Adding upstream version 252.22.upstream/252.22

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

1 files changed, 3918 insertions, 0 deletions

diff --git a/src/home/homework-luks.c b/src/home/homework-luks.c
new file mode 100644
index 0000000..16616b8
--- /dev/null
+++ b/src/home/homework-luks.c
@@ -0,0 +1,3918 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <linux/loop.h>
+#include <poll.h>
+#include <sys/file.h>
+#include <sys/ioctl.h>
+#include <sys/xattr.h>
+
+#if HAVE_VALGRIND_MEMCHECK_H
+#include <valgrind/memcheck.h>
+#endif
+
+#include "sd-daemon.h"
+#include "sd-device.h"
+#include "sd-event.h"
+#include "sd-id128.h"
+
+#include "blkid-util.h"
+#include "blockdev-util.h"
+#include "btrfs-util.h"
+#include "chattr-util.h"
+#include "device-util.h"
+#include "devnum-util.h"
+#include "dm-util.h"
+#include "env-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fdisk-util.h"
+#include "fileio.h"
+#include "filesystems.h"
+#include "fs-util.h"
+#include "fsck-util.h"
+#include "glyph-util.h"
+#include "gpt.h"
+#include "home-util.h"
+#include "homework-luks.h"
+#include "homework-mount.h"
+#include "io-util.h"
+#include "keyring-util.h"
+#include "memory-util.h"
+#include "missing_magic.h"
+#include "mkdir.h"
+#include "mkfs-util.h"
+#include "mount-util.h"
+#include "openssl-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "process-util.h"
+#include "random-util.h"
+#include "resize-fs.h"
+#include "strv.h"
+#include "sync-util.h"
+#include "tmpfile-util.h"
+#include "udev-util.h"
+#include "user-util.h"
+
+/* Round down to the nearest 4K size. Given that newer hardware generally prefers 4K sectors, let's align our
+ * partitions to that too. In the worst case we'll waste 3.5K per partition that way, but I think I can live
+ * with that. */
+#define DISK_SIZE_ROUND_DOWN(x) ((x) & ~UINT64_C(4095))
+
+/* Rounds up to the nearest 4K boundary. Returns UINT64_MAX on overflow */
+#define DISK_SIZE_ROUND_UP(x)                                           \
+        ({                                                              \
+                uint64_t _x = (x);                                      \
+                _x > UINT64_MAX - 4095U ? UINT64_MAX : (_x + 4095U) & ~UINT64_C(4095); \
+        })
+
+/* How much larger will the image on disk be than the fs inside it, i.e. the space we pay for the GPT and
+ * LUKS2 envelope. (As measured on cryptsetup 2.4.1) */
+#define GPT_LUKS2_OVERHEAD UINT64_C(18874368)
+
+static int resize_image_loop(UserRecord *h, HomeSetup *setup, uint64_t old_image_size, uint64_t new_image_size, uint64_t *ret_image_size);
+
+int run_mark_dirty(int fd, bool b) {
+        char x = '1';
+        int r, ret;
+
+        /* Sets or removes the 'user.home-dirty' xattr on the specified file. We use this to detect when a
+         * home directory was not properly unmounted. */
+
+        assert(fd >= 0);
+
+        r = fd_verify_regular(fd);
+        if (r < 0)
+                return r;
+
+        if (b) {
+                ret = fsetxattr(fd, "user.home-dirty", &x, 1, XATTR_CREATE);
+                if (ret < 0 && errno != EEXIST)
+                        return log_debug_errno(errno, "Could not mark home directory as dirty: %m");
+
+        } else {
+                r = fsync_full(fd);
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to synchronize image before marking it clean: %m");
+
+                ret = fremovexattr(fd, "user.home-dirty");
+                if (ret < 0 && !ERRNO_IS_XATTR_ABSENT(errno))
+                        return log_debug_errno(errno, "Could not mark home directory as clean: %m");
+        }
+
+        r = fsync_full(fd);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to synchronize dirty flag to disk: %m");
+
+        return ret >= 0;
+}
+
+int run_mark_dirty_by_path(const char *path, bool b) {
+        _cleanup_close_ int fd = -1;
+
+        assert(path);
+
+        fd = open(path, O_RDWR|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return log_debug_errno(errno, "Failed to open %s to mark dirty or clean: %m", path);
+
+        return run_mark_dirty(fd, b);
+}
+
+static int probe_file_system_by_fd(
+                int fd,
+                char **ret_fstype,
+                sd_id128_t *ret_uuid) {
+
+        _cleanup_(blkid_free_probep) blkid_probe b = NULL;
+        _cleanup_free_ char *s = NULL;
+        const char *fstype = NULL, *uuid = NULL;
+        sd_id128_t id;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret_fstype);
+        assert(ret_uuid);
+
+        b = blkid_new_probe();
+        if (!b)
+                return -ENOMEM;
+
+        errno = 0;
+        r = blkid_probe_set_device(b, fd, 0, 0);
+        if (r != 0)
+                return errno > 0 ? -errno : -ENOMEM;
+
+        (void) blkid_probe_enable_superblocks(b, 1);
+        (void) blkid_probe_set_superblocks_flags(b, BLKID_SUBLKS_TYPE|BLKID_SUBLKS_UUID);
+
+        errno = 0;
+        r = blkid_do_safeprobe(b);
+        if (IN_SET(r, -2, 1)) /* nothing found or ambiguous result */
+                return -ENOPKG;
+        if (r != 0)
+                return errno > 0 ? -errno : -EIO;
+
+        (void) blkid_probe_lookup_value(b, "TYPE", &fstype, NULL);
+        if (!fstype)
+                return -ENOPKG;
+
+        (void) blkid_probe_lookup_value(b, "UUID", &uuid, NULL);
+        if (!uuid)
+                return -ENOPKG;
+
+        r = sd_id128_from_string(uuid, &id);
+        if (r < 0)
+                return r;
+
+        s = strdup(fstype);
+        if (!s)
+                return -ENOMEM;
+
+        *ret_fstype = TAKE_PTR(s);
+        *ret_uuid = id;
+
+        return 0;
+}
+
+static int probe_file_system_by_path(const char *path, char **ret_fstype, sd_id128_t *ret_uuid) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
+        if (fd < 0)
+                return negative_errno();
+
+        return probe_file_system_by_fd(fd, ret_fstype, ret_uuid);
+}
+
+static int block_get_size_by_fd(int fd, uint64_t *ret) {
+        struct stat st;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!S_ISBLK(st.st_mode))
+                return -ENOTBLK;
+
+        return RET_NERRNO(ioctl(fd, BLKGETSIZE64, ret));
+}
+
+static int block_get_size_by_path(const char *path, uint64_t *ret) {
+        _cleanup_close_ int fd = -1;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
+        if (fd < 0)
+                return -errno;
+
+        return block_get_size_by_fd(fd, ret);
+}
+
+static int run_fsck(const char *node, const char *fstype) {
+        int r, exit_status;
+        pid_t fsck_pid;
+        _cleanup_free_ char *fsck_path = NULL;
+
+        assert(node);
+        assert(fstype);
+
+        r = fsck_exists_for_fstype(fstype);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if fsck for file system %s exists: %m", fstype);
+        if (r == 0) {
+                log_warning("No fsck for file system %s installed, ignoring.", fstype);
+                return 0;
+        }
+
+        r = find_executable("fsck", &fsck_path);
+        /* We proceed anyway if we can't determine whether the fsck
+         * binary for some specific fstype exists,
+         * but the lack of the main fsck binary should be considered
+         * an error. */
+        if (r < 0)
+                return log_error_errno(r, "Cannot find fsck binary: %m");
+
+        r = safe_fork("(fsck)",
+                      FORK_RESET_SIGNALS|FORK_RLIMIT_NOFILE_SAFE|FORK_DEATHSIG|FORK_LOG|FORK_STDOUT_TO_STDERR|FORK_CLOSE_ALL_FDS,
+                      &fsck_pid);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                /* Child */
+                execl(fsck_path, fsck_path, "-aTl", node, NULL);
+                log_open();
+                log_error_errno(errno, "Failed to execute fsck: %m");
+                _exit(FSCK_OPERATIONAL_ERROR);
+        }
+
+        exit_status = wait_for_terminate_and_check("fsck", fsck_pid, WAIT_LOG_ABNORMAL);
+        if (exit_status < 0)
+                return exit_status;
+        if ((exit_status & ~FSCK_ERROR_CORRECTED) != 0) {
+                log_warning("fsck failed with exit status %i.", exit_status);
+
+                if ((exit_status & (FSCK_SYSTEM_SHOULD_REBOOT|FSCK_ERRORS_LEFT_UNCORRECTED)) != 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EIO), "File system is corrupted, refusing.");
+
+                log_warning("Ignoring fsck error.");
+        }
+
+        log_info("File system check completed.");
+
+        return 1;
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(key_serial_t, keyring_unlink, -1);
+
+static int upload_to_keyring(
+                UserRecord *h,
+                const char *password,
+                key_serial_t *ret_key_serial) {
+
+        _cleanup_free_ char *name = NULL;
+        key_serial_t serial;
+
+        assert(h);
+        assert(password);
+
+        /* If auto-shrink-on-logout is turned on, we need to keep the key we used to unlock the LUKS volume
+         * around, since we'll need it when automatically resizing (since we can't ask the user there
+         * again). We do this by uploading it into the kernel keyring, specifically the "session" one. This
+         * is done under the assumption systemd-homed gets its private per-session keyring (i.e. default
+         * service behaviour, given that KeyringMode=private is the default). It will survive between our
+         * systemd-homework invocations that way.
+         *
+         * If auto-shrink-on-logout is disabled we'll skip this step, to be frugal with sensitive data. */
+
+        if (user_record_auto_resize_mode(h) != AUTO_RESIZE_SHRINK_AND_GROW) {  /* Won't need it */
+                if (ret_key_serial)
+                        *ret_key_serial = -1;
+                return 0;
+        }
+
+        name = strjoin("homework-user-", h->user_name);
+        if (!name)
+                return -ENOMEM;
+
+        serial = add_key("user", name, password, strlen(password), KEY_SPEC_SESSION_KEYRING);
+        if (serial == -1)
+                return -errno;
+
+        if (ret_key_serial)
+                *ret_key_serial = serial;
+
+        return 1;
+}
+
+static int luks_try_passwords(
+                UserRecord *h,
+                struct crypt_device *cd,
+                char **passwords,
+                void *volume_key,
+                size_t *volume_key_size,
+                key_serial_t *ret_key_serial) {
+
+        int r;
+
+        assert(h);
+        assert(cd);
+
+        STRV_FOREACH(pp, passwords) {
+                size_t vks = *volume_key_size;
+
+                r = sym_crypt_volume_key_get(
+                                cd,
+                                CRYPT_ANY_SLOT,
+                                volume_key,
+                                &vks,
+                                *pp,
+                                strlen(*pp));
+                if (r >= 0) {
+                        if (ret_key_serial) {
+                                /* If ret_key_serial is non-NULL, let's try to upload the password that
+                                 * worked, and return its serial. */
+                                r = upload_to_keyring(h, *pp, ret_key_serial);
+                                if (r < 0) {
+                                        log_debug_errno(r, "Failed to upload LUKS password to kernel keyring, ignoring: %m");
+                                        *ret_key_serial = -1;
+                                }
+                        }
+
+                        *volume_key_size = vks;
+                        return 0;
+                }
+
+                log_debug_errno(r, "Password %zu didn't work for unlocking LUKS superblock: %m", (size_t) (pp - passwords));
+        }
+
+        return -ENOKEY;
+}
+
+static int luks_setup(
+                UserRecord *h,
+                const char *node,
+                const char *dm_name,
+                sd_id128_t uuid,
+                const char *cipher,
+                const char *cipher_mode,
+                uint64_t volume_key_size,
+                char **passwords,
+                const PasswordCache *cache,
+                bool discard,
+                struct crypt_device **ret,
+                sd_id128_t *ret_found_uuid,
+                void **ret_volume_key,
+                size_t *ret_volume_key_size,
+                key_serial_t *ret_key_serial) {
+
+        _cleanup_(keyring_unlinkp) key_serial_t key_serial = -1;
+        _cleanup_(sym_crypt_freep) struct crypt_device *cd = NULL;
+        _cleanup_(erase_and_freep) void *vk = NULL;
+        sd_id128_t p;
+        size_t vks;
+        char **list;
+        int r;
+
+        assert(h);
+        assert(node);
+        assert(dm_name);
+        assert(ret);
+
+        r = sym_crypt_init(&cd, node);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate libcryptsetup context: %m");
+
+        cryptsetup_enable_logging(cd);
+
+        r = sym_crypt_load(cd, CRYPT_LUKS2, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to load LUKS superblock: %m");
+
+        r = sym_crypt_get_volume_key_size(cd);
+        if (r <= 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine LUKS volume key size");
+        vks = (size_t) r;
+
+        if (!sd_id128_is_null(uuid) || ret_found_uuid) {
+                const char *s;
+
+                s = sym_crypt_get_uuid(cd);
+                if (!s)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock has no UUID.");
+
+                r = sd_id128_from_string(s, &p);
+                if (r < 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock has invalid UUID.");
+
+                /* Check that the UUID matches, if specified */
+                if (!sd_id128_is_null(uuid) &&
+                    !sd_id128_equal(uuid, p))
+                        return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock has wrong UUID.");
+        }
+
+        if (cipher && !streq_ptr(cipher, sym_crypt_get_cipher(cd)))
+                return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock declares wrong cipher.");
+
+        if (cipher_mode && !streq_ptr(cipher_mode, sym_crypt_get_cipher_mode(cd)))
+                return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock declares wrong cipher mode.");
+
+        if (volume_key_size != UINT64_MAX && vks != volume_key_size)
+                return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock declares wrong volume key size.");
+
+        vk = malloc(vks);
+        if (!vk)
+                return log_oom();
+
+        r = -ENOKEY;
+        FOREACH_POINTER(list,
+                        cache ? cache->keyring_passswords : NULL,
+                        cache ? cache->pkcs11_passwords : NULL,
+                        cache ? cache->fido2_passwords : NULL,
+                        passwords) {
+                r = luks_try_passwords(h, cd, list, vk, &vks, ret_key_serial ? &key_serial : NULL);
+                if (r != -ENOKEY)
+                        break;
+        }
+        if (r == -ENOKEY)
+                return log_error_errno(r, "No valid password for LUKS superblock.");
+        if (r < 0)
+                return log_error_errno(r, "Failed to unlock LUKS superblock: %m");
+
+        r = sym_crypt_activate_by_volume_key(
+                        cd,
+                        dm_name,
+                        vk, vks,
+                        discard ? CRYPT_ACTIVATE_ALLOW_DISCARDS : 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to unlock LUKS superblock: %m");
+
+        log_info("Setting up LUKS device /dev/mapper/%s completed.", dm_name);
+
+        *ret = TAKE_PTR(cd);
+
+        if (ret_found_uuid) /* Return the UUID actually found if the caller wants to know */
+                *ret_found_uuid = p;
+        if (ret_volume_key)
+                *ret_volume_key = TAKE_PTR(vk);
+        if (ret_volume_key_size)
+                *ret_volume_key_size = vks;
+        if (ret_key_serial)
+                *ret_key_serial = TAKE_KEY_SERIAL(key_serial);
+
+        return 0;
+}
+
+static int make_dm_names(UserRecord *h, HomeSetup *setup) {
+        assert(h);
+        assert(h->user_name);
+        assert(setup);
+
+        if (!setup->dm_name) {
+                setup->dm_name = strjoin("home-", h->user_name);
+                if (!setup->dm_name)
+                        return log_oom();
+        }
+
+        if (!setup->dm_node) {
+                setup->dm_node = path_join("/dev/mapper/", setup->dm_name);
+                if (!setup->dm_node)
+                        return log_oom();
+        }
+
+        return 0;
+}
+
+static int acquire_open_luks_device(
+                UserRecord *h,
+                HomeSetup *setup,
+                bool graceful) {
+
+        _cleanup_(sym_crypt_freep) struct crypt_device *cd = NULL;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(!setup->crypt_device);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        r = make_dm_names(h, setup);
+        if (r < 0)
+                return r;
+
+        r = sym_crypt_init_by_name(&cd, setup->dm_name);
+        if ((ERRNO_IS_DEVICE_ABSENT(r) || r == -EINVAL) && graceful)
+                return 0;
+        if (r < 0)
+                return log_error_errno(r, "Failed to initialize cryptsetup context for %s: %m", setup->dm_name);
+
+        cryptsetup_enable_logging(cd);
+
+        setup->crypt_device = TAKE_PTR(cd);
+        return 1;
+}
+
+static int luks_open(
+                UserRecord *h,
+                HomeSetup *setup,
+                const PasswordCache *cache,
+                sd_id128_t *ret_found_uuid,
+                void **ret_volume_key,
+                size_t *ret_volume_key_size) {
+
+        _cleanup_(erase_and_freep) void *vk = NULL;
+        sd_id128_t p;
+        char **list;
+        size_t vks;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(!setup->crypt_device);
+
+        /* Opens a LUKS device that is already set up. Re-validates the password while doing so (which also
+         * provides us with the volume key, which we want). */
+
+        r = acquire_open_luks_device(h, setup, /* graceful= */ false);
+        if (r < 0)
+                return r;
+
+        r = sym_crypt_load(setup->crypt_device, CRYPT_LUKS2, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to load LUKS superblock: %m");
+
+        r = sym_crypt_get_volume_key_size(setup->crypt_device);
+        if (r <= 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine LUKS volume key size");
+        vks = (size_t) r;
+
+        if (ret_found_uuid) {
+                const char *s;
+
+                s = sym_crypt_get_uuid(setup->crypt_device);
+                if (!s)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock has no UUID.");
+
+                r = sd_id128_from_string(s, &p);
+                if (r < 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "LUKS superblock has invalid UUID.");
+        }
+
+        vk = malloc(vks);
+        if (!vk)
+                return log_oom();
+
+        r = -ENOKEY;
+        FOREACH_POINTER(list,
+                        cache ? cache->keyring_passswords : NULL,
+                        cache ? cache->pkcs11_passwords : NULL,
+                        cache ? cache->fido2_passwords : NULL,
+                        h->password) {
+                r = luks_try_passwords(h, setup->crypt_device, list, vk, &vks, NULL);
