Adding upstream version 255.4.upstream/255.4

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

1 files changed, 2164 insertions, 0 deletions

diff --git a/src/shared/btrfs-util.c b/src/shared/btrfs-util.c
new file mode 100644
index 0000000..b3e4b50
--- /dev/null
+++ b/src/shared/btrfs-util.c
@@ -0,0 +1,2164 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/btrfs_tree.h>
+#include <linux/fs.h>
+#include <linux/loop.h>
+#include <linux/magic.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/file.h>
+#include <sys/ioctl.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "blockdev-util.h"
+#include "btrfs-util.h"
+#include "chase.h"
+#include "chattr-util.h"
+#include "copy.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "io-util.h"
+#include "macro.h"
+#include "path-util.h"
+#include "rm-rf.h"
+#include "smack-util.h"
+#include "sparse-endian.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "time-util.h"
+
+/* WARNING: Be careful with file system ioctls! When we get an fd, we
+ * need to make sure it either refers to only a regular file or
+ * directory, or that it is located on btrfs, before invoking any
+ * btrfs ioctls. The ioctl numbers are reused by some device drivers
+ * (such as DRM), and hence might have bad effects when invoked on
+ * device nodes (that reference drivers) rather than fds to normal
+ * files or directories. */
+
+int btrfs_is_subvol_at(int dir_fd, const char *path) {
+        struct stat st;
+
+        assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
+
+        /* On btrfs subvolumes always have the inode 256 */
+
+        if (fstatat(dir_fd, strempty(path), &st, isempty(path) ? AT_EMPTY_PATH : 0) < 0)
+                return -errno;
+
+        if (!btrfs_might_be_subvol(&st))
+                return 0;
+
+        return is_fs_type_at(dir_fd, path, BTRFS_SUPER_MAGIC);
+}
+
+int btrfs_subvol_set_read_only_at(int dir_fd, const char *path, bool b) {
+        _cleanup_close_ int fd = -EBADF;
+        uint64_t flags, nflags;
+        struct stat st;
+
+        assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
+
+        fd = xopenat(dir_fd, path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY, /* xopen_flags = */ 0, /* mode = */ 0);
+        if (fd < 0)
+                return fd;
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!btrfs_might_be_subvol(&st))
+                return -EINVAL;
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
+                return -errno;
+
+        nflags = UPDATE_FLAG(flags, BTRFS_SUBVOL_RDONLY, b);
+        if (flags == nflags)
+                return 0;
+
+        return RET_NERRNO(ioctl(fd, BTRFS_IOC_SUBVOL_SETFLAGS, &nflags));
+}
+
+int btrfs_subvol_get_read_only_fd(int fd) {
+        uint64_t flags;
+        struct stat st;
+
+        assert(fd >= 0);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!btrfs_might_be_subvol(&st))
+                return -EINVAL;
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
+                return -errno;
+
+        return !!(flags & BTRFS_SUBVOL_RDONLY);
+}
+
+int btrfs_get_block_device_at(int dir_fd, const char *path, dev_t *ret) {
+        struct btrfs_ioctl_fs_info_args fsi = {};
+        _cleanup_close_ int fd = -EBADF;
+        uint64_t id;
+        int r;
+
+        assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
+        assert(path);
+        assert(ret);
+
+        fd = xopenat(dir_fd, path, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY, /* xopen_flags = */ 0, /* mode = */ 0);
+        if (fd < 0)
+                return fd;
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        if (ioctl(fd, BTRFS_IOC_FS_INFO, &fsi) < 0)
+                return -errno;
+
+        /* We won't do this for btrfs RAID */
+        if (fsi.num_devices != 1) {
+                *ret = 0;
+                return 0;
+        }
+
+        for (id = 1; id <= fsi.max_id; id++) {
+                struct btrfs_ioctl_dev_info_args di = {
+                        .devid = id,
+                };
+                struct stat st;
+
+                if (ioctl(fd, BTRFS_IOC_DEV_INFO, &di) < 0) {
+                        if (errno == ENODEV)
+                                continue;
+
+                        return -errno;
+                }
+
+                /* For the root fs — when no initrd is involved — btrfs returns /dev/root on any kernels from
+                 * the past few years. That sucks, as we have no API to determine the actual root then. let's
+                 * return an recognizable error for this case, so that the caller can maybe print a nice
+                 * message about this.
