = strlen(name);
 563
 564         if ((size_t) sz + 1 > bufsiz)
 565                 return NULL;
 566
 567         memcpy(buf, name, sz + 1);
 568         sysfs_devname_sys_to_dev(buf);
 569
 570         return buf;
 571 }
 572
 573 #define SUBSYSTEM_LINKNAME      "/subsystem"
 574
 575 /*
 576  * For example:
 577  *
 578  * chain: /sys/dev/block/../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/ \
 579  *                           1-1.2:1.0/host65/target65:0:0/65:0:0:0/block/sdb
 580  *
 581  * The function check if <chain>/subsystem symlink exists, if yes then returns
 582  * basename of the readlink result, and remove the last subdirectory from the
 583  * <chain> path.
 584  */
 585 static char *get_subsystem(char *chain, char *buf, size_t bufsz)
 586 {
 587         size_t len;
 588         char *p;
 589
 590         if (!chain || !*chain)
 591                 return NULL;
 592
 593         len = strlen(chain);
 594         if (len + sizeof(SUBSYSTEM_LINKNAME) > PATH_MAX)
 595                 return NULL;
 596
 597         do {
 598                 ssize_t sz;
 599
 600                 /* append "/subsystem" to the path */
 601                 memcpy(chain + len, SUBSYSTEM_LINKNAME, sizeof(SUBSYSTEM_LINKNAME));
 602
 603                 /* try if subsystem symlink exists */
 604                 sz = readlink(chain, buf, bufsz - 1);
 605
 606                 /* remove last subsystem from chain */
 607                 chain[len] = '\0';
 608                 p = strrchr(chain, '/');
 609                 if (p) {
 610                         *p = '\0';
 611                         len = p - chain;
 612                 }
 613
 614                 if (sz > 0) {
 615                         /* we found symlink to subsystem, return basename */
 616                         buf[sz] = '\0';
 617                         return basename(buf);
 618                 }
 619
 620         } while (p);
 621
 622         return NULL;
 623 }
 624
 625 /*
 626  * Returns complete path to the device, the patch contains all all sybsystems
 627  * used for the device.
 628  */
 629 char *sysfs_get_devchain(struct sysfs_cxt *cxt, char *buf, size_t bufsz)
 630 {
 631         /* read /sys/dev/block/<maj>:<min> symlink */
 632         ssize_t sz = sysfs_readlink(cxt, NULL, buf, bufsz);
 633         if (sz <= 0 || sz + sizeof(_PATH_SYS_DEVBLOCK "/") > bufsz)
 634                 return NULL;
 635
 636         buf[sz++] = '\0';
 637
 638         /* create absolute patch from the link */
 639         memmove(buf + sizeof(_PATH_SYS_DEVBLOCK "/") - 1, buf, sz);
 640         memcpy(buf, _PATH_SYS_DEVBLOCK "/", sizeof(_PATH_SYS_DEVBLOCK "/") - 1);
 641
 642         return buf;
 643 }
 644
 645 /*
 646  * The @subsys returns the next subsystem in the chain. Function modifies
 647  * @devchain string.