+                if (r != -ENOKEY)
+                        break;
+        }
+        if (r == -ENOKEY)
+                return log_error_errno(r, "No valid password for LUKS superblock.");
+        if (r < 0)
+                return log_error_errno(r, "Failed to unlocks LUKS superblock: %m");
+
+        log_info("Discovered used LUKS device /dev/mapper/%s, and validated password.", setup->dm_name);
+
+        /* This is needed so that crypt_resize() can operate correctly for pre-existing LUKS devices. We need
+         * to tell libcryptsetup the volume key explicitly, so that it is in the kernel keyring. */
+        r = sym_crypt_activate_by_volume_key(setup->crypt_device, NULL, vk, vks, CRYPT_ACTIVATE_KEYRING_KEY);
+        if (r < 0)
+                return log_error_errno(r, "Failed to upload volume key again: %m");
+
+        log_info("Successfully re-activated LUKS device.");
+
+        if (ret_found_uuid)
+                *ret_found_uuid = p;
+        if (ret_volume_key)
+                *ret_volume_key = TAKE_PTR(vk);
+        if (ret_volume_key_size)
+                *ret_volume_key_size = vks;
+
+        return 0;
+}
+
+static int fs_validate(
+                const char *dm_node,
+                sd_id128_t uuid,
+                char **ret_fstype,
+                sd_id128_t *ret_found_uuid) {
+
+        _cleanup_free_ char *fstype = NULL;
+        sd_id128_t u = SD_ID128_NULL; /* avoid false maybe-unitialized warning */
+        int r;
+
+        assert(dm_node);
+        assert(ret_fstype);
+
+        r = probe_file_system_by_path(dm_node, &fstype, &u);
+        if (r < 0)
+                return log_error_errno(r, "Failed to probe file system: %m");
+
+        /* Limit the set of supported file systems a bit, as protection against little tested kernel file
+         * systems. Also, we only support the resize ioctls for these file systems. */
+        if (!supported_fstype(fstype))
+                return log_error_errno(SYNTHETIC_ERRNO(EPROTONOSUPPORT), "Image contains unsupported file system: %s", strna(fstype));
+
+        if (!sd_id128_is_null(uuid) &&
+            !sd_id128_equal(uuid, u))
+                return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE), "File system has wrong UUID.");
+
+        log_info("Probing file system completed (found %s).", fstype);
+
+        *ret_fstype = TAKE_PTR(fstype);
+
+        if (ret_found_uuid) /* Return the UUID actually found if the caller wants to know */
+                *ret_found_uuid = u;
+
+        return 0;
+}
+
+static int luks_validate(
+                int fd,
+                const char *label,
+                sd_id128_t partition_uuid,
+                sd_id128_t *ret_partition_uuid,
+                uint64_t *ret_offset,
+                uint64_t *ret_size) {
+
+        _cleanup_(blkid_free_probep) blkid_probe b = NULL;
+        sd_id128_t found_partition_uuid = SD_ID128_NULL;
+        const char *fstype = NULL, *pttype = NULL;
+        blkid_loff_t offset = 0, size = 0;
+        blkid_partlist pl;
+        bool found = false;
+        int r, n;
+
+        assert(fd >= 0);
+        assert(label);
+        assert(ret_offset);
+        assert(ret_size);
+
+        b = blkid_new_probe();
+        if (!b)
+                return -ENOMEM;
+
+        errno = 0;
+        r = blkid_probe_set_device(b, fd, 0, 0);
+        if (r != 0)
+                return errno > 0 ? -errno : -ENOMEM;
+
+        (void) blkid_probe_enable_superblocks(b, 1);
+        (void) blkid_probe_set_superblocks_flags(b, BLKID_SUBLKS_TYPE);
+        (void) blkid_probe_enable_partitions(b, 1);
+        (void) blkid_probe_set_partitions_flags(b, BLKID_PARTS_ENTRY_DETAILS);
+
+        errno = 0;
+        r = blkid_do_safeprobe(b);
+        if (IN_SET(r, -2, 1)) /* nothing found or ambiguous result */
+                return -ENOPKG;
+        if (r != 0)
+                return errno > 0 ? -errno : -EIO;
+
+        (void) blkid_probe_lookup_value(b, "TYPE", &fstype, NULL);
+        if (streq_ptr(fstype, "crypto_LUKS")) {
+                /* Directly a LUKS image */
+                *ret_offset = 0;
+                *ret_size = UINT64_MAX; /* full disk */
+                *ret_partition_uuid = SD_ID128_NULL;
+                return 0;
+        } else if (fstype)
+                return -ENOPKG;
+
+        (void) blkid_probe_lookup_value(b, "PTTYPE", &pttype, NULL);
+        if (!streq_ptr(pttype, "gpt"))
+                return -ENOPKG;
+
+        errno = 0;
+        pl = blkid_probe_get_partitions(b);
+        if (!pl)
+                return errno > 0 ? -errno : -ENOMEM;
+
+        errno = 0;
+        n = blkid_partlist_numof_partitions(pl);
+        if (n < 0)
+                return errno > 0 ? -errno : -EIO;
+
+        for (int i = 0; i < n; i++) {
+                blkid_partition pp;
+                sd_id128_t id = SD_ID128_NULL;
+                const char *sid;
+
+                errno = 0;
+                pp = blkid_partlist_get_partition(pl, i);
+                if (!pp)
+                        return errno > 0 ? -errno : -EIO;
+
+                if (sd_id128_string_equal(blkid_partition_get_type_string(pp), SD_GPT_USER_HOME) <= 0)
+                        continue;
+
+                if (!streq_ptr(blkid_partition_get_name(pp), label))
+                        continue;
+
+                sid = blkid_partition_get_uuid(pp);
+                if (sid) {
+                        r = sd_id128_from_string(sid, &id);
+                        if (r < 0)
+                                log_debug_errno(r, "Couldn't parse partition UUID %s, weird: %m", sid);
+
+                        if (!sd_id128_is_null(partition_uuid) && !sd_id128_equal(id, partition_uuid))
+                                continue;
+                }
+
+                if (found)
+                        return -ENOPKG;
+
+                offset = blkid_partition_get_start(pp);
+                size = blkid_partition_get_size(pp);
+                found_partition_uuid = id;
+
+                found = true;
+        }
+
+        if (!found)
+                return -ENOPKG;
+
+        if (offset < 0)
+                return -EINVAL;
+        if ((uint64_t) offset > UINT64_MAX / 512U)
+                return -EINVAL;
+        if (size <= 0)
+                return -EINVAL;
+        if ((uint64_t) size > UINT64_MAX / 512U)
+                return -EINVAL;
+
+        *ret_offset = offset * 512U;
+        *ret_size = size * 512U;
+        *ret_partition_uuid = found_partition_uuid;
+
+        return 0;
+}
+
+static int crypt_device_to_evp_cipher(struct crypt_device *cd, const EVP_CIPHER **ret) {
+        _cleanup_free_ char *cipher_name = NULL;
+        const char *cipher, *cipher_mode, *e;
+        size_t key_size, key_bits;
+        const EVP_CIPHER *cc;
+        int r;
+
+        assert(cd);
+
+        /* Let's find the right OpenSSL EVP_CIPHER object that matches the encryption settings of the LUKS
+         * device */
+
+        cipher = sym_crypt_get_cipher(cd);
+        if (!cipher)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Cannot get cipher from LUKS device.");
+
+        cipher_mode = sym_crypt_get_cipher_mode(cd);
+        if (!cipher_mode)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Cannot get cipher mode from LUKS device.");
+
+        e = strchr(cipher_mode, '-');
+        if (e)
+                cipher_mode = strndupa_safe(cipher_mode, e - cipher_mode);
+
+        r = sym_crypt_get_volume_key_size(cd);
+        if (r <= 0)
+                return log_error_errno(r < 0 ? r : SYNTHETIC_ERRNO(EINVAL), "Cannot get volume key size from LUKS device.");
+
+        key_size = r;
+        key_bits = key_size * 8;
+        if (streq(cipher_mode, "xts"))
+                key_bits /= 2;
+
+        if (asprintf(&cipher_name, "%s-%zu-%s", cipher, key_bits, cipher_mode) < 0)
+                return log_oom();
+
+        cc = EVP_get_cipherbyname(cipher_name);
+        if (!cc)
+                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Selected cipher mode '%s' not supported, can't encrypt JSON record.", cipher_name);
+
+        /* Verify that our key length calculations match what OpenSSL thinks */
+        r = EVP_CIPHER_key_length(cc);
+        if (r < 0 || (uint64_t) r != key_size)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Key size of selected cipher doesn't meet our expectations.");
+
+        *ret = cc;
+        return 0;
+}
+
+static int luks_validate_home_record(
+                struct crypt_device *cd,
+                UserRecord *h,
+                const void *volume_key,
+                PasswordCache *cache,
+                UserRecord **ret_luks_home_record) {
+
+        int r;
+
+        assert(cd);
+        assert(h);
+
+        for (int token = 0; token < sym_crypt_token_max(CRYPT_LUKS2); token++) {
+                _cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *rr = NULL;
+                _cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
+                _cleanup_(user_record_unrefp) UserRecord *lhr = NULL;
+                _cleanup_free_ void *encrypted = NULL, *iv = NULL;
+                size_t decrypted_size, encrypted_size, iv_size;
+                int decrypted_size_out1, decrypted_size_out2;
+                _cleanup_free_ char *decrypted = NULL;
+                const char *text, *type;
+                crypt_token_info state;
+                JsonVariant *jr, *jiv;
+                unsigned line, column;
+                const EVP_CIPHER *cc;
+
+                state = sym_crypt_token_status(cd, token, &type);
+                if (state == CRYPT_TOKEN_INACTIVE) /* First unconfigured token, give up */
+                        break;
+                if (IN_SET(state, CRYPT_TOKEN_INTERNAL, CRYPT_TOKEN_INTERNAL_UNKNOWN, CRYPT_TOKEN_EXTERNAL))
+                        continue;
+                if (state != CRYPT_TOKEN_EXTERNAL_UNKNOWN)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unexpected token state of token %i: %i", token, (int) state);
+
+                if (!streq(type, "systemd-homed"))
+                        continue;
+
+                r = sym_crypt_token_json_get(cd, token, &text);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to read LUKS token %i: %m", token);
+
+                r = json_parse(text, JSON_PARSE_SENSITIVE, &v, &line, &column);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse LUKS token JSON data %u:%u: %m", line, column);
+
+                jr = json_variant_by_key(v, "record");
+                if (!jr)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "LUKS token lacks 'record' field.");
+                jiv = json_variant_by_key(v, "iv");
+                if (!jiv)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "LUKS token lacks 'iv' field.");
+
+                r = json_variant_unbase64(jr, &encrypted, &encrypted_size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to base64 decode record: %m");
+
+                r = json_variant_unbase64(jiv, &iv, &iv_size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to base64 decode IV: %m");
+
+                r = crypt_device_to_evp_cipher(cd, &cc);
+                if (r < 0)
+                        return r;
+                if (iv_size > INT_MAX || EVP_CIPHER_iv_length(cc) != (int) iv_size)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "IV size doesn't match.");
+
+                context = EVP_CIPHER_CTX_new();
+                if (!context)
+                        return log_oom();
+
+                if (EVP_DecryptInit_ex(context, cc, NULL, volume_key, iv) != 1)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initialize decryption context.");
+
+                decrypted_size = encrypted_size + EVP_CIPHER_key_length(cc) * 2;
+                decrypted = new(char, decrypted_size);
+                if (!decrypted)
+                        return log_oom();
+
+                if (EVP_DecryptUpdate(context, (uint8_t*) decrypted, &decrypted_size_out1, encrypted, encrypted_size) != 1)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to decrypt JSON record.");
+
+                assert((size_t) decrypted_size_out1 <= decrypted_size);
+
+                if (EVP_DecryptFinal_ex(context, (uint8_t*) decrypted + decrypted_size_out1, &decrypted_size_out2) != 1)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to finish decryption of JSON record.");
+
+                assert((size_t) decrypted_size_out1 + (size_t) decrypted_size_out2 < decrypted_size);
+                decrypted_size = (size_t) decrypted_size_out1 + (size_t) decrypted_size_out2;
+
+                if (memchr(decrypted, 0, decrypted_size))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Inner NUL byte in JSON record, refusing.");
+
+                decrypted[decrypted_size] = 0;
+
+                r = json_parse(decrypted, JSON_PARSE_SENSITIVE, &rr, NULL, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse decrypted JSON record, refusing.");
+
+                lhr = user_record_new();
+                if (!lhr)
+                        return log_oom();
+
+                r = user_record_load(lhr, rr, USER_RECORD_LOAD_EMBEDDED|USER_RECORD_PERMISSIVE);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to parse user record: %m");
+
+                if (!user_record_compatible(h, lhr))
+                        return log_error_errno(SYNTHETIC_ERRNO(EREMCHG), "LUKS home record not compatible with host record, refusing.");
+
+                r = user_record_authenticate(lhr, h, cache, /* strict_verify= */ true);
+                if (r < 0)
+                        return r;
+                assert(r > 0); /* Insist that a password was verified */
+
+                *ret_luks_home_record = TAKE_PTR(lhr);
+                return 0;
+        }
+
+        return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Couldn't find home record in LUKS2 header, refusing.");
+}
+
+static int format_luks_token_text(
+                struct crypt_device *cd,
+                UserRecord *hr,
+                const void *volume_key,
+                char **ret) {
+
+        int r, encrypted_size_out1 = 0, encrypted_size_out2 = 0, iv_size, key_size;
+        _cleanup_(EVP_CIPHER_CTX_freep) EVP_CIPHER_CTX *context = NULL;
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        _cleanup_free_ void *iv = NULL, *encrypted = NULL;
+        size_t text_length, encrypted_size;
+        _cleanup_free_ char *text = NULL;
+        const EVP_CIPHER *cc;
+
+        assert(cd);
+        assert(hr);
+        assert(volume_key);
+        assert(ret);
+
+        r = crypt_device_to_evp_cipher(cd, &cc);
+        if (r < 0)
+                return r;
+
+        key_size = EVP_CIPHER_key_length(cc);
+        iv_size = EVP_CIPHER_iv_length(cc);
+
+        if (iv_size > 0) {
+                iv = malloc(iv_size);
+                if (!iv)
+                        return log_oom();
+
+                r = crypto_random_bytes(iv, iv_size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to generate IV: %m");
+        }
+
+        context = EVP_CIPHER_CTX_new();
+        if (!context)
+                return log_oom();
+
+        if (EVP_EncryptInit_ex(context, cc, NULL, volume_key, iv) != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to initialize encryption context.");
+
+        r = json_variant_format(hr->json, 0, &text);
+        if (r < 0)
+                return log_error_errno(r, "Failed to format user record for LUKS: %m");
+
+        text_length = strlen(text);
+        encrypted_size = text_length + 2*key_size - 1;
+
+        encrypted = malloc(encrypted_size);
+        if (!encrypted)
+                return log_oom();
+
+        if (EVP_EncryptUpdate(context, encrypted, &encrypted_size_out1, (uint8_t*) text, text_length) != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to encrypt JSON record.");
+
+        assert((size_t) encrypted_size_out1 <= encrypted_size);
+
+        if (EVP_EncryptFinal_ex(context, (uint8_t*) encrypted + encrypted_size_out1, &encrypted_size_out2) != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to finish encryption of JSON record. ");
+
+        assert((size_t) encrypted_size_out1 + (size_t) encrypted_size_out2 <= encrypted_size);
+
+        r = json_build(&v,
+                       JSON_BUILD_OBJECT(
+                                       JSON_BUILD_PAIR("type", JSON_BUILD_CONST_STRING("systemd-homed")),
+                                       JSON_BUILD_PAIR("keyslots", JSON_BUILD_EMPTY_ARRAY),
+                                       JSON_BUILD_PAIR("record", JSON_BUILD_BASE64(encrypted, encrypted_size_out1 + encrypted_size_out2)),
+                                       JSON_BUILD_PAIR("iv", JSON_BUILD_BASE64(iv, iv_size))));
+        if (r < 0)
+                return log_error_errno(r, "Failed to prepare LUKS JSON token object: %m");
+
+        r = json_variant_format(v, 0, ret);
+        if (r < 0)
+                return log_error_errno(r, "Failed to format encrypted user record for LUKS: %m");
+
+        return 0;
+}
+
+int home_store_header_identity_luks(
+                UserRecord *h,
+                HomeSetup *setup,
+                UserRecord *old_home) {
+
+        _cleanup_(user_record_unrefp) UserRecord *header_home = NULL;
+        _cleanup_free_ char *text = NULL;
+        int r;
+
+        assert(h);
+
+        if (!setup->crypt_device)
+                return 0;
+
+        assert(setup->volume_key);
+
+        /* Let's store the user's identity record in the LUKS2 "token" header data fields, in an encrypted
+         * fashion. Why that? If we'd rely on the record being embedded in the payload file system itself we
+         * would have to mount the file system before we can validate the JSON record, its signatures and
+         * whether it matches what we are looking for. However, kernel file system implementations are
+         * generally not ready to be used on untrusted media. Hence let's store the record independently of
+         * the file system, so that we can validate it first, and only then mount the file system. To keep
+         * things simple we use the same encryption settings for this record as for the file system itself. */
+
+        r = user_record_clone(h, USER_RECORD_EXTRACT_EMBEDDED|USER_RECORD_PERMISSIVE, &header_home);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine new header record: %m");
+
+        if (old_home && user_record_equal(old_home, header_home)) {
+                log_debug("Not updating header home record.");
+                return 0;
+        }
+
+        r = format_luks_token_text(setup->crypt_device, header_home, setup->volume_key, &text);
+        if (r < 0)
+                return r;
+
+        for (int token = 0; token < sym_crypt_token_max(CRYPT_LUKS2); token++) {
+                crypt_token_info state;
+                const char *type;
+
+                state = sym_crypt_token_status(setup->crypt_device, token, &type);
+                if (state == CRYPT_TOKEN_INACTIVE) /* First unconfigured token, we are done */
+                        break;
+                if (IN_SET(state, CRYPT_TOKEN_INTERNAL, CRYPT_TOKEN_INTERNAL_UNKNOWN, CRYPT_TOKEN_EXTERNAL))
+                        continue; /* Not ours */
+                if (state != CRYPT_TOKEN_EXTERNAL_UNKNOWN)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unexpected token state of token %i: %i", token, (int) state);