+                 *
+                 * https://bugzilla.kernel.org/show_bug.cgi?id=89721 */
+                if (path_equal((char*) di.path, "/dev/root"))
+                        return -EUCLEAN;
+
+                if (stat((char*) di.path, &st) < 0)
+                        return -errno;
+
+                if (!S_ISBLK(st.st_mode))
+                        return -ENOTBLK;
+
+                if (major(st.st_rdev) == 0)
+                        return -ENODEV;
+
+                *ret = st.st_rdev;
+                return 1;
+        }
+
+        return -ENODEV;
+}
+
+int btrfs_subvol_get_id_fd(int fd, uint64_t *ret) {
+        struct btrfs_ioctl_ino_lookup_args args = {
+                .objectid = BTRFS_FIRST_FREE_OBJECTID
+        };
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        if (ioctl(fd, BTRFS_IOC_INO_LOOKUP, &args) < 0)
+                return -errno;
+
+        *ret = args.treeid;
+        return 0;
+}
+
+int btrfs_subvol_get_id(int fd, const char *subvol, uint64_t *ret) {
+        _cleanup_close_ int subvol_fd = -EBADF;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        subvol_fd = openat(fd, subvol, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (subvol_fd < 0)
+                return -errno;
+
+        return btrfs_subvol_get_id_fd(subvol_fd, ret);
+}
+
+static bool btrfs_ioctl_search_args_inc(struct btrfs_ioctl_search_args *args) {
+        assert(args);
+
+        /* the objectid, type, offset together make up the btrfs key,
+         * which is considered a single 136byte integer when
+         * comparing. This call increases the counter by one, dealing
+         * with the overflow between the overflows */
+
+        if (args->key.min_offset < UINT64_MAX) {
+                args->key.min_offset++;
+                return true;
+        }
+
+        if (args->key.min_type < UINT8_MAX) {
+                args->key.min_type++;
+                args->key.min_offset = 0;
+                return true;
+        }
+
+        if (args->key.min_objectid < UINT64_MAX) {
+                args->key.min_objectid++;
+                args->key.min_offset = 0;
+                args->key.min_type = 0;
+                return true;
+        }
+
+        return 0;
+}
+
+static void btrfs_ioctl_search_args_set(struct btrfs_ioctl_search_args *args, const struct btrfs_ioctl_search_header *h) {
+        assert(args);
+        assert(h);
+
+        args->key.min_objectid = h->objectid;
+        args->key.min_type = h->type;
+        args->key.min_offset = h->offset;
+}
+
+static int btrfs_ioctl_search_args_compare(const struct btrfs_ioctl_search_args *args) {
+        int r;
+
+        assert(args);
+
+        /* Compare min and max */
+
+        r = CMP(args->key.min_objectid, args->key.max_objectid);
+        if (r != 0)
+                return r;
+
+        r = CMP(args->key.min_type, args->key.max_type);
+        if (r != 0)
+                return r;
+
+        return CMP(args->key.min_offset, args->key.max_offset);
+}
+
+typedef struct BtrfsForeachIterator {
+        const void *p;
+        size_t i;
+} BtrfsForeachIterator;
+
+/* Iterates through a series of struct btrfs_file_extent_item elements. They are unfortunately not aligned,
+ * hence we copy out the header from them */
+#define FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args)               \
+        for (BtrfsForeachIterator iterator = {                          \
+                        .p = ({                                         \
+                               memcpy(&(sh), (args).buf, sizeof(struct btrfs_ioctl_search_header)); \
+                               (body) = (const void*) ((const uint8_t*) (args).buf + sizeof(struct btrfs_ioctl_search_header)); \
+                               (args).buf;                              \
+                        }),                                             \
+             };                                                         \
+             iterator.i < (args).key.nr_items;                          \
+             iterator.i++,                                              \
+             memcpy(&(sh), iterator.p = (const uint8_t*) iterator.p + sizeof(struct btrfs_ioctl_search_header) + (sh).len, sizeof(struct btrfs_ioctl_search_header)), \
+             (body) = (const void*) ((const uint8_t*) iterator.p + sizeof(struct btrfs_ioctl_search_header)))
+
+int btrfs_subvol_get_info_fd(int fd, uint64_t subvol_id, BtrfsSubvolInfo *ret) {
+        struct btrfs_ioctl_search_args args = {
+                /* Tree of tree roots */
+                .key.tree_id = BTRFS_ROOT_TREE_OBJECTID,
+
+                /* Look precisely for the subvolume items */
+                .key.min_type = BTRFS_ROOT_ITEM_KEY,
+                .key.max_type = BTRFS_ROOT_ITEM_KEY,
+
+                .key.min_offset = 0,
+                .key.max_offset = UINT64_MAX,
+
+                /* No restrictions on the other components */
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        bool found = false;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        } else {
+                r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOTTY;
+        }
+
+        args.key.min_objectid = args.key.max_objectid = subvol_id;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
+                        return -errno;
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+                        /* Make sure we start the next search at least from this entry */
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.objectid != subvol_id)
+                                continue;
+                        if (sh.type != BTRFS_ROOT_ITEM_KEY)
+                                continue;
+
+                        /* Older versions of the struct lacked the otime setting */
+                        if (sh.len < offsetof(struct btrfs_root_item, otime) + sizeof(struct btrfs_timespec))
+                                continue;
+
+                        const struct btrfs_root_item *ri = body;
+                        ret->otime = (usec_t) le64toh(ri->otime.sec) * USEC_PER_SEC +
+                                (usec_t) le32toh(ri->otime.nsec) / NSEC_PER_USEC;
+
+                        ret->subvol_id = subvol_id;
+                        ret->read_only = le64toh(ri->flags) & BTRFS_ROOT_SUBVOL_RDONLY;
+
+                        assert_cc(sizeof(ri->uuid) == sizeof(ret->uuid));
+                        memcpy(&ret->uuid, ri->uuid, sizeof(ret->uuid));