 648  *
 649  * Returns: 0 in success, <0 on error, 1 on end of chain
 650  */
 651 int sysfs_next_subsystem(struct sysfs_cxt *cxt __attribute__((unused)),
 652                          char *devchain, char **subsys)
 653 {
 654         char subbuf[PATH_MAX];
 655         char *sub;
 656
 657         if (!subsys || !devchain)
 658                 return -EINVAL;
 659
 660         *subsys = NULL;
 661
 662         while ((sub = get_subsystem(devchain, subbuf, sizeof(subbuf)))) {
 663                 *subsys = strdup(sub);
 664                 if (!*subsys)
 665                         return -ENOMEM;
 666                 return 0;
 667         }
 668
 669         return 1;
 670 }
 671
 672
 673 static int is_hotpluggable_subsystem(const char *name)
 674 {
 675         static const char * const hotplug_subsystems[] = {
 676                 "usb",
 677                 "ieee1394",
 678                 "pcmcia",
 679                 "mmc",
 680                 "ccw"
 681         };
 682         size_t i;
 683
 684         for (i = 0; i < ARRAY_SIZE(hotplug_subsystems); i++)
 685                 if (strcmp(name, hotplug_subsystems[i]) == 0)
 686                         return 1;
 687
 688         return 0;
 689 }
 690
 691 int sysfs_is_hotpluggable(struct sysfs_cxt *cxt)
 692 {
 693         char buf[PATH_MAX], *chain, *sub;
 694         int rc = 0;
 695
 696
 697         /* check /sys/dev/block/<maj>:<min>/removable attribute */
 698         if (sysfs_read_int(cxt, "removable", &rc) == 0 && rc == 1)
 699                 return 1;
 700
 701         chain = sysfs_get_devchain(cxt, buf, sizeof(buf));
 702
 703         while (chain && sysfs_next_subsystem(cxt, chain, &sub) == 0) {
 704                 rc = is_hotpluggable_subsystem(sub);
 705                 if (rc) {
 706                         free(sub);
 707                         break;
 708                 }
 709                 free(sub);
 710         }
 711
 712         return rc;
 713 }
 714
 715 static int get_dm_wholedisk(struct sysfs_cxt *cxt, char *diskname,
 716                 size_t len, dev_t *diskdevno)
 717 {
 718     int rc = 0;
 719     char *name;
 720
 721     /* Note, sysfs_get_slave() returns the first slave only,
 722      * if there is more slaves, then return NULL
 723      */
 724     name = sysfs_get_slave(cxt);
 725     if (!name)
 726         return -1;
 727
 728     if (diskname && len) {
 729         strncpy(diskname, name, len);
 730         diskname[len - 1] = '\0';
 731     }
 732
 733     if (diskdevno) {
 734         *diskdevno = sysfs_devname_to_devno(name, NULL);
 735         if (!*diskdevno)
 736             rc = -1;
 737     }
 738
 739     free(name);
 740     return rc;
 741 }
 742
 743 /*
 744  * Returns by @diskdevno whole disk device devno and (optionaly) by
 745  * @diskname the whole disk device name.
 746  */
 747 int sysfs_devno_to_wholedisk(dev_t dev, char *diskname,
 748             size_t len, dev_t *diskdevno)
 749 {
 750     struct sysfs_cxt cxt;
 751     int is_part = 0;
 752
 753     if (!dev || sysfs_init(&cxt, dev, NULL) != 0)
 754         return -1;
 755
 756     is_part = sysfs_has_attribute(&cxt, "partition");
 757     if (!is_part) {
 758         /*
 759          * Extra case for partitions mapped by device-mapper.
 760          *
 761          * All regualar partitions (added by BLKPG ioctl or kernel PT
 762          * parser) have the /sys/.../partition file. The partitions
 763          * mapped by DM don't have such file, but they have "part"
 764          * prefix in DM UUID.
