Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 828 insertions, 0 deletions

diff --git a/src/shared/blockdev-util.c b/src/shared/blockdev-util.c
new file mode 100644
index 0000000..c906aec
--- /dev/null
+++ b/src/shared/blockdev-util.c
@@ -0,0 +1,828 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <linux/blkpg.h>
+#include <sys/file.h>
+#include <sys/ioctl.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+#include "sd-device.h"
+
+#include "alloc-util.h"
+#include "blockdev-util.h"
+#include "btrfs-util.h"
+#include "device-util.h"
+#include "devnum-util.h"
+#include "dirent-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "missing_magic.h"
+#include "parse-util.h"
+
+static int fd_get_devnum(int fd, BlockDeviceLookupFlag flags, dev_t *ret) {
+        struct stat st;
+        dev_t devnum;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (S_ISBLK(st.st_mode))
+                devnum = st.st_rdev;
+        else if (!FLAGS_SET(flags, BLOCK_DEVICE_LOOKUP_BACKING))
+                return -ENOTBLK;
+        else if (!S_ISREG(st.st_mode) && !S_ISDIR(st.st_mode))
+                return -ENOTBLK;
+        else if (major(st.st_dev) != 0)
+                devnum = st.st_dev;
+        else {
+                /* If major(st.st_dev) is zero, this might mean we are backed by btrfs, which needs special
+                 * handing, to get the backing device node. */
+
+                r = btrfs_get_block_device_fd(fd, &devnum);
+                if (r == -ENOTTY) /* not btrfs */
+                        return -ENOTBLK;
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = devnum;
+        return 0;
+}
+
+int block_device_is_whole_disk(sd_device *dev) {
+        const char *s;
+        int r;
+
+        assert(dev);
+
+        r = sd_device_get_subsystem(dev, &s);
+        if (r < 0)
+                return r;
+
+        if (!streq(s, "block"))
+                return -ENOTBLK;
+
+        r = sd_device_get_devtype(dev, &s);
+        if (r < 0)
+                return r;
+
+        return streq(s, "disk");
+}
+
+int block_device_get_whole_disk(sd_device *dev, sd_device **ret) {
+        int r;
+
+        assert(dev);
+        assert(ret);
+
+        /* Do not unref returned sd_device object. */
+
+        r = block_device_is_whole_disk(dev);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                r = sd_device_get_parent(dev, &dev);
+                if (r == -ENOENT) /* Already removed? Let's return a recognizable error. */
+                        return -ENODEV;
+                if (r < 0)
+                        return r;
+
+                r = block_device_is_whole_disk(dev);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENXIO;
+        }
+
+        *ret = dev;
+        return 0;
+}
+
+int block_device_get_originating(sd_device *dev, sd_device **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *first_found = NULL;
+        const char *suffix;
+        dev_t devnum = 0;  /* avoid false maybe-uninitialized warning */
+
+        /* 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. */
+
+        assert(dev);
+        assert(ret);
+
+        FOREACH_DEVICE_CHILD_WITH_SUFFIX(dev, child, suffix) {
+                sd_device *child_whole_disk;
+                dev_t n;
+
+                if (!path_startswith(suffix, "slaves"))
+                        continue;
+
+                if (block_device_get_whole_disk(child, &child_whole_disk) < 0)
+                        continue;
+
+                if (sd_device_get_devnum(child_whole_disk, &n) < 0)
+                        continue;
+
+                if (!first_found) {
+                        first_found = sd_device_ref(child);
+                        devnum = n;
+                        continue;
+                }
+
+                /* 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 by iterating over every node in the 'slaves/' directory and comparing them with
+                 * the first that gets returned by readdir(), to ensure they all point to the same device. */
+                if (n != devnum)
+                        return -ENOTUNIQ;
+        }
+
+        if (!first_found)
+                return -ENOENT;
+
+        *ret = TAKE_PTR(first_found);
+        return 1; /* found */
+}
+
+int block_device_new_from_fd(int fd, BlockDeviceLookupFlag flags, sd_device **ret) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL;
+        dev_t devnum;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        r = fd_get_devnum(fd, flags, &devnum);
+        if (r < 0)
+                return r;
+
+        r = sd_device_new_from_devnum(&dev, 'b', devnum);
+        if (r < 0)
+                return r;
+