+                        memcpy(&ret->parent_uuid, ri->parent_uuid, sizeof(ret->parent_uuid));
+
+                        found = true;
+                        goto finish;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+finish:
+        return found ? 0 : -ENODATA;
+}
+
+int btrfs_qgroup_get_quota_fd(int fd, uint64_t qgroupid, BtrfsQuotaInfo *ret) {
+
+        struct btrfs_ioctl_search_args args = {
+                /* Tree of quota items */
+                .key.tree_id = BTRFS_QUOTA_TREE_OBJECTID,
+
+                /* The object ID is always 0 */
+                .key.min_objectid = 0,
+                .key.max_objectid = 0,
+
+                /* Look precisely for the quota items */
+                .key.min_type = BTRFS_QGROUP_STATUS_KEY,
+                .key.max_type = BTRFS_QGROUP_LIMIT_KEY,
+
+                /* No restrictions on the other components */
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        bool found_info = false, found_limit = false;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (qgroupid == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &qgroupid);
+                if (r < 0)
+                        return r;
+        } else {
+                r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOTTY;
+        }
+
+        args.key.min_offset = args.key.max_offset = qgroupid;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0) {
+                        if (errno == ENOENT) /* quota tree is missing: quota disabled */
+                                break;
+
+                        return -errno;
+                }
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+
+                        /* Make sure we start the next search at least from this entry */
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.objectid != 0)
+                                continue;
+                        if (sh.offset != qgroupid)
+                                continue;
+
+                        if (sh.type == BTRFS_QGROUP_INFO_KEY) {
+                                const struct btrfs_qgroup_info_item *qii = body;
+
+                                ret->referenced = le64toh(qii->rfer);
+                                ret->exclusive = le64toh(qii->excl);
+
+                                found_info = true;
+
+                        } else if (sh.type == BTRFS_QGROUP_LIMIT_KEY) {
+                                const struct btrfs_qgroup_limit_item *qli = body;
+
+                                if (le64toh(qli->flags) & BTRFS_QGROUP_LIMIT_MAX_RFER)
+                                        ret->referenced_max = le64toh(qli->max_rfer);
+                                else
+                                        ret->referenced_max = UINT64_MAX;
+
+                                if (le64toh(qli->flags) & BTRFS_QGROUP_LIMIT_MAX_EXCL)
+                                        ret->exclusive_max = le64toh(qli->max_excl);
+                                else
+                                        ret->exclusive_max = UINT64_MAX;
+
+                                found_limit = true;
+                        }
+
+                        if (found_info && found_limit)
+                                goto finish;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+finish:
+        if (!found_limit && !found_info)
+                return -ENODATA;
+
+        if (!found_info) {
+                ret->referenced = UINT64_MAX;
+                ret->exclusive = UINT64_MAX;
+        }
+
+        if (!found_limit) {
+                ret->referenced_max = UINT64_MAX;
+                ret->exclusive_max = UINT64_MAX;
+        }
+
+        return 0;
+}
+
+int btrfs_qgroup_get_quota(const char *path, uint64_t qgroupid, BtrfsQuotaInfo *ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_qgroup_get_quota_fd(fd, qgroupid, ret);
+}
+
+int btrfs_subvol_find_subtree_qgroup(int fd, uint64_t subvol_id, uint64_t *ret) {
+        uint64_t level, lowest = UINT64_MAX, lowest_qgroupid = 0;
+        _cleanup_free_ uint64_t *qgroups = NULL;
+        int r, n;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        /* This finds the "subtree" qgroup for a specific
+         * subvolume. This only works for subvolumes that have been
+         * prepared with btrfs_subvol_auto_qgroup_fd() with
+         * insert_intermediary_qgroup=true (or equivalent). For others
+         * it will return the leaf qgroup instead. The two cases may
+         * be distinguished via the return value, which is 1 in case
+         * an appropriate "subtree" qgroup was found, and 0
+         * otherwise. */
+
+        if (subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        }
+
+        r = btrfs_qgroupid_split(subvol_id, &level, NULL);
+        if (r < 0)
+                return r;
+        if (level != 0) /* Input must be a leaf qgroup */
+                return -EINVAL;
+
+        n = btrfs_qgroup_find_parents(fd, subvol_id, &qgroups);
+        if (n < 0)
+                return n;
+
+        for (int i = 0; i < n; i++) {
+                uint64_t id;
+
+                r = btrfs_qgroupid_split(qgroups[i], &level, &id);
+                if (r < 0)
+                        return r;
+
+                if (id != subvol_id)
+                        continue;
+
+                if (lowest == UINT64_MAX || level < lowest) {
+                        lowest_qgroupid = qgroups[i];
+                        lowest = level;
+                }
+        }
+
+        if (lowest == UINT64_MAX) {
+                /* No suitable higher-level qgroup found, let's return
+                 * the leaf qgroup instead, and indicate that with the
+                 * return value. */
+
+                *ret = subvol_id;
+                return 0;
+        }
+
+        *ret = lowest_qgroupid;
+        return 1;
+}
+
+int btrfs_subvol_get_subtree_quota_fd(int fd, uint64_t subvol_id, BtrfsQuotaInfo *ret) {
+        uint64_t qgroupid;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        /* This determines the quota data of the qgroup with the
+         * lowest level, that shares the id part with the specified
+         * subvolume. This is useful for determining the quota data
+         * for entire subvolume subtrees, as long as the subtrees have
+         * been set up with btrfs_qgroup_subvol_auto_fd() or in a
+         * compatible way */
+
+        r = btrfs_subvol_find_subtree_qgroup(fd, subvol_id, &qgroupid);
+        if (r < 0)
+                return r;