 765          */
 766         char *uuid = sysfs_strdup(&cxt, "dm/uuid");
 767         char *tmp = uuid;
 768         char *prefix = uuid ? strsep(&tmp, "-") : NULL;
 769
 770         if (prefix && strncasecmp(prefix, "part", 4) == 0)
 771             is_part = 1;
 772         free(uuid);
 773
 774         if (is_part &&
 775             get_dm_wholedisk(&cxt, diskname, len, diskdevno) == 0)
 776             /*
 777              * partitioned device, mapped by DM
 778              */
 779             goto done;
 780
 781         is_part = 0;
 782     }
 783
 784     if (!is_part) {
 785         /*
 786          * unpartitioned device
 787          */
 788         if (diskname && len) {
 789             if (!sysfs_get_devname(&cxt, diskname, len))
 790                 goto err;
 791         }
 792         if (diskdevno)
 793             *diskdevno = dev;
 794
 795     } else {
 796         /*
 797          * partitioned device
 798          *  - readlink /sys/dev/block/8:1   = ../../block/sda/sda1
 799          *  - dirname  ../../block/sda/sda1 = ../../block/sda
 800          *  - basename ../../block/sda      = sda
 801          */
 802         char linkpath[PATH_MAX];
 803         char *name;
 804         ssize_t linklen;
 805
 806         linklen = sysfs_readlink(&cxt, NULL, linkpath, sizeof(linkpath) - 1);
 807         if (linklen < 0)
 808             goto err;
 809         linkpath[linklen] = '\0';
 810
 811         stripoff_last_component(linkpath);      /* dirname */
 812         name = stripoff_last_component(linkpath);   /* basename */
 813         if (!name)
 814             goto err;
 815
 816         sysfs_devname_sys_to_dev(name);
 817         if (diskname && len) {
 818             strncpy(diskname, name, len);
 819             diskname[len - 1] = '\0';
 820         }
 821
 822         if (diskdevno) {
 823             *diskdevno = sysfs_devname_to_devno(name, NULL);
 824             if (!*diskdevno)
 825                 goto err;
 826         }
 827     }
 828
 829 done:
 830     sysfs_deinit(&cxt);
 831     return 0;
 832 err:
 833     sysfs_deinit(&cxt);
 834     return -1;
 835 }
 836
 837 /*
 838  * Returns 1 if the device is private LVM device.
 839  */
 840 int sysfs_devno_is_lvm_private(dev_t devno)
 841 {
 842         struct sysfs_cxt cxt = UL_SYSFSCXT_EMPTY;
 843         char *uuid = NULL;
 844         int rc = 0;
 845
 846         if (sysfs_init(&cxt, devno, NULL) != 0)
 847                 return 0;
 848
 849         uuid = sysfs_strdup(&cxt, "dm/uuid");
 850
 851         /* Private LVM devices use "LVM-<uuid>-<name>" uuid format (important
 852          * is the "LVM" prefix and "-<name>" postfix).
 853          */
 854         if (uuid && strncmp(uuid, "LVM-", 4) == 0) {
 855                 char *p = strrchr(uuid + 4, '-');
 856
 857                 if (p && *(p + 1))
 858                         rc = 1;
 859         }
 860
 861         sysfs_deinit(&cxt);
 862         free(uuid);
 863         return rc;
 864 }
 865
 866 /*
 867  * Return 0 or 1, or < 0 in case of error
 868  */
 869 int sysfs_devno_is_wholedisk(dev_t devno)
 870 {
 871         dev_t disk;
 872
 873         if (sysfs_devno_to_wholedisk(devno, NULL, 0, &disk) != 0)
 874                 return -1;
 875
 876         return devno == disk;
 877 }
 878
 879
 880 int sysfs_scsi_get_hctl(struct sysfs_cxt *cxt, int *h, int *c, int *t, int *l)
 881 {
 882         char buf[PATH_MAX], *hctl;
 883         ssize_t len;
 884
 885         if (!cxt)
 886                 return -EINVAL;
 887         if (cxt->has_hctl)
 888                 goto done;
 889
