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systemd-mount: support discovery of loop backing file
``` $ suro systemd-mount /path/to/disk.img Started unit run-media-system-disk.img.mount for mount point: /run/media/system/disk.img ``` Closes #6226.
This commit is contained in:
Yu Watanabe
parent
601b08420d
commit
f0aac575fc
@ -83,7 +83,8 @@
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checker to execute a priori), and may make use of the auto-mounting logic.</para>
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<para>The command takes either one or two arguments. If only one argument is specified it should refer to a block
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device containing a file system (e.g. <literal>/dev/sdb1</literal>), which is then probed for a label and other
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device or regular file containing a file system (e.g. <literal>/dev/sdb1</literal> or
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<literal>/path/to/disk.img</literal>). If it is a block device, which is then probed for a label and other
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metadata, and is mounted to a directory whose name is generated from the label. In this mode the block device must
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exist at the time of invocation of the command, so that it may be probed. If the device is found to be a removable
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block device (e.g. a USB stick) an automount point instead of a regular mount point is created (i.e. the
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@ -636,6 +636,125 @@ static int start_transient_automount(
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return 0;
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}
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static int find_mount_points(const char *what, char ***list) {
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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_cleanup_strv_free_ char **l = NULL;
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size_t bufsize = 0, n = 0;
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assert(what);
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assert(list);
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/* Returns all mount points obtained from /proc/self/mountinfo in *list,
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* and the number of mount points as return value. */
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proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
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if (!proc_self_mountinfo)
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return log_error_errno(errno, "Can't open /proc/self/mountinfo: %m");
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for (;;) {
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_cleanup_free_ char *path = NULL, *where = NULL, *dev = NULL;
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int r;
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r = fscanf(proc_self_mountinfo,
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"%*s " /* (1) mount id */
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"%*s " /* (2) parent id */
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"%*s " /* (3) major:minor */
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"%*s " /* (4) root */
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"%ms " /* (5) mount point */
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"%*s" /* (6) mount options */
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"%*[^-]" /* (7) optional fields */
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"- " /* (8) separator */
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"%*s " /* (9) file system type */
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"%ms" /* (10) mount source */
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"%*s" /* (11) mount options 2 */
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"%*[^\n]", /* some rubbish at the end */
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&path, &dev);
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if (r != 2) {
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if (r == EOF)
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break;
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continue;
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}
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if (!streq(what, dev))
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continue;
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r = cunescape(path, UNESCAPE_RELAX, &where);
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if (r < 0)
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continue;
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/* one extra slot is needed for the terminating NULL */
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if (!GREEDY_REALLOC(l, bufsize, n + 2))
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return log_oom();
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l[n] = strdup(where);
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if (!l[n])
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return log_oom();
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n++;
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}
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l[n] = NULL;
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*list = l;
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l = NULL; /* avoid freeing */
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return n;
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}
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static int find_loop_device(const char *backing_file, char **loop_dev) {
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_cleanup_closedir_ DIR *d = NULL;
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struct dirent *de;
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_cleanup_free_ char *l = NULL;
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assert(backing_file);
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assert(loop_dev);
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d = opendir("/sys/devices/virtual/block");
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if (!d) {
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if (errno == ENOENT)
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return -ENOENT;
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return log_error_errno(errno, "Can't open directory /sys/devices/virtual/block: %m");
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}
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FOREACH_DIRENT(de, d, return -errno) {
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_cleanup_free_ char *sys = NULL, *fname = NULL;
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int r;
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dirent_ensure_type(d, de);
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if (de->d_type != DT_DIR)
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continue;
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if (!startswith(de->d_name, "loop"))
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continue;
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sys = strjoin("/sys/devices/virtual/block/", de->d_name, "/loop/backing_file");
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if (!sys)
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return log_oom();
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r = read_one_line_file(sys, &fname);
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if (r < 0)
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continue;
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if (files_same(fname, backing_file, 0) <= 0)
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continue;
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l = strjoin("/dev/", de->d_name);
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if (!l)
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return log_oom();
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break;
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}
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if (!l)
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return -ENOENT;
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*loop_dev = l;
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l = NULL; /* avoid freeing */
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return 0;
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}
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static int stop_mount(
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sd_bus *bus,
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const char *where,
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@ -729,64 +848,13 @@ static int stop_mounts(
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return 0;
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}
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static int umount_by_mountinfo(sd_bus *bus, const char *what) {
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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int r, r2 = 0;
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proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
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if (!proc_self_mountinfo)
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return -errno;
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for (;;) {
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_cleanup_free_ char *path = NULL, *where = NULL, *dev = NULL;
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int k;
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k = fscanf(proc_self_mountinfo,
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"%*s " /* (1) mount id */
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"%*s " /* (2) parent id */