+
+        return btrfs_qgroup_get_quota_fd(fd, qgroupid, ret);
+}
+
+int btrfs_subvol_get_subtree_quota(const char *path, uint64_t subvol_id, BtrfsQuotaInfo *ret) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_subvol_get_subtree_quota_fd(fd, subvol_id, ret);
+}
+
+int btrfs_defrag_fd(int fd) {
+        int r;
+
+        assert(fd >= 0);
+
+        r = fd_verify_regular(fd);
+        if (r < 0)
+                return r;
+
+        return RET_NERRNO(ioctl(fd, BTRFS_IOC_DEFRAG, NULL));
+}
+
+int btrfs_defrag(const char *p) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(p, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_defrag_fd(fd);
+}
+
+int btrfs_quota_enable_fd(int fd, bool b) {
+        struct btrfs_ioctl_quota_ctl_args args = {
+                .cmd = b ? BTRFS_QUOTA_CTL_ENABLE : BTRFS_QUOTA_CTL_DISABLE,
+        };
+        int r;
+
+        assert(fd >= 0);
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        return RET_NERRNO(ioctl(fd, BTRFS_IOC_QUOTA_CTL, &args));
+}
+
+int btrfs_quota_enable(const char *path, bool b) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_quota_enable_fd(fd, b);
+}
+
+int btrfs_qgroup_set_limit_fd(int fd, uint64_t qgroupid, uint64_t referenced_max) {
+
+        struct btrfs_ioctl_qgroup_limit_args args = {
+                .lim.max_rfer = referenced_max,
+                .lim.flags = BTRFS_QGROUP_LIMIT_MAX_RFER,
+        };
+        int r;
+
+        assert(fd >= 0);
+
+        if (qgroupid == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &qgroupid);
+                if (r < 0)
+                        return r;
+        } else {
+                r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOTTY;
+        }
+
+        args.qgroupid = qgroupid;
+
+        for (unsigned c = 0;; c++) {
+                if (ioctl(fd, BTRFS_IOC_QGROUP_LIMIT, &args) < 0) {
+
+                        if (errno == EBUSY && c < 10) {
+                                (void) btrfs_quota_scan_wait(fd);
+                                continue;
+                        }
+
+                        return -errno;
+                }
+
+                break;
+        }
+
+        return 0;
+}
+
+int btrfs_qgroup_set_limit(const char *path, uint64_t qgroupid, uint64_t referenced_max) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_qgroup_set_limit_fd(fd, qgroupid, referenced_max);
+}
+
+int btrfs_subvol_set_subtree_quota_limit_fd(int fd, uint64_t subvol_id, uint64_t referenced_max) {
+        uint64_t qgroupid;
+        int r;
+
+        assert(fd >= 0);
+
+        r = btrfs_subvol_find_subtree_qgroup(fd, subvol_id, &qgroupid);
+        if (r < 0)
+                return r;
+
+        return btrfs_qgroup_set_limit_fd(fd, qgroupid, referenced_max);
+}
+
+int btrfs_subvol_set_subtree_quota_limit(const char *path, uint64_t subvol_id, uint64_t referenced_max) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_subvol_set_subtree_quota_limit_fd(fd, subvol_id, referenced_max);
+}
+
+int btrfs_qgroupid_make(uint64_t level, uint64_t id, uint64_t *ret) {
+        assert(ret);
+
+        if (level >= (UINT64_C(1) << (64 - BTRFS_QGROUP_LEVEL_SHIFT)))
+                return -EINVAL;
+
+        if (id >= (UINT64_C(1) << BTRFS_QGROUP_LEVEL_SHIFT))
+                return -EINVAL;
+
+        *ret = (level << BTRFS_QGROUP_LEVEL_SHIFT) | id;
+        return 0;
+}
+
+int btrfs_qgroupid_split(uint64_t qgroupid, uint64_t *level, uint64_t *id) {
+        assert(level || id);
+
+        if (level)
+                *level = qgroupid >> BTRFS_QGROUP_LEVEL_SHIFT;
+
+        if (id)
+                *id = qgroupid & ((UINT64_C(1) << BTRFS_QGROUP_LEVEL_SHIFT) - 1);
+
+        return 0;
+}
+
+static int qgroup_create_or_destroy(int fd, bool b, uint64_t qgroupid) {
+
+        struct btrfs_ioctl_qgroup_create_args args = {
+                .create = b,
+                .qgroupid = qgroupid,
+        };
+        int r;
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        for (unsigned c = 0;; c++) {
+                if (ioctl(fd, BTRFS_IOC_QGROUP_CREATE, &args) < 0) {
+
+                        /* On old kernels if quota is not enabled, we get EINVAL. On newer kernels we get
+                         * ENOTCONN. Let's always convert this to ENOTCONN to make this recognizable
+                         * everywhere the same way. */
+
+                        if (IN_SET(errno, EINVAL, ENOTCONN))
+                                return -ENOTCONN;
+
+                        if (errno == EBUSY && c < 10) {
+                                (void) btrfs_quota_scan_wait(fd);
+                                continue;
+                        }
+
+                        return -errno;
+                }
+
+                break;
+        }
+
+        return 0;
+}
+
+int btrfs_qgroup_create(int fd, uint64_t qgroupid) {
+        return qgroup_create_or_destroy(fd, true, qgroupid);
+}
+
+int btrfs_qgroup_destroy(int fd, uint64_t qgroupid) {
+        return qgroup_create_or_destroy(fd, false, qgroupid);
+}
+
+int btrfs_qgroup_destroy_recursive(int fd, uint64_t qgroupid) {
+        _cleanup_free_ uint64_t *qgroups = NULL;
+        uint64_t subvol_id;
+        int n, r;
+
+        /* Destroys the specified qgroup, but unassigns it from all
+         * its parents first. Also, it recursively destroys all
+         * qgroups it is assigned to that have the same id part of the
+         * qgroupid as the specified group. */
+
+        r = btrfs_qgroupid_split(qgroupid, NULL, &subvol_id);
+        if (r < 0)
+                return r;
+
+        n = btrfs_qgroup_find_parents(fd, qgroupid, &qgroups);
+        if (n < 0)
+                return n;
+
+        for (int i = 0; i < n; i++) {
+                uint64_t id;
+
+                r = btrfs_qgroupid_split(qgroups[i], NULL, &id);
+                if (r < 0)
+                        return r;
+
+                r = btrfs_qgroup_unassign(fd, qgroupid, qgroups[i]);
+                if (r < 0)
+                        return r;
+
+                if (id != subvol_id)
+                        continue;
+
+                /* The parent qgroupid shares the same id part with
+                 * us? If so, destroy it too. */
+
+                (void) btrfs_qgroup_destroy_recursive(fd, qgroups[i]);
+        }
+
+        return btrfs_qgroup_destroy(fd, qgroupid);
+}
+
+int btrfs_quota_scan_start(int fd) {
+        struct btrfs_ioctl_quota_rescan_args args = {};
+
+        assert(fd >= 0);
+