+        if (FLAGS_SET(flags, BLOCK_DEVICE_LOOKUP_ORIGINATING)) {
+                _cleanup_(sd_device_unrefp) sd_device *dev_origin = NULL;
+                sd_device *dev_whole_disk;
+
+                r = block_device_get_whole_disk(dev, &dev_whole_disk);
+                if (r < 0)
+                        return r;
+
+                r = block_device_get_originating(dev_whole_disk, &dev_origin);
+                if (r < 0 && r != -ENOENT)
+                        return r;
+                if (r > 0)
+                        device_unref_and_replace(dev, dev_origin);
+        }
+
+        if (FLAGS_SET(flags, BLOCK_DEVICE_LOOKUP_WHOLE_DISK)) {
+                sd_device *dev_whole_disk;
+
+                r = block_device_get_whole_disk(dev, &dev_whole_disk);
+                if (r < 0)
+                        return r;
+
+                *ret = sd_device_ref(dev_whole_disk);
+                return 0;
+        }
+
+        *ret = sd_device_ref(dev);
+        return 0;
+}
+
+int block_device_new_from_path(const char *path, BlockDeviceLookupFlag flags, sd_device **ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        assert(path);
+        assert(ret);
+
+        fd = open(path, O_CLOEXEC|O_PATH);
+        if (fd < 0)
+                return -errno;
+
+        return block_device_new_from_fd(fd, flags, ret);
+}
+
+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 (major(d) == 0)
+                return -ENODEV;
+
+        /* 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 (errno != ENOENT)
+                return -errno;
+
+        /* If it is a partition find the originating device */
+        xsprintf_sys_block_path(p, "/partition", d);
+        if (access(p, F_OK) < 0)
+                return -errno;
+
+        /* 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_devnum(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 -errno;
+
+        *ret = devt;
+        return 1;
+}
+
+int get_block_device_fd(int fd, dev_t *ret) {
+        struct stat st;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        /* Gets the block device directly backing a file system. If the block device is encrypted, returns
+         * the device mapper block device. */
+
+        if (fstat(fd, &st))
+                return -errno;
+
+        if (major(st.st_dev) != 0) {
+                *ret = st.st_dev;
+                return 1;
+        }
+
+        r = btrfs_get_block_device_fd(fd, ret);
+        if (r > 0)
+                return 1;
+        if (r != -ENOTTY) /* not btrfs */
+                return r;
+
+        *ret = 0;
+        return 0;
+}
+
+int get_block_device(const char *path, dev_t *ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        assert(path);
+        assert(ret);
+
+        fd = open(path, O_RDONLY|O_NOFOLLOW|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        return get_block_device_fd(fd, ret);
+}
+
+int block_get_originating(dev_t dt, dev_t *ret) {
+        _cleanup_(sd_device_unrefp) sd_device *dev = NULL, *origin = NULL;
+        int r;
+
+        assert(ret);
+
+        r = sd_device_new_from_devnum(&dev, 'b', dt);
+        if (r < 0)
+                return r;
+
+        r = block_device_get_originating(dev, &origin);
+        if (r < 0)
+                return r;
+
+        return sd_device_get_devnum(origin, ret);
+}
+
+int get_block_device_harder_fd(int fd, dev_t *ret) {
+        int r;
+
+        assert(fd >= 0);
+        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_fd(fd, ret);
+        if (r <= 0)
+                return r;
+
+        r = block_get_originating(*ret, ret);
+        if (r < 0)
+                log_debug_errno(r, "Failed to chase block device, ignoring: %m");
+
+        return 1;
+}
+
+int get_block_device_harder(const char *path, dev_t *ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        assert(path);
+        assert(ret);
+
+        fd = open(path, O_RDONLY|O_NOFOLLOW|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        return get_block_device_harder_fd(fd, ret);
+}
+
+int lock_whole_block_device(dev_t devt, int operation) {
+        _cleanup_close_ int lock_fd = -EBADF;
+        dev_t whole_devt;
+        int r;
+
+        /* Let's get a BSD file lock on the whole block device, as per: https://systemd.io/BLOCK_DEVICE_LOCKING */
+
+        r = block_get_whole_disk(devt, &whole_devt);
+        if (r < 0)
+                return r;
+
+        lock_fd = r = device_open_from_devnum(S_IFBLK, whole_devt, O_RDONLY|O_CLOEXEC|O_NONBLOCK, NULL);
+        if (r < 0)
+                return r;
+
+        if (flock(lock_fd, operation) < 0)
+                return -errno;
+
+        return TAKE_FD(lock_fd);
+}
+
+int blockdev_partscan_enabled(int fd) {
