/src/util-linux/lib/loopdev.c

Source

/*
 * No copyright is claimed.  This code is in the public domain; do with
 * it what you wish.
 *
 * Written by Karel Zak <kzak@redhat.com>
 *
 * -- based on mount/losetup.c
 *
 * Simple library for work with loop devices.
 *
 *  - requires kernel 2.6.x
 *  - reads info from /sys/block/loop<N>/loop/<attr> (new kernels)
 *  - reads info by ioctl
 *  - supports *unlimited* number of loop devices
 *  - supports /dev/loop<N> as well as /dev/loop/<N>
 *  - minimize overhead (fd, loopinfo, ... are shared for all operations)
 *  - setup (associate device and backing file)
 *  - delete (dis-associate file)
 *  - old LOOP_{SET,GET}_STATUS (32bit) ioctls are unsupported
 *  - extendible
 */
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <inttypes.h>
#include <dirent.h>

#include "linux_version.h"
#include "c.h"
#include "timeutils.h"
#include "sysfs.h"
#include "pathnames.h"
#include "loopdev.h"
#include "canonicalize.h"
#include "blkdev.h"
#include "debug.h"
#include "fileutils.h"

#define LOOPDEV_MAX_TRIES 10

/*
 * Debug stuff (based on include/debug.h)
 */
static UL_DEBUG_DEFINE_MASK(loopdev);
UL_DEBUG_DEFINE_MASKNAMES(loopdev) = UL_DEBUG_EMPTY_MASKNAMES;

#define LOOPDEV_DEBUG_INIT  (1 << 1)
#define LOOPDEV_DEBUG_CXT (1 << 2)
#define LOOPDEV_DEBUG_ITER  (1 << 3)
#define LOOPDEV_DEBUG_SETUP (1 << 4)

#define DBG(m, x)   __UL_DBG(loopdev, LOOPDEV_DEBUG_, m, x)
#define DBG_OBJ(m, h, x)  __UL_DBG_OBJ(loopdev, LOOPDEV_DEBUG_, m, h, x)
#define ON_DBG(m, x)    __UL_DBG_CALL(loopdev, LOOPDEV_DEBUG_, m, x)

static void loopdev_init_debug(void)
{
  if (loopdev_debug_mask)
    return;
  __UL_INIT_DEBUG_FROM_ENV(loopdev, LOOPDEV_DEBUG_, 0, LOOPDEV_DEBUG);
}

/*
 * see loopcxt_init()
 */
#define loopcxt_ioctl_enabled(_lc)  (!((_lc)->flags & LOOPDEV_FL_NOIOCTL))
#define loopcxt_sysfs_available(_lc)  (!((_lc)->flags & LOOPDEV_FL_NOSYSFS)) \
           && !loopcxt_ioctl_enabled(_lc)

/*
 * Calls @x and repeat on EAGAIN
 */
#define repeat_on_eagain(x) __extension__ ({      \
    int _c = 0, _e;         \
    do {           \
      errno = 0;        \
      _e = x;         \
      if (_e == 0 || errno != EAGAIN)   \
        break;       \
      if (_c >= LOOPDEV_MAX_TRIES)   \
        break;       \
      xusleep(250000);      \
      _c++;         \
    } while (1);          \
    _e == 0 ? 0 : errno ? -errno : -1;   \
  })

/*
 * @lc: context
 * @device: device name, absolute device path or NULL to reset the current setting
 *
 * Sets device, absolute paths (e.g. "/dev/loop<N>") are unchanged, device
 * names ("loop<N>") are converted to the path (/dev/loop<N> or to
 * /dev/loop/<N>)
 *
 * This sets the device name, but does not check if the device exists!
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_set_device(struct loopdev_cxt *lc, const char *device)
{
  if (!lc)
    return -EINVAL;

  if (lc->fd >= 0) {
    close(lc->fd);
    DBG_OBJ(CXT, lc, ul_debug("closing old open fd"));
  }
  lc->fd = -1;
  lc->is_lost = 0;
  lc->devno = 0;
  lc->mode = O_RDONLY;
  lc->blocksize = 0;
  lc->has_info = 0;
  lc->info_failed = 0;
  *lc->device = '\0';
  memset(&lc->config, 0, sizeof(lc->config));

  /* set new */
  if (device) {
    if (*device != '/') {
      const char *dir = _PATH_DEV;

      /* compose device name for /dev/loop<n> or /dev/loop/<n> */
      if (lc->flags & LOOPDEV_FL_DEVSUBDIR) {
        if (strlen(device) < 5)
          return -1;
        device += 4;
        dir = _PATH_DEV_LOOP "/"; /* _PATH_DEV uses trailing slash */
      }
      snprintf(lc->device, sizeof(lc->device), "%s%s",
        dir, device);
    } else
      xstrncpy(lc->device, device, sizeof(lc->device));

    DBG_OBJ(CXT, lc, ul_debug("%s name assigned", device));
  }

  ul_unref_path(lc->sysfs);
  lc->sysfs = NULL;
  return 0;
}

int loopcxt_has_device(struct loopdev_cxt *lc)
{
  return lc && *lc->device;
}

dev_t loopcxt_get_devno(struct loopdev_cxt *lc)
{
  if (!lc || !loopcxt_has_device(lc))
    return 0;
  if (!lc->devno)
    lc->devno = sysfs_devname_to_devno(lc->device);
  return lc->devno;
}

int loopcxt_is_lost(struct loopdev_cxt *lc)
{
  if (!lc || !loopcxt_has_device(lc))
    return 0;
  if (lc->is_lost)
    return 1;

  lc->is_lost = access(lc->device, F_OK) != 0
      && loopcxt_get_devno(lc) != 0;

  return lc->is_lost;
}

/*
 * @lc: context
 * @flags: LOOPDEV_FL_* flags
 *
 * Initialize loop handler.
 *
 * We have two sets of the flags:
 *
 *  * LOOPDEV_FL_* flags control loopcxt_* API behavior
 *
 *  * LO_FLAGS_* are kernel flags used for LOOP_{SET,GET}_STAT64 ioctls
 *
 * Returns: <0 on error, 0 on success.
 */
int loopcxt_init(struct loopdev_cxt *lc, int flags)
{
  int rc;
  struct stat st;
  struct loopdev_cxt dummy = UL_LOOPDEVCXT_EMPTY;

  if (!lc)
    return -EINVAL;

  loopdev_init_debug();
  DBG_OBJ(CXT, lc, ul_debug("initialize context"));

  memcpy(lc, &dummy, sizeof(dummy));
  lc->flags = flags;

  rc = loopcxt_set_device(lc, NULL);
  if (rc)
    return rc;

  if (stat(_PATH_SYS_BLOCK, &st) || !S_ISDIR(st.st_mode)) {
    lc->flags |= LOOPDEV_FL_NOSYSFS;
    lc->flags &= ~LOOPDEV_FL_NOIOCTL;
    DBG_OBJ(CXT, lc, ul_debug("init: disable /sys usage"));
  }

  if (!(lc->flags & LOOPDEV_FL_NOSYSFS) &&
      get_linux_version() >= KERNEL_VERSION(2,6,37)) {
    /*
     * Use only sysfs for basic information about loop devices
     */
    lc->flags |= LOOPDEV_FL_NOIOCTL;
    DBG_OBJ(CXT, lc, ul_debug("init: ignore ioctls"));
  }

  if (!(lc->flags & LOOPDEV_FL_CONTROL) && !stat(_PATH_DEV_LOOPCTL, &st)) {
    lc->flags |= LOOPDEV_FL_CONTROL;
    DBG_OBJ(CXT, lc, ul_debug("init: loop-control detected "));
  }

  return 0;
}

/*
 * @lc: context
 *
 * Deinitialize loop context
 */
void loopcxt_deinit(struct loopdev_cxt *lc)
{
  int errsv = errno;

  if (!lc)
    return;

