1 /*
2 * realpath.c - realpath() aware of device mapper
3 * Originated from the util-linux project.
4 */
5
6 #ifdef HAVE_CONFIG_H
7 #include "config.h"
8 #endif
9
10 #include <stdlib.h>
11 #include <stdio.h>
12 #include <string.h>
13
14 #ifdef HAVE_LIMITS_H
15 #include <limits.h>
16 #endif
17 #ifdef HAVE_CTYPE_H
18 #include <ctype.h>
19 #endif
20
21 #include "param.h"
22 #include "realpath.h"
23
24 /* If there is no realpath() on the system, provide a dummy one. */
25 #ifndef HAVE_REALPATH
ntfs_realpath(const char * path,char * resolved_path)26 char *ntfs_realpath(const char *path, char *resolved_path)
27 {
28 strncpy(resolved_path, path, PATH_MAX);
29 resolved_path[PATH_MAX] = '\0';
30 return resolved_path;
31 }
32 #endif
33
34
35 #ifdef linux
36
37 /*
38 * Converts private "dm-N" names to "/dev/mapper/<name>"
39 *
40 * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs
41 * provides the real DM device names in /sys/block/<ptname>/dm/name
42 */
43 static char *
canonicalize_dm_name(const char * ptname,char * canonical)44 canonicalize_dm_name(const char *ptname, char *canonical)
45 {
46 FILE *f;
47 size_t sz;
48 char name[MAPPERNAMELTH + 16];
49 char path[sizeof(name) + 16];
50 char *res = NULL;
51
52 snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
53 if (!(f = fopen(path, "r")))
54 return NULL;
55
56 /* read "<name>\n" from sysfs */
57 if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
58 name[sz - 1] = '\0';
59 snprintf(path, sizeof(path), "/dev/mapper/%s", name);
60 res = strcpy(canonical, path);
61 }
62 fclose(f);
63 return res;
64 }
65
66 /*
67 * Canonicalize a device path
68 *
69 * Workaround from "basinilya" for fixing device mapper paths.
70 *
71 * Background (Phillip Susi, 2011-04-09)
72 * - ntfs-3g canonicalizes the device name so that if you mount with
73 * /dev/mapper/foo, the device name listed in mtab is /dev/dm-n,
74 * so you can not umount /dev/mapper/foo
75 * - umount won't even recognize and translate /dev/dm-n to the mount
76 * point, apparently because of the '-' involved. Editing mtab and
77 * removing the '-' allows you to umount /dev/dmn successfully.
78 *
79 * This code restores the devmapper name after canonicalization,
80 * until a proper fix is implemented.
81 */
82
ntfs_realpath_canonicalize(const char * path,char * canonical)83 char *ntfs_realpath_canonicalize(const char *path, char *canonical)
84 {
85 char *p;
86
87 if (path == NULL)
88 return NULL;
89
90 if (!ntfs_realpath(path, canonical))
91 return NULL;
92
93 p = strrchr(canonical, '/');
94 if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) {
95 p = canonicalize_dm_name(p+1, canonical);
96 if (p)
97 return p;
98 }
99
100 return canonical;
101 }
102
103 #endif
104