+        _cleanup_free_ char *p = NULL, *buf = NULL;
+        unsigned long long ull;
+        struct stat st;
+        int r;
+
+        /* Checks if partition scanning is correctly enabled on the block device */
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!S_ISBLK(st.st_mode))
+                return -ENOTBLK;
+
+        if (asprintf(&p, "/sys/dev/block/%u:%u/capability", major(st.st_rdev), minor(st.st_rdev)) < 0)
+                return -ENOMEM;
+
+        r = read_one_line_file(p, &buf);
+        if (r == -ENOENT) /* If the capability file doesn't exist then we are most likely looking at a
+                           * partition block device, not the whole block device. And that means we have no
+                           * partition scanning on for it (we do for its parent, but not for the partition
+                           * itself). */
+                return false;
+        if (r < 0)
+                return r;
+
+        r = safe_atollu_full(buf, 16, &ull);
+        if (r < 0)
+                return r;
+
+#ifndef GENHD_FL_NO_PART_SCAN
+#define GENHD_FL_NO_PART_SCAN (0x0200)
+#endif
+
+        return !FLAGS_SET(ull, GENHD_FL_NO_PART_SCAN);
+}
+
+static int blockdev_is_encrypted(const char *sysfs_path, unsigned depth_left) {
+        _cleanup_free_ char *p = NULL, *uuids = NULL;
+        _cleanup_closedir_ DIR *d = NULL;
+        int r, found_encrypted = false;
+
+        assert(sysfs_path);
+
+        if (depth_left == 0)
+                return -EINVAL;
+
+        p = path_join(sysfs_path, "dm/uuid");
+        if (!p)
+                return -ENOMEM;
+
+        r = read_one_line_file(p, &uuids);
+        if (r != -ENOENT) {
+                if (r < 0)
+                        return r;
+
+                /* The DM device's uuid attribute is prefixed with "CRYPT-" if this is a dm-crypt device. */
+                if (startswith(uuids, "CRYPT-"))
+                        return true;
+        }
+
+        /* Not a dm-crypt device itself. But maybe it is on top of one? Follow the links in the "slaves/"
+         * subdir. */
+
+        p = mfree(p);
+        p = path_join(sysfs_path, "slaves");
+        if (!p)
+                return -ENOMEM;
+
+        d = opendir(p);
+        if (!d) {
+                if (errno == ENOENT) /* Doesn't have underlying devices */
+                        return false;
+
+                return -errno;
+        }
+
+        for (;;) {
+                _cleanup_free_ char *q = NULL;
+                struct dirent *de;
+
+                errno = 0;
+                de = readdir_no_dot(d);
+                if (!de) {
+                        if (errno != 0)
+                                return -errno;
+
+                        break; /* No more underlying devices */
+                }
+
+                q = path_join(p, de->d_name);
+                if (!q)
+                        return -ENOMEM;
+
+                r = blockdev_is_encrypted(q, depth_left - 1);
+                if (r < 0)
+                        return r;
+                if (r == 0) /* we found one that is not encrypted? then propagate that immediately */
+                        return false;
+
+                found_encrypted = true;
+        }
+
+        return found_encrypted;
+}
+
+int fd_is_encrypted(int fd) {
+        char p[SYS_BLOCK_PATH_MAX(NULL)];
+        dev_t devt;
+        int r;
+
+        r = get_block_device_fd(fd, &devt);
+        if (r < 0)
+                return r;
+        if (r == 0) /* doesn't have a block device */
+                return false;
+
+        xsprintf_sys_block_path(p, NULL, devt);
+
+        return blockdev_is_encrypted(p, 10 /* safety net: maximum recursion depth */);
+}
+
+int path_is_encrypted(const char *path) {
+        char p[SYS_BLOCK_PATH_MAX(NULL)];
+        dev_t devt;
+        int r;
+
+        r = get_block_device(path, &devt);
+        if (r < 0)
+                return r;
+        if (r == 0) /* doesn't have a block device */
+                return false;
+
+        xsprintf_sys_block_path(p, NULL, devt);
+
+        return blockdev_is_encrypted(p, 10 /* safety net: maximum recursion depth */);
+}
+
+int fd_get_whole_disk(int fd, bool backing, dev_t *ret) {
+        dev_t devt;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        r = fd_get_devnum(fd, backing ? BLOCK_DEVICE_LOOKUP_BACKING : 0, &devt);
+        if (r < 0)
+                return r;
+
+        return block_get_whole_disk(devt, ret);
+}
+
+int path_get_whole_disk(const char *path, bool backing, dev_t *ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_CLOEXEC|O_PATH);
+        if (fd < 0)
+                return -errno;
+
+        return fd_get_whole_disk(fd, backing, ret);