  DBG_OBJ(CXT, lc, ul_debug("de-initialize"));

  free(lc->filename);
  lc->filename = NULL;

  ignore_result( loopcxt_set_device(lc, NULL) );
  loopcxt_deinit_iterator(lc);

  errno = errsv;
}

/*
 * @lc: context
 *
 * Returns newly allocated device path.
 */
char *loopcxt_strdup_device(struct loopdev_cxt *lc)
{
  if (!lc || !*lc->device)
    return NULL;
  return strdup(lc->device);
}

/*
 * @lc: context
 *
 * Returns pointer device name in the @lc struct.
 */
const char *loopcxt_get_device(struct loopdev_cxt *lc)
{
  return lc && *lc->device ? lc->device : NULL;
}

/*
 * @lc: context
 *
 * Returns pointer to the sysfs context (see lib/sysfs.c)
 */
static struct path_cxt *loopcxt_get_sysfs(struct loopdev_cxt *lc)
{
  if (!lc || !*lc->device || (lc->flags & LOOPDEV_FL_NOSYSFS))
    return NULL;

  if (!lc->sysfs) {
    dev_t devno = loopcxt_get_devno(lc);
    if (!devno) {
      DBG_OBJ(CXT, lc, ul_debug("sysfs: failed devname to devno"));
      return NULL;
    }

    lc->sysfs = ul_new_sysfs_path(devno, NULL, NULL);
    if (!lc->sysfs)
      DBG_OBJ(CXT, lc, ul_debug("sysfs: init failed"));
  }

  return lc->sysfs;
}

static int __loopcxt_get_fd(struct loopdev_cxt *lc, mode_t mode)
{
  int old = -1;

  if (!lc || !*lc->device)
    return -EINVAL;

  /* It's okay to return a FD with read-write permissions if someone
   * asked for read-only, but you shouldn't do the opposite.
   *
   * (O_RDONLY is a widely usable default.)
   */
  if (lc->fd >= 0 && mode == O_RDWR && lc->mode == O_RDONLY) {
    DBG_OBJ(CXT, lc, ul_debug("closing already open device (mode mismatch)"));
    old = lc->fd;
    lc->fd = -1;
  }

  if (lc->fd < 0) {
    lc->mode = mode;
    lc->fd = open(lc->device, lc->mode | O_CLOEXEC);
    DBG_OBJ(CXT, lc, ul_debug("open %s [%s]: %m", lc->device,
        mode == O_RDONLY ? "ro" :
        mode == O_RDWR ? "rw" : "??"));

    if (lc->fd < 0 && old >= 0) {
      /* restore original on error */
      lc->fd = old;
      old = -1;
    }
  }

  if (old >= 0)
    close(old);
  return lc->fd;
}

/* default is read-only file descriptor, it's enough for all ioctls */
int loopcxt_get_fd(struct loopdev_cxt *lc)
{
  return __loopcxt_get_fd(lc, O_RDONLY);
}

/*
 * @lc: context
 * @flags: LOOPITER_FL_* flags
 *
 * Iterator can be used to scan list of the free or used loop devices.
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_init_iterator(struct loopdev_cxt *lc, int flags)
{
  struct loopdev_iter *iter;
  struct stat st;

  if (!lc)
    return -EINVAL;


  iter = &lc->iter;
  DBG_OBJ(ITER, iter, ul_debug("initialize"));

  /* always zeroize
   */
  memset(iter, 0, sizeof(*iter));
  iter->ncur = -1;
  iter->flags = flags;
  iter->default_check = 1;

  if (!lc->extra_check) {
    /*
     * Check for /dev/loop/<N> subdirectory
     */
    if (!(lc->flags & LOOPDEV_FL_DEVSUBDIR) &&
        stat(_PATH_DEV_LOOP, &st) == 0 && S_ISDIR(st.st_mode))
      lc->flags |= LOOPDEV_FL_DEVSUBDIR;

    lc->extra_check = 1;
  }
  return 0;
}

/*
 * @lc: context
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_deinit_iterator(struct loopdev_cxt *lc)
{
  struct loopdev_iter *iter;

  if (!lc)
    return -EINVAL;

  iter = &lc->iter;
  DBG_OBJ(ITER, iter, ul_debug("de-initialize"));

  free(iter->minors);
  if (iter->proc)
    fclose(iter->proc);
  if (iter->sysblock)
    closedir(iter->sysblock);

  memset(iter, 0, sizeof(*iter));
  return 0;
}

/*
 * Same as loopcxt_set_device, but also checks if the device is
 * associated with any file.
 *
 * Returns: <0 on error, 0 on success, 1 device does not match with
 *         LOOPITER_FL_{USED,FREE} flags.
 */
static int loopiter_set_device(struct loopdev_cxt *lc, const char *device)
{
  int rc = loopcxt_set_device(lc, device);
  int used;

  if (rc)
    return rc;

  if (!(lc->iter.flags & LOOPITER_FL_USED) &&
      !(lc->iter.flags & LOOPITER_FL_FREE))
    return 0; /* caller does not care about device status */

  used = loopcxt_get_offset(lc, NULL) == 0;

  if ((lc->iter.flags & LOOPITER_FL_USED) && used)
    return 0;

  if ((lc->iter.flags & LOOPITER_FL_FREE) && !used)
    return 0;

  DBG_OBJ(ITER, &lc->iter, ul_debug("failed to use %s device", lc->device));

  ignore_result( loopcxt_set_device(lc, NULL) );
  return 1;
}

static int cmpnum(const void *p1, const void *p2)
{
  return (((* (const int *) p1) > (* (const int *) p2)) -
      ((* (const int *) p1) < (* (const int *) p2)));
}

/*
 * The classic scandir() is more expensive and less portable.
 * We needn't full loop device names -- loop numbers (loop<N>)
 * are enough.
 */
static int loop_scandir(const char *dirname, int **ary, int hasprefix)
{
  DIR *dir;
  struct dirent *d;
  unsigned int n, count = 0, arylen = 0;

  if (!dirname || !ary)
    return 0;

  DBG(ITER, ul_debug("scan dir: %s", dirname));

  dir = opendir(dirname);
  if (!dir)
    return 0;
  free(*ary);
  *ary = NULL;

  while((d = readdir(dir))) {
#ifdef _DIRENT_HAVE_D_TYPE
    if (d->d_type != DT_BLK && d->d_type != DT_UNKNOWN &&
        d->d_type != DT_LNK)
      continue;
#endif
    if (is_dotdir_dirent(d))
      continue;

    if (hasprefix) {
      /* /dev/loop<N> */
      if (sscanf(d->d_name, "loop%u", &n) != 1)
        continue;
    } else {
      /* /dev/loop/<N> */
      char *end = NULL;

      errno = 0;
      n = strtol(d->d_name, &end, 10);
      if (d->d_name == end || (end && *end) || errno)
        continue;
    }
    if (n < LOOPDEV_DEFAULT_NNODES)
      continue;     /* ignore loop<0..7> */

    if (count + 1 > arylen) {
      int *tmp;

      arylen += 1;

      tmp = reallocarray(*ary, arylen, sizeof(int));
      if (!tmp) {
        free(*ary);
        *ary = NULL;
        closedir(dir);
        return -1;
      }
      *ary = tmp;
    }
    if (*ary)
      (*ary)[count++] = n;
  }
  if (count && *ary)
    qsort(*ary, count, sizeof(int), cmpnum);

  closedir(dir);
  return count;
}

/*
 * Set the next *used* loop device according to /proc/partitions.
 *
 * Loop devices smaller than 512 bytes are invisible for this function.
 */
static int loopcxt_next_from_proc(struct loopdev_cxt *lc)
{
  struct loopdev_iter *iter = &lc->iter;
  char buf[BUFSIZ];