+
+                if (!streq(type, "systemd-homed"))
+                        continue;
+
+                r = sym_crypt_token_json_set(setup->crypt_device, token, text);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to set JSON token for slot %i: %m", token);
+
+                /* Now, let's free the text so that for all further matching tokens we all crypt_json_token_set()
+                 * with a NULL text in order to invalidate the tokens. */
+                text = mfree(text);
+        }
+
+        if (text)
+                return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Didn't find any record token to update.");
+
+        log_info("Wrote LUKS header user record.");
+
+        return 1;
+}
+
+int run_fitrim(int root_fd) {
+        struct fstrim_range range = {
+                .len = UINT64_MAX,
+        };
+
+        /* If discarding is on, discard everything right after mounting, so that the discard setting takes
+         * effect on activation. (Also, optionally, trim on logout) */
+
+        assert(root_fd >= 0);
+
+        if (ioctl(root_fd, FITRIM, &range) < 0) {
+                if (ERRNO_IS_NOT_SUPPORTED(errno) || errno == EBADF) {
+                        log_debug_errno(errno, "File system does not support FITRIM, not trimming.");
+                        return 0;
+                }
+
+                return log_warning_errno(errno, "Failed to invoke FITRIM, ignoring: %m");
+        }
+
+        log_info("Discarded unused %s.", FORMAT_BYTES(range.len));
+        return 1;
+}
+
+int run_fallocate(int backing_fd, const struct stat *st) {
+        struct stat stbuf;
+
+        assert(backing_fd >= 0);
+
+        /* If discarding is off, let's allocate the whole image before mounting, so that the setting takes
+         * effect on activation */
+
+        if (!st) {
+                if (fstat(backing_fd, &stbuf) < 0)
+                        return log_error_errno(errno, "Failed to fstat(): %m");
+
+                st = &stbuf;
+        }
+
+        if (!S_ISREG(st->st_mode))
+                return 0;
+
+        if (st->st_blocks >= DIV_ROUND_UP(st->st_size, 512)) {
+                log_info("Backing file is fully allocated already.");
+                return 0;
+        }
+
+        if (fallocate(backing_fd, FALLOC_FL_KEEP_SIZE, 0, st->st_size) < 0) {
+
+                if (ERRNO_IS_NOT_SUPPORTED(errno)) {
+                        log_debug_errno(errno, "fallocate() not supported on file system, ignoring.");
+                        return 0;
+                }
+
+                if (ERRNO_IS_DISK_SPACE(errno)) {
+                        log_debug_errno(errno, "Not enough disk space to fully allocate home.");
+                        return -ENOSPC; /* make recognizable */
+                }
+
+                return log_error_errno(errno, "Failed to allocate backing file blocks: %m");
+        }
+
+        log_info("Allocated additional %s.",
+                 FORMAT_BYTES((DIV_ROUND_UP(st->st_size, 512) - st->st_blocks) * 512));
+        return 1;
+}
+
+int run_fallocate_by_path(const char *backing_path) {
+        _cleanup_close_ int backing_fd = -1;
+
+        backing_fd = open(backing_path, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
+        if (backing_fd < 0)
+                return log_error_errno(errno, "Failed to open '%s' for fallocate(): %m", backing_path);
+
+        return run_fallocate(backing_fd, NULL);
+}
+
+static int lock_image_fd(int image_fd, const char *ip) {
+        int r;
+
+        /* If the $SYSTEMD_LUKS_LOCK environment variable is set we'll take an exclusive BSD lock on the
+         * image file, and send it to our parent. homed will keep it open to ensure no other instance of
+         * homed (across the network or such) will also mount the file. */
+
+        assert(image_fd >= 0);
+        assert(ip);
+
+        r = getenv_bool("SYSTEMD_LUKS_LOCK");
+        if (r == -ENXIO)
+                return 0;
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse $SYSTEMD_LUKS_LOCK environment variable: %m");
+        if (r == 0)
+                return 0;
+
+        if (flock(image_fd, LOCK_EX|LOCK_NB) < 0) {
+
+                if (errno == EAGAIN)
+                        log_error_errno(errno, "Image file '%s' already locked, can't use.", ip);
+                else
+                        log_error_errno(errno, "Failed to lock image file '%s': %m", ip);
+
+                return errno != EAGAIN ? -errno : -EADDRINUSE; /* Make error recognizable */
+        }
+
+        log_info("Successfully locked image file '%s'.", ip);
+
+        /* Now send it to our parent to keep safe while the home dir is active */
+        r = sd_pid_notify_with_fds(0, false, "SYSTEMD_LUKS_LOCK_FD=1", &image_fd, 1);
+        if (r < 0)
+                log_warning_errno(r, "Failed to send LUKS lock fd to parent, ignoring: %m");
+
+        return 0;
+}
+
+static int open_image_file(
+                UserRecord *h,
+                const char *force_image_path,
+                struct stat *ret_stat) {
+
+        _cleanup_close_ int image_fd = -1;
+        struct stat st;
+        const char *ip;
+        int r;
+
+        assert(h || force_image_path);
+
+        ip = force_image_path ?: user_record_image_path(h);
+
+        image_fd = open(ip, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
+        if (image_fd < 0)
+                return log_error_errno(errno, "Failed to open image file %s: %m", ip);
+
+        if (fstat(image_fd, &st) < 0)
+                return log_error_errno(errno, "Failed to fstat() image file: %m");
+        if (!S_ISREG(st.st_mode) && !S_ISBLK(st.st_mode))
+                return log_error_errno(
+                                S_ISDIR(st.st_mode) ? SYNTHETIC_ERRNO(EISDIR) : SYNTHETIC_ERRNO(EBADFD),
+                                "Image file %s is not a regular file or block device: %m", ip);
+
+        /* Locking block devices doesn't really make sense, as this might interfere with
+         * udev's workings, and these locks aren't network propagated anyway, hence not what
+         * we are after here. */
+        if (S_ISREG(st.st_mode)) {
+                r = lock_image_fd(image_fd, ip);
+                if (r < 0)
+                        return r;
+        }
+
+        if (ret_stat)
+                *ret_stat = st;
+
+        return TAKE_FD(image_fd);
+}
+
+int home_setup_luks(
+                UserRecord *h,
+                HomeSetupFlags flags,
+                const char *force_image_path,
+                HomeSetup *setup,
+                PasswordCache *cache,
+                UserRecord **ret_luks_home) {
+
+        sd_id128_t found_partition_uuid, found_fs_uuid = SD_ID128_NULL, found_luks_uuid = SD_ID128_NULL;
+        _cleanup_(user_record_unrefp) UserRecord *luks_home = NULL;
+        _cleanup_(erase_and_freep) void *volume_key = NULL;
+        size_t volume_key_size = 0;
+        uint64_t offset, size;
+        struct stat st;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(user_record_storage(h) == USER_LUKS);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        r = make_dm_names(h, setup);
+        if (r < 0)
+                return r;
+
+        /* Reuse the image fd if it has already been opened by an earlier step */
+        if (setup->image_fd < 0) {
+                setup->image_fd = open_image_file(h, force_image_path, &st);
+                if (setup->image_fd < 0)
+                        return setup->image_fd;
+        } else if (fstat(setup->image_fd, &st) < 0)
+                return log_error_errno(errno, "Failed to stat image: %m");
+
+        if (FLAGS_SET(flags, HOME_SETUP_ALREADY_ACTIVATED)) {
+                struct loop_info64 info;
+                const char *n;
+
+                if (!setup->crypt_device) {
+                        r = luks_open(h,
+                                      setup,
+                                      cache,
+                                      &found_luks_uuid,
+                                      &volume_key,
+                                      &volume_key_size);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (ret_luks_home) {
+                        r = luks_validate_home_record(setup->crypt_device, h, volume_key, cache, &luks_home);
+                        if (r < 0)
+                                return r;
+                }
+
+                n = sym_crypt_get_device_name(setup->crypt_device);
+                if (!n)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine backing device for DM %s.", setup->dm_name);
+
+                if (!setup->loop) {
+                        r = loop_device_open_from_path(n, O_RDWR, LOCK_UN, &setup->loop);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to open loopback device %s: %m", n);
+                }
+
+                if (ioctl(setup->loop->fd, LOOP_GET_STATUS64, &info) < 0) {
+                        _cleanup_free_ char *sysfs = NULL;
+
+                        if (!IN_SET(errno, ENOTTY, EINVAL))
+                                return log_error_errno(errno, "Failed to get block device metrics of %s: %m", n);
+
+                        if (ioctl(setup->loop->fd, BLKGETSIZE64, &size) < 0)
+                                return log_error_errno(r, "Failed to read block device size of %s: %m", n);
+
+                        if (fstat(setup->loop->fd, &st) < 0)
+                                return log_error_errno(r, "Failed to stat block device %s: %m", n);
+                        assert(S_ISBLK(st.st_mode));
+
+                        if (asprintf(&sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/partition", DEVNUM_FORMAT_VAL(st.st_rdev)) < 0)
+                                return log_oom();
+
+                        if (access(sysfs, F_OK) < 0) {
+                                if (errno != ENOENT)
+                                        return log_error_errno(errno, "Failed to determine whether %s exists: %m", sysfs);
+
+                                offset = 0;
+                        } else {
+                                _cleanup_free_ char *buffer = NULL;
+
+                                if (asprintf(&sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/start", DEVNUM_FORMAT_VAL(st.st_rdev)) < 0)
+                                        return log_oom();
+
+                                r = read_one_line_file(sysfs, &buffer);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to read partition start offset: %m");
+
+                                r = safe_atou64(buffer, &offset);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to parse partition start offset: %m");
+
+                                if (offset > UINT64_MAX / 512U)
+                                        return log_error_errno(SYNTHETIC_ERRNO(E2BIG), "Offset too large for 64 byte range, refusing.");
+
+                                offset *= 512U;
+                        }
+                } else {
+#if HAVE_VALGRIND_MEMCHECK_H
+                        VALGRIND_MAKE_MEM_DEFINED(&info, sizeof(info));
+#endif
+
+                        offset = info.lo_offset;
+                        size = info.lo_sizelimit;
+                }
+
+                found_partition_uuid = found_fs_uuid = SD_ID128_NULL;
+
+                log_info("Discovered used loopback device %s.", setup->loop->node);
+
+                if (setup->root_fd < 0) {
+                        setup->root_fd = open(user_record_home_directory(h), O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                        if (setup->root_fd < 0)
+                                return log_error_errno(errno, "Failed to open home directory: %m");
+                }
+        } else {
+                _cleanup_free_ char *fstype = NULL, *subdir = NULL;
+                const char *ip;
+
+                /* When we aren't reopening the home directory we are allocating it fresh, hence the relevant
+                 * objects can't be allocated yet. */
+                assert(setup->root_fd < 0);
+                assert(!setup->crypt_device);
+                assert(!setup->loop);
+
+                ip = force_image_path ?: user_record_image_path(h);
+
+                subdir = path_join(HOME_RUNTIME_WORK_DIR, user_record_user_name_and_realm(h));
+                if (!subdir)
+                        return log_oom();
+
+                r = luks_validate(setup->image_fd, user_record_user_name_and_realm(h), h->partition_uuid, &found_partition_uuid, &offset, &size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to validate disk label: %m");
+
+                /* Everything before this point left the image untouched. We are now starting to make
+                 * changes, hence mark the image dirty */
+                if (run_mark_dirty(setup->image_fd, true) > 0)
+                        setup->do_mark_clean = true;
+
+                if (!user_record_luks_discard(h)) {
+                        r = run_fallocate(setup->image_fd, &st);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = loop_device_make(setup->image_fd, O_RDWR, offset, size, user_record_luks_sector_size(h), 0, LOCK_UN, &setup->loop);
+                if (r == -ENOENT) {
+                        log_error_errno(r, "Loopback block device support is not available on this system.");
+                        return -ENOLINK; /* make recognizable */
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to allocate loopback context: %m");
+
+                log_info("Setting up loopback device %s completed.", setup->loop->node ?: ip);
+
+                r = luks_setup(h,
+                               setup->loop->node ?: ip,
+                               setup->dm_name,
+                               h->luks_uuid,
+                               h->luks_cipher,
+                               h->luks_cipher_mode,
+                               h->luks_volume_key_size,
+                               h->password,
+                               cache,
+                               user_record_luks_discard(h) || user_record_luks_offline_discard(h),
+                               &setup->crypt_device,
+                               &found_luks_uuid,
+                               &volume_key,
+                               &volume_key_size,
+                               &setup->key_serial);
+                if (r < 0)
+                        return r;
+
+                setup->undo_dm = true;
+
+                if (ret_luks_home) {
+                        r = luks_validate_home_record(setup->crypt_device, h, volume_key, cache, &luks_home);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = fs_validate(setup->dm_node, h->file_system_uuid, &fstype, &found_fs_uuid);
+                if (r < 0)
+                        return r;
+
+                r = run_fsck(setup->dm_node, fstype);
+                if (r < 0)
+                        return r;
+
+                r = home_unshare_and_mount(setup->dm_node, fstype, user_record_luks_discard(h), user_record_mount_flags(h), h->luks_extra_mount_options);
+                if (r < 0)
+                        return r;
+
+                setup->undo_mount = true;
+
+                setup->root_fd = open(subdir, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                if (setup->root_fd < 0)
+                        return log_error_errno(errno, "Failed to open home directory: %m");
+
+                if (user_record_luks_discard(h))
+                        (void) run_fitrim(setup->root_fd);
+
+                setup->do_offline_fallocate = !(setup->do_offline_fitrim = user_record_luks_offline_discard(h));
+        }
+
+        if (!sd_id128_is_null(found_partition_uuid))
+                setup->found_partition_uuid = found_partition_uuid;
+        if (!sd_id128_is_null(found_luks_uuid))
+                setup->found_luks_uuid = found_luks_uuid;
+        if (!sd_id128_is_null(found_fs_uuid))
+                setup->found_fs_uuid = found_fs_uuid;
+
+        setup->partition_offset = offset;
+        setup->partition_size = size;
+
+        if (volume_key) {
+                erase_and_free(setup->volume_key);
+                setup->volume_key = TAKE_PTR(volume_key);
+                setup->volume_key_size = volume_key_size;
+        }
+
+        if (ret_luks_home)
+                *ret_luks_home = TAKE_PTR(luks_home);
+
+        return 0;
+}
+
+static void print_size_summary(uint64_t host_size, uint64_t encrypted_size, const struct statfs *sfs) {
+        assert(sfs);
+
+        log_info("Image size is %s, file system size is %s, file system payload size is %s, file system free is %s.",
+                 FORMAT_BYTES(host_size),
+                 FORMAT_BYTES(encrypted_size),
+                 FORMAT_BYTES((uint64_t) sfs->f_blocks * (uint64_t) sfs->f_frsize),
+                 FORMAT_BYTES((uint64_t) sfs->f_bfree * (uint64_t) sfs->f_frsize));
+}
+
+static int home_auto_grow_luks(
+                UserRecord *h,
+                HomeSetup *setup,
+                PasswordCache *cache) {
+
+        struct statfs sfs;
+
+        assert(h);
+        assert(setup);
+
+        if (!IN_SET(user_record_auto_resize_mode(h), AUTO_RESIZE_GROW, AUTO_RESIZE_SHRINK_AND_GROW))
+                return 0;
+
+        assert(setup->root_fd >= 0);
+
+        if (fstatfs(setup->root_fd, &sfs) < 0)
+                return log_error_errno(errno, "Failed to statfs home directory: %m");
+
+        if (!fs_can_online_shrink_and_grow(sfs.f_type)) {
+                log_debug("Not auto-grow file system, since selected file system cannot do both online shrink and grow.");
+                return 0;
+        }
+
+        log_debug("Initiating auto-grow...");
+
+        return home_resize_luks(
+                        h,
+                        HOME_SETUP_ALREADY_ACTIVATED|
+                        HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES|
+                        HOME_SETUP_RESIZE_DONT_SHRINK|
+                        HOME_SETUP_RESIZE_DONT_UNDO,
+                        setup,
+                        cache,
+                        NULL);
+}
+
+int home_activate_luks(
+                UserRecord *h,
+                HomeSetupFlags flags,
+                HomeSetup *setup,
+                PasswordCache *cache,
+                UserRecord **ret_home) {
+
+        _cleanup_(user_record_unrefp) UserRecord *new_home = NULL, *luks_home_record = NULL;
+        uint64_t host_size, encrypted_size;
+        const char *hdo, *hd;
+        struct statfs sfs;
+        int r;
+
+        assert(h);
+        assert(user_record_storage(h) == USER_LUKS);
+        assert(setup);
+        assert(ret_home);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        assert_se(hdo = user_record_home_directory(h));
+        hd = strdupa_safe(hdo); /* copy the string out, since it might change later in the home record object */
+
+        r = home_get_state_luks(h, setup);
+        if (r < 0)
+                return r;
+        if (r > 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EEXIST), "Device mapper device %s already exists, refusing.", setup->dm_node);
+
+        r = home_setup_luks(
+                        h,
+                        0,
+                        NULL,
+                        setup,
+                        cache,
+                        &luks_home_record);
+        if (r < 0)
+                return r;
+
