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* get_device_by_label.h
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* Copyright 1999 by Andries Brouwer
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* Copyright 1999, 2000 by Theodore Ts'o
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* This file may be redistributed under the terms of the GNU Public
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* Taken from aeb's mount, 990619
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* Updated from aeb's mount, 20000725
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* Added call to ext2fs_find_block_device, so that we can find devices
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* even if devfs (ugh) is compiled in, but not mounted, since
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* this messes up /proc/partitions, by TYT.
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#include <sys/types.h>
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#ifdef HAVE_SYS_MKDEV_H
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#include <sys/mkdev.h>
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#ifdef HAVE_SYS_SYSMACROS_H
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#include <sys/sysmacros.h>
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#include "nls-enable.h"
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#include "get_device_by_label.h"
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/* function prototype from libext2 */
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extern char *ext2fs_find_block_device(dev_t device);
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#define PROC_PARTITIONS "/proc/partitions"
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#define DEVLABELDIR "/dev"
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#define VG_DIR "/proc/lvm/VGs"
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#define EXT2_SUPER_MAGIC 0xEF53
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struct ext2_super_block {
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unsigned char s_dummy1[56];
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unsigned char s_magic[2];
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unsigned char s_dummy2[46];
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unsigned char s_uuid[16];
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unsigned char s_volume_name[16];
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#define ext2magic(s) ((unsigned int) s.s_magic[0] + (((unsigned int) s.s_magic[1]) << 8))
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#define XFS_SUPER_MAGIC "XFSB"
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struct xfs_super_block {
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unsigned char s_magic[4];
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unsigned char s_dummy[28];
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unsigned char s_uuid[16];
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unsigned char s_dummy2[60];
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unsigned char s_fname[12];
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static struct uuidCache_s {
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struct uuidCache_s *next;
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char *string_copy(const char *s)
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ret = malloc(strlen(s)+1);
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/* for now, only ext2 and xfs are supported */
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get_label_uuid(const char *device, char **label, char *uuid) {
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/* start with ext2 and xfs tests, taken from mount_guess_fstype */
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/* should merge these later */
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unsigned char *sb_uuid = 0, *sb_label = 0;
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struct ext2_super_block e2sb;
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struct xfs_super_block xfsb;
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fd = open(device, O_RDONLY);
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if (lseek(fd, 1024, SEEK_SET) == 1024
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&& read(fd, (char *) &e2sb, sizeof(e2sb)) == sizeof(e2sb)
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&& (ext2magic(e2sb) == EXT2_SUPER_MAGIC)) {
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sb_uuid = e2sb.s_uuid;
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sb_label = e2sb.s_volume_name;
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label_size = sizeof(e2sb.s_volume_name);
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} else if (lseek(fd, 0, SEEK_SET) == 0
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&& read(fd, (char *) &xfsb, sizeof(xfsb)) == sizeof(xfsb)
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&& strncmp((char *) &xfsb.s_magic, XFS_SUPER_MAGIC, 4) == 0) {
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sb_uuid = xfsb.s_uuid;
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sb_label = xfsb.s_fname;
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label_size = sizeof(xfsb.s_fname);
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memcpy(uuid, sb_uuid, sizeof(e2sb.s_uuid));
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if ((*label = calloc(label_size + 1, 1)) != NULL)
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memcpy(*label, sb_label, label_size);
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uuidcache_addentry(char *device, char *label, char *uuid) {
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struct uuidCache_s *last;
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last = uuidCache = malloc(sizeof(*uuidCache));
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for (last = uuidCache; last->next; last = last->next) ;
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last->next = malloc(sizeof(*uuidCache));
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last->device = device;
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memcpy(last->uuid, uuid, sizeof(last->uuid));
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* This function initializes the UUID cache with devices from the LVM
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* proc hierarchy. We currently depend on the names of the LVM
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* hierarchy giving us the device structure in /dev. (XXX is this a
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static void init_lvm(void)
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DIR *vg_dir, *lv_list;
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char *vdirname, *lvm_device;
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char uuid[16], *label, *vname, *lname;
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struct dirent *vg_iter, *lv_iter;
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if ((vg_dir = opendir(VG_DIR)) == NULL)
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while ((vg_iter = readdir(vg_dir)) != 0) {
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vname = vg_iter->d_name;
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if (!strcmp(vname, ".") || !strcmp(vname, ".."))
