src/basic/blockdev-util.c

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