src/shared/loop-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #if HAVE_VALGRIND_MEMCHECK_H
   4 #include <valgrind/memcheck.h>
   5 #endif
   6
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <linux/blkpg.h>
  10 #include <linux/fs.h>
  11 #include <linux/loop.h>
  12 #include <sys/file.h>
  13 #include <sys/ioctl.h>
  14 #include <unistd.h>
  15
  16 #include "sd-device.h"
  17
  18 #include "alloc-util.h"
  19 #include "blockdev-util.h"
  20 #include "device-util.h"
  21 #include "errno-util.h"
  22 #include "fd-util.h"
  23 #include "fileio.h"
  24 #include "loop-util.h"
  25 #include "missing_loop.h"
  26 #include "parse-util.h"
  27 #include "random-util.h"
  28 #include "stat-util.h"
  29 #include "stdio-util.h"
  30 #include "string-util.h"
  31 #include "tmpfile-util.h"
  32
  33 static void cleanup_clear_loop_close(int *fd) {
  34         if (*fd < 0)
  35                 return;
  36
  37         (void) ioctl(*fd, LOOP_CLR_FD);
  38         (void) safe_close(*fd);
  39 }
  40
  41 static int loop_is_bound(int fd) {
  42         struct loop_info64 info;
  43
  44         assert(fd >= 0);
  45
  46         if (ioctl(fd, LOOP_GET_STATUS64, &info) < 0) {
  47                 if (errno == ENXIO)
  48                         return false; /* not bound! */
  49
  50                 return -errno;
  51         }
  52
  53         return true; /* bound! */
  54 }
  55
  56 static int device_has_block_children(sd_device *d) {
  57         _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
  58         const char *main_sn, *main_ss;
  59         sd_device *q;
  60         int r;
  61
  62         assert(d);
  63
  64         /* Checks if the specified device currently has block device children (i.e. partition block
  65          * devices). */
  66
  67         r = sd_device_get_sysname(d, &main_sn);
  68         if (r < 0)
  69                 return r;
  70
  71         r = sd_device_get_subsystem(d, &main_ss);
  72         if (r < 0)
  73                 return r;
  74
  75         if (!streq(main_ss, "block"))
  76                 return -EINVAL;
  77
  78         r = sd_device_enumerator_new(&e);
  79         if (r < 0)
  80                 return r;
  81
  82         r = sd_device_enumerator_allow_uninitialized(e);
  83         if (r < 0)
  84                 return r;
  85
  86         r = sd_device_enumerator_add_match_parent(e, d);
  87         if (r < 0)
  88                 return r;
  89
  90         FOREACH_DEVICE(e, q) {
  91                 const char *ss, *sn;
  92
  93                 r = sd_device_get_subsystem(q, &ss);
  94                 if (r < 0)
  95                         continue;
  96
  97                 if (!streq(ss, "block"))
  98                         continue;
  99
 100                 r = sd_device_get_sysname(q, &sn);
 101                 if (r < 0)
 102                         continue;
 103
 104                 if (streq(sn, main_sn))
 105                         continue;
 106
 107                 return 1; /* we have block device children */
 108         }
 109
 110         return 0;
 111 }
 112
 113 static int loop_configure(
 114                 int fd,
 115                 int nr,
 116                 const struct loop_config *c,
 117                 bool *try_loop_configure) {
 118
 119         _cleanup_(sd_device_unrefp) sd_device *d = NULL;
 120         _cleanup_free_ char *sysname = NULL;
 121         _cleanup_close_ int lock_fd = -1;
 122         int r;
 123
 124         assert(fd >= 0);
 125         assert(nr >= 0);
 126         assert(c);
 127         assert(try_loop_configure);
 128
 129         if (asprintf(&sysname, "loop%i", nr) < 0)
 130                 return -ENOMEM;
 131
 132         r = sd_device_new_from_subsystem_sysname(&d, "block", sysname);
 133         if (r < 0)
 134                 return r;
 135
 136         /* Let's lock the device before we do anything. We take the BSD lock on a second, separately opened
 137          * fd for the device. udev after all watches for close() events (specifically IN_CLOSE_WRITE) on
 138          * block devices to reprobe them, hence by having a separate fd we will later close() we can ensure
 139          * we trigger udev after everything is done. If we'd lock our own fd instead and keep it open for a
 140          * long time udev would possibly never run on it again, even though the fd is unlocked, simply
