src/basic/blockdev-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <sys/file.h>
   4 #include <unistd.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_magic.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         if (errno != ENOENT)
  34                 return -errno;
  35
  36         /* If it is a partition find the originating device */
  37         xsprintf_sys_block_path(p, "/partition", d);
  38         if (access(p, F_OK) < 0)
  39                 return -errno;
  40
  41         /* Get parent dev_t */
  42         xsprintf_sys_block_path(p, "/../dev", d);
  43         r = read_one_line_file(p, &s);
  44         if (r < 0)
  45                 return r;
  46
  47         r = parse_dev(s, &devt);
  48         if (r < 0)
  49                 return r;
  50
  51         /* Only return this if it is really good enough for us. */
  52         xsprintf_sys_block_path(p, "/queue", devt);
  53         if (access(p, F_OK) < 0)
  54                 return -errno;
  55
  56         *ret = devt;
  57         return 1;
  58 }
  59
  60 int get_block_device(const char *path, dev_t *ret) {
  61         _cleanup_close_ int fd = -1;
  62         struct stat st;
  63         int r;
  64
  65         assert(path);
  66         assert(ret);
  67
  68         /* Gets the block device directly backing a file system. If the block device is encrypted, returns
  69          * the device mapper block device. */
  70
  71         fd = open(path, O_NOFOLLOW|O_CLOEXEC);
  72         if (fd < 0)
  73                 return -errno;
  74
  75         if (fstat(fd, &st))
  76                 return -errno;
  77
  78         if (major(st.st_dev) != 0) {
  79                 *ret = st.st_dev;
  80                 return 1;
  81         }
  82
  83         r = btrfs_get_block_device_fd(fd, ret);
  84         if (r > 0)
  85                 return 1;
  86         if (r != -ENOTTY) /* not btrfs */
  87                 return r;
  88
  89         *ret = 0;
  90         return 0;
  91 }
  92
  93 int block_get_originating(dev_t dt, dev_t *ret) {
  94         _cleanup_closedir_ DIR *d = NULL;
  95         _cleanup_free_ char *t = NULL;
  96         char p[SYS_BLOCK_PATH_MAX("/slaves")];
  97         struct dirent *de, *found = NULL;
  98         const char *q;
  99         dev_t devt;
 100         int r;
 101
 102         /* For the specified block device tries to chase it through the layers, in case LUKS-style DM stacking is used,
 103          * trying to find the next underlying layer.  */
 104
 105         xsprintf_sys_block_path(p, "/slaves", dt);
 106         d = opendir(p);
 107         if (!d)
 108                 return -errno;
 109
 110         FOREACH_DIRENT_ALL(de, d, return -errno) {
 111
 112                 if (dot_or_dot_dot(de->d_name))
 113                         continue;
 114
 115                 if (!IN_SET(de->d_type, DT_LNK, DT_UNKNOWN))
 116                         continue;
 117
 118                 if (found) {
 119                         _cleanup_free_ char *u = NULL, *v = NULL, *a = NULL, *b = NULL;
 120
 121                         /* We found a device backed by multiple other devices. We don't really support automatic
 122                          * discovery on such setups, with the exception of dm-verity partitions. In this case there are
 123                          * two backing devices: the data partition and the hash partition. We are fine with such
 124                          * setups, however, only if both partitions are on the same physical device. Hence, let's
 125                          * verify this. */
 126
 127                         u = path_join(p, de->d_name, "../dev");
 128                         if (!u)
 129                                 return -ENOMEM;
 130
 131                         v = path_join(p, found->d_name, "../dev");
 132                         if (!v)
 133                                 return -ENOMEM;
 134
 135                         r = read_one_line_file(u, &a);
 136                         if (r < 0)
 137                                 return log_debug_errno(r, "Failed to read %s: %m", u);
 138
 139                         r = read_one_line_file(v, &b);
 140                         if (r < 0)
 141                                 return log_debug_errno(r, "Failed to read %s: %m", v);
 142
 143                         /* Check if the parent device is the same. If not, then the two backing devices are on
 144                          * different physical devices, and we don't support that. */
 145                         if (!streq(a, b))
 146                                 return -ENOTUNIQ;
 147                 }
 148
 149                 found = de;
 150         }
 151
 152         if (!found)
 153                 return -ENOENT;
 154
 155         q = strjoina(p, "/", found->d_name, "/dev");
 156
 157         r = read_one_line_file(q, &t);
 158         if (r < 0)
 159                 return r;
 160
 161         r = parse_dev(t, &devt);
 162         if (r < 0)
 163                 return -EINVAL;
 164
 165         if (major(devt) == 0)
 166                 return -ENOENT;
 167
 168         *ret = devt;
 169         return 1;
 170 }
 171
 172 int get_block_device_harder(const char *path, dev_t *ret) {
 173         int r;
 174
 175         assert(path);
 176         assert(ret);
 177
 178         /* Gets the backing block device for a file system, and handles LUKS encrypted file systems, looking for its
 179          * immediate parent, if there is one. */
 180
 181         r = get_block_device(path, ret);
 182         if (r <= 0)
 183                 return r;
 184
 185         r = block_get_originating(*ret, ret);
 186         if (r < 0)
 187                 log_debug_errno(r, "Failed to chase block device '%s', ignoring: %m", path);
 188
 189         return 1;
 190 }
 191
 192 int lock_whole_block_device(dev_t devt, int operation) {
 193         _cleanup_free_ char *whole_node = NULL;
 194         _cleanup_close_ int lock_fd = -1;
 195         dev_t whole_devt;
 196         int r;
 197
 198         /* Let's get a BSD file lock on the whole block device, as per: https://systemd.io/BLOCK_DEVICE_LOCKING */
 199
 200         r = block_get_whole_disk(devt, &whole_devt);
 201         if (r < 0)
 202                 return r;
 203
 204         r = device_path_make_major_minor(S_IFBLK, whole_devt, &whole_node);
 205         if (r < 0)
 206                 return r;
 207
 208         lock_fd = open(whole_node, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
 209         if (lock_fd < 0)
 210                 return -errno;
 211
 212         if (flock(lock_fd, operation) < 0)
 213                 return -errno;
 214
 215         return TAKE_FD(lock_fd);
 216 }
 217
 218 int blockdev_partscan_enabled(int fd) {
 219         _cleanup_free_ char *p = NULL, *buf = NULL;
 220         unsigned long long ull;
 221         struct stat st;
 222         int r;
 223
 224         /* Checks if partition scanning is correctly enabled on the block device */
 225
 226         if (fstat(fd, &st) < 0)
 227                 return -errno;
 228
 229         if (!S_ISBLK(st.st_mode))
 230                 return -ENOTBLK;
 231
 232         if (asprintf(&p, "/sys/dev/block/%u:%u/capability", major(st.st_rdev), minor(st.st_rdev)) < 0)
 233                 return -ENOMEM;
 234
 235         r = read_one_line_file(p, &buf);
 236         if (r == -ENOENT) /* If the capability file doesn't exist then we are most likely looking at a
 237                            * partition block device, not the whole block device. And that means we have no
 238                            * partition scanning on for it (we do for its parent, but not for the partition
 239                            * itself). */
 240                 return false;
 241         if (r < 0)
 242                 return r;
 243
 244         r = safe_atollu_full(buf, 16, &ull);
 245         if (r < 0)
 246                 return r;
 247
 248 #ifndef GENHD_FL_NO_PART_SCAN
 249 #define GENHD_FL_NO_PART_SCAN (0x0200)
 250 #endif
 251
 252         return !FLAGS_SET(ull, GENHD_FL_NO_PART_SCAN);
 253 }