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vdirname = malloc(strlen(VG_DIR)+strlen(vname)+8);
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sprintf(vdirname, "%s/%s/LVs", VG_DIR, vname);
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lv_list = opendir(vdirname);
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while ((lv_iter = readdir(lv_list)) != 0) {
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lname = lv_iter->d_name;
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if (!strcmp(lname, ".") || !strcmp(lname, ".."))
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lvm_device = malloc(strlen(DEVLABELDIR) +
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sprintf(lvm_device, "%s/%s/%s", DEVLABELDIR,
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if (!get_label_uuid(lvm_device, &label, uuid)) {
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uuidcache_addentry(string_copy(lvm_device),
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uuidcache_init(void) {
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static char ptname[100];
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char uuid[16], *label, *devname;
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procpt = fopen(PROC_PARTITIONS, "r");
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for (firstPass = 1; firstPass >= 0; firstPass--) {
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fseek(procpt, 0, SEEK_SET);
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while (fgets(line, sizeof(line), procpt)) {
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if (sscanf (line, " %d %d %d %[^\n ]",
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&ma, &mi, &sz, ptname) != 4)
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/* skip extended partitions (heuristic: size 1) */
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/* look only at md devices on first pass */
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handleOnFirst = !strncmp(ptname, "md", 2);
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if (firstPass != handleOnFirst)
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/* skip entire disk (minor 0, 64, ... on ide;
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/* heuristic: partition name ends in a digit */
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for(s = ptname; *s; s++);
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if (isdigit(s[-1])) {
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* We first look in /dev for the device, but
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* if we don't find it, or if the stat
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* information doesn't check out, we use
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* ext2fs_find_block_device to find it.
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sprintf(device, "%s/%s", DEVLABELDIR, ptname);
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dev = makedev(ma, mi);
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if ((stat(device, &statbuf) < 0) ||
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(statbuf.st_rdev != dev)) {
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devname = ext2fs_find_block_device(dev);
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devname = string_copy(device);
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if (!get_label_uuid(devname, &label, uuid))
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uuidcache_addentry(devname, label, uuid);
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get_spec_by_x(int n, const char *t) {
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struct uuidCache_s *uc;
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if (!memcmp(t, uc->uuid, sizeof(uc->uuid)))
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return string_copy(uc->device);
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if (!strcmp(t, uc->label))
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return string_copy(uc->device);
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static char fromhex(char c)
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return (c - 'a' + 10);
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return (c - 'A' + 10);
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get_spec_by_uuid(const char *s)
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if (strlen(s) != 36 ||
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s[8] != '-' || s[13] != '-' || s[18] != '-' || s[23] != '-')
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for (i=0; i<16; i++) {
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if (!isxdigit(s[0]) || !isxdigit(s[1]))
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uuid[i] = ((fromhex(s[0])<<4) | fromhex(s[1]));
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return get_spec_by_x(UUID, uuid);
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fprintf(stderr, _("WARNING: %s: bad UUID"), s);
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get_spec_by_volume_label(const char *s) {
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return get_spec_by_x(VOL, s);
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get_volume_label_by_spec(const char *spec) {
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struct uuidCache_s *uc;
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if (!strcmp(spec, uc->device))
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* Interpret the device name if necessary.
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* Frees the pointer passed to it if we return a different device string.
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char *interpret_spec(char *spec)
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if (!strncmp(spec, "UUID=", 5))
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dev = get_spec_by_uuid(spec+5);
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else if (!strncmp(spec, "LABEL=", 6))
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dev = get_spec_by_volume_label(spec+6);
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dev = string_copy(spec);
added
removed
misc/get_device_by_label.c