 141          * because we never close() it. It also has the nice benefit we can use the _cleanup_close_ logic to
 142          * automatically release the lock, after we are done. */
 143         lock_fd = fd_reopen(fd, O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
 144         if (lock_fd < 0)
 145                 return lock_fd;
 146         if (flock(lock_fd, LOCK_EX) < 0)
 147                 return -errno;
 148
 149         /* Let's see if the device is really detached, i.e. currently has no associated partition block
 150          * devices. On various kernels (such as 5.8) it is possible to have a loopback block device that
 151          * superficially is detached but still has partition block devices associated for it. They only go
 152          * away when the device is reattached. (Yes, LOOP_CLR_FD doesn't work then, because officially
 153          * nothing is attached and LOOP_CTL_REMOVE doesn't either, since it doesn't care about partition
 154          * block devices. */
 155         r = device_has_block_children(d);
 156         if (r < 0)
 157                 return r;
 158         if (r > 0) {
 159                 r = loop_is_bound(fd);
 160                 if (r < 0)
 161                         return r;
 162                 if (r > 0)
 163                         return -EBUSY;
 164
 165                 return -EUCLEAN; /* Bound but children? Tell caller to reattach something so that the
 166                                   * partition block devices are gone too. */
 167         }
 168
 169         if (*try_loop_configure) {
 170                 if (ioctl(fd, LOOP_CONFIGURE, c) < 0) {
 171                         /* Do fallback only if LOOP_CONFIGURE is not supported, propagate all other
 172                          * errors. Note that the kernel is weird: non-existing ioctls currently return EINVAL
 173                          * rather than ENOTTY on loopback block devices. They should fix that in the kernel,
 174                          * but in the meantime we accept both here. */
 175                         if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL)
 176                                 return -errno;
 177
 178                         *try_loop_configure = false;
 179                 } else {
 180                         bool good = true;
 181
 182                         if (c->info.lo_sizelimit != 0) {
 183                                 /* Kernel 5.8 vanilla doesn't properly propagate the size limit into the
 184                                  * block device. If it's used, let's immediately check if it had the desired
 185                                  * effect hence. And if not use classic LOOP_SET_STATUS64. */
 186                                 uint64_t z;
 187
 188                                 if (ioctl(fd, BLKGETSIZE64, &z) < 0) {
 189                                         r = -errno;
 190                                         goto fail;
 191                                 }
 192
 193                                 if (z != c->info.lo_sizelimit) {
 194                                         log_debug("LOOP_CONFIGURE is broken, doesn't honour .lo_sizelimit. Falling back to LOOP_SET_STATUS64.");
 195                                         good = false;
 196                                 }
 197                         }
 198
 199                         if (FLAGS_SET(c->info.lo_flags, LO_FLAGS_PARTSCAN)) {
 200                                 /* Kernel 5.8 vanilla doesn't properly propagate the partition scanning flag
 201                                  * into the block device. Let's hence verify if things work correctly here
 202                                  * before returning. */
 203
 204                                 r = blockdev_partscan_enabled(fd);
 205                                 if (r < 0)
 206                                         goto fail;
 207                                 if (r == 0) {
 208                                         log_debug("LOOP_CONFIGURE is broken, doesn't honour LO_FLAGS_PARTSCAN. Falling back to LOOP_SET_STATUS64.");
 209                                         good = false;
 210                                 }
 211                         }
 212
 213                         if (!good) {