  DBG_OBJ(ITER, iter, ul_debug("scan /proc/partitions"));

  if (!iter->proc)
    iter->proc = fopen(_PATH_PROC_PARTITIONS, "r" UL_CLOEXECSTR);
  if (!iter->proc)
    return 1;

  while (fgets(buf, sizeof(buf), iter->proc)) {
    unsigned int m;
    char name[128 + 1];


    if (sscanf(buf, " %u %*s %*s %128[^\n ]",
         &m, name) != 2 || m != LOOPDEV_MAJOR)
      continue;

    DBG_OBJ(ITER, iter, ul_debug("checking %s", name));

    if (loopiter_set_device(lc, name) == 0)
      return 0;
  }

  return 1;
}

/*
 * Set the next *used* loop device according to
 * /sys/block/loopN/loop/backing_file (kernel >= 2.6.37 is required).
 *
 * This is preferred method.
 */
static int loopcxt_next_from_sysfs(struct loopdev_cxt *lc)
{
  struct loopdev_iter *iter = &lc->iter;
  struct dirent *d;
  int fd;

  DBG_OBJ(ITER, iter, ul_debug("scanning /sys/block"));

  if (!iter->sysblock)
    iter->sysblock = opendir(_PATH_SYS_BLOCK);

  if (!iter->sysblock)
    return 1;

  fd = dirfd(iter->sysblock);

  while ((d = readdir(iter->sysblock))) {
    char name[NAME_MAX + 18 + 1];
    struct stat st;

    DBG_OBJ(ITER, iter, ul_debug("check %s", d->d_name));

    if (is_dotdir_dirent(d) || strncmp(d->d_name, "loop", 4) != 0)
      continue;

    snprintf(name, sizeof(name), "%s/loop/backing_file", d->d_name);
    if (fstatat(fd, name, &st, 0) != 0)
      continue;

    if (loopiter_set_device(lc, d->d_name) == 0)
      return 0;
  }

  return 1;
}

/*
 * @lc: context, has to initialized by loopcxt_init_iterator()
 *
 * Returns: 0 on success, < 0 on error, 1 at the end of scanning. The details
 *          about the current loop device are available by
 *          loopcxt_get_{fd,backing_file,device,offset, ...} functions.
 */
int loopcxt_next(struct loopdev_cxt *lc)
{
  struct loopdev_iter *iter;

  if (!lc)
    return -EINVAL;


  iter = &lc->iter;
  if (iter->done)
    return 1;

  DBG_OBJ(ITER, iter, ul_debug("next"));

  /* A) Look for used loop devices in /proc/partitions ("losetup -a" only)
   */
  if (iter->flags & LOOPITER_FL_USED) {
    int rc;

    if (loopcxt_sysfs_available(lc))
      rc = loopcxt_next_from_sysfs(lc);
    else
      rc = loopcxt_next_from_proc(lc);
    if (rc == 0)
      return 0;
    goto done;
  }

  /* B) Classic way, try first eight loop devices (default number
   *    of loop devices). This is enough for 99% of all cases.
   */
  if (iter->default_check) {
    DBG_OBJ(ITER, iter, ul_debug("next: default check"));
    for (++iter->ncur; iter->ncur < LOOPDEV_DEFAULT_NNODES;
              iter->ncur++) {
      char name[16];
      snprintf(name, sizeof(name), "loop%d", iter->ncur);

      if (loopiter_set_device(lc, name) == 0)
        return 0;
    }
    iter->default_check = 0;
  }

  /* C) the worst possibility, scan whole /dev or /dev/loop/<N>
   */
  if (!iter->minors) {
    DBG_OBJ(ITER, iter, ul_debug("next: scanning /dev"));
    iter->nminors = (lc->flags & LOOPDEV_FL_DEVSUBDIR) ?
      loop_scandir(_PATH_DEV_LOOP, &iter->minors, 0) :
      loop_scandir(_PATH_DEV, &iter->minors, 1);
    iter->ncur = -1;
  }
  for (++iter->ncur; iter->ncur < iter->nminors; iter->ncur++) {
    char name[16];
    snprintf(name, sizeof(name), "loop%d", iter->minors[iter->ncur]);

    if (loopiter_set_device(lc, name) == 0)
      return 0;
  }
done:
  loopcxt_deinit_iterator(lc);
  return 1;
}

/*
 * @device: path to device
 */
int is_loopdev(const char *device)
{
  struct stat st;
  int rc = 0;

  if (!device || stat(device, &st) != 0 || !S_ISBLK(st.st_mode))
    rc = 0;
  else if (major(st.st_rdev) == LOOPDEV_MAJOR)
    rc = 1;
  else if (sysfs_devno_is_wholedisk(st.st_rdev)) {
    /* It's possible that kernel creates a device with a different
     * major number ... check by /sys it's really loop device.
     */
    char name[PATH_MAX], *cn, *p = NULL;

    snprintf(name, sizeof(name), _PATH_SYS_DEVBLOCK "/%u:%u",
        major(st.st_rdev), minor(st.st_rdev));
    cn = ul_canonicalize_path(name);
    if (cn)
      p = stripoff_last_component(cn);
    rc = p && ul_startswith(p, "loop");
    free(cn);
  }

  if (rc == 0)
    errno = ENODEV;
  return rc;
}

/*
 * @lc: context
 *
 * Returns result from LOOP_GET_STAT64 ioctl or NULL on error.
 */
struct loop_info64 *loopcxt_get_info(struct loopdev_cxt *lc)
{
  int fd;

  if (!lc || lc->info_failed) {
    errno = EINVAL;
    return NULL;
  }
  errno = 0;
  if (lc->has_info)
    return &lc->config.info;

  fd = loopcxt_get_fd(lc);
  if (fd < 0)
    return NULL;

  if (ioctl(fd, LOOP_GET_STATUS64, &lc->config.info) == 0) {
    lc->has_info = 1;
    lc->info_failed = 0;
    DBG_OBJ(CXT, lc, ul_debug("reading loop_info64 OK"));
    return &lc->config.info;
  }

  lc->info_failed = 1;
  DBG_OBJ(CXT, lc, ul_debug("reading loop_info64 FAILED"));

  return NULL;
}

/*
 * @lc: context
 *
 * Returns (allocated) string with path to the file associated
 * with the current loop device.
 */
char *loopcxt_get_backing_file(struct loopdev_cxt *lc)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);
  char *res = NULL;

  if (sysfs)
    /*
     * This is always preferred, the loop_info64
     * has too small buffer for the filename.
     */
    ul_path_read_string(sysfs, &res, "loop/backing_file");

  if (!res && loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);

    if (lo) {
      lo->lo_file_name[LO_NAME_SIZE - 2] = '*';
      lo->lo_file_name[LO_NAME_SIZE - 1] = '\0';
      res = strdup((char *) lo->lo_file_name);
    }
  }