+}
+
+int block_device_add_partition(
+                int fd,
+                const char *name,
+                int nr,
+                uint64_t start,
+                uint64_t size) {
+
+        assert(fd >= 0);
+        assert(name);
+        assert(nr > 0);
+
+        struct blkpg_partition bp = {
+                .pno = nr,
+                .start = start,
+                .length = size,
+        };
+
+        struct blkpg_ioctl_arg ba = {
+                .op = BLKPG_ADD_PARTITION,
+                .data = &bp,
+                .datalen = sizeof(bp),
+        };
+
+        if (strlen(name) >= sizeof(bp.devname))
+                return -EINVAL;
+
+        strcpy(bp.devname, name);
+
+        return RET_NERRNO(ioctl(fd, BLKPG, &ba));
+}
+
+int block_device_remove_partition(
+                int fd,
+                const char *name,
+                int nr) {
+
+        assert(fd >= 0);
+        assert(name);
+        assert(nr > 0);
+
+        struct blkpg_partition bp = {
+                .pno = nr,
+        };
+
+        struct blkpg_ioctl_arg ba = {
+                .op = BLKPG_DEL_PARTITION,
+                .data = &bp,
+                .datalen = sizeof(bp),
+        };
+
+        if (strlen(name) >= sizeof(bp.devname))
+                return -EINVAL;
+
+        strcpy(bp.devname, name);
+
+        return RET_NERRNO(ioctl(fd, BLKPG, &ba));
+}
+
+int block_device_resize_partition(
+                int fd,
+                int nr,
+                uint64_t start,
+                uint64_t size) {
+
+        assert(fd >= 0);
+        assert(nr > 0);
+
+        struct blkpg_partition bp = {
+                .pno = nr,
+                .start = start,
+                .length = size,
+        };
+
+        struct blkpg_ioctl_arg ba = {
+                .op = BLKPG_RESIZE_PARTITION,
+                .data = &bp,
+                .datalen = sizeof(bp),
+        };
+
+        return RET_NERRNO(ioctl(fd, BLKPG, &ba));
+}
+
+int partition_enumerator_new(sd_device *dev, sd_device_enumerator **ret) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        const char *s;
+        int r;
+
+        assert(dev);
+        assert(ret);
+
+        /* Refuse invocation on partition block device, insist on "whole" device */
+        r = block_device_is_whole_disk(dev);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENXIO; /* return a recognizable error */
+
+        r = sd_device_enumerator_new(&e);
+        if (r < 0)
+                return r;
+
+        r = sd_device_enumerator_allow_uninitialized(e);
+        if (r < 0)
+                return r;
+
+        r = sd_device_enumerator_add_match_parent(e, dev);
+        if (r < 0)
+                return r;
+
+        r = sd_device_get_sysname(dev, &s);
+        if (r < 0)
+                return r;
+
+        /* Also add sysname check for safety. Hopefully, this also improves performance. */
+        s = strjoina(s, "*");
+        r = sd_device_enumerator_add_match_sysname(e, s);
+        if (r < 0)
+                return r;
+
+        r = sd_device_enumerator_add_match_subsystem(e, "block", /* match = */ true);
+        if (r < 0)
+                return r;
+
+        r = sd_device_enumerator_add_match_property(e, "DEVTYPE", "partition");
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(e);
+        return 0;
+}
+
+int block_device_remove_all_partitions(sd_device *dev, int fd) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        _cleanup_(sd_device_unrefp) sd_device *dev_unref = NULL;
+        _cleanup_close_ int fd_close = -EBADF;
+        bool has_partitions = false;
+        int r, k = 0;
+
+        assert(dev || fd >= 0);
+
+        if (!dev) {
+                r = block_device_new_from_fd(fd, 0, &dev_unref);
+                if (r < 0)
+                        return r;
+
+                dev = dev_unref;
+        }
+
+        r = partition_enumerator_new(dev, &e);
+        if (r < 0)
+                return r;
+
+        if (fd < 0) {
+                fd_close = sd_device_open(dev, O_CLOEXEC|O_NONBLOCK|O_NOCTTY|O_RDONLY);
+                if (fd_close < 0)
+                        return fd_close;
+
+                fd = fd_close;
+        }
+
+        FOREACH_DEVICE(e, part) {
+                const char *v, *devname;
+                int nr;
+
+                has_partitions = true;
+
+                r = sd_device_get_devname(part, &devname);
+                if (r < 0)
+                        return r;
+
+                r = sd_device_get_property_value(part, "PARTN", &v);
+                if (r < 0)
+                        return r;
+
+                r = safe_atoi(v, &nr);
+                if (r < 0)
+                        return r;
