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