  DBG_OBJ(CXT, lc, ul_debug("get_backing_file [%s]", res));
  return res;
}

/*
 * @lc: context
 *
 * Returns (allocated) string with loop reference. The same as backing file by
 * default.
 */
char *loopcxt_get_refname(struct loopdev_cxt *lc)
{
  char *res = NULL;
  struct loop_info64 *lo = loopcxt_get_info(lc);

  if (lo) {
    lo->lo_file_name[LO_NAME_SIZE - 1] = '\0';
    res = strdup((char *) lo->lo_file_name);
  }

  DBG_OBJ(CXT, lc, ul_debug("get_refname [%s]", res));
  return res;
}

/*
 * @lc: context
 * @offset: returns offset number for the given device
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_offset(struct loopdev_cxt *lc, uint64_t *offset)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);
  int rc = -EINVAL;

  if (sysfs)
    if (ul_path_read_u64(sysfs, offset, "loop/offset") == 0)
      rc = 0;

  if (rc && loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);
    if (lo) {
      if (offset)
        *offset = lo->lo_offset;
      rc = 0;
    } else
      rc = -errno;
  }

  DBG_OBJ(CXT, lc, ul_debug("get_offset [rc=%d]", rc));
  return rc;
}

/*
 * @lc: context
 * @blocksize: returns logical blocksize for the given device
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_blocksize(struct loopdev_cxt *lc, uint64_t *blocksize)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);
  int rc = -EINVAL;

  if (sysfs)
    if (ul_path_read_u64(sysfs, blocksize, "queue/logical_block_size") == 0)
      rc = 0;

  /* Fallback based on BLKSSZGET ioctl */
  if (rc) {
    int fd = loopcxt_get_fd(lc);
    int sz = 0;

    if (fd < 0)
      return -EINVAL;
    rc = blkdev_get_sector_size(fd, &sz);
    if (rc)
      return rc;

    *blocksize = sz;
  }

  DBG_OBJ(CXT, lc, ul_debug("get_blocksize [rc=%d]", rc));
  return rc;
}

/*
 * @lc: context
 * @sizelimit: returns size limit for the given device
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_sizelimit(struct loopdev_cxt *lc, uint64_t *size)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);
  int rc = -EINVAL;

  if (sysfs)
    if (ul_path_read_u64(sysfs, size, "loop/sizelimit") == 0)
      rc = 0;

  if (rc && loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);
    if (lo) {
      if (size)
        *size = lo->lo_sizelimit;
      rc = 0;
    } else
      rc = -errno;
  }

  DBG_OBJ(CXT, lc, ul_debug("get_sizelimit [rc=%d]", rc));
  return rc;
}

/*
 * @lc: context
 * @type: returns encryption type
 *
 * Cryptoloop is DEPRECATED!
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_encrypt_type(struct loopdev_cxt *lc, uint32_t *type)
{
  struct loop_info64 *lo = loopcxt_get_info(lc);
  int rc;

  /* not provided by sysfs */
  if (lo) {
    if (type)
      *type = lo->lo_encrypt_type;
    rc = 0;
  } else
    rc = -errno;

  DBG_OBJ(CXT, lc, ul_debug("get_encrypt_type [rc=%d]", rc));
  return rc;
}

/*
 * @lc: context
 *
 * Cryptoloop is DEPRECATED!
 *
 * Returns: <0 on error, 0 on success
 */
const char *loopcxt_get_crypt_name(struct loopdev_cxt *lc)
{
  struct loop_info64 *lo = loopcxt_get_info(lc);

  if (lo)
    return (char *) lo->lo_crypt_name;

  DBG_OBJ(CXT, lc, ul_debug("get_crypt_name failed"));
  return NULL;
}

/*
 * @lc: context
 * @devno: returns backing file devno
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_backing_devno(struct loopdev_cxt *lc, dev_t *devno)
{
  struct loop_info64 *lo = loopcxt_get_info(lc);
  int rc;

  if (lo) {
    if (devno)
      *devno = lo->lo_device;
    rc = 0;
  } else
    rc = -errno;

  DBG_OBJ(CXT, lc, ul_debug("get_backing_devno [rc=%d]", rc));
  return rc;
}

/*
 * @lc: context
 * @ino: returns backing file inode
 *
 * Returns: <0 on error, 0 on success
 */
int loopcxt_get_backing_inode(struct loopdev_cxt *lc, ino_t *ino)
{
  struct loop_info64 *lo = loopcxt_get_info(lc);
  int rc;

  if (lo) {
    if (ino)
      *ino = lo->lo_inode;
    rc = 0;
  } else
    rc = -errno;

  DBG_OBJ(CXT, lc, ul_debug("get_backing_inode [rc=%d]", rc));
  return rc;
}

/*
 * Check if the kernel supports partitioned loop devices.
 *
 * Notes:
 *   - kernels < 3.2 support partitioned loop devices and PT scanning
 *     only if max_part= module parameter is non-zero
 *
 *   - kernels >= 3.2 always support partitioned loop devices
 *
 *   - kernels >= 3.2 always support BLKPG_{ADD,DEL}_PARTITION ioctls
 *
 *   - kernels >= 3.2 enable PT scanner only if max_part= is non-zero or if the
 *     LO_FLAGS_PARTSCAN flag is set for the device. The PT scanner is disabled
 *     by default.
 *
 *  See kernel commit e03c8dd14915fabc101aa495828d58598dc5af98.
 */
int loopmod_supports_partscan(void)
{
  int rc, ret = 0;
  FILE *f;

  if (get_linux_version() >= KERNEL_VERSION(3,2,0))
    return 1;

  f = fopen("/sys/module/loop/parameters/max_part", "r" UL_CLOEXECSTR);
  if (!f)
    return 0;
  rc = fscanf(f, "%d", &ret);
  fclose(f);
  return rc == 1 ? ret : 0;
}

/*
 * @lc: context
 *
 * Returns: 1 if the partscan flags is set *or* (for old kernels) partitions
 * scanning is enabled for all loop devices.
 */
int loopcxt_is_partscan(struct loopdev_cxt *lc)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);

  if (sysfs) {
    /* kernel >= 3.2 */
    int fl;
    if (ul_path_read_s32(sysfs, &fl, "loop/partscan") == 0)
      return fl;
  }

  /* old kernels (including kernels without loopN/loop/<flags> directory */
  return loopmod_supports_partscan();
}

/*
 * @lc: context
 *
 * Returns: 1 if the autoclear flags is set.
 */
int loopcxt_is_autoclear(struct loopdev_cxt *lc)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);

  if (sysfs) {
    int fl;
    if (ul_path_read_s32(sysfs, &fl, "loop/autoclear") == 0)
      return fl;
  }

  if (loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);
    if (lo)
      return lo->lo_flags & LO_FLAGS_AUTOCLEAR;
  }
  return 0;
}

/*
 * @lc: context
 *
 * Returns: 1 if the readonly flags is set.
 */
int loopcxt_is_readonly(struct loopdev_cxt *lc)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);

  if (sysfs) {
    int fl;
    if (ul_path_read_s32(sysfs, &fl, "ro") == 0)
      return fl;
  }

  if (loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);
    if (lo)
      return lo->lo_flags & LO_FLAGS_READ_ONLY;
  }
  return 0;
}

/*
 * @lc: context
 *
 * Returns: 1 if the dio flags is set.
 */
int loopcxt_is_dio(struct loopdev_cxt *lc)
{
  struct path_cxt *sysfs = loopcxt_get_sysfs(lc);

  if (sysfs) {
    int fl;
    if (ul_path_read_s32(sysfs, &fl, "loop/dio") == 0)
      return fl;
  }
  if (loopcxt_ioctl_enabled(lc)) {
    struct loop_info64 *lo = loopcxt_get_info(lc);
    if (lo)
      return lo->lo_flags & LO_FLAGS_DIRECT_IO;
  }
  return 0;
}

