src/basic/blockdev-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 Lennart Poettering
   6 ***/
   7
   8 #include <sys/stat.h>
   9 #include <sys/statfs.h>
  10
  11 #include "alloc-util.h"
  12 #include "blockdev-util.h"
  13 #include "btrfs-util.h"
  14 #include "dirent-util.h"
  15 #include "fd-util.h"
  16 #include "fileio.h"
  17 #include "missing.h"
  18 #include "stat-util.h"
  19
  20 int block_get_whole_disk(dev_t d, dev_t *ret) {
  21         char p[SYS_BLOCK_PATH_MAX("/partition")];
  22         _cleanup_free_ char *s = NULL;
  23         unsigned n, m;
  24         int r;
  25
  26         assert(ret);
  27
  28         /* If it has a queue this is good enough for us */
  29         xsprintf_sys_block_path(p, "/queue", d);
  30         if (access(p, F_OK) >= 0) {
  31                 *ret = d;
  32                 return 0;
  33         }
  34
  35         /* If it is a partition find the originating device */
  36         xsprintf_sys_block_path(p, "/partition", d);
  37         if (access(p, F_OK) < 0)
  38                 return -ENOENT;
  39
  40         /* Get parent dev_t */
  41         xsprintf_sys_block_path(p, "/../dev", d);
  42         r = read_one_line_file(p, &s);
  43         if (r < 0)
  44                 return r;
  45
  46         r = sscanf(s, "%u:%u", &m, &n);
  47         if (r != 2)
  48                 return -EINVAL;
  49
  50         /* Only return this if it is really good enough for us. */
  51         xsprintf_sys_block_path(p, "/queue", makedev(m, n));
  52         if (access(p, F_OK) < 0)
  53                 return -ENOENT;
  54
  55         *ret = makedev(m, n);
  56         return 0;
  57 }
  58
  59 int get_block_device(const char *path, dev_t *dev) {
  60         struct stat st;
  61         struct statfs sfs;
  62
  63         assert(path);
  64         assert(dev);
  65
  66         /* Get's the block device directly backing a file system. If
  67          * the block device is encrypted, returns the device mapper
  68          * block device. */
  69
  70         if (lstat(path, &st))
  71                 return -errno;
  72
  73         if (major(st.st_dev) != 0) {
  74                 *dev = st.st_dev;
  75                 return 1;
  76         }
  77
  78         if (statfs(path, &sfs) < 0)
  79                 return -errno;
  80
  81         if (F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC))
  82                 return btrfs_get_block_device(path, dev);
  83
  84         return 0;
  85 }
  86
  87 int get_block_device_harder(const char *path, dev_t *dev) {
  88         _cleanup_closedir_ DIR *d = NULL;
  89         _cleanup_free_ char *t = NULL;
  90         char p[SYS_BLOCK_PATH_MAX("/slaves")];
  91         struct dirent *de, *found = NULL;
  92         const char *q;
  93         unsigned maj, min;
  94         dev_t dt;
  95         int r;
  96
  97         assert(path);
  98         assert(dev);
  99
 100         /* Gets the backing block device for a file system, and
 101          * handles LUKS encrypted file systems, looking for its
 102          * immediate parent, if there is one. */
 103
 104         r = get_block_device(path, &dt);
 105         if (r <= 0)
 106                 return r;
 107
 108         xsprintf_sys_block_path(p, "/slaves", dt);
 109         d = opendir(p);
 110         if (!d) {
 111                 if (errno == ENOENT)
 112                         goto fallback;
 113
 114                 return -errno;
 115         }
 116
 117         FOREACH_DIRENT_ALL(de, d, return -errno) {
 118
 119                 if (dot_or_dot_dot(de->d_name))
 120                         continue;
 121
 122                 if (!IN_SET(de->d_type, DT_LNK, DT_UNKNOWN))
 123                         continue;
 124
 125                 if (found) {
 126                         _cleanup_free_ char *u = NULL, *v = NULL, *a = NULL, *b = NULL;
 127
 128                         /* We found a device backed by multiple other devices. We don't really support automatic
 129                          * discovery on such setups, with the exception of dm-verity partitions. In this case there are
 130                          * two backing devices: the data partition and the hash partition. We are fine with such
 131                          * setups, however, only if both partitions are on the same physical device. Hence, let's
 132                          * verify this. */
 133
 134                         u = strjoin(p, "/", de->d_name, "/../dev");
 135                         if (!u)
 136                                 return -ENOMEM;
 137
 138                         v = strjoin(p, "/", found->d_name, "/../dev");
 139                         if (!v)
 140                                 return -ENOMEM;
 141
 142                         r = read_one_line_file(u, &a);
 143                         if (r < 0) {
 144                                 log_debug_errno(r, "Failed to read %s: %m", u);
 145                                 goto fallback;
 146                         }
 147
 148                         r = read_one_line_file(v, &b);
 149                         if (r < 0) {
 150                                 log_debug_errno(r, "Failed to read %s: %m", v);
 151                                 goto fallback;
 152                         }
 153
 154                         /* Check if the parent device is the same. If not, then the two backing devices are on
 155                          * different physical devices, and we don't support that. */
 156                         if (!streq(a, b))
 157                                 goto fallback;
 158                 }
 159
 160                 found = de;
 161         }
 162
 163         if (!found)
 164                 goto fallback;
 165
 166         q = strjoina(p, "/", found->d_name, "/dev");
 167
 168         r = read_one_line_file(q, &t);
 169         if (r == -ENOENT)
 170                 goto fallback;
 171         if (r < 0)
 172                 return r;
 173
 174         if (sscanf(t, "%u:%u", &maj, &min) != 2)
 175                 return -EINVAL;
 176
 177         if (maj == 0)
 178                 goto fallback;
 179
 180         *dev = makedev(maj, min);
 181         return 1;
 182
 183 fallback:
 184         *dev = dt;
 185         return 1;
 186 }