+        r = home_auto_grow_luks(h, setup, cache);
+        if (r < 0)
+                return r;
+
+        r = block_get_size_by_fd(setup->loop->fd, &host_size);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get loopback block device size: %m");
+
+        r = block_get_size_by_path(setup->dm_node, &encrypted_size);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get LUKS block device size: %m");
+
+        r = home_refresh(
+                        h,
+                        flags,
+                        setup,
+                        luks_home_record,
+                        cache,
+                        &sfs,
+                        &new_home);
+        if (r < 0)
+                return r;
+
+        r = home_extend_embedded_identity(new_home, h, setup);
+        if (r < 0)
+                return r;
+
+        setup->root_fd = safe_close(setup->root_fd);
+
+        r = home_move_mount(user_record_user_name_and_realm(h), hd);
+        if (r < 0)
+                return r;
+
+        setup->undo_mount = false;
+        setup->do_offline_fitrim = false;
+
+        loop_device_relinquish(setup->loop);
+
+        r = sym_crypt_deactivate_by_name(NULL, setup->dm_name, CRYPT_DEACTIVATE_DEFERRED);
+        if (r < 0)
+                log_warning_errno(r, "Failed to relinquish DM device, ignoring: %m");
+
+        setup->undo_dm = false;
+        setup->do_offline_fallocate = false;
+        setup->do_mark_clean = false;
+        setup->do_drop_caches = false;
+        TAKE_KEY_SERIAL(setup->key_serial); /* Leave key in kernel keyring */
+
+        log_info("Activation completed.");
+
+        print_size_summary(host_size, encrypted_size, &sfs);
+
+        *ret_home = TAKE_PTR(new_home);
+        return 1;
+}
+
+int home_deactivate_luks(UserRecord *h, HomeSetup *setup) {
+        bool we_detached = false;
+        int r;
+
+        assert(h);
+        assert(setup);
+
+        /* Note that the DM device and loopback device are set to auto-detach, hence strictly speaking we
+         * don't have to explicitly have to detach them. However, we do that nonetheless (in case of the DM
+         * device), to avoid races: by explicitly detaching them we know when the detaching is complete. We
+         * don't bother about the loopback device because unlike the DM device it doesn't have a fixed
+         * name. */
+
+        if (!setup->crypt_device) {
+                r = acquire_open_luks_device(h, setup, /* graceful= */ true);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to initialize cryptsetup context for %s: %m", setup->dm_name);
+                if (r == 0)
+                        log_debug("LUKS device %s has already been detached.", setup->dm_name);
+        }
+
+        if (setup->crypt_device) {
+                log_info("Discovered used LUKS device %s.", setup->dm_node);
+
+                cryptsetup_enable_logging(setup->crypt_device);
+
+                r = sym_crypt_deactivate_by_name(setup->crypt_device, setup->dm_name, 0);
+                if (ERRNO_IS_DEVICE_ABSENT(r) || r == -EINVAL)
+                        log_debug_errno(r, "LUKS device %s is already detached.", setup->dm_node);
+                else if (r < 0)
+                        return log_info_errno(r, "LUKS device %s couldn't be deactivated: %m", setup->dm_node);
+                else {
+                        log_info("LUKS device detaching completed.");
+                        we_detached = true;
+                }
+        }
+
+        (void) wait_for_block_device_gone(setup, USEC_PER_SEC * 30);
+        setup->undo_dm = false;
+
+        if (user_record_luks_offline_discard(h))
+                log_debug("Not allocating on logout.");
+        else
+                (void) run_fallocate_by_path(user_record_image_path(h));
+
+        run_mark_dirty_by_path(user_record_image_path(h), false);
+        return we_detached;
+}
+
+int home_trim_luks(UserRecord *h, HomeSetup *setup) {
+        assert(h);
+        assert(setup);
+        assert(setup->root_fd >= 0);
+
+        if (!user_record_luks_offline_discard(h)) {
+                log_debug("Not trimming on logout.");
+                return 0;
+        }
+
+        (void) run_fitrim(setup->root_fd);
+        return 0;
+}
+
+static struct crypt_pbkdf_type* build_good_pbkdf(struct crypt_pbkdf_type *buffer, UserRecord *hr) {
+        assert(buffer);
+        assert(hr);
+
+        *buffer = (struct crypt_pbkdf_type) {
+                .hash = user_record_luks_pbkdf_hash_algorithm(hr),
+                .type = user_record_luks_pbkdf_type(hr),
+                .time_ms = user_record_luks_pbkdf_time_cost_usec(hr) / USEC_PER_MSEC,
+                .max_memory_kb = user_record_luks_pbkdf_memory_cost(hr) / 1024,
+                .parallel_threads = user_record_luks_pbkdf_parallel_threads(hr),
+        };
+
+        return buffer;
+}
+
+static struct crypt_pbkdf_type* build_minimal_pbkdf(struct crypt_pbkdf_type *buffer, UserRecord *hr) {
+        assert(buffer);
+        assert(hr);
+
+        /* For PKCS#11 derived keys (which are generated randomly and are of high quality already) we use a
+         * minimal PBKDF */
+        *buffer = (struct crypt_pbkdf_type) {
+                .hash = user_record_luks_pbkdf_hash_algorithm(hr),
+                .type = CRYPT_KDF_PBKDF2,
+                .iterations = 1,
+                .time_ms = 1,
+        };
+
+        return buffer;
+}
+
+static int luks_format(
+                const char *node,
+                const char *dm_name,
+                sd_id128_t uuid,
+                const char *label,
+                const PasswordCache *cache,
+                char **effective_passwords,
+                bool discard,
+                UserRecord *hr,
+                struct crypt_device **ret) {
+
+        _cleanup_(user_record_unrefp) UserRecord *reduced = NULL;
+        _cleanup_(sym_crypt_freep) struct crypt_device *cd = NULL;
+        _cleanup_(erase_and_freep) void *volume_key = NULL;
+        struct crypt_pbkdf_type good_pbkdf, minimal_pbkdf;
+        _cleanup_free_ char *text = NULL;
+        size_t volume_key_size;
+        int slot = 0, r;
+
+        assert(node);
+        assert(dm_name);
+        assert(hr);
+        assert(ret);
+
+        r = sym_crypt_init(&cd, node);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate libcryptsetup context: %m");
+
+        cryptsetup_enable_logging(cd);
+
+        /* Normally we'd, just leave volume key generation to libcryptsetup. However, we can't, since we
+         * can't extract the volume key from the library again, but we need it in order to encrypt the JSON
+         * record. Hence, let's generate it on our own, so that we can keep track of it. */
+
+        volume_key_size = user_record_luks_volume_key_size(hr);
+        volume_key = malloc(volume_key_size);
+        if (!volume_key)
+                return log_oom();
+
+        r = crypto_random_bytes(volume_key, volume_key_size);
+        if (r < 0)
+                return log_error_errno(r, "Failed to generate volume key: %m");
+
+#if HAVE_CRYPT_SET_METADATA_SIZE
+        /* Increase the metadata space to 4M, the largest LUKS2 supports */
+        r = sym_crypt_set_metadata_size(cd, 4096U*1024U, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to change LUKS2 metadata size: %m");
+#endif
+
+        build_good_pbkdf(&good_pbkdf, hr);
+        build_minimal_pbkdf(&minimal_pbkdf, hr);
+
+        r = sym_crypt_format(
+                        cd,
+                        CRYPT_LUKS2,
+                        user_record_luks_cipher(hr),
+                        user_record_luks_cipher_mode(hr),
+                        SD_ID128_TO_UUID_STRING(uuid),
+                        volume_key,
+                        volume_key_size,
+                        &(struct crypt_params_luks2) {
+                                .label = label,
+                                .subsystem = "systemd-home",
+                                .sector_size = user_record_luks_sector_size(hr),
+                                .pbkdf = &good_pbkdf,
+                        });
+        if (r < 0)
+                return log_error_errno(r, "Failed to format LUKS image: %m");
+
+        log_info("LUKS formatting completed.");
+
+        STRV_FOREACH(pp, effective_passwords) {
+
+                if (password_cache_contains(cache, *pp)) { /* is this a fido2 or pkcs11 password? */
+                        log_debug("Using minimal PBKDF for slot %i", slot);
+                        r = sym_crypt_set_pbkdf_type(cd, &minimal_pbkdf);
+                } else {
+                        log_debug("Using good PBKDF for slot %i", slot);
+                        r = sym_crypt_set_pbkdf_type(cd, &good_pbkdf);
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to tweak PBKDF for slot %i: %m", slot);
+
+                r = sym_crypt_keyslot_add_by_volume_key(
+                                cd,
+                                slot,
+                                volume_key,
+                                volume_key_size,
+                                *pp,
+                                strlen(*pp));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to set up LUKS password for slot %i: %m", slot);
+
+                log_info("Writing password to LUKS keyslot %i completed.", slot);
+                slot++;
+        }
+
+        r = sym_crypt_activate_by_volume_key(
+                        cd,
+                        dm_name,
+                        volume_key,
+                        volume_key_size,
+                        discard ? CRYPT_ACTIVATE_ALLOW_DISCARDS : 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to activate LUKS superblock: %m");
+
+        log_info("LUKS activation by volume key succeeded.");
+
+        r = user_record_clone(hr, USER_RECORD_EXTRACT_EMBEDDED|USER_RECORD_PERMISSIVE, &reduced);
+        if (r < 0)
+                return log_error_errno(r, "Failed to prepare home record for LUKS: %m");
+
+        r = format_luks_token_text(cd, reduced, volume_key, &text);
+        if (r < 0)
+                return r;
+
+        r = sym_crypt_token_json_set(cd, CRYPT_ANY_TOKEN, text);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set LUKS JSON token: %m");
+
+        log_info("Writing user record as LUKS token completed.");
+
+        if (ret)
+                *ret = TAKE_PTR(cd);
+
+        return 0;
+}
+
+static int make_partition_table(
+                int fd,
+                const char *label,
+                sd_id128_t uuid,
+                uint64_t *ret_offset,
+                uint64_t *ret_size,
+                sd_id128_t *ret_disk_uuid) {
+
+        _cleanup_(fdisk_unref_partitionp) struct fdisk_partition *p = NULL, *q = NULL;
+        _cleanup_(fdisk_unref_parttypep) struct fdisk_parttype *t = NULL;
+        _cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
+        _cleanup_free_ char *path = NULL, *disk_uuid_as_string = NULL;
+        uint64_t offset, size, first_lba, start, last_lba, end;
+        sd_id128_t disk_uuid;
+        int r;
+
+        assert(fd >= 0);
+        assert(label);
+        assert(ret_offset);
+        assert(ret_size);
+
+        t = fdisk_new_parttype();
+        if (!t)
+                return log_oom();
+
+        r = fdisk_parttype_set_typestr(t, SD_GPT_USER_HOME_STR);
+        if (r < 0)
+                return log_error_errno(r, "Failed to initialize partition type: %m");
+
+        c = fdisk_new_context();
+        if (!c)
+                return log_oom();
+
+        if (asprintf(&path, "/proc/self/fd/%i", fd) < 0)
+                return log_oom();
+
+        r = fdisk_assign_device(c, path, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to open device: %m");
+
+        r = fdisk_create_disklabel(c, "gpt");
+        if (r < 0)
+                return log_error_errno(r, "Failed to create GPT disk label: %m");
+
+        p = fdisk_new_partition();
+        if (!p)
+                return log_oom();
+
+        r = fdisk_partition_set_type(p, t);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set partition type: %m");
+
+        r = fdisk_partition_partno_follow_default(p, 1);
+        if (r < 0)
+                return log_error_errno(r, "Failed to place partition at first free partition index: %m");
+
+        first_lba = fdisk_get_first_lba(c); /* Boundary where usable space starts */
+        assert(first_lba <= UINT64_MAX/512);
+        start = DISK_SIZE_ROUND_UP(first_lba * 512); /* Round up to multiple of 4K */
+
+        log_debug("Starting partition at offset %" PRIu64, start);
+
+        if (start == UINT64_MAX)
+                return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "Overflow while rounding up start LBA.");
+
+        last_lba = fdisk_get_last_lba(c); /* One sector before boundary where usable space ends */
+        assert(last_lba < UINT64_MAX/512);
+        end = DISK_SIZE_ROUND_DOWN((last_lba + 1) * 512); /* Round down to multiple of 4K */
+
+        if (end <= start)
+                return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "Resulting partition size zero or negative.");
+
+        r = fdisk_partition_set_start(p, start / 512);
+        if (r < 0)
+                return log_error_errno(r, "Failed to place partition at offset %" PRIu64 ": %m", start);
+
+        r = fdisk_partition_set_size(p, (end - start) / 512);
+        if (r < 0)
+                return log_error_errno(r, "Failed to end partition at offset %" PRIu64 ": %m", end);
+
+        r = fdisk_partition_set_name(p, label);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set partition name: %m");
+
+        r = fdisk_partition_set_uuid(p, SD_ID128_TO_UUID_STRING(uuid));
+        if (r < 0)
+                return log_error_errno(r, "Failed to set partition UUID: %m");
+
+        r = fdisk_add_partition(c, p, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add partition: %m");
+
+        r = fdisk_write_disklabel(c);
+        if (r < 0)
+                return log_error_errno(r, "Failed to write disk label: %m");
+
+        r = fdisk_get_disklabel_id(c, &disk_uuid_as_string);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine disk label UUID: %m");
+
+        r = sd_id128_from_string(disk_uuid_as_string, &disk_uuid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse disk label UUID: %m");
+
+        r = fdisk_get_partition(c, 0, &q);
+        if (r < 0)
+                return log_error_errno(r, "Failed to read created partition metadata: %m");
+
+        assert(fdisk_partition_has_start(q));
+        offset = fdisk_partition_get_start(q);
+        if (offset > UINT64_MAX / 512U)
+                return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "Partition offset too large.");
+
+        assert(fdisk_partition_has_size(q));
+        size = fdisk_partition_get_size(q);
+        if (size > UINT64_MAX / 512U)
+                return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "Partition size too large.");
+
+        *ret_offset = offset * 512U;
+        *ret_size = size * 512U;
+        *ret_disk_uuid = disk_uuid;
+
+        return 0;
+}
+
+static bool supported_fs_size(const char *fstype, uint64_t host_size) {
+        uint64_t m;
+
+        m = minimal_size_by_fs_name(fstype);
+        if (m == UINT64_MAX)
+                return false;
+
+        return host_size >= m;
+}
+
+static int wait_for_devlink(const char *path) {
+        _cleanup_close_ int inotify_fd = -1;
+        usec_t until;
+        int r;
+
+        /* let's wait for a device link to show up in /dev, with a timeout. This is good to do since we
+         * return a /dev/disk/by-uuid/… link to our callers and they likely want to access it right-away,
+         * hence let's wait until udev has caught up with our changes, and wait for the symlink to be
+         * created. */
+
+        until = usec_add(now(CLOCK_MONOTONIC), 45 * USEC_PER_SEC);
+
+        for (;;) {
+                _cleanup_free_ char *dn = NULL;
+                usec_t w;
+
+                if (laccess(path, F_OK) < 0) {
+                        if (errno != ENOENT)
+                                return log_error_errno(errno, "Failed to determine whether %s exists: %m", path);
+                } else
+                        return 0; /* Found it */
+
+                if (inotify_fd < 0) {
+                        /* We need to wait for the device symlink to show up, let's create an inotify watch for it */
+                        inotify_fd = inotify_init1(IN_NONBLOCK|IN_CLOEXEC);
+                        if (inotify_fd < 0)
+                                return log_error_errno(errno, "Failed to allocate inotify fd: %m");
+                }
+
+                r = path_extract_directory(path, &dn);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to extract directory from device node path '%s': %m", path);
+                for (;;) {
+                        _cleanup_free_ char *ndn = NULL;
+
+                        log_info("Watching %s", dn);
+
+                        if (inotify_add_watch(inotify_fd, dn, IN_CREATE|IN_MOVED_TO|IN_ONLYDIR|IN_DELETE_SELF|IN_MOVE_SELF) < 0) {
+                                if (errno != ENOENT)
+                                        return log_error_errno(errno, "Failed to add watch on %s: %m", dn);
+                        } else
+                                break;
+
+                        r = path_extract_directory(dn, &ndn);
+                        if (r == -EADDRNOTAVAIL) /* Arrived at the top? */
+                                break;
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to extract directory from device node path '%s': %m", dn);
+
+                        free_and_replace(dn, ndn);
+                }
+
+                w = now(CLOCK_MONOTONIC);
+                if (w >= until)
+                        return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Device link %s still hasn't shown up, giving up.", path);
+
+                r = fd_wait_for_event(inotify_fd, POLLIN, usec_sub_unsigned(until, w));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to watch inotify: %m");
+
+                (void) flush_fd(inotify_fd);
+        }
+}
+
+static int calculate_initial_image_size(UserRecord *h, int image_fd, const char *fstype, uint64_t *ret) {
+        uint64_t upper_boundary, lower_boundary;
+        struct statfs sfs;
+
+        assert(h);
+        assert(image_fd >= 0);
+        assert(ret);
+
+        if (fstatfs(image_fd, &sfs) < 0)
+                return log_error_errno(errno, "statfs() on image failed: %m");
+
+        upper_boundary = DISK_SIZE_ROUND_DOWN((uint64_t) sfs.f_bsize * sfs.f_bavail);
+
+        if (h->disk_size != UINT64_MAX)
+                *ret = MIN(DISK_SIZE_ROUND_DOWN(h->disk_size), upper_boundary);
+        else if (h->disk_size_relative == UINT64_MAX) {
+
+                if (upper_boundary > UINT64_MAX / USER_DISK_SIZE_DEFAULT_PERCENT)
+                        return log_error_errno(SYNTHETIC_ERRNO(EOVERFLOW), "Disk size too large.");
+
+                *ret = DISK_SIZE_ROUND_DOWN(upper_boundary * USER_DISK_SIZE_DEFAULT_PERCENT / 100);
+
+                log_info("Sizing home to %u%% of available disk space, which is %s.",
+                         USER_DISK_SIZE_DEFAULT_PERCENT,
+                         FORMAT_BYTES(*ret));
+        } else {
