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Add devlabel_dev to read volume labels from /dev/disk/by-label

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This commit is contained in:
Andrea Mazzoleni 2026-08-10 12:16:19 +02:00
parent f818d9426b
commit c4d509438f
1 changed files with 128 additions and 9 deletions
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137
cmdline/unixapp.c
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@ -1294,8 +1294,125 @@ static int devuuid_dev(uint64_t device, char* uuid, size_t uuid_size)
closedir(d);
return -1;
}
#endif
static int hexval(char c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'a' && c <= 'f')
return c - 'a' + 10;
if (c >= 'A' && c <= 'F')
return c - 'A' + 10;
return -1;
}
/**
* Decode udev \xNN hex escapes into raw string.
* Return 0 on success, -1 if truncated.
*/
static int udev_decode(char* dst, size_t dst_size, const char* src)
{
size_t i = 0;
while (*src != 0) {
if (i + 1 >= dst_size)
return -1;
if (src[0] == '\\' && src[1] == 'x' && src[2] != 0 && src[3] != 0) {
int h1 = hexval(src[2]);
int h2 = hexval(src[3]);
if (h1 >= 0 && h2 >= 0) {
dst[i++] = (char)((h1 << 4) | h2);
src += 4;
continue;
}
}
dst[i++] = *src++;
}
dst[i] = 0;
return 0;
}
/**
* Get the filesystem LABEL using the /dev/disk/by-label/ links.
*/
static int devlabel_dev(uint64_t device, char* label, size_t label_size)
{
ssize_t ret;
DIR* d;
struct dirent* dd;
struct stat st;
/* scan the LABEL directory searching for the device */
d = opendir("/dev/disk/by-label");
if (!d) {
/* LCOV_EXCL_START */
log_tag("label:by-label:%u:%u: opendir(/dev/disk/by-label) failed, %s\n", major(device), minor(device), strerror(errno));
/* directory missing?, likely we are not in Linux */
return -1;
/* LCOV_EXCL_STOP */
}
int dir_fd = dirfd(d);
if (dir_fd == -1) {
/* LCOV_EXCL_START */
log_tag("label:by-label:%u:%u: dirfd(/dev/disk/by-label) failed, %s\n", major(device), minor(device), strerror(errno));
closedir(d);
return -1;
/* LCOV_EXCL_STOP */
}
while ((dd = readdir(d)) != 0) {
/* skip "." and ".." files */
if (strcmp(dd->d_name, ".") == 0 || strcmp(dd->d_name, "..") == 0)
continue;
ret = fstatat(dir_fd, dd->d_name, &st, 0);
if (ret != 0) {
/* LCOV_EXCL_START */
log_tag("label:by-label:%u:%u: fstatat(%s) failed, %s\n", major(device), minor(device), dd->d_name, strerror(errno));
/* generic error, ignore and continue the search */
continue;
/* LCOV_EXCL_STOP */
}
/* if it matches, we have the label */
if (S_ISBLK(st.st_mode) && st.st_rdev == (dev_t)device) {
char buf[PATH_MAX];
char path[PATH_MAX];
/* resolve the link */
pathprint(path, sizeof(path), "/dev/disk/by-label/%s", dd->d_name);
ret = readlink(path, buf, sizeof(buf));
if (ret < 0 || ret >= PATH_MAX) {
/* LCOV_EXCL_START */
log_tag("label:by-label:%u:%u: readlink(/dev/disk/by-label/%s) failed, %s\n", major(device), minor(device), dd->d_name, strerror(errno));
/* generic error, ignore and continue the search */
continue;
/* LCOV_EXCL_STOP */
}
buf[ret] = 0;
/* found */
if (udev_decode(label, label_size, dd->d_name) != 0) {
/* LCOV_EXCL_START */
closedir(d);
return -1;
/* LCOV_EXCL_STOP */
}
log_tag("label:by-label:%u:%u:%s: found %s\n", major(device), minor(device), label, buf);
closedir(d);
return 0;
}
}
log_tag("label:by-label:%u:%u: /dev/disk/by-label doesn't contain a matching block device\n", major(device), minor(device));
/* not found */
closedir(d);
return -1;
}
#endif
/**
* Get the LABEL using the generic Linux FS_IOC_GETFSLABEL ioctl.
@ -1317,15 +1434,13 @@ static int devlabel_ioctl(const char* path, char* label, size_t label_size)
if (fd < 0 && (errno == ENOENT || errno == ENOTDIR)) {
char dir[PATH_MAX];
char* slash;
if (strlen(path) + 1 > sizeof(dir)) {
/* LCOV_EXCL_START */
return -1;
/* LCOV_EXCL_STOP */
}
strcpy(dir, path);
pathcpy(dir, sizeof(dir), path);
slash = strrchr(dir, '/');
if (slash) {
*slash = 0;
if (slash == dir)
slash[1] = 0;
else
*slash = 0;
fd = open(dir, O_RDONLY | O_DIRECTORY | O_CLOEXEC);
}
}
@ -1937,7 +2052,11 @@ int fsinfo(const char* path, int* has_persistent_inode, int* has_syncronized_har
if (fslabel) {
fslabel[0] = 0;
#if HAVE_LINUX_DEVICE
devlabel_ioctl(path, fslabel, fslabel_size);
if (devlabel_ioctl(path, fslabel, fslabel_size) != 0) {
struct stat fst;
if (stat(path, &fst) == 0)
devlabel_dev(fst.st_dev, fslabel, fslabel_size);
}
#else
(void)fslabel_size;
#endif