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"%*s " /* (3) major:minor */
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"%*s " /* (4) root */
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"%ms " /* (5) mount point */
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"%*s" /* (6) mount options */
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"%*[^-]" /* (7) optional fields */
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"- " /* (8) separator */
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"%*s " /* (9) file system type */
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"%ms" /* (10) mount source */
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"%*s" /* (11) mount options 2 */
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"%*[^\n]", /* some rubbish at the end */
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&path, &dev);
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if (k != 2) {
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if (k == EOF)
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break;
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continue;
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}
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if (!streq(what, dev))
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continue;
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r = cunescape(path, UNESCAPE_RELAX, &where);
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if (r < 0) {
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r2 = r;
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continue;
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}
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r = stop_mounts(bus, where);
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if (r < 0) {
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r2 = r;
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continue;
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}
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}
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return r2;
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}
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static int umount_by_device(sd_bus *bus, const char *what) {
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_cleanup_udev_device_unref_ struct udev_device *d = NULL;
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_cleanup_udev_unref_ struct udev *udev = NULL;
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_cleanup_free_ char *where = NULL;
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_cleanup_strv_free_ char **list = NULL;
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struct stat st;
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const char *v;
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char **l;
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int r, r2 = 0;
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assert(what);
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@ -814,78 +882,33 @@ static int umount_by_device(sd_bus *bus, const char *what) {
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}
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v = udev_device_get_property_value(d, "SYSTEMD_MOUNT_WHERE");
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if (!isempty(v)) {
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where = strdup(v);
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if (!where)
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return log_oom();
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r2 = stop_mounts(bus, where);
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}
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if (!isempty(v))
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r2 = stop_mounts(bus, v);
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v = udev_device_get_devnode(d);
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if (!isempty(v)) {
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r = umount_by_mountinfo(bus, v);
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r = find_mount_points(what, &list);
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if (r < 0)
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return r;
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for (l = list; *l; l++) {
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r = stop_mounts(bus, *l);
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if (r < 0)
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return r;
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r2 = r;
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}
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return r2;
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}
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static int umount_loop(sd_bus *bus, const char *backing_file) {
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_cleanup_closedir_ DIR *d = NULL;
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struct dirent *de;
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int r, r2 = 0;
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bool found = false;
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_cleanup_free_ char *loop_dev = NULL;
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int r;
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assert(backing_file);
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d = opendir("/sys/devices/virtual/block");
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if (!d) {
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if (errno == ENOENT)
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return log_error_errno(errno, "File %s is not mounted.", backing_file);
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return log_error_errno(errno, "Can't open directory /sys/devices/virtual/block: %m");
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}
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r = find_loop_device(backing_file, &loop_dev);
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if (r < 0)
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return log_error_errno(r, r == -ENOENT ? "File %s is not mounted." : "Can't get loop device for %s: %m", backing_file);
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FOREACH_DIRENT(de, d, return -errno) {
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_cleanup_free_ char *sys = NULL, *what = NULL, *fname = NULL;
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dirent_ensure_type(d, de);
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if (de->d_type != DT_DIR)
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continue;
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if (!startswith(de->d_name, "loop"))
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continue;
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sys = strjoin("/sys/devices/virtual/block/", de->d_name, "/loop/backing_file");
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if (!sys)
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return log_oom();
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r = read_one_line_file(sys, &fname);
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if (r < 0) {
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if (r != -ENOENT)
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r2 = log_error_errno(r, "Can't read %s: %m", sys);
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continue;
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}
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if (!files_same(fname, backing_file, 0))
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continue;
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found = true;
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what = strjoin("/dev/", de->d_name);
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if (!what)
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return log_oom();
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r = umount_by_device(bus, what);
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if (r < 0)
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r2 = r;
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}
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if (!found)
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return log_error_errno(ENOENT, "File %s is not mounted.", backing_file);
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return r2;
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return umount_by_device(bus, loop_dev);
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}
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static int action_umount(
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@ -1019,6 +1042,8 @@ static int acquire_mount_where(struct udev_device *d) {
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}
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escaped = xescape(name, "\\");
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if (!escaped)
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return log_oom();
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if (!filename_is_valid(escaped))
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return 0;
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@ -1033,6 +1058,32 @@ static int acquire_mount_where(struct udev_device *d) {
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return 1;
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}
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static int acquire_mount_where_for_loop_dev(const char *loop_dev) {
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_cleanup_strv_free_ char **list = NULL;
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int r;
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if (arg_mount_where)
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return 0;
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r = find_mount_points(loop_dev, &list);
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if (r < 0)