 890         len = sysfs_readlink(cxt, "device", buf, sizeof(buf) - 1);
 891         if (len < 0)
 892                 return len;
 893
 894         buf[len] = '\0';
 895         hctl = strrchr(buf, '/');
 896         if (!hctl)
 897                 return -1;
 898         hctl++;
 899
 900         if (sscanf(hctl, "%u:%u:%u:%u", &cxt->scsi_host, &cxt->scsi_channel,
 901                                 &cxt->scsi_target, &cxt->scsi_lun) != 4)
 902                 return -1;
 903
 904         cxt->has_hctl = 1;
 905 done:
 906         if (h)
 907                 *h = cxt->scsi_host;
 908         if (c)
 909                 *c = cxt->scsi_channel;
 910         if (t)
 911                 *t = cxt->scsi_target;
 912         if (l)
 913                 *l = cxt->scsi_lun;
 914         return 0;
 915 }
 916
 917
 918 static char *sysfs_scsi_host_attribute_path(struct sysfs_cxt *cxt,
 919                 const char *type, char *buf, size_t bufsz, const char *attr)
 920 {
 921         int len;
 922         int host;
 923
 924         if (sysfs_scsi_get_hctl(cxt, &host, NULL, NULL, NULL))
 925                 return NULL;
 926
 927         if (attr)
 928                 len = snprintf(buf, bufsz, _PATH_SYS_CLASS "/%s_host/host%d/%s",
 929                                 type, host, attr);
 930         else
 931                 len = snprintf(buf, bufsz, _PATH_SYS_CLASS "/%s_host/host%d",
 932                                 type, host);
 933
 934         return (len < 0 || (size_t) len >= bufsz) ? NULL : buf;
 935 }
 936
 937 char *sysfs_scsi_host_strdup_attribute(struct sysfs_cxt *cxt,
 938                 const char *type, const char *attr)
 939 {
 940         char buf[1024];
 941         int rc;
 942         FILE *f;
 943
 944         if (!attr || !type ||
 945             !sysfs_scsi_host_attribute_path(cxt, type, buf, sizeof(buf), attr))
 946                 return NULL;
 947
 948         if (!(f = fopen(buf, "r" UL_CLOEXECSTR)))
 949                 return NULL;
 950
 951         rc = fscanf(f, "%1023[^\n]", buf);
 952         fclose(f);
 953
 954         return rc == 1 ? strdup(buf) : NULL;
 955 }
 956
 957 int sysfs_scsi_host_is(struct sysfs_cxt *cxt, const char *type)
 958 {
 959         char buf[PATH_MAX];
 960         struct stat st;
 961
 962         if (!type || !sysfs_scsi_host_attribute_path(cxt, type,
 963                                 buf, sizeof(buf), NULL))
 964                 return 0;
 965
 966         return stat(buf, &st) == 0 && S_ISDIR(st.st_mode);
 967 }
 968
 969 static char *sysfs_scsi_attribute_path(struct sysfs_cxt *cxt,
 970                 char *buf, size_t bufsz, const char *attr)
 971 {
 972         int len, h, c, t, l;
 973
 974         if (sysfs_scsi_get_hctl(cxt, &h, &c, &t, &l) != 0)
 975                 return NULL;
 976
 977         if (attr)
 978                 len = snprintf(buf, bufsz, _PATH_SYS_SCSI "/devices/%d:%d:%d:%d/%s",
 979                                 h,c,t,l, attr);
 980         else
 981                 len = snprintf(buf, bufsz, _PATH_SYS_SCSI "/devices/%d:%d:%d:%d",
 982                                 h,c,t,l);
 983         return (len < 0 || (size_t) len >= bufsz) ? NULL : buf;
 984 }
 985
 986 int sysfs_scsi_has_attribute(struct sysfs_cxt *cxt, const char *attr)
 987 {
 988         char path[PATH_MAX];
 989         struct stat st;
 990
 991         if (!sysfs_scsi_attribute_path(cxt, path, sizeof(path), attr))
 992                 return 0;
 993
 994         return stat(path, &st) == 0;
 995 }
 996
 997 int sysfs_scsi_path_contains(struct sysfs_cxt *cxt, const char *pattern)
 998 {
 999         char path[PATH_MAX], linkc[PATH_MAX];