+                *ret = DISK_SIZE_ROUND_DOWN((uint64_t) ((double) upper_boundary * (double) CLAMP(h->disk_size_relative, 0U, UINT32_MAX) / (double) UINT32_MAX));
+
+                log_info("Sizing home to %" PRIu64 ".%01" PRIu64 "%% of available disk space, which is %s.",
+                         (h->disk_size_relative * 100) / UINT32_MAX,
+                         ((h->disk_size_relative * 1000) / UINT32_MAX) % 10,
+                         FORMAT_BYTES(*ret));
+        }
+
+        lower_boundary = minimal_size_by_fs_name(fstype);
+        if (lower_boundary != UINT64_MAX) {
+                assert(GPT_LUKS2_OVERHEAD < UINT64_MAX - lower_boundary);
+                lower_boundary += GPT_LUKS2_OVERHEAD;
+        }
+        if (lower_boundary == UINT64_MAX || lower_boundary < USER_DISK_SIZE_MIN)
+                lower_boundary = USER_DISK_SIZE_MIN;
+
+        if (*ret < lower_boundary)
+                *ret = lower_boundary;
+
+        return 0;
+}
+
+static int home_truncate(
+                UserRecord *h,
+                int fd,
+                uint64_t size) {
+
+        bool trunc;
+        int r;
+
+        assert(h);
+        assert(fd >= 0);
+
+        trunc = user_record_luks_discard(h);
+        if (!trunc) {
+                r = fallocate(fd, 0, 0, size);
+                if (r < 0 && ERRNO_IS_NOT_SUPPORTED(errno)) {
+                        /* Some file systems do not support fallocate(), let's gracefully degrade
+                         * (ZFS, reiserfs, …) and fall back to truncation */
+                        log_notice_errno(errno, "Backing file system does not support fallocate(), falling back to ftruncate(), i.e. implicitly using non-discard mode.");
+                        trunc = true;
+                }
+        }
+
+        if (trunc)
+                r = ftruncate(fd, size);
+
+        if (r < 0) {
+                if (ERRNO_IS_DISK_SPACE(errno)) {
+                        log_debug_errno(errno, "Not enough disk space to allocate home of size %s.", FORMAT_BYTES(size));
+                        return -ENOSPC; /* make recognizable */
+                }
+
+                return log_error_errno(errno, "Failed to truncate home image: %m");
+        }
+
+        return !trunc; /* Return == 0 if we managed to truncate, > 0 if we managed to allocate */
+}
+
+int home_create_luks(
+                UserRecord *h,
+                HomeSetup *setup,
+                const PasswordCache *cache,
+                char **effective_passwords,
+                UserRecord **ret_home) {
+
+        _cleanup_free_ char *subdir = NULL, *disk_uuid_path = NULL;
+        uint64_t encrypted_size,
+                host_size = 0, partition_offset = 0, partition_size = 0; /* Unnecessary initialization to appease gcc */
+        _cleanup_(user_record_unrefp) UserRecord *new_home = NULL;
+        sd_id128_t partition_uuid, fs_uuid, luks_uuid, disk_uuid;
+        _cleanup_close_ int mount_fd = -1;
+        const char *fstype, *ip;
+        struct statfs sfs;
+        int r;
+
+        assert(h);
+        assert(h->storage < 0 || h->storage == USER_LUKS);
+        assert(setup);
+        assert(!setup->temporary_image_path);
+        assert(setup->image_fd < 0);
+        assert(ret_home);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        assert_se(ip = user_record_image_path(h));
+
+        fstype = user_record_file_system_type(h);
+        if (!supported_fstype(fstype))
+                return log_error_errno(SYNTHETIC_ERRNO(EPROTONOSUPPORT), "Unsupported file system type: %s", fstype);
+
+        r = mkfs_exists(fstype);
+        if (r < 0)
+                return log_error_errno(r, "Failed to check if mkfs binary for %s exists: %m", fstype);
+        if (r == 0) {
+                if (h->file_system_type || streq(fstype, "ext4") || !supported_fstype("ext4"))
+                        return log_error_errno(SYNTHETIC_ERRNO(EPROTONOSUPPORT), "mkfs binary for file system type %s does not exist.", fstype);
+
+                /* If the record does not explicitly declare a file system to use, and the compiled-in
+                 * default does not actually exist, than do an automatic fallback onto ext4, as the baseline
+                 * fs of Linux. We won't search for a working fs type here beyond ext4, i.e. nothing fancier
+                 * than a single, conservative fallback to baseline. This should be useful in minimal
+                 * environments where mkfs.btrfs or so are not made available, but mkfs.ext4 as Linux' most
+                 * boring, most basic fs is. */
+                log_info("Formatting tool for compiled-in default file system %s not available, falling back to ext4 instead.", fstype);
+                fstype = "ext4";
+        }
+
+        if (sd_id128_is_null(h->partition_uuid)) {
+                r = sd_id128_randomize(&partition_uuid);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to acquire partition UUID: %m");
+        } else
+                partition_uuid = h->partition_uuid;
+
+        if (sd_id128_is_null(h->luks_uuid)) {
+                r = sd_id128_randomize(&luks_uuid);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to acquire LUKS UUID: %m");
+        } else
+                luks_uuid = h->luks_uuid;
+
+        if (sd_id128_is_null(h->file_system_uuid)) {
+                r = sd_id128_randomize(&fs_uuid);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to acquire file system UUID: %m");
+        } else
+                fs_uuid = h->file_system_uuid;
+
+        r = make_dm_names(h, setup);
+        if (r < 0)
+                return r;
+
+        r = access(setup->dm_node, F_OK);
+        if (r < 0) {
+                if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to determine whether %s exists: %m", setup->dm_node);
+        } else
+                return log_error_errno(SYNTHETIC_ERRNO(EEXIST), "Device mapper device %s already exists, refusing.", setup->dm_node);
+
+        if (path_startswith(ip, "/dev/")) {
+                _cleanup_free_ char *sysfs = NULL;
+                uint64_t block_device_size;
+                struct stat st;
+
+                /* Let's place the home directory on a real device, i.e. an USB stick or such */
+
+                setup->image_fd = open_image_file(h, ip, &st);
+                if (setup->image_fd < 0)
+                        return setup->image_fd;
+
+                if (!S_ISBLK(st.st_mode))
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTBLK), "Device is not a block device, refusing.");
+
+                if (asprintf(&sysfs, "/sys/dev/block/" DEVNUM_FORMAT_STR "/partition", DEVNUM_FORMAT_VAL(st.st_rdev)) < 0)
+                        return log_oom();
+                if (access(sysfs, F_OK) < 0) {
+                        if (errno != ENOENT)
+                                return log_error_errno(errno, "Failed to check whether %s exists: %m", sysfs);
+                } else
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTBLK), "Operating on partitions is currently not supported, sorry. Please specify a top-level block device.");
+
+                if (flock(setup->image_fd, LOCK_EX) < 0) /* make sure udev doesn't read from it while we operate on the device */
+                        return log_error_errno(errno, "Failed to lock block device %s: %m", ip);
+
+                if (ioctl(setup->image_fd, BLKGETSIZE64, &block_device_size) < 0)
+                        return log_error_errno(errno, "Failed to read block device size: %m");
+
+                if (h->disk_size == UINT64_MAX) {
+
+                        /* If a relative disk size is requested, apply it relative to the block device size */
+                        if (h->disk_size_relative < UINT32_MAX)
+                                host_size = CLAMP(DISK_SIZE_ROUND_DOWN(block_device_size * h->disk_size_relative / UINT32_MAX),
+                                                  USER_DISK_SIZE_MIN, USER_DISK_SIZE_MAX);
+                        else
+                                host_size = block_device_size; /* Otherwise, take the full device */
+
+                } else if (h->disk_size > block_device_size)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMSGSIZE), "Selected disk size larger than backing block device, refusing.");
+                else
+                        host_size = DISK_SIZE_ROUND_DOWN(h->disk_size);
+
+                if (!supported_fs_size(fstype, LESS_BY(host_size, GPT_LUKS2_OVERHEAD)))
+                        return log_error_errno(SYNTHETIC_ERRNO(ERANGE),
+                                               "Selected file system size too small for %s.", fstype);
+
+                /* After creation we should reference this partition by its UUID instead of the block
+                 * device. That's preferable since the user might have specified a device node such as
+                 * /dev/sdb to us, which might look very different when replugged. */
+                if (asprintf(&disk_uuid_path, "/dev/disk/by-uuid/" SD_ID128_UUID_FORMAT_STR, SD_ID128_FORMAT_VAL(luks_uuid)) < 0)
+                        return log_oom();
+
+                if (user_record_luks_discard(h) || user_record_luks_offline_discard(h)) {
+                        /* If we want online or offline discard, discard once before we start using things. */
+
+                        if (ioctl(setup->image_fd, BLKDISCARD, (uint64_t[]) { 0, block_device_size }) < 0)
+                                log_full_errno(errno == EOPNOTSUPP ? LOG_DEBUG : LOG_WARNING, errno,
+                                               "Failed to issue full-device BLKDISCARD on device, ignoring: %m");
+                        else
+                                log_info("Full device discard completed.");
+                }
+        } else {
+                _cleanup_free_ char *t = NULL;
+
+                r = mkdir_parents(ip, 0755);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to create parent directory of %s: %m", ip);
+
+                r = tempfn_random(ip, "homework", &t);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to derive temporary file name for %s: %m", ip);
+
+                setup->image_fd = open(t, O_RDWR|O_CREAT|O_EXCL|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0600);
+                if (setup->image_fd < 0)
+                        return log_error_errno(errno, "Failed to create home image %s: %m", t);
+
+                setup->temporary_image_path = TAKE_PTR(t);
+
+                r = chattr_full(t, setup->image_fd, FS_NOCOW_FL|FS_NOCOMP_FL, FS_NOCOW_FL|FS_NOCOMP_FL, NULL, NULL, CHATTR_FALLBACK_BITWISE);
+                if (r < 0 && r != -ENOANO) /* ENOANO → some bits didn't work; which we skip logging about because chattr_full() already debug logs about those flags */
+                        log_full_errno(ERRNO_IS_NOT_SUPPORTED(r) ? LOG_DEBUG : LOG_WARNING, r,
+                                       "Failed to set file attributes on %s, ignoring: %m", setup->temporary_image_path);
+
+                r = calculate_initial_image_size(h, setup->image_fd, fstype, &host_size);
+                if (r < 0)
+                        return r;
+
+                r = resize_image_loop(h, setup, 0, host_size, &host_size);
+                if (r < 0)
+                        return r;
+
+                log_info("Allocating image file completed.");
+        }
+
+        r = make_partition_table(
+                        setup->image_fd,
+                        user_record_user_name_and_realm(h),
+                        partition_uuid,
+                        &partition_offset,
+                        &partition_size,
+                        &disk_uuid);
+        if (r < 0)
+                return r;
+
+        log_info("Writing of partition table completed.");
+
+        r = loop_device_make(setup->image_fd, O_RDWR, partition_offset, partition_size, user_record_luks_sector_size(h), 0, LOCK_EX, &setup->loop);
+        if (r < 0) {
+                if (r == -ENOENT) { /* this means /dev/loop-control doesn't exist, i.e. we are in a container
+                                     * or similar and loopback bock devices are not available, return a
+                                     * recognizable error in this case. */
+                        log_error_errno(r, "Loopback block device support is not available on this system.");
+                        return -ENOLINK; /* Make recognizable */
+                }
+
+                return log_error_errno(r, "Failed to set up loopback device for %s: %m", setup->temporary_image_path);
+        }
+
+        log_info("Setting up loopback device %s completed.", setup->loop->node ?: ip);
+
+        r = luks_format(setup->loop->node,
+                        setup->dm_name,
+                        luks_uuid,
+                        user_record_user_name_and_realm(h),
+                        cache,
+                        effective_passwords,
+                        user_record_luks_discard(h) || user_record_luks_offline_discard(h),
+                        h,
+                        &setup->crypt_device);
+        if (r < 0)
+                return r;
+
+        setup->undo_dm = true;
+
+        r = block_get_size_by_path(setup->dm_node, &encrypted_size);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get encrypted block device size: %m");
+
+        log_info("Setting up LUKS device %s completed.", setup->dm_node);
+
+        r = make_filesystem(setup->dm_node, fstype, user_record_user_name_and_realm(h), NULL, fs_uuid, user_record_luks_discard(h));
+        if (r < 0)
+                return r;
+
+        log_info("Formatting file system completed.");
+
+        r = home_unshare_and_mount(setup->dm_node, fstype, user_record_luks_discard(h), user_record_mount_flags(h), h->luks_extra_mount_options);
+        if (r < 0)
+                return r;
+
+        setup->undo_mount = true;
+
+        subdir = path_join(HOME_RUNTIME_WORK_DIR, user_record_user_name_and_realm(h));
+        if (!subdir)
+                return log_oom();
+
+        /* Prefer using a btrfs subvolume if we can, fall back to directory otherwise */
+        r = btrfs_subvol_make_fallback(subdir, 0700);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create user directory in mounted image file: %m");
+
+        setup->root_fd = open(subdir, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+        if (setup->root_fd < 0)
+                return log_error_errno(errno, "Failed to open user directory in mounted image file: %m");
+
+        (void) home_shift_uid(setup->root_fd, NULL, UID_NOBODY, h->uid, &mount_fd);
+
+        if (mount_fd >= 0) {
+                /* If we have established a new mount, then we can use that as new root fd to our home directory. */
+                safe_close(setup->root_fd);
+
+                setup->root_fd = fd_reopen(mount_fd, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
+                if (setup->root_fd < 0)
+                        return log_error_errno(setup->root_fd, "Unable to convert mount fd into proper directory fd: %m");
+
+                mount_fd = safe_close(mount_fd);
+        }
+
+        r = home_populate(h, setup->root_fd);
+        if (r < 0)
+                return r;
+
+        r = home_sync_and_statfs(setup->root_fd, &sfs);
+        if (r < 0)
+                return r;
+
+        r = user_record_clone(h, USER_RECORD_LOAD_MASK_SECRET|USER_RECORD_LOG|USER_RECORD_PERMISSIVE, &new_home);
+        if (r < 0)
+                return log_error_errno(r, "Failed to clone record: %m");
+
+        r = user_record_add_binding(
+                        new_home,
+                        USER_LUKS,
+                        disk_uuid_path ?: ip,
+                        partition_uuid,
+                        luks_uuid,
+                        fs_uuid,
+                        sym_crypt_get_cipher(setup->crypt_device),
+                        sym_crypt_get_cipher_mode(setup->crypt_device),
+                        luks_volume_key_size_convert(setup->crypt_device),
+                        fstype,
+                        NULL,
+                        h->uid,
+                        (gid_t) h->uid);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add binding to record: %m");
+
+        if (user_record_luks_offline_discard(h)) {
+                r = run_fitrim(setup->root_fd);
+                if (r < 0)
+                        return r;
+        }
+
+        setup->root_fd = safe_close(setup->root_fd);
+
+        r = home_setup_undo_mount(setup, LOG_ERR);
+        if (r < 0)
+                return r;
+
+        r = home_setup_undo_dm(setup, LOG_ERR);
+        if (r < 0)
+                return r;
+
+        setup->loop = loop_device_unref(setup->loop);
+
+        if (!user_record_luks_offline_discard(h)) {
+                r= run_fallocate(setup->image_fd, NULL /* refresh stat() data */);
+                if (r < 0)
+                        return r;
+        }
+
+        /* Sync everything to disk before we move things into place under the final name. */
+        if (fsync(setup->image_fd) < 0)
+                return log_error_errno(r, "Failed to synchronize image to disk: %m");
+
+        if (disk_uuid_path)
+                /* Reread partition table if this is a block device */
+                (void) ioctl(setup->image_fd, BLKRRPART, 0);
+        else {
+                assert(setup->temporary_image_path);
+
+                if (rename(setup->temporary_image_path, ip) < 0)
+                        return log_error_errno(errno, "Failed to rename image file: %m");
+
+                setup->temporary_image_path = mfree(setup->temporary_image_path);
+
+                /* If we operate on a file, sync the containing directory too. */
+                r = fsync_directory_of_file(setup->image_fd);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to synchronize directory of image file to disk: %m");
+
+                log_info("Moved image file into place.");
+        }
+
+        /* Let's close the image fd now. If we are operating on a real block device this will release the BSD
+         * lock that ensures udev doesn't interfere with what we are doing */
+        setup->image_fd = safe_close(setup->image_fd);
+
+        if (disk_uuid_path)
+                (void) wait_for_devlink(disk_uuid_path);
+
+        log_info("Creation completed.");
+
+        print_size_summary(host_size, encrypted_size, &sfs);
+
+        log_debug("GPT + LUKS2 overhead is %" PRIu64 " (expected %" PRIu64 ")", host_size - encrypted_size, GPT_LUKS2_OVERHEAD);
+
+        *ret_home = TAKE_PTR(new_home);
+        return 0;
+}
+
+int home_get_state_luks(UserRecord *h, HomeSetup *setup) {
+        int r;
+
+        assert(h);
+        assert(setup);
+
+        r = make_dm_names(h, setup);
+        if (r < 0)
+                return r;
+
+        r = access(setup->dm_node, F_OK);
+        if (r < 0 && errno != ENOENT)
+                return log_error_errno(errno, "Failed to determine whether %s exists: %m", setup->dm_node);
+
+        return r >= 0;
+}
+
+enum {
+        CAN_RESIZE_ONLINE,
+        CAN_RESIZE_OFFLINE,
+};
+
+static int can_resize_fs(int fd, uint64_t old_size, uint64_t new_size) {
+        struct statfs sfs;
+
+        assert(fd >= 0);
+
+        /* Filter out bogus requests early */
+        if (old_size == 0 || old_size == UINT64_MAX ||
+            new_size == 0 || new_size == UINT64_MAX)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Invalid resize parameters.");