/*
 * @lc: context
 * @st: backing file stat or NULL
 * @backing_file: filename
 * @offset: offset (use LOOPDEV_FL_OFFSET if specified)
 * @sizelimit: size limit (use LOOPDEV_FL_SIZELIMIT if specified)
 * @flags: LOOPDEV_FL_{OFFSET,SIZELIMIT}
 *
 * Returns 1 if the current @lc loopdev is associated with the given backing
 * file. Note that the preferred way is to use devno and inode number rather
 * than filename. The @backing_file filename is poor solution usable in case
 * that you don't have rights to call stat().
 *
 * LOOPDEV_FL_SIZELIMIT requires LOOPDEV_FL_OFFSET being set as well.
 *
 * Don't forget that old kernels provide very restricted (in size) backing
 * filename by LOOP_GET_STAT64 ioctl only.
 */
int loopcxt_is_used(struct loopdev_cxt *lc,
        struct stat *st,
        const char *backing_file,
        uint64_t offset,
        uint64_t sizelimit,
        int flags)
{
  ino_t ino = 0;
  dev_t dev = 0;

  if (!lc)
    return 0;

  DBG_OBJ(CXT, lc, ul_debug("checking %s vs. %s",
        loopcxt_get_device(lc),
        backing_file));

  if (st && loopcxt_get_backing_inode(lc, &ino) == 0 &&
      loopcxt_get_backing_devno(lc, &dev) == 0) {

    if (ino == st->st_ino && dev == st->st_dev)
      goto found;

    /* don't use filename if we have devno and inode */
    return 0;
  }

  /* poor man's solution */
  if (backing_file) {
    char *name = loopcxt_get_backing_file(lc);
    int rc = name && strcmp(name, backing_file) == 0;

    free(name);
    if (rc)
      goto found;
  }

  return 0;
found:
  if (flags & LOOPDEV_FL_OFFSET) {
    uint64_t off = 0;

    int rc = loopcxt_get_offset(lc, &off) == 0 && off == offset;

    if (rc && flags & LOOPDEV_FL_SIZELIMIT) {
      uint64_t sz = 0;

      return loopcxt_get_sizelimit(lc, &sz) == 0 && sz == sizelimit;
    }
    return rc;
  }
  return 1;
}

/*
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 */
int loopcxt_set_offset(struct loopdev_cxt *lc, uint64_t offset)
{
  if (!lc)
    return -EINVAL;
  lc->config.info.lo_offset = offset;

  DBG_OBJ(CXT, lc, ul_debug("set offset=%"PRIu64, offset));
  return 0;
}

/*
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 */
int loopcxt_set_sizelimit(struct loopdev_cxt *lc, uint64_t sizelimit)
{
  if (!lc)
    return -EINVAL;
  lc->config.info.lo_sizelimit = sizelimit;

  DBG_OBJ(CXT, lc, ul_debug("set sizelimit=%"PRIu64, sizelimit));
  return 0;
}

/*
 * The blocksize will be used by loopcxt_set_device(). For already exiting
 * devices use  loopcxt_ioctl_blocksize().
 *
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 */
int loopcxt_set_blocksize(struct loopdev_cxt *lc, uint64_t blocksize)
{
  if (!lc)
    return -EINVAL;
  lc->blocksize = blocksize;

  DBG_OBJ(CXT, lc, ul_debug("set blocksize=%"PRIu64, blocksize));
  return 0;
}

/*
 * @lc: context
 * @flags: kernel LO_FLAGS_{READ_ONLY,USE_AOPS,AUTOCLEAR} flags
 *
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 *
 * Returns: 0 on success, <0 on error.
 */
int loopcxt_set_flags(struct loopdev_cxt *lc, uint32_t flags)
{
  if (!lc)
    return -EINVAL;
  lc->config.info.lo_flags = flags;

  DBG_OBJ(CXT, lc, ul_debug("set flags=%u", (unsigned) flags));
  return 0;
}

/*
 * @lc: context
 * @refname: reference name (used to overwrite lo_file_name where is backing
 *           file by default)
 *
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 *
 * Returns: 0 on success, <0 on error.
 */
int loopcxt_set_refname(struct loopdev_cxt *lc, const char *refname)
{
  if (!lc)
    return -EINVAL;

  memset(lc->config.info.lo_file_name, 0, sizeof(lc->config.info.lo_file_name));
  if (refname)
    xstrncpy((char *)lc->config.info.lo_file_name, refname, LO_NAME_SIZE);

  DBG_OBJ(CXT, lc, ul_debug("set refname=%s", (char *)lc->config.info.lo_file_name));
  return 0;
}

/*
 * @lc: context
 * @filename: backing file path (the path will be canonicalized)
 *
 * The setting is removed by loopcxt_set_device() loopcxt_next()!
 *
 * Returns: 0 on success, <0 on error.
 */
int loopcxt_set_backing_file(struct loopdev_cxt *lc, const char *filename)
{
  if (!lc)
    return -EINVAL;

  if (lc->flags & LOOPDEV_FL_NOFOLLOW)
    lc->filename = strdup(filename);
  else
    lc->filename = ul_canonicalize_path(filename);
  if (!lc->filename)
    return -errno;

  if (!lc->config.info.lo_file_name[0])
    loopcxt_set_refname(lc, lc->filename);

  DBG_OBJ(CXT, lc, ul_debug("set backing file=%s", lc->filename));
  return 0;
}

/*
 * In kernels prior to v3.9, if the offset or sizelimit options
 * are used, the block device's size won't be synced automatically.
 * blockdev --getsize64 and filesystems will use the backing
 * file size until the block device has been re-opened or the
 * LOOP_SET_CAPACITY ioctl is called to sync the sizes.
 *
 * Since mount -oloop uses the LO_FLAGS_AUTOCLEAR option and passes
 * the open file descriptor to the mount system call, we need to use
 * the ioctl. Calling losetup directly doesn't have this problem since
 * it closes the device when it exits and whatever consumes the device
 * next will re-open it, causing the resync.
 */
static int loopcxt_check_size(struct loopdev_cxt *lc, int file_fd)
{
  uint64_t size, expected_size;
  int dev_fd;
  struct stat st;

  if (!lc->config.info.lo_offset && !lc->config.info.lo_sizelimit)
    return 0;

  if (fstat(file_fd, &st)) {
    DBG_OBJ(CXT, lc, ul_debug("failed to fstat backing file"));
    return -errno;
  }
  if (S_ISBLK(st.st_mode)) {
    if (blkdev_get_size(file_fd,
        (unsigned long long *) &expected_size)) {
      DBG_OBJ(CXT, lc, ul_debug("failed to determine device size"));
      return -errno;
    }
  } else
    expected_size = st.st_size;

  if (expected_size == 0 || expected_size <= lc->config.info.lo_offset) {
    DBG_OBJ(CXT, lc, ul_debug("failed to determine expected size"));
    return 0; /* ignore this error */
  }

  if (lc->config.info.lo_offset > 0)
    expected_size -= lc->config.info.lo_offset;

  if (lc->config.info.lo_sizelimit > 0 && lc->config.info.lo_sizelimit < expected_size)
    expected_size = lc->config.info.lo_sizelimit;

  dev_fd = loopcxt_get_fd(lc);
  if (dev_fd < 0) {
    DBG_OBJ(CXT, lc, ul_debug("failed to get loop FD"));
    return -errno;
  }

  if (blkdev_get_size(dev_fd, (unsigned long long *) &size)) {
    DBG_OBJ(CXT, lc, ul_debug("failed to determine loopdev size"));
    return -errno;
  }