 214                                 /* LOOP_CONFIGURE doesn't work. Remember that. */
 215                                 *try_loop_configure = false;
 216
 217                                 /* We return EBUSY here instead of retrying immediately with LOOP_SET_FD,
 218                                  * because LOOP_CLR_FD is async: if the operation cannot be executed right
 219                                  * away it just sets the autoclear flag on the device. This means there's a
 220                                  * good chance we cannot actually reuse the loopback device right-away. Hence
 221                                  * let's assume it's busy, avoid the trouble and let the calling loop call us
 222                                  * again with a new, likely unused device. */
 223                                 r = -EBUSY;
 224                                 goto fail;
 225                         }
 226
 227                         return 0;
 228                 }
 229         }
 230
 231         /* Since kernel commit 5db470e229e22b7eda6e23b5566e532c96fb5bc3 (kernel v5.0) the LOOP_SET_STATUS64
 232          * ioctl can return EAGAIN in case we change the lo_offset field, if someone else is accessing the
 233          * block device while we try to reconfigure it. This is a pretty common case, since udev might
 234          * instantly start probing the device as soon as we attach an fd to it. Hence handle it in two ways:
 235          * first, let's take the BSD lock that that ensures that udev will not step in between the point in
 236          * time where we attach the fd and where we reconfigure the device. Secondly, let's wait 50ms on
 237          * EAGAIN and retry. The former should be an efficient mechanism to avoid we have to wait 50ms
 238          * needlessly if we are just racing against udev. The latter is protection against all other cases,
 239          * i.e. peers that do not take the BSD lock. */
 240
 241         if (ioctl(fd, LOOP_SET_FD, c->fd) < 0)
 242                 return -errno;
 243
 244         for (unsigned n_attempts = 0;;) {
 245                 if (ioctl(fd, LOOP_SET_STATUS64, &c->info) >= 0)
 246                         break;
 247                 if (errno != EAGAIN || ++n_attempts >= 64) {
 248                         r = log_debug_errno(errno, "Failed to configure loopback device: %m");
 249                         goto fail;
 250                 }
 251
 252                 /* Sleep some random time, but at least 10ms, at most 250ms. Increase the delay the more
 253                  * failed attempts we see */
 254                 (void) usleep(UINT64_C(10) * USEC_PER_MSEC +
 255                               random_u64() % (UINT64_C(240) * USEC_PER_MSEC * n_attempts/64));
 256         }
 257
 258         return 0;
 259
 260 fail:
 261         (void) ioctl(fd, LOOP_CLR_FD);
 262         return r;
 263 }
 264
 265 static int attach_empty_file(int loop, int nr) {
 266         _cleanup_close_ int fd = -1;
 267
 268         /* So here's the thing: on various kernels (5.8 at least) loop block devices might enter a state
 269          * where they are detached but nonetheless have partitions, when used heavily. Accessing these
 270          * partitions results in immediatey IO errors. There's no pretty way to get rid of them
 271          * again. Neither LOOP_CLR_FD nor LOOP_CTL_REMOVE suffice (see above). What does work is to
 272          * reassociate them with a new fd however. This is what we do here hence: we associate the devices
 273          * with an empty file (i.e. an image that definitely has no partitions). We then immediately clear it
 274          * again. This suffices to make the partitions go away. Ugly but appears to work. */
 275
 276         log_debug("Found unattached loopback block device /dev/loop%i with partitions. Attaching empty file to remove them.", nr);
 277
 278         fd = open_tmpfile_unlinkable(NULL, O_RDONLY);
 279         if (fd < 0)
 280                 return fd;
 281
 282         if (flock(loop, LOCK_EX) < 0)
 283                 return -errno;
 284
 285         if (ioctl(loop, LOOP_SET_FD, fd) < 0)
 286                 return -errno;
 287
 288         if (ioctl(loop, LOOP_SET_STATUS64, &(struct loop_info64) {
 289                                 .lo_flags = LO_FLAGS_READ_ONLY|