+        return RET_NERRNO(ioctl(fd, BTRFS_IOC_QUOTA_RESCAN, &args));
+}
+
+int btrfs_quota_scan_wait(int fd) {
+        assert(fd >= 0);
+
+        return RET_NERRNO(ioctl(fd, BTRFS_IOC_QUOTA_RESCAN_WAIT));
+}
+
+int btrfs_quota_scan_ongoing(int fd) {
+        struct btrfs_ioctl_quota_rescan_args args = {};
+
+        assert(fd >= 0);
+
+        if (ioctl(fd, BTRFS_IOC_QUOTA_RESCAN_STATUS, &args) < 0)
+                return -errno;
+
+        return !!args.flags;
+}
+
+static int qgroup_assign_or_unassign(int fd, bool b, uint64_t child, uint64_t parent) {
+        struct btrfs_ioctl_qgroup_assign_args args = {
+                .assign = b,
+                .src = child,
+                .dst = parent,
+        };
+        int r;
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        for (unsigned c = 0;; c++) {
+                r = ioctl(fd, BTRFS_IOC_QGROUP_ASSIGN, &args);
+                if (r < 0) {
+                        if (errno == EBUSY && c < 10) {
+                                (void) btrfs_quota_scan_wait(fd);
+                                continue;
+                        }
+
+                        return -errno;
+                }
+
+                if (r == 0)
+                        return 0;
+
+                /* If the return value is > 0, we need to request a rescan */
+
+                (void) btrfs_quota_scan_start(fd);
+                return 1;
+        }
+}
+
+int btrfs_qgroup_assign(int fd, uint64_t child, uint64_t parent) {
+        return qgroup_assign_or_unassign(fd, true, child, parent);
+}
+
+int btrfs_qgroup_unassign(int fd, uint64_t child, uint64_t parent) {
+        return qgroup_assign_or_unassign(fd, false, child, parent);
+}
+
+static int subvol_remove_children(int fd, const char *subvolume, uint64_t subvol_id, BtrfsRemoveFlags flags) {
+        struct btrfs_ioctl_search_args args = {
+                .key.tree_id = BTRFS_ROOT_TREE_OBJECTID,
+
+                .key.min_objectid = BTRFS_FIRST_FREE_OBJECTID,
+                .key.max_objectid = BTRFS_LAST_FREE_OBJECTID,
+
+                .key.min_type = BTRFS_ROOT_BACKREF_KEY,
+                .key.max_type = BTRFS_ROOT_BACKREF_KEY,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        struct btrfs_ioctl_vol_args vol_args = {};
+        _cleanup_close_ int subvol_fd = -EBADF;
+        struct stat st;
+        bool made_writable = false;
+        int r;
+
+        assert(fd >= 0);
+        assert(subvolume);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (!S_ISDIR(st.st_mode))
+                return -EINVAL;
+
+        subvol_fd = openat(fd, subvolume, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+        if (subvol_fd < 0)
+                return -errno;
+
+        /* Let's check if this is actually a subvolume. Note that this is mostly redundant, as BTRFS_IOC_SNAP_DESTROY
+         * would fail anyway if it is not. However, it's a good thing to check this ahead of time so that we can return
+         * ENOTTY unconditionally in this case. This is different from the ioctl() which will return EPERM/EACCES if we
+         * don't have the privileges to remove subvolumes, regardless if the specified directory is actually a
+         * subvolume or not. In order to make it easy for callers to cover the "this is not a btrfs subvolume" case
+         * let's prefer ENOTTY over EPERM/EACCES though. */
+        r = btrfs_is_subvol_fd(subvol_fd);
+        if (r < 0)
+                return r;
+        if (r == 0) /* Not a btrfs subvolume */
+                return -ENOTTY;
+
+        if (subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(subvol_fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        }
+
+        /* First, try to remove the subvolume. If it happens to be
+         * already empty, this will just work. */
+        strncpy(vol_args.name, subvolume, sizeof(vol_args.name)-1);
+        if (ioctl(fd, BTRFS_IOC_SNAP_DESTROY, &vol_args) >= 0) {
+                (void) btrfs_qgroup_destroy_recursive(fd, subvol_id); /* for the leaf subvolumes, the qgroup id is identical to the subvol id */
+                return 0;
+        }
+        if (!(flags & BTRFS_REMOVE_RECURSIVE) || errno != ENOTEMPTY)
+                return -errno;
+
+        /* OK, the subvolume is not empty, let's look for child
+         * subvolumes, and remove them, first */
+
+        args.key.min_offset = args.key.max_offset = subvol_id;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
+                        return -errno;
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+                        _cleanup_free_ char *p = NULL;
+
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.type != BTRFS_ROOT_BACKREF_KEY)
+                                continue;
+                        if (sh.offset != subvol_id)
+                                continue;
+
+                        const struct btrfs_root_ref *ref = body;
+                        p = memdup_suffix0((char*) ref + sizeof(struct btrfs_root_ref), le64toh(ref->name_len));
+                        if (!p)
+                                return -ENOMEM;
+
+                        struct btrfs_ioctl_ino_lookup_args ino_args = {
+                                .treeid = subvol_id,
+                                .objectid = htole64(ref->dirid),
+                        };
+
+                        if (ioctl(fd, BTRFS_IOC_INO_LOOKUP, &ino_args) < 0)
+                                return -errno;
+
+                        if (!made_writable) {
+                                r = btrfs_subvol_set_read_only_fd(subvol_fd, false);
+                                if (r < 0)
+                                        return r;
+
+                                made_writable = true;
+                        }
+
+                        if (isempty(ino_args.name))
+                                /* Subvolume is in the top-level
+                                 * directory of the subvolume. */
+                                r = subvol_remove_children(subvol_fd, p, sh.objectid, flags);
+                        else {
+                                _cleanup_close_ int child_fd = -EBADF;
+
+                                /* Subvolume is somewhere further down,
+                                 * hence we need to open the
+                                 * containing directory first */
+
+                                child_fd = openat(subvol_fd, ino_args.name, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                                if (child_fd < 0)