+
+        if ((old_size & 511) != 0 || (new_size & 511) != 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Resize parameters not multiple of 512.");
+
+        if (fstatfs(fd, &sfs) < 0)
+                return log_error_errno(errno, "Failed to fstatfs() file system: %m");
+
+        if (is_fs_type(&sfs, BTRFS_SUPER_MAGIC)) {
+
+                if (new_size < BTRFS_MINIMAL_SIZE)
+                        return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "New file system size too small for btrfs (needs to be 256M at least.");
+
+                /* btrfs can grow and shrink online */
+
+        } else if (is_fs_type(&sfs, XFS_SB_MAGIC)) {
+
+                if (new_size < XFS_MINIMAL_SIZE)
+                        return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "New file system size too small for xfs (needs to be 14M at least).");
+
+                /* XFS can grow, but not shrink */
+                if (new_size < old_size)
+                        return log_error_errno(SYNTHETIC_ERRNO(EMSGSIZE), "Shrinking this type of file system is not supported.");
+
+        } else if (is_fs_type(&sfs, EXT4_SUPER_MAGIC)) {
+
+                if (new_size < EXT4_MINIMAL_SIZE)
+                        return log_error_errno(SYNTHETIC_ERRNO(ERANGE), "New file system size too small for ext4 (needs to be 1M at least).");
+
+                /* ext4 can grow online, and shrink offline */
+                if (new_size < old_size)
+                        return CAN_RESIZE_OFFLINE;
+
+        } else
+                return log_error_errno(SYNTHETIC_ERRNO(ESOCKTNOSUPPORT), "Resizing this type of file system is not supported.");
+
+        return CAN_RESIZE_ONLINE;
+}
+
+static int ext4_offline_resize_fs(
+                HomeSetup *setup,
+                uint64_t new_size,
+                bool discard,
+                unsigned long flags,
+                const char *extra_mount_options) {
+
+        _cleanup_free_ char *size_str = NULL;
+        bool re_open = false, re_mount = false;
+        pid_t resize_pid, fsck_pid;
+        int r, exit_status;
+
+        assert(setup);
+        assert(setup->dm_node);
+
+        /* First, unmount the file system */
+        if (setup->root_fd >= 0) {
+                setup->root_fd = safe_close(setup->root_fd);
+                re_open = true;
+        }
+
+        if (setup->undo_mount) {
+                r = home_setup_undo_mount(setup, LOG_ERR);
+                if (r < 0)
+                        return r;
+
+                re_mount = true;
+        }
+
+        log_info("Temporary unmounting of file system completed.");
+
+        /* resize2fs requires that the file system is force checked first, do so. */
+        r = safe_fork("(e2fsck)",
+                      FORK_RESET_SIGNALS|FORK_RLIMIT_NOFILE_SAFE|FORK_DEATHSIG|FORK_LOG|FORK_STDOUT_TO_STDERR|FORK_CLOSE_ALL_FDS,
+                      &fsck_pid);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                /* Child */
+                execlp("e2fsck" ,"e2fsck", "-fp", setup->dm_node, NULL);
+                log_open();
+                log_error_errno(errno, "Failed to execute e2fsck: %m");
+                _exit(EXIT_FAILURE);
+        }
+
+        exit_status = wait_for_terminate_and_check("e2fsck", fsck_pid, WAIT_LOG_ABNORMAL);
+        if (exit_status < 0)
+                return exit_status;
+        if ((exit_status & ~FSCK_ERROR_CORRECTED) != 0) {
+                log_warning("e2fsck failed with exit status %i.", exit_status);
+
+                if ((exit_status & (FSCK_SYSTEM_SHOULD_REBOOT|FSCK_ERRORS_LEFT_UNCORRECTED)) != 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EIO), "File system is corrupted, refusing.");
+
+                log_warning("Ignoring fsck error.");
+        }
+
+        log_info("Forced file system check completed.");
+
+        /* We use 512 sectors here, because resize2fs doesn't do byte sizes */
+        if (asprintf(&size_str, "%" PRIu64 "s", new_size / 512) < 0)
+                return log_oom();
+
+        /* Resize the thing */
+        r = safe_fork("(e2resize)",
+                      FORK_RESET_SIGNALS|FORK_RLIMIT_NOFILE_SAFE|FORK_DEATHSIG|FORK_LOG|FORK_WAIT|FORK_STDOUT_TO_STDERR|FORK_CLOSE_ALL_FDS,
+                      &resize_pid);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                /* Child */
+                execlp("resize2fs" ,"resize2fs", setup->dm_node, size_str, NULL);
+                log_open();
+                log_error_errno(errno, "Failed to execute resize2fs: %m");
+                _exit(EXIT_FAILURE);
+        }
+
+        log_info("Offline file system resize completed.");
+
+        /* Re-establish mounts and reopen the directory */
+        if (re_mount) {
+                r = home_mount_node(setup->dm_node, "ext4", discard, flags, extra_mount_options);
+                if (r < 0)
+                        return r;
+
+                setup->undo_mount = true;
+        }
+
+        if (re_open) {
+                setup->root_fd = open(HOME_RUNTIME_WORK_DIR, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                if (setup->root_fd < 0)
+                        return log_error_errno(errno, "Failed to reopen file system: %m");
+        }
+
+        log_info("File system mounted again.");
+
+        return 0;
+}
+
+static int prepare_resize_partition(
+                int fd,
+                uint64_t partition_offset,
+                uint64_t old_partition_size,
+                sd_id128_t *ret_disk_uuid,
+                struct fdisk_table **ret_table,
+                struct fdisk_partition **ret_partition) {
+
+        _cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
+        _cleanup_(fdisk_unref_tablep) struct fdisk_table *t = NULL;
+        _cleanup_free_ char *path = NULL, *disk_uuid_as_string = NULL;
+        struct fdisk_partition *found = NULL;
+        sd_id128_t disk_uuid;
+        size_t n_partitions;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret_disk_uuid);
+        assert(ret_table);
+
+        assert((partition_offset & 511) == 0);
+        assert((old_partition_size & 511) == 0);
+        assert(UINT64_MAX - old_partition_size >= partition_offset);
+
+        if (partition_offset == 0) {
+                /* If the offset is at the beginning we assume no partition table, let's exit early. */
+                log_debug("Not rewriting partition table, operating on naked device.");
+                *ret_disk_uuid = SD_ID128_NULL;
+                *ret_table = NULL;
+                *ret_partition = NULL;
+                return 0;
+        }
+
+        c = fdisk_new_context();
+        if (!c)
+                return log_oom();
+
+        if (asprintf(&path, "/proc/self/fd/%i", fd) < 0)
+                return log_oom();
+
+        r = fdisk_assign_device(c, path, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to open device: %m");
+
+        if (!fdisk_is_labeltype(c, FDISK_DISKLABEL_GPT))
+                return log_error_errno(SYNTHETIC_ERRNO(ENOMEDIUM), "Disk has no GPT partition table.");
+
+        r = fdisk_get_disklabel_id(c, &disk_uuid_as_string);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire disk UUID: %m");
+
+        r = sd_id128_from_string(disk_uuid_as_string, &disk_uuid);
+        if (r < 0)
+                return log_error_errno(r, "Failed parse disk UUID: %m");
+
+        r = fdisk_get_partitions(c, &t);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire partition table: %m");
+
+        n_partitions = fdisk_table_get_nents(t);
+        for (size_t i = 0; i < n_partitions; i++)  {
+                struct fdisk_partition *p;
+
+                p = fdisk_table_get_partition(t, i);
+                if (!p)
+                        return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to read partition metadata: %m");
+
+                if (fdisk_partition_is_used(p) <= 0)
+                        continue;
+                if (fdisk_partition_has_start(p) <= 0 || fdisk_partition_has_size(p) <= 0 || fdisk_partition_has_end(p) <= 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Found partition without a size.");
+
+                if (fdisk_partition_get_start(p) == partition_offset / 512U &&
+                    fdisk_partition_get_size(p) == old_partition_size / 512U) {
+
+                        if (found)
+                                return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ), "Partition found twice, refusing.");
+
+                        found = p;
+                } else if (fdisk_partition_get_end(p) > partition_offset / 512U)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Can't extend, not last partition in image.");
+        }
+
+        if (!found)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOPKG), "Failed to find matching partition to resize.");
+
+        *ret_disk_uuid = disk_uuid;
+        *ret_table = TAKE_PTR(t);
+        *ret_partition = found;
+
+        return 1;
+}
+
+static int get_maximum_partition_size(
+                int fd,
+                struct fdisk_partition *p,
+                uint64_t *ret_maximum_partition_size) {
+
+        _cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
+        uint64_t start_lba, start, last_lba, end;
+        int r;
+
+        assert(fd >= 0);
+        assert(p);
+        assert(ret_maximum_partition_size);
+
+        c = fdisk_new_context();
+        if (!c)
+                return log_oom();
+
+        r = fdisk_assign_device(c, FORMAT_PROC_FD_PATH(fd), 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to open device: %m");
+
+        start_lba = fdisk_partition_get_start(p);
+        assert(start_lba <= UINT64_MAX/512);
+        start = start_lba * 512;
+
+        last_lba = fdisk_get_last_lba(c); /* One sector before boundary where usable space ends */
+        assert(last_lba < UINT64_MAX/512);
+        end = DISK_SIZE_ROUND_DOWN((last_lba + 1) * 512); /* Round down to multiple of 4K */
+
+        if (start > end)
+                return log_error_errno(SYNTHETIC_ERRNO(EBADMSG), "Last LBA is before partition start.");
+
+        *ret_maximum_partition_size = DISK_SIZE_ROUND_DOWN(end - start);
+
+        return 1;
+}
+
+static int ask_cb(struct fdisk_context *c, struct fdisk_ask *ask, void *userdata) {
+        char *result;
+
+        assert(c);
+
+        switch (fdisk_ask_get_type(ask)) {
+
+        case FDISK_ASKTYPE_STRING:
+                result = new(char, 37);
+                if (!result)
+                        return log_oom();
+
+                fdisk_ask_string_set_result(ask, sd_id128_to_uuid_string(*(sd_id128_t*) userdata, result));
+                break;
+
+        default:
+                log_debug("Unexpected question from libfdisk, ignoring.");
+        }
+
+        return 0;
+}
+
+static int apply_resize_partition(
+                int fd,
+                sd_id128_t disk_uuids,
+                struct fdisk_table *t,
+                struct fdisk_partition *p,
+                size_t new_partition_size) {
+
+        _cleanup_(fdisk_unref_contextp) struct fdisk_context *c = NULL;
+        _cleanup_free_ void *two_zero_lbas = NULL;
+        _cleanup_free_ char *path = NULL;
+        ssize_t n;
+        int r;
+
+        assert(fd >= 0);
+        assert(!t == !p);
+
+        if (!t) /* no partition table to apply, exit early */
+                return 0;
+
+        assert(p);
+
+        /* Before writing our partition patch the final size in */
+        r = fdisk_partition_size_explicit(p, 1);
+        if (r < 0)
+                return log_error_errno(r, "Failed to enable explicit partition size: %m");
+
+        r = fdisk_partition_set_size(p, new_partition_size / 512U);
+        if (r < 0)
+                return log_error_errno(r, "Failed to change partition size: %m");
+
+        two_zero_lbas = malloc0(1024U);
+        if (!two_zero_lbas)
+                return log_oom();
+
+        /* libfdisk appears to get confused by the existing PMBR. Let's explicitly flush it out. */
+        n = pwrite(fd, two_zero_lbas, 1024U, 0);
+        if (n < 0)
+                return log_error_errno(errno, "Failed to wipe partition table: %m");
+        if (n != 1024)
+                return log_error_errno(SYNTHETIC_ERRNO(EIO), "Short write while wiping partition table.");
+
+        c = fdisk_new_context();
+        if (!c)
+                return log_oom();
+
+        if (asprintf(&path, "/proc/self/fd/%i", fd) < 0)
+                return log_oom();
+
+        r = fdisk_assign_device(c, path, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to open device: %m");
+
+        r = fdisk_create_disklabel(c, "gpt");
+        if (r < 0)
+                return log_error_errno(r, "Failed to create GPT disk label: %m");
+
+        r = fdisk_apply_table(c, t);
+        if (r < 0)
+                return log_error_errno(r, "Failed to apply partition table: %m");
+
+        r = fdisk_set_ask(c, ask_cb, &disk_uuids);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set libfdisk query function: %m");
+
+        r = fdisk_set_disklabel_id(c);
+        if (r < 0)
+                return log_error_errno(r, "Failed to change disklabel ID: %m");
+
+        r = fdisk_write_disklabel(c);
+        if (r < 0)
+                return log_error_errno(r, "Failed to write disk label: %m");
+
+        return 1;
+}
+
+/* Always keep at least 16M free, so that we can safely log in and update the user record while doing so */
+#define HOME_MIN_FREE (16U*1024U*1024U)
+
+static int get_smallest_fs_size(int fd, uint64_t *ret) {
+        uint64_t minsz, needed;
+        struct statfs sfs;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        /* Determines the minimal disk size we might be able to shrink the file system referenced by the fd to. */
+
+        if (syncfs(fd) < 0) /* let's sync before we query the size, so that the values returned are accurate */
+                return log_error_errno(errno, "Failed to synchronize home file system: %m");
+
+        if (fstatfs(fd, &sfs) < 0)
+                return log_error_errno(errno, "Failed to statfs() home file system: %m");
+
+        /* Let's determine the minimal file system size of the used fstype */
+        minsz = minimal_size_by_fs_magic(sfs.f_type);
+        if (minsz == UINT64_MAX)
+                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Don't know minimum file system size of file system type '%s' of home directory.", fs_type_to_string(sfs.f_type));
+
+        if (minsz < USER_DISK_SIZE_MIN)
+                minsz = USER_DISK_SIZE_MIN;
+
+        if (sfs.f_bfree > sfs.f_blocks)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Detected amount of free blocks is greater than the total amount of file system blocks. Refusing.");
+
+        /* Calculate how much disk space is currently in use. */
+        needed = sfs.f_blocks - sfs.f_bfree;
+        if (needed > UINT64_MAX / sfs.f_bsize)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "File system size out of range.");
+
+        needed *= sfs.f_bsize;
+
+        /* Add some safety margin of free space we'll always keep */
+        if (needed > UINT64_MAX - HOME_MIN_FREE) /* Check for overflow */
+                needed = UINT64_MAX;
+        else
+                needed += HOME_MIN_FREE;
+
+        *ret = DISK_SIZE_ROUND_UP(MAX(needed, minsz));
+        return 0;
+}
+
+static int get_largest_image_size(int fd, const struct stat *st, uint64_t *ret) {
+        uint64_t used, avail, sum;
+        struct statfs sfs;
+        int r;
+
+        assert(fd >= 0);
+        assert(st);
+        assert(ret);
+
+        /* Determines the maximum file size we might be able to grow the image file referenced by the fd to. */
+
+        r = stat_verify_regular(st);
+        if (r < 0)
+                return log_error_errno(r, "Image file is not a regular file, refusing: %m");
+
+        if (syncfs(fd) < 0)
+                return log_error_errno(errno, "Failed to synchronize file system backing image file: %m");
+
+        if (fstatfs(fd, &sfs) < 0)
+                return log_error_errno(errno, "Failed to statfs() image file: %m");
+
+        used = (uint64_t) st->st_blocks * 512;
+        avail = (uint64_t) sfs.f_bsize * sfs.f_bavail;
+
+        if (avail > UINT64_MAX - used)
+                sum = UINT64_MAX;
+        else
+                sum = avail + used;
+
+        *ret = DISK_SIZE_ROUND_DOWN(MIN(sum, USER_DISK_SIZE_MAX));
+        return 0;
+}
+
+static int resize_fs_loop(
+                UserRecord *h,
+                HomeSetup *setup,
+                int resize_type,
+                uint64_t old_fs_size,
+                uint64_t new_fs_size,
+                uint64_t *ret_fs_size) {
+
+        uint64_t current_fs_size;
+        unsigned n_iterations = 0;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(setup->root_fd >= 0);
+
+        /* A bisection loop trying to find the closest size to what the user asked for. (Well, we bisect like
+         * this only when we *shrink* the fs — if we grow the fs there's no need to bisect.) */
+
+        current_fs_size = old_fs_size;
+        for (uint64_t lower_boundary = new_fs_size, upper_boundary = old_fs_size, try_fs_size = new_fs_size;;) {
+                bool worked;
+
+                n_iterations++;
+
+                /* Now resize the file system */
+                if (resize_type == CAN_RESIZE_ONLINE) {
+                        r = resize_fs(setup->root_fd, try_fs_size, NULL);
+                        if (r < 0) {
+                                if (!ERRNO_IS_DISK_SPACE(r) || new_fs_size > old_fs_size) /* Not a disk space issue? Not trying to shrink? */
+                                        return log_error_errno(r, "Failed to resize file system: %m");
+
+                                log_debug_errno(r, "Shrinking from %s to %s didn't work, not enough space for contained data.", FORMAT_BYTES(current_fs_size), FORMAT_BYTES(try_fs_size));
+                                worked = false;
+                        } else {
+                                log_debug("Successfully resized from %s to %s.", FORMAT_BYTES(current_fs_size), FORMAT_BYTES(try_fs_size));
+                                current_fs_size = try_fs_size;
+                                worked = true;
+                        }
+
+                        /* If we hit a disk space issue and are shrinking the fs, then maybe it helps to
+                         * increase the image size. */
+                } else {
+                        r = ext4_offline_resize_fs(setup, try_fs_size, user_record_luks_discard(h), user_record_mount_flags(h), h->luks_extra_mount_options);
+                        if (r < 0)
+                                return r;
+
+                        /* For now, when we fail to shrink an ext4 image we'll not try again via the
+                         * bisection logic. We might add that later, but give this involves shelling out
+                         * multiple programs it's a bit too cumbersome to my taste. */
+
+                        worked = true;
+                        current_fs_size = try_fs_size;
+                }
+
+                if (new_fs_size > old_fs_size) /* If we are growing we are done after one iteration */
+                        break;
+
+                /* If we are shrinking then let's adjust our bisection boundaries and try again. */