 290                                             LO_FLAGS_AUTOCLEAR|
 291                                             LO_FLAGS_PARTSCAN, /* enable partscan, so that the partitions really go away */
 292                         }) < 0)
 293                 return -errno;
 294
 295         if (ioctl(loop, LOOP_CLR_FD) < 0)
 296                 return -errno;
 297
 298         /* The caller is expected to immediately close the loopback device after this, so that the BSD lock
 299          * is released, and udev sees the changes. */
 300         return 0;
 301 }
 302
 303 int loop_device_make(
 304                 int fd,
 305                 int open_flags,
 306                 uint64_t offset,
 307                 uint64_t size,
 308                 uint32_t loop_flags,
 309                 LoopDevice **ret) {
 310
 311         _cleanup_free_ char *loopdev = NULL;
 312         bool try_loop_configure = true;
 313         struct loop_config config;
 314         LoopDevice *d = NULL;
 315         struct stat st;
 316         int nr = -1, r;
 317
 318         assert(fd >= 0);
 319         assert(ret);
 320         assert(IN_SET(open_flags, O_RDWR, O_RDONLY));
 321
 322         if (fstat(fd, &st) < 0)
 323                 return -errno;
 324
 325         if (S_ISBLK(st.st_mode)) {
 326                 if (ioctl(fd, LOOP_GET_STATUS64, &config.info) >= 0) {
 327                         /* Oh! This is a loopback device? That's interesting! */
 328
 329 #if HAVE_VALGRIND_MEMCHECK_H
 330                         /* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
 331                         VALGRIND_MAKE_MEM_DEFINED(&config.info, sizeof(config.info));
 332 #endif
 333                         nr = config.info.lo_number;
 334
 335                         if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
 336                                 return -ENOMEM;
 337                 }
 338
 339                 if (offset == 0 && IN_SET(size, 0, UINT64_MAX)) {
 340                         _cleanup_close_ int copy = -1;
 341
 342                         /* If this is already a block device, store a copy of the fd as it is */
 343
 344                         copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
 345                         if (copy < 0)
 346                                 return -errno;
 347
 348                         d = new(LoopDevice, 1);
 349                         if (!d)
 350                                 return -ENOMEM;
 351                         *d = (LoopDevice) {
 352                                 .fd = TAKE_FD(copy),
 353                                 .nr = nr,
 354                                 .node = TAKE_PTR(loopdev),
 355                                 .relinquished = true, /* It's not allocated by us, don't destroy it when this object is freed */
 356                         };
 357
 358                         *ret = d;
 359                         return d->fd;
 360                 }
 361         } else {
 362                 r = stat_verify_regular(&st);
 363                 if (r < 0)
 364                         return r;
 365         }
 366
 367         _cleanup_close_ int control = -1;
 368         _cleanup_(cleanup_clear_loop_close) int loop_with_fd = -1;
 369
 370         control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
 371         if (control < 0)
 372                 return -errno;
 373
 374         config = (struct loop_config) {
 375                 .fd = fd,
 376                 .info = {
 377                         /* Use the specified flags, but configure the read-only flag from the open flags, and force autoclear */
 378                         .lo_flags = (loop_flags & ~LO_FLAGS_READ_ONLY) | ((open_flags & O_ACCMODE) == O_RDONLY ? LO_FLAGS_READ_ONLY : 0) | LO_FLAGS_AUTOCLEAR,
 379                         .lo_offset = offset,
 380                         .lo_sizelimit = size == UINT64_MAX ? 0 : size,
 381                 },
 382         };
 383
 384         /* Loop around LOOP_CTL_GET_FREE, since at the moment we attempt to open the returned device it might
 385          * be gone already, taken by somebody else racing against us. */
 386         for (unsigned n_attempts = 0;;) {
 387                 _cleanup_close_ int loop = -1;
 388
 389                 nr = ioctl(control, LOOP_CTL_GET_FREE);
