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