+                if (worked)
+                        upper_boundary = MIN(upper_boundary, try_fs_size);
+                else
+                        lower_boundary = MAX(lower_boundary, try_fs_size);
+
+                /* OK, this attempt to shrink didn't work. Let's try between the old size and what worked. */
+                if (lower_boundary >= upper_boundary) {
+                        log_debug("Image can't be shrunk further (range to try is empty).");
+                        break;
+                }
+
+                /* Let's find a new value to try half-way between the lower boundary and the upper boundary
+                 * to try now. */
+                try_fs_size = DISK_SIZE_ROUND_DOWN(lower_boundary + (upper_boundary - lower_boundary) / 2);
+                if (try_fs_size <= lower_boundary || try_fs_size >= upper_boundary) {
+                        log_debug("Image can't be shrunk further (remaining range to try too small).");
+                        break;
+                }
+        }
+
+        log_debug("Bisection loop completed after %u iterations.", n_iterations);
+
+        if (ret_fs_size)
+                *ret_fs_size = current_fs_size;
+
+        return 0;
+}
+
+static int resize_image_loop(
+                UserRecord *h,
+                HomeSetup *setup,
+                uint64_t old_image_size,
+                uint64_t new_image_size,
+                uint64_t *ret_image_size) {
+
+        uint64_t current_image_size;
+        unsigned n_iterations = 0;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(setup->image_fd >= 0);
+
+        /* A bisection loop trying to find the closest size to what the user asked for. (Well, we bisect like
+         * this only when we *grow* the image — if we shrink the image then there's no need to bisect.) */
+
+        current_image_size = old_image_size;
+        for (uint64_t lower_boundary = old_image_size, upper_boundary = new_image_size, try_image_size = new_image_size;;) {
+                bool worked;
+
+                n_iterations++;
+
+                r = home_truncate(h, setup->image_fd, try_image_size);
+                if (r < 0) {
+                        if (!ERRNO_IS_DISK_SPACE(r) || new_image_size < old_image_size) /* Not a disk space issue? Not trying to grow? */
+                                return r;
+
+                        log_debug_errno(r, "Growing from %s to %s didn't work, not enough space on backing disk.", FORMAT_BYTES(current_image_size), FORMAT_BYTES(try_image_size));
+                        worked = false;
+                } else if (r > 0) { /* Success: allocation worked */
+                        log_debug("Resizing from %s to %s via allocation worked successfully.", FORMAT_BYTES(current_image_size), FORMAT_BYTES(try_image_size));
+                        current_image_size = try_image_size;
+                        worked = true;
+                } else { /* Success, but through truncation, not allocation. */
+                        log_debug("Resizing from %s to %s via truncation worked successfully.", FORMAT_BYTES(old_image_size), FORMAT_BYTES(try_image_size));
+                        current_image_size = try_image_size;
+                        break; /* there's no point in the bisection logic if this was plain truncation and
+                                * not allocation, let's exit immediately. */
+                }
+
+                if (new_image_size < old_image_size) /* If we are shrinking we are done after one iteration */
+                        break;
+
+                /* If we are growing then let's adjust our bisection boundaries and try again */
+                if (worked)
+                        lower_boundary = MAX(lower_boundary, try_image_size);
+                else
+                        upper_boundary = MIN(upper_boundary, try_image_size);
+
+                if (lower_boundary >= upper_boundary) {
+                        log_debug("Image can't be grown further (range to try is empty).");
+                        break;
+                }
+
+                try_image_size = DISK_SIZE_ROUND_DOWN(lower_boundary + (upper_boundary - lower_boundary) / 2);
+                if (try_image_size <= lower_boundary || try_image_size >= upper_boundary) {
+                        log_debug("Image can't be grown further (remaining range to try too small).");
+                        break;
+                }
+        }
+
+        log_debug("Bisection loop completed after %u iterations.", n_iterations);
+
+        if (ret_image_size)
+                *ret_image_size = current_image_size;
+
+        return 0;
+}
+
+int home_resize_luks(
+                UserRecord *h,
+                HomeSetupFlags flags,
+                HomeSetup *setup,
+                PasswordCache *cache,
+                UserRecord **ret_home) {
+
+        uint64_t old_image_size, new_image_size, old_fs_size, new_fs_size, crypto_offset, crypto_offset_bytes,
+                new_partition_size, smallest_fs_size, resized_fs_size;
+        _cleanup_(user_record_unrefp) UserRecord *header_home = NULL, *embedded_home = NULL, *new_home = NULL;
+        _cleanup_(fdisk_unref_tablep) struct fdisk_table *table = NULL;
+        struct fdisk_partition *partition = NULL;
+        _cleanup_close_ int opened_image_fd = -1;
+        _cleanup_free_ char *whole_disk = NULL;
+        int r, resize_type, image_fd = -1;
+        sd_id128_t disk_uuid;
+        const char *ip, *ipo;
+        struct statfs sfs;
+        struct stat st;
+        enum {
+                INTENTION_DONT_KNOW = 0,    /* These happen to match the return codes of CMP() */
+                INTENTION_SHRINK = -1,
+                INTENTION_GROW = 1,
+        } intention = INTENTION_DONT_KNOW;
+
+        assert(h);
+        assert(user_record_storage(h) == USER_LUKS);
+        assert(setup);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        assert_se(ipo = user_record_image_path(h));
+        ip = strdupa_safe(ipo); /* copy out since original might change later in home record object */
+
+        if (setup->image_fd < 0) {
+                setup->image_fd = open_image_file(h, NULL, &st);
+                if (setup->image_fd < 0)
+                        return setup->image_fd;
+        } else {
+                if (fstat(setup->image_fd, &st) < 0)
+                        return log_error_errno(errno, "Failed to stat image file %s: %m", ip);
+        }
+
+        image_fd = setup->image_fd;
+
+        if (S_ISBLK(st.st_mode)) {
+                dev_t parent;
+
+                r = block_get_whole_disk(st.st_rdev, &parent);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to acquire whole block device for %s: %m", ip);
+                if (r > 0) {
+                        /* If we shall resize a file system on a partition device, then let's figure out the
+                         * whole disk device and operate on that instead, since we need to rewrite the
+                         * partition table to resize the partition. */
+
+                        log_info("Operating on partition device %s, using parent device.", ip);
+
+                        opened_image_fd = r = device_open_from_devnum(S_IFBLK, parent, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK, &whole_disk);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to open whole block device for %s: %m", ip);
+
+                        image_fd = opened_image_fd;
+
+                        if (fstat(image_fd, &st) < 0)
+                                return log_error_errno(errno, "Failed to stat whole block device %s: %m", whole_disk);
+                } else
+                        log_info("Operating on whole block device %s.", ip);
+
+                if (ioctl(image_fd, BLKGETSIZE64, &old_image_size) < 0)
+                        return log_error_errno(errno, "Failed to determine size of original block device: %m");
+
+                if (flock(image_fd, LOCK_EX) < 0) /* make sure udev doesn't read from it while we operate on the device */
+                        return log_error_errno(errno, "Failed to lock block device %s: %m", ip);
+
+                new_image_size = old_image_size; /* we can't resize physical block devices */
+        } else {
+                r = stat_verify_regular(&st);
+                if (r < 0)
+                        return log_error_errno(r, "Image %s is not a block device nor regular file: %m", ip);
+
+                old_image_size = st.st_size;
+
+                /* Note an asymetry here: when we operate on loopback files the specified disk size we get we
+                 * apply onto the loopback file as a whole. When we operate on block devices we instead apply
+                 * to the partition itself only. */
+
+                if (FLAGS_SET(flags, HOME_SETUP_RESIZE_MINIMIZE)) {
+                        new_image_size = 0;
+                        intention = INTENTION_SHRINK;
+                } else {
+                        uint64_t new_image_size_rounded;
+
+                        new_image_size_rounded = DISK_SIZE_ROUND_DOWN(h->disk_size);
+
+                        if (old_image_size >= new_image_size_rounded && old_image_size <= h->disk_size) {
+                                /* If exact match, or a match after we rounded down, don't do a thing */
+                                log_info("Image size already matching, skipping operation.");
+                                return 0;
+                        }
+
+                        new_image_size = new_image_size_rounded;
+                        intention = CMP(new_image_size, old_image_size); /* Is this a shrink */
+                }
+        }
+
+        r = home_setup_luks(
+                        h,
+                        flags,
+                        whole_disk,
+                        setup,
+                        cache,
+                        FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES) ? NULL : &header_home);
+        if (r < 0)
+                return r;
+
+        if (!FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES)) {
+                r = home_load_embedded_identity(h, setup->root_fd, header_home, USER_RECONCILE_REQUIRE_NEWER_OR_EQUAL, cache, &embedded_home, &new_home);
+                if (r < 0)
+                        return r;
+        }
+
+        r = home_maybe_shift_uid(h, flags, setup);
+        if (r < 0)
+                return r;
+
+        log_info("offset = %" PRIu64 ", size = %" PRIu64 ", image = %" PRIu64, setup->partition_offset, setup->partition_size, old_image_size);
+
+        if ((UINT64_MAX - setup->partition_offset) < setup->partition_size ||
+            setup->partition_offset + setup->partition_size > old_image_size)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Old partition doesn't fit in backing storage, refusing.");
+
+        /* Get target partition information in here for new_partition_size calculation */
+        r = prepare_resize_partition(
+                        image_fd,
+                        setup->partition_offset,
+                        setup->partition_size,
+                        &disk_uuid,
+                        &table,
+                        &partition);
+        if (r < 0)
+                return r;
+
+        if (S_ISREG(st.st_mode)) {
+                uint64_t partition_table_extra, largest_size;
+
+                partition_table_extra = old_image_size - setup->partition_size;
+
+                r = get_largest_image_size(setup->image_fd, &st, &largest_size);
+                if (r < 0)
+                        return r;
+                if (new_image_size > largest_size)
+                        new_image_size = largest_size;
+
+                if (new_image_size < partition_table_extra)
+                        new_image_size = partition_table_extra;
+
+                new_partition_size = DISK_SIZE_ROUND_DOWN(new_image_size - partition_table_extra);
+        } else {
+                assert(S_ISBLK(st.st_mode));
+
+                if (FLAGS_SET(flags, HOME_SETUP_RESIZE_MINIMIZE)) {
+                        new_partition_size = 0;
+                        intention = INTENTION_SHRINK;
+                } else {
+                        uint64_t new_partition_size_rounded = DISK_SIZE_ROUND_DOWN(h->disk_size);
+
+                        if (h->disk_size == UINT64_MAX && partition) {
+                                r = get_maximum_partition_size(image_fd, partition, &new_partition_size_rounded);
+                                if (r < 0)
+                                        return r;
+                        }
+
+                        if (setup->partition_size >= new_partition_size_rounded &&
+                            setup->partition_size <= h->disk_size) {
+                                log_info("Partition size already matching, skipping operation.");
+                                return 0;
+                        }
+
+                        new_partition_size = new_partition_size_rounded;
+                        intention = CMP(new_partition_size, setup->partition_size);
+                }
+        }
+
+        if ((UINT64_MAX - setup->partition_offset) < new_partition_size ||
+            setup->partition_offset + new_partition_size > new_image_size)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "New partition doesn't fit into backing storage, refusing.");
+
+        crypto_offset = sym_crypt_get_data_offset(setup->crypt_device);
+        if (crypto_offset > UINT64_MAX/512U)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "LUKS2 data offset out of range, refusing.");
+        crypto_offset_bytes = (uint64_t) crypto_offset * 512U;
+        if (setup->partition_size <= crypto_offset_bytes)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Weird, old crypto payload offset doesn't actually fit in partition size?");
+
+        /* Make sure at least the LUKS header fit in */
+        if (new_partition_size <= crypto_offset_bytes) {
+                uint64_t add;
+
+                add = DISK_SIZE_ROUND_UP(crypto_offset_bytes) - new_partition_size;
+                new_partition_size += add;
+                if (S_ISREG(st.st_mode))
+                        new_image_size += add;
+        }
+
+        old_fs_size = setup->partition_size - crypto_offset_bytes;
+        new_fs_size = DISK_SIZE_ROUND_DOWN(new_partition_size - crypto_offset_bytes);
+
+        r = get_smallest_fs_size(setup->root_fd, &smallest_fs_size);
+        if (r < 0)
+                return r;
+
+        if (new_fs_size < smallest_fs_size) {
+                uint64_t add;
+
+                add = DISK_SIZE_ROUND_UP(smallest_fs_size) - new_fs_size;
+                new_fs_size += add;
+                new_partition_size += add;
+                if (S_ISREG(st.st_mode))
+                        new_image_size += add;
+        }
+
+        if (new_fs_size == old_fs_size) {
+                log_info("New file system size identical to old file system size, skipping operation.");
+                return 0;
+        }
+
+        if (FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_GROW) && new_fs_size > old_fs_size) {
+                log_info("New file system size would be larger than old, but shrinking requested, skipping operation.");
+                return 0;
+        }
+
+        if (FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SHRINK) && new_fs_size < old_fs_size) {
+                log_info("New file system size would be smaller than old, but growing requested, skipping operation.");
+                return 0;
+        }
+
+        if (CMP(new_fs_size, old_fs_size) != intention) {
+                if (intention < 0)
+                        log_info("Shrink operation would enlarge file system, skipping operation.");
+                else {
+                        assert(intention > 0);
+                        log_info("Grow operation would shrink file system, skipping operation.");
+                }
+                return 0;
+        }
+
+        /* Before we start doing anything, let's figure out if we actually can */
+        resize_type = can_resize_fs(setup->root_fd, old_fs_size, new_fs_size);
+        if (resize_type < 0)
+                return resize_type;
+        if (resize_type == CAN_RESIZE_OFFLINE && FLAGS_SET(flags, HOME_SETUP_ALREADY_ACTIVATED))
+                return log_error_errno(SYNTHETIC_ERRNO(ETXTBSY), "File systems of this type can only be resized offline, but is currently online.");
+
+        log_info("Ready to resize image size %s %s %s, partition size %s %s %s, file system size %s %s %s.",
+                 FORMAT_BYTES(old_image_size),
+                 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT),
+                 FORMAT_BYTES(new_image_size),
+                 FORMAT_BYTES(setup->partition_size),
+                 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT),
+                 FORMAT_BYTES(new_partition_size),
+                 FORMAT_BYTES(old_fs_size),
+                 special_glyph(SPECIAL_GLYPH_ARROW_RIGHT),
+                 FORMAT_BYTES(new_fs_size));
+
+        if (new_fs_size > old_fs_size) { /* → Grow */
+
+                if (S_ISREG(st.st_mode)) {
+                        uint64_t resized_image_size;
+
+                        /* Grow file size */
+                        r = resize_image_loop(h, setup, old_image_size, new_image_size, &resized_image_size);
+                        if (r < 0)
+                                return r;
+
+                        if (resized_image_size == old_image_size) {
+                                log_info("Couldn't change image size.");
+                                return 0;
+                        }
+
+                        assert(resized_image_size > old_image_size);
+
+                        log_info("Growing of image file from %s to %s completed.", FORMAT_BYTES(old_image_size), FORMAT_BYTES(resized_image_size));
+
+                        if (resized_image_size < new_image_size) {
+                                uint64_t sub;
+
+                                /* If the growing we managed to do is smaller than what we wanted we need to
+                                 * adjust the partition/file system sizes we are going for, too */
+                                sub = new_image_size - resized_image_size;
+                                assert(new_partition_size >= sub);
+                                new_partition_size -= sub;
+                                assert(new_fs_size >= sub);
+                                new_fs_size -= sub;
+                        }
+
+                        new_image_size = resized_image_size;
+                } else {
+                        assert(S_ISBLK(st.st_mode));
+                        assert(new_image_size == old_image_size);
+                }
+
+                /* Make sure loopback device sees the new bigger size */
+                r = loop_device_refresh_size(setup->loop, UINT64_MAX, new_partition_size);
+                if (r == -ENOTTY)
+                        log_debug_errno(r, "Device is not a loopback device, not refreshing size.");
+                else if (r < 0)
+                        return log_error_errno(r, "Failed to refresh loopback device size: %m");
+                else
+                        log_info("Refreshing loop device size completed.");