  /* It's block device, so, align to 512-byte sectors */
  if (expected_size % 512) {
    DBG_OBJ(CXT, lc, ul_debug("expected size misaligned to 512-byte sectors"));
    expected_size = (expected_size >> 9) << 9;
  }

  if (expected_size != size) {
    DBG_OBJ(CXT, lc, ul_debug("warning: loopdev and expected "
              "size mismatch (%ju/%ju)",
              size, expected_size));

    if (loopcxt_ioctl_capacity(lc)) {
      /* ioctl not available */
      if (errno == ENOTTY || errno == EINVAL)
        errno = ERANGE;
      return -errno;
    }

    if (blkdev_get_size(dev_fd, (unsigned long long *) &size))
      return -errno;

    if (expected_size != size) {
      errno = ERANGE;
      DBG_OBJ(CXT, lc, ul_debug("failed to set loopdev size, "
          "size: %ju, expected: %ju",
          size, expected_size));
      return -errno;
    }
  }

  return 0;
}


/*
 * @lc: context
 *
 * Associate the current device (see loopcxt_{set,get}_device()) with
 * a file (see loopcxt_set_backing_file()).
 *
 * The device is initialized read-write by default. If you want read-only
 * device then set LO_FLAGS_READ_ONLY by loopcxt_set_flags(). The LOOPDEV_FL_*
 * flags are ignored and modified according to LO_FLAGS_*.
 *
 * If the device is already open by loopcxt_get_fd() then this setup device
 * function will re-open the device to fix read/write mode.
 *
 * The device is also initialized read-only if the backing file is not
 * possible to open read-write (e.g. read-only FS).
 *
 * Returns: <0 on error, 0 on success.
 */
int loopcxt_setup_device(struct loopdev_cxt *lc)
{
  int file_fd, dev_fd;
  mode_t flags = O_CLOEXEC, mode = O_RDWR;
  int rc = -1, cnt = 0;
  int errsv = 0;
  int fallback = 0;

  if (!lc || !*lc->device || !lc->filename)
    return -EINVAL;

  DBG_OBJ(SETUP, lc, ul_debug("device setup requested"));

  /*
   * Open backing file and device
   */
  if (lc->config.info.lo_flags & LO_FLAGS_READ_ONLY)
    mode = O_RDONLY;

  if (lc->config.info.lo_flags & LO_FLAGS_DIRECT_IO)
    flags |= O_DIRECT;
  if (lc->flags & LOOPDEV_FL_NOFOLLOW)
    file_fd = ul_open_no_symlinks(lc->filename, mode | flags, 0);
  else
    file_fd = open(lc->filename, mode | flags);

  if (file_fd < 0 && mode != O_RDONLY
      && (errno == EROFS || errno == EACCES)) {
    mode = O_RDONLY;
    if (lc->flags & LOOPDEV_FL_NOFOLLOW)
      file_fd = ul_open_no_symlinks(lc->filename, mode | flags, 0);
    else
      file_fd = open(lc->filename, mode | flags);
  }
  if (file_fd < 0) {
    DBG_OBJ(SETUP, lc, ul_debug("open backing file failed: %m"));
    return -errno;
  }
  DBG_OBJ(SETUP, lc, ul_debug("backing file open: OK"));

  if (mode == O_RDONLY)
    lc->config.info.lo_flags |= LO_FLAGS_READ_ONLY; /* kernel loopdev mode */
  else
    lc->config.info.lo_flags &= ~LO_FLAGS_READ_ONLY;

  do {
    errno = 0;

    dev_fd = __loopcxt_get_fd(lc, mode);
    if (dev_fd >= 0 || lc->control_ok == 0)
      break;
    if (errno != EACCES && errno != ENOENT)
      break;
    /* We have permissions to open /dev/loop-control, but open
     * /dev/loopN failed with EACCES, it's probably because udevd
     * does not applied chown yet. Let's wait a moment. */
    xusleep(25000);
  } while (cnt++ < 16);

  if (dev_fd < 0) {
    rc = -errno;
    goto err;
  }

  DBG_OBJ(SETUP, lc, ul_debug("device open: OK"));

  /*
   * Atomic way to configure all by one ioctl call
   * -- since Linux v5.8-rc1, commit 3448914e8cc550ba792d4ccc74471d1ca4293aae
   */
  lc->config.fd = file_fd;
  if (lc->blocksize > 0)
    lc->config.block_size = lc->blocksize;

  rc = repeat_on_eagain( ioctl(dev_fd, LOOP_CONFIGURE, &lc->config) );
  if (rc != 0) {
    errsv = errno;
    if (errno != EINVAL && errno != ENOTTY && errno != ENOSYS) {
      DBG_OBJ(SETUP, lc, ul_debug("LOOP_CONFIGURE failed: %m"));
      goto err;
    }
    fallback = 1;
  } else {
    DBG_OBJ(SETUP, lc, ul_debug("LOOP_CONFIGURE: OK"));
  }

  /*
   * Old deprecated way; first assign backing file FD and then in the
   * second step set loop device properties.
   */
  if (fallback) {
    if (ioctl(dev_fd, LOOP_SET_FD, file_fd) < 0) {
      rc = -errno;
      errsv = errno;
      DBG_OBJ(SETUP, lc, ul_debug("LOOP_SET_FD failed: %m"));
      goto err;
    }

    DBG_OBJ(SETUP, lc, ul_debug("LOOP_SET_FD: OK"));

    if (lc->blocksize > 0
      && (rc = loopcxt_ioctl_blocksize(lc, lc->blocksize)) < 0) {
      errsv = -rc;
      goto err;
    }

    if ((rc = loopcxt_ioctl_status(lc)) < 0) {
      errsv = -rc;
      goto err;
    }
  }

  if ((rc = loopcxt_check_size(lc, file_fd)))
    goto err;

  close(file_fd);

  memset(&lc->config, 0, sizeof(lc->config));
  lc->has_info = 0;
  lc->info_failed = 0;

  DBG_OBJ(SETUP, lc, ul_debug("success [rc=0]"));
  return 0;
err:
  if (file_fd >= 0)
    close(file_fd);
  if (dev_fd >= 0 && rc != -EBUSY)
    ioctl(dev_fd, LOOP_CLR_FD, 0);
  if (errsv)
    errno = errsv;

  DBG_OBJ(SETUP, lc, ul_debug("failed [rc=%d]", rc));
  return rc;
}


/*
 * @lc: context
 *
 * Update status of the current device (see loopcxt_{set,get}_device()).
 *
 * Note that once initialized, kernel accepts only selected changes:
 * LO_FLAGS_AUTOCLEAR and LO_FLAGS_PARTSCAN
 * For more see linux/drivers/block/loop.c:loop_set_status()
 *
 * Returns: <0 on error, 0 on success.
 */
int loopcxt_ioctl_status(struct loopdev_cxt *lc)
{
  int dev_fd, rc;

  errno = 0;
  dev_fd = loopcxt_get_fd(lc);

  if (dev_fd < 0)
    return -errno;

  DBG_OBJ(SETUP, lc, ul_debug("calling LOOP_SET_STATUS64"));

  rc = repeat_on_eagain( ioctl(dev_fd, LOOP_SET_STATUS64, &lc->config.info) );
  if (rc != 0) {
    DBG_OBJ(SETUP, lc, ul_debug("LOOP_SET_STATUS64 failed: %m"));
    return rc;
  }