 390                 if (nr < 0)
 391                         return -errno;
 392
 393                 if (asprintf(&loopdev, "/dev/loop%i", nr) < 0)
 394                         return -ENOMEM;
 395
 396                 loop = open(loopdev, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
 397                 if (loop < 0) {
 398                         /* Somebody might've gotten the same number from the kernel, used the device,
 399                          * and called LOOP_CTL_REMOVE on it. Let's retry with a new number. */
 400                         if (!IN_SET(errno, ENOENT, ENXIO))
 401                                 return -errno;
 402                 } else {
 403                         r = loop_configure(loop, nr, &config, &try_loop_configure);
 404                         if (r >= 0) {
 405                                 loop_with_fd = TAKE_FD(loop);
 406                                 break;
 407                         }
 408                         if (r == -EUCLEAN) {
 409                                 /* Make left-over partition disappear hack (see above) */
 410                                 r = attach_empty_file(loop, nr);
 411                                 if (r < 0 && r != -EBUSY)
 412                                         return r;
 413                         } else if (r != -EBUSY)
 414                                 return r;
 415                 }
 416
 417                 if (++n_attempts >= 64) /* Give up eventually */
 418                         return -EBUSY;
 419
 420                 loopdev = mfree(loopdev);
 421
 422                 /* Wait some random time, to make collision less likely. Let's pick a random time in the
 423                  * range 0ms…250ms, linearly scaled by the number of failed attempts. */
 424                 (void) usleep(random_u64() % (UINT64_C(10) * USEC_PER_MSEC +
 425                                               UINT64_C(240) * USEC_PER_MSEC * n_attempts/64));
 426         }
 427
 428         d = new(LoopDevice, 1);
 429         if (!d)
 430                 return -ENOMEM;
 431         *d = (LoopDevice) {
 432                 .fd = TAKE_FD(loop_with_fd),
 433                 .node = TAKE_PTR(loopdev),
 434                 .nr = nr,
 435         };
 436
 437         *ret = d;
 438         return 0;
 439 }
 440
 441 int loop_device_make_by_path(const char *path, int open_flags, uint32_t loop_flags, LoopDevice **ret) {
 442         _cleanup_close_ int fd = -1;
 443         int r;
 444
 445         assert(path);
 446         assert(ret);
 447         assert(open_flags < 0 || IN_SET(open_flags, O_RDWR, O_RDONLY));
 448
 449         /* Passing < 0 as open_flags here means we'll try to open the device writable if we can, retrying
 450          * read-only if we cannot. */
 451
 452         fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|(open_flags >= 0 ? open_flags : O_RDWR));
 453         if (fd < 0) {
 454                 r = -errno;
 455
 456                 /* Retry read-only? */
 457                 if (open_flags >= 0 || !(ERRNO_IS_PRIVILEGE(r) || r == -EROFS))
 458                         return r;
 459
 460                 fd = open(path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_RDONLY);
 461                 if (fd < 0)
 462                         return r; /* Propagate original error */
 463
 464                 open_flags = O_RDONLY;
 465         } else if (open_flags < 0)
 466                 open_flags = O_RDWR;
 467
 468         return loop_device_make(fd, open_flags, 0, 0, loop_flags, ret);
 469 }
 470
 471 LoopDevice* loop_device_unref(LoopDevice *d) {
 472         if (!d)
 473                 return NULL;
 474
 475         if (d->fd >= 0) {
 476                 /* Implicitly sync the device, since otherwise in-flight blocks might not get written */
 477                 if (fsync(d->fd) < 0)
 478                         log_debug_errno(errno, "Failed to sync loop block device, ignoring: %m");
 479
 480                 if (d->nr >= 0 && !d->relinquished) {
 481                         if (ioctl(d->fd, LOOP_CLR_FD) < 0)
 482                                 log_debug_errno(errno, "Failed to clear loop device: %m");
 483
 484                 }
 485
 486                 safe_close(d->fd);
 487         }
 488
 489         if (d->nr >= 0 && !d->relinquished) {