+
+                r = apply_resize_partition(image_fd, disk_uuid, table, partition, new_partition_size);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        log_info("Growing of partition completed.");
+
+                if (S_ISBLK(st.st_mode) && ioctl(image_fd, BLKRRPART, 0) < 0)
+                        log_debug_errno(errno, "BLKRRPART failed on block device, ignoring: %m");
+
+                /* Tell LUKS about the new bigger size too */
+                r = sym_crypt_resize(setup->crypt_device, setup->dm_name, new_fs_size / 512U);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to grow LUKS device: %m");
+
+                log_info("LUKS device growing completed.");
+        } else {
+                /* → Shrink */
+
+                if (!FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES)) {
+                        r = home_store_embedded_identity(new_home, setup->root_fd, h->uid, embedded_home);
+                        if (r < 0)
+                                return r;
+                }
+
+                if (S_ISREG(st.st_mode)) {
+                        if (user_record_luks_discard(h))
+                                /* Before we shrink, let's trim the file system, so that we need less space on disk during the shrinking */
+                                (void) run_fitrim(setup->root_fd);
+                        else {
+                                /* If discard is off, let's ensure all backing blocks are allocated, so that our resize operation doesn't fail half-way */
+                                r = run_fallocate(image_fd, &st);
+                                if (r < 0)
+                                        return r;
+                        }
+                }
+        }
+
+        /* Now try to resize the file system. The requested size might not always be possible, in which case
+         * we'll try to get as close as we can get. The result is returned in 'resized_fs_size' */
+        r = resize_fs_loop(h, setup, resize_type, old_fs_size, new_fs_size, &resized_fs_size);
+        if (r < 0)
+                return r;
+
+        if (resized_fs_size == old_fs_size) {
+                log_info("Couldn't change file system size.");
+                return 0;
+        }
+
+        log_info("File system resizing from %s to %s completed.", FORMAT_BYTES(old_fs_size), FORMAT_BYTES(resized_fs_size));
+
+        if (resized_fs_size > new_fs_size) {
+                uint64_t add;
+
+                /* If the shrinking we managed to do is larger than what we wanted we need to adjust the partition/image sizes. */
+                add = resized_fs_size - new_fs_size;
+                new_partition_size += add;
+                if (S_ISREG(st.st_mode))
+                        new_image_size += add;
+        }
+
+        new_fs_size = resized_fs_size;
+
+        /* Immediately sync afterwards */
+        r = home_sync_and_statfs(setup->root_fd, NULL);
+        if (r < 0)
+                return r;
+
+        if (new_fs_size < old_fs_size) { /* → Shrink */
+
+                /* Shrink the LUKS device now, matching the new file system size */
+                r = sym_crypt_resize(setup->crypt_device, setup->dm_name, new_fs_size / 512);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to shrink LUKS device: %m");
+
+                log_info("LUKS device shrinking completed.");
+
+                /* Refresh the loop devices size */
+                r = loop_device_refresh_size(setup->loop, UINT64_MAX, new_partition_size);
+                if (r == -ENOTTY)
+                        log_debug_errno(r, "Device is not a loopback device, not refreshing size.");
+                else if (r < 0)
+                        return log_error_errno(r, "Failed to refresh loopback device size: %m");
+                else
+                        log_info("Refreshing loop device size completed.");
+
+                if (S_ISREG(st.st_mode)) {
+                        /* Shrink the image file */
+                        if (ftruncate(image_fd, new_image_size) < 0)
+                                return log_error_errno(errno, "Failed to shrink image file %s: %m", ip);
+
+                        log_info("Shrinking of image file completed.");
+                } else {
+                        assert(S_ISBLK(st.st_mode));
+                        assert(new_image_size == old_image_size);
+                }
+
+                r = apply_resize_partition(image_fd, disk_uuid, table, partition, new_partition_size);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        log_info("Shrinking of partition completed.");
+
+                if (S_ISBLK(st.st_mode) && ioctl(image_fd, BLKRRPART, 0) < 0)
+                        log_debug_errno(errno, "BLKRRPART failed on block device, ignoring: %m");
+
+        } else { /* → Grow */
+                if (!FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES)) {
+                        r = home_store_embedded_identity(new_home, setup->root_fd, h->uid, embedded_home);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        if (!FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES)) {
+                r = home_store_header_identity_luks(new_home, setup, header_home);
+                if (r < 0)
+                        return r;
+
+                r = home_extend_embedded_identity(new_home, h, setup);
+                if (r < 0)
+                        return r;
+        }
+
+        if (user_record_luks_discard(h))
+                (void) run_fitrim(setup->root_fd);
+
+        r = home_sync_and_statfs(setup->root_fd, &sfs);
+        if (r < 0)
+                return r;
+
+        if (!FLAGS_SET(flags, HOME_SETUP_RESIZE_DONT_UNDO)) {
+                r = home_setup_done(setup);
+                if (r < 0)
+                        return r;
+        }
+
+        log_info("Resizing completed.");
+
+        print_size_summary(new_image_size, new_fs_size, &sfs);
+
+        if (ret_home)
+                *ret_home = TAKE_PTR(new_home);
+
+        return 0;
+}
+
+int home_passwd_luks(
+                UserRecord *h,
+                HomeSetupFlags flags,
+                HomeSetup *setup,
+                const PasswordCache *cache, /* the passwords acquired via PKCS#11/FIDO2 security tokens */
+                char **effective_passwords  /* new passwords */) {
+
+        size_t volume_key_size, max_key_slots, n_effective;
+        _cleanup_(erase_and_freep) void *volume_key = NULL;
+        struct crypt_pbkdf_type good_pbkdf, minimal_pbkdf;
+        const char *type;
+        char **list;
+        int r;
+
+        assert(h);
+        assert(user_record_storage(h) == USER_LUKS);
+        assert(setup);
+
+        r = dlopen_cryptsetup();
+        if (r < 0)
+                return r;
+
+        type = sym_crypt_get_type(setup->crypt_device);
+        if (!type)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine crypto device type.");
+
+        r = sym_crypt_keyslot_max(type);
+        if (r <= 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine number of key slots.");
+        max_key_slots = r;
+
+        r = sym_crypt_get_volume_key_size(setup->crypt_device);
+        if (r <= 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to determine volume key size.");
+        volume_key_size = (size_t) r;
+
+        volume_key = malloc(volume_key_size);
+        if (!volume_key)
+                return log_oom();
+
+        r = -ENOKEY;
+        FOREACH_POINTER(list,
+                        cache ? cache->keyring_passswords : NULL,
+                        cache ? cache->pkcs11_passwords : NULL,
+                        cache ? cache->fido2_passwords : NULL,
+                        h->password) {
+
+                r = luks_try_passwords(h, setup->crypt_device, list, volume_key, &volume_key_size, NULL);
+                if (r != -ENOKEY)
+                        break;
+        }
+        if (r == -ENOKEY)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOKEY), "Failed to unlock LUKS superblock with supplied passwords.");
+        if (r < 0)
+                return log_error_errno(r, "Failed to unlocks LUKS superblock: %m");
+
+        n_effective = strv_length(effective_passwords);
+
+        build_good_pbkdf(&good_pbkdf, h);
+        build_minimal_pbkdf(&minimal_pbkdf, h);
+
+        for (size_t i = 0; i < max_key_slots; i++) {
+                r = sym_crypt_keyslot_destroy(setup->crypt_device, i);
+                if (r < 0 && !IN_SET(r, -ENOENT, -EINVAL)) /* Returns EINVAL or ENOENT if there's no key in this slot already */
+                        return log_error_errno(r, "Failed to destroy LUKS password: %m");
+
+                if (i >= n_effective) {
+                        if (r >= 0)
+                                log_info("Destroyed LUKS key slot %zu.", i);
+                        continue;
+                }
+
+                if (password_cache_contains(cache, effective_passwords[i])) { /* Is this a FIDO2 or PKCS#11 password? */
+                        log_debug("Using minimal PBKDF for slot %zu", i);
+                        r = sym_crypt_set_pbkdf_type(setup->crypt_device, &minimal_pbkdf);
+                } else {
+                        log_debug("Using good PBKDF for slot %zu", i);
+                        r = sym_crypt_set_pbkdf_type(setup->crypt_device, &good_pbkdf);
+                }
+                if (r < 0)
+                        return log_error_errno(r, "Failed to tweak PBKDF for slot %zu: %m", i);
+
+                r = sym_crypt_keyslot_add_by_volume_key(
+                                setup->crypt_device,
+                                i,
+                                volume_key,
+                                volume_key_size,
+                                effective_passwords[i],
+                                strlen(effective_passwords[i]));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to set up LUKS password: %m");
+
+                log_info("Updated LUKS key slot %zu.", i);
+
+                /* If we changed the password, then make sure to update the copy in the keyring, so that
+                 * auto-rebalance continues to work. We only do this if we operate on an active home dir. */
+                if (i == 0 && FLAGS_SET(flags, HOME_SETUP_ALREADY_ACTIVATED))
+                        upload_to_keyring(h, effective_passwords[i], NULL);
+        }
+
+        return 1;
+}
+
+int home_lock_luks(UserRecord *h, HomeSetup *setup) {
+        const char *p;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(setup->root_fd < 0);
+        assert(!setup->crypt_device);
+
+        r = acquire_open_luks_device(h, setup, /* graceful= */ false);
+        if (r < 0)
+                return r;
+
+        log_info("Discovered used LUKS device %s.", setup->dm_node);
+
+        assert_se(p = user_record_home_directory(h));
+        r = syncfs_path(AT_FDCWD, p);
+        if (r < 0) /* Snake oil, but let's better be safe than sorry */
+                return log_error_errno(r, "Failed to synchronize file system %s: %m", p);
+
+        log_info("File system synchronized.");
+
+        /* Note that we don't invoke FIFREEZE here, it appears libcryptsetup/device-mapper already does that on its own for us */
+
+        r = sym_crypt_suspend(setup->crypt_device, setup->dm_name);
+        if (r < 0)
+                return log_error_errno(r, "Failed to suspend cryptsetup device: %s: %m", setup->dm_node);
+
+        log_info("LUKS device suspended.");
+        return 0;
+}
+
+static int luks_try_resume(
+                struct crypt_device *cd,
+                const char *dm_name,
+                char **password) {
+
+        int r;
+
+        assert(cd);
+        assert(dm_name);
+
+        STRV_FOREACH(pp, password) {
+                r = sym_crypt_resume_by_passphrase(
+                                cd,
+                                dm_name,
+                                CRYPT_ANY_SLOT,
+                                *pp,
+                                strlen(*pp));
+                if (r >= 0) {
+                        log_info("Resumed LUKS device %s.", dm_name);
+                        return 0;
+                }
+
+                log_debug_errno(r, "Password %zu didn't work for resuming device: %m", (size_t) (pp - password));
+        }
+
+        return -ENOKEY;
+}
+
+int home_unlock_luks(UserRecord *h, HomeSetup *setup, const PasswordCache *cache) {
+        char **list;
+        int r;
+
+        assert(h);
+        assert(setup);
+        assert(!setup->crypt_device);
+
+        r = acquire_open_luks_device(h, setup, /* graceful= */ false);
+        if (r < 0)
+                return r;
+
+        log_info("Discovered used LUKS device %s.", setup->dm_node);
+
+        r = -ENOKEY;
+        FOREACH_POINTER(list,
+                        cache ? cache->pkcs11_passwords : NULL,
+                        cache ? cache->fido2_passwords : NULL,
+                        h->password) {
+                r = luks_try_resume(setup->crypt_device, setup->dm_name, list);
+                if (r != -ENOKEY)
+                        break;
+        }
+        if (r == -ENOKEY)
+                return log_error_errno(r, "No valid password for LUKS superblock.");
+        if (r < 0)
+                return log_error_errno(r, "Failed to resume LUKS superblock: %m");
+
+        log_info("LUKS device resumed.");
+        return 0;
+}
+
+static int device_is_gone(HomeSetup *setup) {
+        _cleanup_(sd_device_unrefp) sd_device *d = NULL;
+        struct stat st;
+        int r;
+
+        assert(setup);
+
+        if (!setup->dm_node)
+                return true;
+
+        if (stat(setup->dm_node, &st) < 0) {
+                if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to stat block device node %s: %m", setup->dm_node);
+
+                return true;
+        }
+
+        r = sd_device_new_from_stat_rdev(&d, &st);
+        if (r < 0) {
+                if (r != -ENODEV)
+                        return log_error_errno(errno, "Failed to allocate device object from block device node %s: %m", setup->dm_node);
+
+                return true;
+        }
+
+        return false;
+}
+
+static int device_monitor_handler(sd_device_monitor *monitor, sd_device *device, void *userdata) {
+        HomeSetup *setup = ASSERT_PTR(userdata);
+        int r;
+
+        if (!device_for_action(device, SD_DEVICE_REMOVE))
+                return 0;
+
+        /* We don't really care for the device object passed to us, we just check if the device node still
+         * exists */
+
+        r = device_is_gone(setup);
+        if (r < 0)
+                return r;
+        if (r > 0) /* Yay! we are done! */
+                (void) sd_event_exit(sd_device_monitor_get_event(monitor), 0);
+
+        return 0;
+}
+
+int wait_for_block_device_gone(HomeSetup *setup, usec_t timeout_usec) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *m = NULL;
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        int r;
+
+        assert(setup);
+
+        /* So here's the thing: we enable "deferred deactivation" on our dm-crypt volumes. This means they
+         * are automatically torn down once not used anymore (i.e. once unmounted). Which is great. It also
+         * means that when we deactivate a home directory and try to tear down the volume that backs it, it
+         * possibly is already torn down or in the process of being torn down, since we race against the
+         * automatic tearing down. Which is fine, we handle errors from that. However, we lose the ability to
+         * naturally wait for the tear down operation to complete: if we are not the ones who tear down the
+         * device we are also not the ones who naturally block on that operation. Hence let's add some code
+         * to actively wait for the device to go away, via sd-device. We'll call this whenever tearing down a
+         * LUKS device, to ensure the device is really really gone before we proceed. Net effect: "homectl
+         * deactivate foo && homectl activate foo" will work reliably, i.e. deactivation immediately followed
+         * by activation will work. Also, by the time deactivation completes we can guarantee that all data
+         * is sync'ed down to the lowest block layer as all higher levels are fully and entirely
+         * destructed. */
+
+        if (!setup->dm_name)
+                return 0;
+
+        assert(setup->dm_node);
+        log_debug("Waiting until %s disappears.", setup->dm_node);
+
+        r = sd_event_new(&event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate event loop: %m");
+
+        r = sd_device_monitor_new(&m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate device monitor: %m");
+
+        r = sd_device_monitor_filter_add_match_subsystem_devtype(m, "block", "disk");
+        if (r < 0)
+                return log_error_errno(r, "Failed to configure device monitor match: %m");
+
+        r = sd_device_monitor_attach_event(m, event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach device monitor to event loop: %m");
+
+        r = sd_device_monitor_start(m, device_monitor_handler, setup);
+        if (r < 0)
+                return log_error_errno(r, "Failed to start device monitor: %m");
+
+        r = device_is_gone(setup);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                log_debug("%s has already disappeared before entering wait loop.", setup->dm_node);
+                return 0; /* gone already */
+        }
+
+        if (timeout_usec != USEC_INFINITY) {
+                r = sd_event_add_time_relative(event, NULL, CLOCK_MONOTONIC, timeout_usec, 0, NULL, NULL);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to add timer event: %m");
+        }
+
+        r = sd_event_loop(event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to run event loop: %m");
+
+        r = device_is_gone(setup);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return log_error_errno(r, "Device %s still around.", setup->dm_node);
+
+        log_debug("Successfully waited until device %s disappeared.", setup->dm_node);
+        return 0;
+}
+
+int home_auto_shrink_luks(UserRecord *h, HomeSetup *setup, PasswordCache *cache) {
+        struct statfs sfs;
+        int r;
+
+        assert(h);
+        assert(user_record_storage(h) == USER_LUKS);
+        assert(setup);
+        assert(setup->root_fd >= 0);
+
+        if (user_record_auto_resize_mode(h) != AUTO_RESIZE_SHRINK_AND_GROW)
+                return 0;
+
+        if (fstatfs(setup->root_fd, &sfs) < 0)
+                return log_error_errno(errno, "Failed to statfs home directory: %m");
+
+        if (!fs_can_online_shrink_and_grow(sfs.f_type)) {
+                log_debug("Not auto-shrinking file system, since selected file system cannot do both online shrink and grow.");
+                return 0;
+        }
+
+        r = home_resize_luks(
+                        h,
+                        HOME_SETUP_ALREADY_ACTIVATED|
+                        HOME_SETUP_RESIZE_DONT_SYNC_IDENTITIES|
+                        HOME_SETUP_RESIZE_MINIMIZE|
+                        HOME_SETUP_RESIZE_DONT_GROW|
+                        HOME_SETUP_RESIZE_DONT_UNDO,
+                        setup,
+                        cache,
+                        NULL);
+        if (r < 0)
+                return r;
+
+        return 1;
+}