+                                        return -errno;
+
+                                r = subvol_remove_children(child_fd, p, sh.objectid, flags);
+                        }
+                        if (r < 0)
+                                return r;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+        /* OK, the child subvolumes should all be gone now, let's try
+         * again to remove the subvolume */
+        if (ioctl(fd, BTRFS_IOC_SNAP_DESTROY, &vol_args) < 0)
+                return -errno;
+
+        (void) btrfs_qgroup_destroy_recursive(fd, subvol_id);
+        return 0;
+}
+
+int btrfs_subvol_remove_at(int dir_fd, const char *path, BtrfsRemoveFlags flags) {
+        _cleanup_free_ char *subvolume = NULL;
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        assert(path);
+
+        fd = chase_and_openat(dir_fd, path, CHASE_PARENT|CHASE_EXTRACT_FILENAME, O_CLOEXEC, &subvolume);
+        if (fd < 0)
+                return fd;
+
+        r = btrfs_validate_subvolume_name(subvolume);
+        if (r < 0)
+                return r;
+
+        return subvol_remove_children(fd, subvolume, 0, flags);
+}
+
+int btrfs_qgroup_copy_limits(int fd, uint64_t old_qgroupid, uint64_t new_qgroupid) {
+
+        struct btrfs_ioctl_search_args args = {
+                /* Tree of quota items */
+                .key.tree_id = BTRFS_QUOTA_TREE_OBJECTID,
+
+                /* The object ID is always 0 */
+                .key.min_objectid = 0,
+                .key.max_objectid = 0,
+
+                /* Look precisely for the quota items */
+                .key.min_type = BTRFS_QGROUP_LIMIT_KEY,
+                .key.max_type = BTRFS_QGROUP_LIMIT_KEY,
+
+                /* For our qgroup */
+                .key.min_offset = old_qgroupid,
+                .key.max_offset = old_qgroupid,
+
+                /* No restrictions on the other components */
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        int r;
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0) {
+                        if (errno == ENOENT) /* quota tree missing: quota is not enabled, hence nothing to copy */
+                                break;
+
+                        return -errno;
+                }
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+                        struct btrfs_ioctl_qgroup_limit_args qargs;
+                        unsigned c;
+
+                        /* Make sure we start the next search at least from this entry */
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.objectid != 0)
+                                continue;
+                        if (sh.type != BTRFS_QGROUP_LIMIT_KEY)
+                                continue;
+                        if (sh.offset != old_qgroupid)
+                                continue;
+
+                        /* We found the entry, now copy things over. */
+
+                        const struct btrfs_qgroup_limit_item *qli = body;
+                        qargs = (struct btrfs_ioctl_qgroup_limit_args) {
+                                .qgroupid = new_qgroupid,
+
+                                .lim.max_rfer = le64toh(qli->max_rfer),
+                                .lim.max_excl = le64toh(qli->max_excl),
+                                .lim.rsv_rfer = le64toh(qli->rsv_rfer),
+                                .lim.rsv_excl = le64toh(qli->rsv_excl),
+
+                                .lim.flags = le64toh(qli->flags) & (BTRFS_QGROUP_LIMIT_MAX_RFER|
+                                                                    BTRFS_QGROUP_LIMIT_MAX_EXCL|
+                                                                    BTRFS_QGROUP_LIMIT_RSV_RFER|
+                                                                    BTRFS_QGROUP_LIMIT_RSV_EXCL),
+                        };
+
+                        for (c = 0;; c++) {
+                                if (ioctl(fd, BTRFS_IOC_QGROUP_LIMIT, &qargs) < 0) {
+                                        if (errno == EBUSY && c < 10) {
+                                                (void) btrfs_quota_scan_wait(fd);
+                                                continue;
+                                        }
+                                        return -errno;
+                                }
+
+                                break;
+                        }
+
+                        return 1;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+        return 0;
+}
+
+static int copy_quota_hierarchy(int fd, uint64_t old_subvol_id, uint64_t new_subvol_id) {
+        _cleanup_free_ uint64_t *old_qgroups = NULL, *old_parent_qgroups = NULL;
+        bool copy_from_parent = false, insert_intermediary_qgroup = false;
+        int n_old_qgroups, n_old_parent_qgroups, r;
+        uint64_t old_parent_id;
+
+        assert(fd >= 0);
+
+        /* Copies a reduced form of quota information from the old to
+         * the new subvolume. */
+
+        n_old_qgroups = btrfs_qgroup_find_parents(fd, old_subvol_id, &old_qgroups);
+        if (n_old_qgroups <= 0) /* Nothing to copy */
+                return n_old_qgroups;
+
+        r = btrfs_subvol_get_parent(fd, old_subvol_id, &old_parent_id);
+        if (r == -ENXIO)
+                /* We have no parent, hence nothing to copy. */
+                n_old_parent_qgroups = 0;
+        else if (r < 0)
+                return r;
+        else {
+                n_old_parent_qgroups = btrfs_qgroup_find_parents(fd, old_parent_id, &old_parent_qgroups);
+                if (n_old_parent_qgroups < 0)
+                        return n_old_parent_qgroups;
+        }
+
+        for (int i = 0; i < n_old_qgroups; i++) {
+                uint64_t id;
+
+                r = btrfs_qgroupid_split(old_qgroups[i], NULL, &id);
+                if (r < 0)
+                        return r;
+
+                if (id == old_subvol_id) {
+                        /* The old subvolume was member of a qgroup
+                         * that had the same id, but a different level
+                         * as it self. Let's set up something similar
+                         * in the destination. */
+                        insert_intermediary_qgroup = true;
+                        break;
+                }
+
+                for (int j = 0; j < n_old_parent_qgroups; j++)
+                        if (old_parent_qgroups[j] == old_qgroups[i])
+                                /* The old subvolume shared a common