  DBG_OBJ(SETUP, lc, ul_debug("LOOP_SET_STATUS64: OK"));
  return 0;
}

int loopcxt_ioctl_capacity(struct loopdev_cxt *lc)
{
  int rc, fd = loopcxt_get_fd(lc);

  if (fd < 0)
    return -EINVAL;

  DBG_OBJ(SETUP, lc, ul_debug("calling LOOP_SET_CAPACITY"));

  /* Kernels prior to v2.6.30 don't support this ioctl */
  rc = repeat_on_eagain( ioctl(fd, LOOP_SET_CAPACITY, 0) );
  if (rc != 0) {
    DBG_OBJ(CXT, lc, ul_debug("LOOP_SET_CAPACITY failed: %m"));
    return rc;
  }

  DBG_OBJ(CXT, lc, ul_debug("capacity set"));
  return 0;
}

int loopcxt_ioctl_dio(struct loopdev_cxt *lc, unsigned long use_dio)
{
  int rc, fd = loopcxt_get_fd(lc);

  if (fd < 0)
    return -EINVAL;

  DBG_OBJ(SETUP, lc, ul_debug("calling LOOP_SET_DIRECT_IO"));

  /* Kernels prior to v4.4 don't support this ioctl */
  rc = repeat_on_eagain( ioctl(fd, LOOP_SET_DIRECT_IO, use_dio) );
  if (rc != 0) {
    DBG_OBJ(CXT, lc, ul_debug("LOOP_SET_DIRECT_IO failed: %m"));
    return rc;
  }

  DBG_OBJ(CXT, lc, ul_debug("direct io set"));
  return 0;
}

/*
 * Kernel uses "unsigned long" as ioctl arg, but we use u64 for all sizes to
 * keep loopdev internal API simple.
 */
int loopcxt_ioctl_blocksize(struct loopdev_cxt *lc, uint64_t blocksize)
{
  int rc, fd = loopcxt_get_fd(lc);

  if (fd < 0)
    return -EINVAL;

  DBG_OBJ(SETUP, lc, ul_debug("calling LOOP_SET_BLOCK_SIZE"));

  rc = repeat_on_eagain(
    ioctl(fd, LOOP_SET_BLOCK_SIZE, (unsigned long) blocksize) );
  if (rc != 0) {
    DBG_OBJ(CXT, lc, ul_debug("LOOP_SET_BLOCK_SIZE failed: %m"));
    return rc;
  }

  DBG_OBJ(CXT, lc, ul_debug("logical block size set"));
  return 0;
}

/*
 * @lc: context
 * @nr: returns loop device number
 *
 * Extracts the loop device number from the device path.
 * Supports both /dev/loop<N> and /dev/loop/<N> formats.
 *
 * Returns: 0 on success, <0 on error
 */
static int loopcxt_get_device_nr(struct loopdev_cxt *lc, int *nr)
{
  const char *p, *dev;
  int rc = -EINVAL;

  errno = 0;
  if (!lc || !nr)
    return rc;
  *nr = -1;

  dev = loopcxt_get_device(lc);
  if (!dev)
    goto done;

  p = strrchr(dev, '/');
  if (!p)
    goto done;

  if (sscanf(p, "/loop%d", nr) != 1 && sscanf(p, "/%d", nr) != 1)
    goto done;

  if (*nr < 0)
    goto done;
  rc = 0;
done:
  if (rc && !errno)
    errno = -rc;
  DBG_OBJ(CXT, lc, ul_debug("get_device_nr [nr=%d]", *nr));
  return rc;
}

int loopcxt_detach_device(struct loopdev_cxt *lc)
{
  int rc, fd = loopcxt_get_fd(lc);

  if (fd < 0)
    return -EINVAL;

  DBG_OBJ(SETUP, lc, ul_debug("calling LOOP_CLR_FD"));

  rc = repeat_on_eagain( ioctl(fd, LOOP_CLR_FD, 0) );
  if (rc != 0) {
    DBG_OBJ(CXT, lc, ul_debug("LOOP_CLR_FD failed: %m"));
    return rc;
  }

  DBG_OBJ(CXT, lc, ul_debug("device removed"));
  return 0;
}

int loopcxt_remove_device(struct loopdev_cxt *lc)
{
  int rc = -EINVAL;
  int ctl, nr = -1;

  if (!(lc->flags & LOOPDEV_FL_CONTROL)) {
    rc = -ENOSYS;
    goto done;
  }

  rc = loopcxt_get_device_nr(lc, &nr);
  if (rc)
    goto done;

  ctl = open(_PATH_DEV_LOOPCTL, O_RDWR|O_CLOEXEC);
  if (ctl >= 0) {
    DBG_OBJ(CXT, lc, ul_debug("remove_device %d", nr));
    rc = ioctl(ctl, LOOP_CTL_REMOVE, nr);
    close(ctl);
  }
  lc->control_ok = rc >= 0 ? 1 : 0;
done:
  DBG_OBJ(CXT, lc, ul_debug("remove_device done [rc=%d]", rc));
  return rc;
}

int loopcxt_add_device(struct loopdev_cxt *lc)
{
  int rc = -EINVAL;
  int ctl, nr = -1;

  if (!(lc->flags & LOOPDEV_FL_CONTROL)) {
    rc = -ENOSYS;
    goto done;
  }

  rc = loopcxt_get_device_nr(lc, &nr);
  if (rc)
    goto done;

  ctl = open(_PATH_DEV_LOOPCTL, O_RDWR|O_CLOEXEC);
  if (ctl >= 0) {
    DBG_OBJ(CXT, lc, ul_debug("add_device %d", nr));
    rc = ioctl(ctl, LOOP_CTL_ADD, nr);
    close(ctl);
  }
  lc->control_ok = rc >= 0 ? 1 : 0;
done:
  DBG_OBJ(CXT, lc, ul_debug("add_device done [rc=%d]", rc));
  return rc;
}

/*
 * Note that LOOP_CTL_GET_FREE ioctl is supported since kernel 3.1. In older
 * kernels we have to check all loop devices to found unused one.
 *
 * See kernel commit 770fe30a46a12b6fb6b63fbe1737654d28e8484.
 *
 * Returns: 0 = success, < 0 error
 */
int loopcxt_find_unused(struct loopdev_cxt *lc)
{
  int rc = -1;

  DBG_OBJ(CXT, lc, ul_debug("find_unused requested"));

  if (lc->flags & LOOPDEV_FL_CONTROL) {
    int ctl;

    DBG_OBJ(CXT, lc, ul_debug("using loop-control"));

    ctl = open(_PATH_DEV_LOOPCTL, O_RDWR|O_CLOEXEC);
    if (ctl >= 0)
      rc = ioctl(ctl, LOOP_CTL_GET_FREE);
    else
      rc = -errno;
    if (rc >= 0) {
      char name[16];
      snprintf(name, sizeof(name), "loop%d", rc);

      rc = loopiter_set_device(lc, name);
    }
    lc->control_ok = ctl >= 0 && rc == 0 ? 1 : 0;
    if (ctl >= 0)
      close(ctl);
    DBG_OBJ(CXT, lc, ul_debug("find_unused by loop-control [rc=%d]", rc));
  }

  if (rc < 0 && rc != -EACCES) {
    DBG_OBJ(CXT, lc, ul_debug("using loop scan"));
    rc = loopcxt_init_iterator(lc, LOOPITER_FL_FREE);
    if (rc)
      return rc;

    rc = loopcxt_next(lc);
    loopcxt_deinit_iterator(lc);
    DBG_OBJ(CXT, lc, ul_debug("find_unused by scan [rc=%d]", rc));
    if (rc)
      return -ENOENT;
  }
  return rc;
}