+
+                r = btrfs_forget_device(devname);
+                if (r < 0 && r != -ENOENT)
+                        log_debug_errno(r, "Failed to forget btrfs device %s, ignoring: %m", devname);
+
+                r = block_device_remove_partition(fd, devname, nr);
+                if (r == -ENODEV) {
+                        log_debug("Kernel removed partition %s before us, ignoring", devname);
+                        continue;
+                }
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to remove partition %s: %m", devname);
+                        k = k < 0 ? k : r;
+                        continue;
+                }
+
+                log_debug("Removed partition %s", devname);
+        }
+
+        return k < 0 ? k : has_partitions;
+}
+
+int block_device_has_partitions(sd_device *dev) {
+        _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
+        int r;
+
+        assert(dev);
+
+        /* Checks if the specified device currently has partitions. */
+
+        r = partition_enumerator_new(dev, &e);
+        if (r < 0)
+                return r;
+
+        return !!sd_device_enumerator_get_device_first(e);
+}
+
+int blockdev_reread_partition_table(sd_device *dev) {
+        _cleanup_close_ int fd = -EBADF;
+
+        assert(dev);
+
+        /* Try to re-read the partition table. This only succeeds if none of the devices is busy. */
+
+        fd = sd_device_open(dev, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
+        if (fd < 0)
+                return fd;
+
+        if (flock(fd, LOCK_EX|LOCK_NB) < 0)
+                return -errno;
+
+        if (ioctl(fd, BLKRRPART, 0) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int blockdev_get_sector_size(int fd, uint32_t *ret) {
+        int ssz = 0;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (ioctl(fd, BLKSSZGET, &ssz) < 0)
+                return -errno;
+        if (ssz <= 0) /* make sure the field is initialized */
+                return log_debug_errno(SYNTHETIC_ERRNO(EIO), "Block device reported invalid sector size %i.", ssz);
+
+        *ret = ssz;
+        return 0;
+}
+
+int blockdev_get_root(int level, dev_t *ret) {
+        _cleanup_free_ char *p = NULL;
+        dev_t devno;
+        int r;
+
+        /* Returns the device node backing the root file system. Traces through
+         * dm-crypt/dm-verity/... Returns > 0 and the devno of the device on success. If there's no block
+         * device (or multiple) returns 0 and a devno of 0. Failure otherwise.
+         *
+         * If the root mount has been replaced by some form of volatile file system (overlayfs), the original
+         * root block device node is symlinked in /run/systemd/volatile-root. Let's read that here. */
+        r = readlink_malloc("/run/systemd/volatile-root", &p);
+        if (r == -ENOENT) { /* volatile-root not found */
+                r = get_block_device_harder("/", &devno);
+                if (r == -EUCLEAN)
+                        return btrfs_log_dev_root(level, r, "root file system");
+                if (r < 0)
+                        return log_full_errno(level, r, "Failed to determine block device of root file system: %m");
+                if (r == 0) { /* Not backed by a single block device. (Could be NFS or so, or could be multi-device RAID or so) */
+                        r = get_block_device_harder("/usr", &devno);
+                        if (r == -EUCLEAN)
+                                return btrfs_log_dev_root(level, r, "/usr");
+                        if (r < 0)
+                                return log_full_errno(level, r, "Failed to determine block device of /usr/ file system: %m");
+                        if (r == 0) { /* /usr/ not backed by single block device, either. */
+                                log_debug("Neither root nor /usr/ file system are on a (single) block device.");
+
+                                if (ret)
+                                        *ret = 0;
+
+                                return 0;
+                        }
+                }
+        } else if (r < 0)
+                return log_full_errno(level, r, "Failed to read symlink /run/systemd/volatile-root: %m");
+        else {
+                mode_t m;
+                r = device_path_parse_major_minor(p, &m, &devno);
+                if (r < 0)
+                        return log_full_errno(level, r, "Failed to parse major/minor device node: %m");
+                if (!S_ISBLK(m))
+                        return log_full_errno(level, SYNTHETIC_ERRNO(ENOTBLK), "Volatile root device is of wrong type.");
+        }
+
+        if (ret)
+                *ret = devno;
+
+        return 1;
+}