+                                 * parent qgroup with its parent
+                                 * subvolume. Let's set up something
+                                 * similar in the destination. */
+                                copy_from_parent = true;
+        }
+
+        if (!insert_intermediary_qgroup && !copy_from_parent)
+                return 0;
+
+        return btrfs_subvol_auto_qgroup_fd(fd, new_subvol_id, insert_intermediary_qgroup);
+}
+
+static int copy_subtree_quota_limits(int fd, uint64_t old_subvol, uint64_t new_subvol) {
+        uint64_t old_subtree_qgroup, new_subtree_qgroup;
+        bool changed;
+        int r;
+
+        /* First copy the leaf limits */
+        r = btrfs_qgroup_copy_limits(fd, old_subvol, new_subvol);
+        if (r < 0)
+                return r;
+        changed = r > 0;
+
+        /* Then, try to copy the subtree limits, if there are any. */
+        r = btrfs_subvol_find_subtree_qgroup(fd, old_subvol, &old_subtree_qgroup);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return changed;
+
+        r = btrfs_subvol_find_subtree_qgroup(fd, new_subvol, &new_subtree_qgroup);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return changed;
+
+        r = btrfs_qgroup_copy_limits(fd, old_subtree_qgroup, new_subtree_qgroup);
+        if (r != 0)
+                return r;
+
+        return changed;
+}
+
+static int subvol_snapshot_children(
+                int old_fd,
+                int new_fd,
+                const char *subvolume,
+                uint64_t old_subvol_id,
+                BtrfsSnapshotFlags flags) {
+
+        struct btrfs_ioctl_search_args args = {
+                .key.tree_id = BTRFS_ROOT_TREE_OBJECTID,
+
+                .key.min_objectid = BTRFS_FIRST_FREE_OBJECTID,
+                .key.max_objectid = BTRFS_LAST_FREE_OBJECTID,
+
+                .key.min_type = BTRFS_ROOT_BACKREF_KEY,
+                .key.max_type = BTRFS_ROOT_BACKREF_KEY,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        struct btrfs_ioctl_vol_args_v2 vol_args = {
+                .flags = flags & BTRFS_SNAPSHOT_READ_ONLY ? BTRFS_SUBVOL_RDONLY : 0,
+                .fd = old_fd,
+        };
+        _cleanup_close_ int subvolume_fd = -EBADF;
+        uint64_t new_subvol_id;
+        int r;
+
+        assert(old_fd >= 0);
+        assert(new_fd >= 0);
+        assert(subvolume);
+
+        strncpy(vol_args.name, subvolume, sizeof(vol_args.name)-1);
+
+        if (ioctl(new_fd, BTRFS_IOC_SNAP_CREATE_V2, &vol_args) < 0)
+                return -errno;
+
+        if (FLAGS_SET(flags, BTRFS_SNAPSHOT_LOCK_BSD)) {
+                subvolume_fd = xopenat_lock(new_fd, subvolume,
+                                            O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW,
+                                            /* xopen_flags = */ 0,
+                                            /* mode = */ 0,
+                                            LOCK_BSD,
+                                            LOCK_EX);
+                if (subvolume_fd < 0)
+                        return subvolume_fd;
+
+                r = btrfs_is_subvol_fd(subvolume_fd);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -EEXIST;
+        }
+
+        if (!(flags & BTRFS_SNAPSHOT_RECURSIVE) &&
+            !(flags & BTRFS_SNAPSHOT_QUOTA))
+                return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
+
+        if (old_subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(old_fd, &old_subvol_id);
+                if (r < 0)
+                        return r;
+        }
+
+        r = btrfs_subvol_get_id(new_fd, vol_args.name, &new_subvol_id);
+        if (r < 0)
+                return r;
+
+        if (flags & BTRFS_SNAPSHOT_QUOTA)
+                (void) copy_quota_hierarchy(new_fd, old_subvol_id, new_subvol_id);
+
+        if (!(flags & BTRFS_SNAPSHOT_RECURSIVE)) {
+
+                if (flags & BTRFS_SNAPSHOT_QUOTA)
+                        (void) copy_subtree_quota_limits(new_fd, old_subvol_id, new_subvol_id);
+
+                return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
+        }
+
+        args.key.min_offset = args.key.max_offset = old_subvol_id;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(old_fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
+                        return -errno;
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+                        _cleanup_free_ char *p = NULL, *c = NULL, *np = NULL;
+                        _cleanup_close_ int old_child_fd = -EBADF, new_child_fd = -EBADF;
+
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.type != BTRFS_ROOT_BACKREF_KEY)
+                                continue;
+
+                        /* Avoid finding the source subvolume a second time */
+                        if (sh.offset != old_subvol_id)
+                                continue;
+
+                        /* Avoid running into loops if the new subvolume is below the old one. */
+                        if (sh.objectid == new_subvol_id)
+                                continue;
+
+                        const struct btrfs_root_ref *ref = body;
+                        p = memdup_suffix0((char*) ref + sizeof(struct btrfs_root_ref), le64toh(ref->name_len));
+                        if (!p)
+                                return -ENOMEM;
+
+                        struct btrfs_ioctl_ino_lookup_args ino_args = {
+                                .treeid = old_subvol_id,
+                                .objectid = htole64(ref->dirid),
+                        };
+
+                        if (ioctl(old_fd, BTRFS_IOC_INO_LOOKUP, &ino_args) < 0)
+                                return -errno;
+
+                        c = path_join(ino_args.name, p);
+                        if (!c)
+                                return -ENOMEM;
+
+                        old_child_fd = openat(old_fd, c, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                        if (old_child_fd < 0)
+                                return -errno;
+
+                        np = path_join(subvolume, ino_args.name);
+                        if (!np)
+                                return -ENOMEM;
+
+                        new_child_fd = openat(new_fd, np, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                        if (new_child_fd < 0)
+                                return -errno;
+
+                        if (flags & BTRFS_SNAPSHOT_READ_ONLY) {