 490                 _cleanup_close_ int control = -1;
 491
 492                 control = open("/dev/loop-control", O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
 493                 if (control < 0)
 494                         log_warning_errno(errno,
 495                                           "Failed to open loop control device, cannot remove loop device %s: %m",
 496                                           strna(d->node));
 497                 else
 498                         for (unsigned n_attempts = 0;;) {
 499                                 if (ioctl(control, LOOP_CTL_REMOVE, d->nr) >= 0)
 500                                         break;
 501                                 if (errno != EBUSY || ++n_attempts >= 64) {
 502                                         log_warning_errno(errno, "Failed to remove device %s: %m", strna(d->node));
 503                                         break;
 504                                 }
 505                                 (void) usleep(50 * USEC_PER_MSEC);
 506                         }
 507         }
 508
 509         free(d->node);
 510         return mfree(d);
 511 }
 512
 513 void loop_device_relinquish(LoopDevice *d) {
 514         assert(d);
 515
 516         /* Don't attempt to clean up the loop device anymore from this point on. Leave the clean-ing up to the kernel
 517          * itself, using the loop device "auto-clear" logic we already turned on when creating the device. */
 518
 519         d->relinquished = true;
 520 }
 521
 522 int loop_device_open(const char *loop_path, int open_flags, LoopDevice **ret) {
 523         _cleanup_close_ int loop_fd = -1;
 524         _cleanup_free_ char *p = NULL;
 525         struct loop_info64 info;
 526         struct stat st;
 527         LoopDevice *d;
 528         int nr;
 529
 530         assert(loop_path);
 531         assert(ret);
 532
 533         loop_fd = open(loop_path, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|open_flags);
 534         if (loop_fd < 0)
 535                 return -errno;
 536
 537         if (fstat(loop_fd, &st) < 0)
 538                 return -errno;
 539         if (!S_ISBLK(st.st_mode))
 540                 return -ENOTBLK;
 541
 542         if (ioctl(loop_fd, LOOP_GET_STATUS64, &info) >= 0) {
 543 #if HAVE_VALGRIND_MEMCHECK_H
 544                 /* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
 545                 VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
 546 #endif
 547                 nr = info.lo_number;
 548         } else
 549                 nr = -1;
 550
 551         p = strdup(loop_path);
 552         if (!p)
 553                 return -ENOMEM;
 554
 555         d = new(LoopDevice, 1);
 556         if (!d)
 557                 return -ENOMEM;
 558
 559         *d = (LoopDevice) {
 560                 .fd = TAKE_FD(loop_fd),
 561                 .nr = nr,
 562                 .node = TAKE_PTR(p),
 563                 .relinquished = true, /* It's not ours, don't try to destroy it when this object is freed */
 564         };
 565
 566         *ret = d;
 567         return d->fd;
 568 }
 569
 570 static int resize_partition(int partition_fd, uint64_t offset, uint64_t size) {
 571         char sysfs[STRLEN("/sys/dev/block/:/partition") + 2*DECIMAL_STR_MAX(dev_t) + 1];
 572         _cleanup_free_ char *whole = NULL, *buffer = NULL;
 573         uint64_t current_offset, current_size, partno;
 574         _cleanup_close_ int whole_fd = -1;
 575         struct stat st;
 576         dev_t devno;
 577         int r;
 578
 579         assert(partition_fd >= 0);
 580
 581         /* Resizes the partition the loopback device refer to (assuming it refers to one instead of an actual
 582          * loopback device), and changes the offset, if needed. This is a fancy wrapper around
 583          * BLKPG_RESIZE_PARTITION. */
 584
 585         if (fstat(partition_fd, &st) < 0)
 586                 return -errno;
 587
 588         assert(S_ISBLK(st.st_mode));
 589
 590         xsprintf(sysfs, "/sys/dev/block/%u:%u/partition", major(st.st_rdev), minor(st.st_rdev));
 591         r = read_one_line_file(sysfs, &buffer);
 592         if (r == -ENOENT) /* not a partition, cannot resize */
 593                 return -ENOTTY;
 594         if (r < 0)
 595                 return r;
 596         r = safe_atou64(buffer, &partno);