1000         struct stat st;
1001         ssize_t len;
1002
1003         if (!sysfs_scsi_attribute_path(cxt, path, sizeof(path), NULL))
1004                 return 0;
1005
1006         if (stat(path, &st) != 0)
1007                 return 0;
1008
1009         len = readlink(path, linkc, sizeof(linkc) - 1);
1010         if (len < 0)
1011                 return 0;
1012
1013         linkc[len] = '\0';
1014         return strstr(linkc, pattern) != NULL;
1015 }
1016
1017 #ifdef TEST_PROGRAM_SYSFS
1018 #include <errno.h>
1019 #include <err.h>
1020 #include <stdlib.h>
1021
1022 int main(int argc, char *argv[])
1023 {
1024         struct sysfs_cxt cxt = UL_SYSFSCXT_EMPTY;
1025         char *devname;
1026         dev_t devno, disk_devno;
1027         char path[PATH_MAX], *sub, *chain;
1028         char diskname[32];
1029         int i, is_part;
1030         uint64_t u64;
1031         ssize_t len;
1032
1033         if (argc != 2)
1034                 errx(EXIT_FAILURE, "usage: %s <devname>", argv[0]);
1035
1036         devname = argv[1];
1037         devno = sysfs_devname_to_devno(devname, NULL);
1038
1039         if (!devno)
1040                 err(EXIT_FAILURE, "failed to read devno");
1041
1042         if (sysfs_init(&cxt, devno, NULL))
1043                 return EXIT_FAILURE;
1044
1045         printf("NAME: %s\n", devname);
1046         printf("DEVNAME: %s\n", sysfs_get_devname(&cxt, path, sizeof(path)));
1047         printf("DEVPATH: %s\n", sysfs_devno_to_devpath(devno, path, sizeof(path)));
1048         printf("DEVNO: %u (%d:%d)\n", (unsigned int) devno, major(devno), minor(devno));
1049         printf("DEVNO-PATH: %s\n", sysfs_devno_path(devno, path, sizeof(path)));
1050
1051         sysfs_devno_to_wholedisk(devno, diskname, sizeof(diskname), &disk_devno);
1052         printf("WHOLEDISK-DEVNO: %u (%d:%d)\n", (unsigned int) disk_devno, major(disk_devno), minor(disk_devno));
1053         printf("WHOLEDISK-DEVNAME: %s\n", diskname);
1054
1055         is_part = sysfs_devno_has_attribute(devno, "partition");
1056         printf("PARTITION: %s\n", is_part ? "YES" : "NOT");
1057
1058         printf("HOTPLUG: %s\n", sysfs_is_hotpluggable(&cxt) ? "yes" : "no");
1059         printf("SLAVES: %d\n", sysfs_count_dirents(&cxt, "slaves"));
1060
1061         len = sysfs_readlink(&cxt, NULL, path, sizeof(path) - 1);
1062         if (len > 0) {
1063                 path[len] = '\0';
1064                 printf("DEVNOLINK: %s\n", path);
1065         }
1066
1067         if (!is_part) {
1068                 printf("First 5 partitions:\n");
1069                 for (i = 1; i <= 5; i++) {
1070                         dev_t dev = sysfs_partno_to_devno(&cxt, i);
1071                         if (dev)
1072                                 printf("\t#%d %d:%d\n", i, major(dev), minor(dev));
1073                 }
1074         }
1075
1076         if (sysfs_read_u64(&cxt, "size", &u64))
1077                 printf("read SIZE failed\n");
1078         else
1079                 printf("SIZE: %jd\n", u64);
1080
1081         if (sysfs_read_int(&cxt, "queue/hw_sector_size", &i))
1082                 printf("read SECTOR failed\n");
1083         else
1084                 printf("SECTOR: %d\n", i);
1085
1086
1087         chain = sysfs_get_devchain(&cxt, path, sizeof(path));
1088         printf("SUBSUSTEMS:\n");
1089
1090         while (chain && sysfs_next_subsystem(&cxt, chain, &sub) == 0) {
1091                 printf("\t%s\n", sub);
1092                 free(sub);
1093         }
1094
1095
1096         sysfs_deinit(&cxt);
1097         return EXIT_SUCCESS;
1098 }
1099 #endif