1 files changed, 181 insertions, 0 deletions
diff --git a/src/basic/blockdev-util.c b/src/basic/blockdev-util.c
new file mode 100644
index 0000000..3017ecd
--- /dev/null
+++ b/src/basic/blockdev-util.c
@@ -0,0 +1,181 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <sys/stat.h>
+#include <sys/statfs.h>
+
+#include "alloc-util.h"
+#include "blockdev-util.h"
+#include "btrfs-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "missing.h"
+#include "parse-util.h"
+#include "stat-util.h"
+
+int block_get_whole_disk(dev_t d, dev_t *ret) {
+        char p[SYS_BLOCK_PATH_MAX("/partition")];
+        _cleanup_free_ char *s = NULL;
+        dev_t devt;
+        int r;
+
+        assert(ret);
+
+        /* If it has a queue this is good enough for us */
+        xsprintf_sys_block_path(p, "/queue", d);
+        if (access(p, F_OK) >= 0) {
+                *ret = d;
+                return 0;
+        }
+
+        /* If it is a partition find the originating device */
+        xsprintf_sys_block_path(p, "/partition", d);
+        if (access(p, F_OK) < 0)
+                return -ENOENT;
+
+        /* Get parent dev_t */
+        xsprintf_sys_block_path(p, "/../dev", d);
+        r = read_one_line_file(p, &s);
+        if (r < 0)
+                return r;
+
+        r = parse_dev(s, &devt);
+        if (r < 0)
+                return r;
+
+        /* Only return this if it is really good enough for us. */
+        xsprintf_sys_block_path(p, "/queue", devt);
+        if (access(p, F_OK) < 0)
+                return -ENOENT;
+
+        *ret = devt;
+        return 0;
+}
+
+int get_block_device(const char *path, dev_t *dev) {
+        struct stat st;
+        struct statfs sfs;
+
+        assert(path);
+        assert(dev);
+
+        /* Get's the block device directly backing a file system. If
+         * the block device is encrypted, returns the device mapper
+         * block device. */
+
+        if (lstat(path, &st))
+                return -errno;
+
+        if (major(st.st_dev) != 0) {
+                *dev = st.st_dev;
+                return 1;
+        }
+
+        if (statfs(path, &sfs) < 0)
+                return -errno;
+
+        if (F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC))
+                return btrfs_get_block_device(path, dev);
+
+        *dev = 0;
+        return 0;
+}
+
+int block_get_originating(dev_t dt, dev_t *ret) {
+        _cleanup_closedir_ DIR *d = NULL;
+        _cleanup_free_ char *t = NULL;
+        char p[SYS_BLOCK_PATH_MAX("/slaves")];
+        struct dirent *de, *found = NULL;
+        const char *q;
+        dev_t devt;
+        int r;
+
+        /* For the specified block device tries to chase it through the layers, in case LUKS-style DM stacking is used,
+         * trying to find the next underlying layer.  */
+
+        xsprintf_sys_block_path(p, "/slaves", dt);
+        d = opendir(p);
+        if (!d)
+                return -errno;
+
+        FOREACH_DIRENT_ALL(de, d, return -errno) {
+
+                if (dot_or_dot_dot(de->d_name))
+                        continue;
+
+                if (!IN_SET(de->d_type, DT_LNK, DT_UNKNOWN))
+                        continue;
+
+                if (found) {
+                        _cleanup_free_ char *u = NULL, *v = NULL, *a = NULL, *b = NULL;
+
+                        /* We found a device backed by multiple other devices. We don't really support automatic
+                         * discovery on such setups, with the exception of dm-verity partitions. In this case there are
+                         * two backing devices: the data partition and the hash partition. We are fine with such
+                         * setups, however, only if both partitions are on the same physical device. Hence, let's
+                         * verify this. */
+
+                        u = strjoin(p, "/", de->d_name, "/../dev");
+                        if (!u)
+                                return -ENOMEM;
+
+                        v = strjoin(p, "/", found->d_name, "/../dev");
+                        if (!v)
+                                return -ENOMEM;
+
+                        r = read_one_line_file(u, &a);
+                        if (r < 0)
+                                return log_debug_errno(r, "Failed to read %s: %m", u);
+
+                        r = read_one_line_file(v, &b);
+                        if (r < 0)
+                                return log_debug_errno(r, "Failed to read %s: %m", v);
+
+                        /* Check if the parent device is the same. If not, then the two backing devices are on
+                         * different physical devices, and we don't support that. */
+                        if (!streq(a, b))
+                                return -ENOTUNIQ;
+                }
+
+                found = de;
+        }
+
+        if (!found)
+                return -ENOENT;
+
+        q = strjoina(p, "/", found->d_name, "/dev");
+
+        r = read_one_line_file(q, &t);
+        if (r < 0)
+                return r;
+
+        r = parse_dev(t, &devt);
+        if (r < 0)
+                return -EINVAL;
+
+        if (major(devt) == 0)
+                return -ENOENT;
+
+        *ret = devt;
+        return 1;
+}
+
+int get_block_device_harder(const char *path, dev_t *ret) {
+        int r;
+
+        assert(path);
+        assert(ret);
+
+        /* Gets the backing block device for a file system, and handles LUKS encrypted file systems, looking for its
+         * immediate parent, if there is one. */
+
+        r = get_block_device(path, ret);
+        if (r <= 0)
+                return r;
+
+        r = block_get_originating(*ret, ret);
+        if (r < 0)
+                log_debug_errno(r, "Failed to chase block device '%s', ignoring: %m", path);
+
+        return 1;
+}