 597         if (r < 0)
 598                 return r;
 599
 600         xsprintf(sysfs, "/sys/dev/block/%u:%u/start", major(st.st_rdev), minor(st.st_rdev));
 601
 602         buffer = mfree(buffer);
 603         r = read_one_line_file(sysfs, &buffer);
 604         if (r < 0)
 605                 return r;
 606         r = safe_atou64(buffer, &current_offset);
 607         if (r < 0)
 608                 return r;
 609         if (current_offset > UINT64_MAX/512U)
 610                 return -EINVAL;
 611         current_offset *= 512U;
 612
 613         if (ioctl(partition_fd, BLKGETSIZE64, &current_size) < 0)
 614                 return -EINVAL;
 615
 616         if (size == UINT64_MAX && offset == UINT64_MAX)
 617                 return 0;
 618         if (current_size == size && current_offset == offset)
 619                 return 0;
 620
 621         xsprintf(sysfs, "/sys/dev/block/%u:%u/../dev", major(st.st_rdev), minor(st.st_rdev));
 622
 623         buffer = mfree(buffer);
 624         r = read_one_line_file(sysfs, &buffer);
 625         if (r < 0)
 626                 return r;
 627         r = parse_dev(buffer, &devno);
 628         if (r < 0)
 629                 return r;
 630
 631         r = device_path_make_major_minor(S_IFBLK, devno, &whole);
 632         if (r < 0)
 633                 return r;
 634
 635         whole_fd = open(whole, O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
 636         if (whole_fd < 0)
 637                 return -errno;
 638
 639         struct blkpg_partition bp = {
 640                 .pno = partno,
 641                 .start = offset == UINT64_MAX ? current_offset : offset,
 642                 .length = size == UINT64_MAX ? current_size : size,
 643         };
 644
 645         struct blkpg_ioctl_arg ba = {
 646                 .op = BLKPG_RESIZE_PARTITION,
 647                 .data = &bp,
 648                 .datalen = sizeof(bp),
 649         };
 650
 651         if (ioctl(whole_fd, BLKPG, &ba) < 0)
 652                 return -errno;
 653
 654         return 0;
 655 }
 656
 657 int loop_device_refresh_size(LoopDevice *d, uint64_t offset, uint64_t size) {
 658         struct loop_info64 info;
 659         assert(d);
 660
 661         /* Changes the offset/start of the loop device relative to the beginning of the underlying file or
 662          * block device. If this loop device actually refers to a partition and not a loopback device, we'll
 663          * try to adjust the partition offsets instead.
 664          *
 665          * If either offset or size is UINT64_MAX we won't change that parameter. */
 666
 667         if (d->fd < 0)
 668                 return -EBADF;
 669
 670         if (d->nr < 0) /* not a loopback device */
 671                 return resize_partition(d->fd, offset, size);
 672
 673         if (ioctl(d->fd, LOOP_GET_STATUS64, &info) < 0)
 674                 return -errno;
 675
 676 #if HAVE_VALGRIND_MEMCHECK_H
 677         /* Valgrind currently doesn't know LOOP_GET_STATUS64. Remove this once it does */
 678         VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
 679 #endif
 680
 681         if (size == UINT64_MAX && offset == UINT64_MAX)
 682                 return 0;
 683         if (info.lo_sizelimit == size && info.lo_offset == offset)
 684                 return 0;
 685
 686         if (size != UINT64_MAX)
 687                 info.lo_sizelimit = size;
 688         if (offset != UINT64_MAX)
 689                 info.lo_offset = offset;
 690
 691         if (ioctl(d->fd, LOOP_SET_STATUS64, &info) < 0)
 692                 return -errno;
 693
 694         return 0;
 695 }
 696
 697 int loop_device_flock(LoopDevice *d, int operation) {
 698         assert(d);
 699
 700         if (d->fd < 0)
 701                 return -EBADF;
 702
 703         if (flock(d->fd, operation) < 0)
 704                 return -errno;
 705
 706         return 0;
 707 }
 708
 709 int loop_device_sync(LoopDevice *d) {
 710         assert(d);
 711
 712         /* We also do this implicitly in loop_device_unref(). Doing this explicitly here has the benefit that
 713          * we can check the return value though. */
 714
 715         if (d->fd < 0)
 716                 return -EBADF;
 717
 718         if (fsync(d->fd) < 0)
 719                 return -errno;
 720
 721         return 0;
 722 }