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return r;
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else if (r == 0) {
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log_error("Can't find mount point of %s. It is expected that %s is already mounted on a place.", loop_dev, loop_dev);
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return -EINVAL;
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} else if (r >= 2) {
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log_error("%s is mounted on %d places. It is expected that %s is mounted on a place.", loop_dev, r, loop_dev);
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return -EINVAL;
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}
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arg_mount_where = strdup(list[0]);
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if (!arg_mount_where)
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return log_oom();
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log_debug("Discovered where=%s", arg_mount_where);
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return 1;
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}
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static int acquire_description(struct udev_device *d) {
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const char *model, *label;
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@ -1104,6 +1155,79 @@ static int acquire_removable(struct udev_device *d) {
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return 1;
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}
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static int discover_loop_backing_file(void) {
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_cleanup_udev_device_unref_ struct udev_device *d = NULL;
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_cleanup_udev_unref_ struct udev *udev = NULL;
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_cleanup_free_ char *loop_dev = NULL;
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struct stat st;
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const char *v;
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int r;
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r = find_loop_device(arg_mount_what, &loop_dev);
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if (r < 0 && r != -ENOENT)
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return log_error_errno(errno, "Can't get loop device for %s: %m", arg_mount_what);
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if (r == -ENOENT) {
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_cleanup_free_ char *escaped = NULL;
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if (arg_mount_where)
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return 0;
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escaped = xescape(basename(arg_mount_what), "\\");
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if (!escaped)
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return log_oom();
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if (!filename_is_valid(escaped))
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return -EINVAL;
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arg_mount_where = strjoin("/run/media/system/", escaped);
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if (!arg_mount_where)
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return log_oom();
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log_debug("Discovered where=%s", arg_mount_where);
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return 0;
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}
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if (stat(loop_dev, &st) < 0)
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return log_error_errno(errno, "Can't stat %s: %m", loop_dev);
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if (!S_ISBLK(st.st_mode)) {
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log_error("Invalid file type: %s", loop_dev);
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return -EINVAL;
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}
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udev = udev_new();
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if (!udev)
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return log_oom();
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d = udev_device_new_from_devnum(udev, 'b', st.st_rdev);
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if (!d)
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return log_oom();
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v = udev_device_get_property_value(d, "ID_FS_USAGE");
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if (!streq_ptr(v, "filesystem")) {
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log_error("%s does not contain a known file system.", arg_mount_what);
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return -EINVAL;
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}
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r = acquire_mount_type(d);
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if (r < 0)
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return r;
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r = acquire_mount_options(d);
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if (r < 0)
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return r;
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r = acquire_mount_where_for_loop_dev(loop_dev);
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if (r < 0)
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return r;
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r = acquire_description(d);
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if (r < 0)
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return r;
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return 0;
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}
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static int discover_device(void) {
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_cleanup_udev_device_unref_ struct udev_device *d = NULL;
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_cleanup_udev_unref_ struct udev *udev = NULL;
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@ -1111,20 +1235,15 @@ static int discover_device(void) {
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const char *v;
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int r;
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if (!arg_discover)
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return 0;
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if (!is_device_path(arg_mount_what)) {
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log_error("Discovery only supported for block devices, don't know what to do.");
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return -EINVAL;
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}
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if (stat(arg_mount_what, &st) < 0)
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return log_error_errno(errno, "Can't stat %s: %m", arg_mount_what);
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if (S_ISREG(st.st_mode))
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return discover_loop_backing_file();
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if (!S_ISBLK(st.st_mode)) {
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log_error("Path %s is not a block device, don't know what to do.", arg_mount_what);
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return -ENOTBLK;
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log_error("Invalid file type: %s", arg_mount_what);
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return -EINVAL;
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}
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udev = udev_new();
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@ -1371,9 +1490,20 @@ int main(int argc, char* argv[]) {
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goto finish;
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}
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r = discover_device();
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if (r < 0)
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path_kill_slashes(arg_mount_what);
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if (!path_is_safe(arg_mount_what)) {
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log_error("Path contains unsafe components: %s", arg_mount_what);
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r = -EINVAL;
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goto finish;
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}
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if (arg_discover) {
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r = discover_device();
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if (r < 0)
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goto finish;
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}
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if (!arg_mount_where) {
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log_error("Can't figure out where to mount %s.", arg_mount_what);
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r = -EINVAL;
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@ -1389,7 +1519,7 @@ int main(int argc, char* argv[]) {
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}
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if (!path_is_safe(arg_mount_where)) {
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log_error("Path contains unsafe components.");
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log_error("Path contains unsafe components: %s", arg_mount_where);
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r = -EINVAL;
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goto finish;
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}
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