/*
 * Return: TRUE/FALSE
 */
int loopdev_is_autoclear(const char *device)
{
  struct loopdev_cxt lc;
  int rc;

  if (!device)
    return 0;

  rc = loopcxt_init(&lc, 0);
  if (!rc)
    rc = loopcxt_set_device(&lc, device);
  if (!rc)
    rc = loopcxt_is_autoclear(&lc);

  loopcxt_deinit(&lc);
  return rc;
}

char *loopdev_get_backing_file(const char *device)
{
  struct loopdev_cxt lc;
  char *res = NULL;

  if (!device)
    return NULL;
  if (loopcxt_init(&lc, 0))
    return NULL;
  if (loopcxt_set_device(&lc, device) == 0)
    res = loopcxt_get_backing_file(&lc);

  loopcxt_deinit(&lc);
  return res;
}

/*
 * Returns: TRUE/FALSE
 */
int loopdev_has_backing_file(const char *device)
{
  char *tmp = loopdev_get_backing_file(device);

  if (tmp) {
    free(tmp);
    return 1;
  }
  return 0;
}

/*
 * Returns: TRUE/FALSE
 */
int loopdev_is_used(const char *device, const char *filename,
        uint64_t offset, uint64_t sizelimit, int flags)
{
  struct loopdev_cxt lc;
  struct stat st;
  int rc = 0;

  if (!device || !filename)
    return 0;

  rc = loopcxt_init(&lc, 0);
  if (!rc)
    rc = loopcxt_set_device(&lc, device);
  if (rc)
    return rc;

  rc = !stat(filename, &st);
  rc = loopcxt_is_used(&lc, rc ? &st : NULL, filename, offset, sizelimit, flags);

  loopcxt_deinit(&lc);
  return rc;
}

/*
 * Returns: 0 = success, < 0 error
 */
int loopdev_detach(const char *device)
{
  struct loopdev_cxt lc;
  int rc;

  if (!device)
    return -EINVAL;

  rc = loopcxt_init(&lc, 0);
  if (!rc)
    rc = loopcxt_set_device(&lc, device);
  if (!rc)
    rc = loopcxt_detach_device(&lc);
  loopcxt_deinit(&lc);
  return rc;
}

/*
 * Returns: 0 = success, < 0 error, 1 not found
 */
int loopcxt_find_by_backing_file(struct loopdev_cxt *lc, const char *filename,
         uint64_t offset, uint64_t sizelimit, int flags)
{
  int rc, hasst;
  struct stat st;

  if (!filename)
    return -EINVAL;

  hasst = !stat(filename, &st);

  rc = loopcxt_init_iterator(lc, LOOPITER_FL_USED);
  if (rc)
    return rc;

  while ((rc = loopcxt_next(lc)) == 0) {

    if (loopcxt_is_used(lc, hasst ? &st : NULL,
            filename, offset, sizelimit, flags))
      break;
  }

  loopcxt_deinit_iterator(lc);
  return rc;
}

/*
 * Returns: 0 = not found, < 0 error, 1 found, 2 found full size and offset match
 */
int loopcxt_find_overlap(struct loopdev_cxt *lc, const char *filename,
         uint64_t offset, uint64_t sizelimit)
{
  int rc, hasst;
  struct stat st;

  if (!filename)
    return -EINVAL;

  DBG_OBJ(CXT, lc, ul_debug("find_overlap requested"));
  hasst = !stat(filename, &st);

  rc = loopcxt_init_iterator(lc, LOOPITER_FL_USED);
  if (rc)
    return rc;

  while ((rc = loopcxt_next(lc)) == 0) {
    uint64_t lc_sizelimit, lc_offset;

    rc = loopcxt_is_used(lc, hasst ? &st : NULL,
             filename, offset, sizelimit, 0);
    /*
     * Either the loopdev is unused or we've got an error which can
     * happen when we are racing with device autoclear. Just ignore
     * this loopdev...
     */
    if (rc <= 0)
      continue;

    DBG_OBJ(CXT, lc, ul_debug("found %s backed by %s",
      loopcxt_get_device(lc), filename));

    rc = loopcxt_get_offset(lc, &lc_offset);
    if (rc) {
      DBG_OBJ(CXT, lc, ul_debug("failed to get offset for device %s",
        loopcxt_get_device(lc)));
      continue;
    }
    rc = loopcxt_get_sizelimit(lc, &lc_sizelimit);
    if (rc) {
      DBG_OBJ(CXT, lc, ul_debug("failed to get sizelimit for device %s",
        loopcxt_get_device(lc)));
      continue;
    }

    /* full match */
    if (lc_sizelimit == sizelimit && lc_offset == offset) {
      DBG_OBJ(CXT, lc, ul_debug("overlapping loop device %s (full match)",
            loopcxt_get_device(lc)));
      rc = 2;
      goto found;
    }

    /* overlap */
    if (lc_sizelimit != 0 && offset >= lc_offset + lc_sizelimit)
      continue;
    if (sizelimit != 0 && offset + sizelimit <= lc_offset)
      continue;

    DBG_OBJ(CXT, lc, ul_debug("overlapping loop device %s",
      loopcxt_get_device(lc)));
      rc = 1;
      goto found;
  }

  if (rc == 1)
    rc = 0; /* not found */
found:
  loopcxt_deinit_iterator(lc);
  DBG_OBJ(CXT, lc, ul_debug("find_overlap done [rc=%d]", rc));
  return rc;
}

/*
 * Returns allocated string with device name
 */
char *loopdev_find_by_backing_file(const char *filename, uint64_t offset, uint64_t sizelimit, int flags)
{
  struct loopdev_cxt lc;
  char *res = NULL;

  if (!filename)
    return NULL;

  if (loopcxt_init(&lc, 0))
    return NULL;
  if (loopcxt_find_by_backing_file(&lc, filename, offset, sizelimit, flags) == 0)
    res = loopcxt_strdup_device(&lc);
  loopcxt_deinit(&lc);

  return res;
}

/*
 * Returns number of loop devices associated with @file, if only one loop
 * device is associated with the given @filename and @loopdev is not NULL then
 * @loopdev returns name of the device.
 */
int loopdev_count_by_backing_file(const char *filename, char **loopdev)
{
  struct loopdev_cxt lc;
  int count = 0, rc;

  if (!filename)
    return -1;

  rc = loopcxt_init(&lc, 0);
  if (rc)
    return rc;
  if (loopcxt_init_iterator(&lc, LOOPITER_FL_USED))
    return -1;

  while(loopcxt_next(&lc) == 0) {
    char *backing = loopcxt_get_backing_file(&lc);

    if (!backing || strcmp(backing, filename) != 0) {
      free(backing);
      continue;
    }

    free(backing);
    if (loopdev && count == 0)
      *loopdev = loopcxt_strdup_device(&lc);
    count++;
  }

  loopcxt_deinit(&lc);

  if (loopdev && count > 1) {
    free(*loopdev);
    *loopdev = NULL;
  }
  return count;
}

#ifdef TEST_PROGRAM_LOOPDEV
int main(int argc, char *argv[])
{
  if (argc < 2)
    goto usage;

  if (strcmp(argv[1], "--is-loopdev") == 0 && argc == 3)
    printf("%s: %s\n", argv[2], is_loopdev(argv[2]) ? "OK" : "FAIL");
  else
    goto usage;

  return EXIT_SUCCESS;
usage:
  fprintf(stderr, "usage: %1$s --is-loopdev <dev>\n",
      program_invocation_short_name);
  return EXIT_FAILURE;
}
#endif


Coverage Report

Created: 2026-08-30 07:13