+                                /* If the snapshot is read-only we need to mark it writable temporarily, to
+                                 * put the subsnapshot into place. */
+
+                                if (subvolume_fd < 0) {
+                                        subvolume_fd = openat(new_fd, subvolume, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+                                        if (subvolume_fd < 0)
+                                                return -errno;
+                                }
+
+                                r = btrfs_subvol_set_read_only_fd(subvolume_fd, false);
+                                if (r < 0)
+                                        return r;
+                        }
+
+                        /* When btrfs clones the subvolumes, child subvolumes appear as empty
+                         * directories. Remove them, so that we can create a new snapshot in their place */
+                        if (unlinkat(new_child_fd, p, AT_REMOVEDIR) < 0) {
+                                int k = -errno;
+
+                                if (flags & BTRFS_SNAPSHOT_READ_ONLY)
+                                        (void) btrfs_subvol_set_read_only_fd(subvolume_fd, true);
+
+                                return k;
+                        }
+
+                        r = subvol_snapshot_children(old_child_fd, new_child_fd, p, sh.objectid,
+                                                     flags & ~(BTRFS_SNAPSHOT_FALLBACK_COPY|BTRFS_SNAPSHOT_LOCK_BSD));
+
+                        /* Restore the readonly flag */
+                        if (flags & BTRFS_SNAPSHOT_READ_ONLY) {
+                                int k;
+
+                                k = btrfs_subvol_set_read_only_fd(subvolume_fd, true);
+                                if (r >= 0 && k < 0)
+                                        return k;
+                        }
+
+                        if (r < 0)
+                                return r;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+        if (flags & BTRFS_SNAPSHOT_QUOTA)
+                (void) copy_subtree_quota_limits(new_fd, old_subvol_id, new_subvol_id);
+
+        return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
+}
+
+int btrfs_subvol_snapshot_at_full(
+                int dir_fdf,
+                const char *from,
+                int dir_fdt,
+                const char *to,
+                BtrfsSnapshotFlags flags,
+                copy_progress_path_t progress_path,
+                copy_progress_bytes_t progress_bytes,
+                void *userdata) {
+
+        _cleanup_free_ char *subvolume = NULL;
+        _cleanup_close_ int old_fd = -EBADF, new_fd = -EBADF, subvolume_fd = -EBADF;
+        int r;
+
+        assert(dir_fdf >= 0 || dir_fdf == AT_FDCWD);
+        assert(dir_fdt >= 0 || dir_fdt == AT_FDCWD);
+        assert(to);
+
+        old_fd = xopenat(dir_fdf, from, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY, /* xopen_flags = */ 0, /* mode = */ 0);
+        if (old_fd < 0)
+                return old_fd;
+
+        new_fd = chase_and_openat(dir_fdt, to, CHASE_PARENT|CHASE_EXTRACT_FILENAME, O_CLOEXEC, &subvolume);
+        if (new_fd < 0)
+                return new_fd;
+
+        r = btrfs_validate_subvolume_name(subvolume);
+        if (r < 0)
+                return r;
+
+        r = btrfs_is_subvol_at(dir_fdf, from);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                bool plain_directory = false;
+
+                /* If the source isn't a proper subvolume, fail unless fallback is requested */
+                if (!(flags & BTRFS_SNAPSHOT_FALLBACK_COPY))
+                        return -EISDIR;
+
+                r = btrfs_subvol_make(new_fd, subvolume);
+                if (r < 0) {
+                        if (ERRNO_IS_NOT_SUPPORTED(r) && (flags & BTRFS_SNAPSHOT_FALLBACK_DIRECTORY)) {
+                                /* If the destination doesn't support subvolumes, then use a plain directory, if that's requested. */
+                                if (mkdirat(new_fd, subvolume, 0755) < 0)
+                                        return -errno;
+
+                                plain_directory = true;
+                        } else
+                                return r;
+                }
+
+                if (FLAGS_SET(flags, BTRFS_SNAPSHOT_LOCK_BSD)) {
+                        subvolume_fd = xopenat_lock(new_fd, subvolume,
+                                                    O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW,
+                                                    /* xopen_flags = */ 0,
+                                                    /* mode = */ 0,
+                                                    LOCK_BSD,
+                                                    LOCK_EX);
+                        if (subvolume_fd < 0)
+                                return subvolume_fd;
+
+                        if (!plain_directory) {
+                                r = btrfs_is_subvol_fd(subvolume_fd);
+                                if (r < 0)
+                                        return r;
+                                if (r == 0)
+                                        return -EEXIST;
+                        }
+                }
+
+                r = copy_directory_at_full(
+                                dir_fdf, from,
+                                new_fd, subvolume,
+                                COPY_MERGE_EMPTY|
+                                COPY_REFLINK|
+                                COPY_SAME_MOUNT|
+                                COPY_HARDLINKS|
+                                COPY_ALL_XATTRS|
+                                (FLAGS_SET(flags, BTRFS_SNAPSHOT_SIGINT) ? COPY_SIGINT : 0)|
+                                (FLAGS_SET(flags, BTRFS_SNAPSHOT_SIGTERM) ? COPY_SIGTERM : 0),
+                                progress_path,
+                                progress_bytes,
+                                userdata);
+                if (r < 0)
+                        goto fallback_fail;
+
+                if (flags & BTRFS_SNAPSHOT_READ_ONLY) {
+
+                        if (plain_directory) {
+                                /* Plain directories have no recursive read-only flag, but something pretty close to
+                                 * it: the IMMUTABLE bit. Let's use this here, if this is requested. */
+
+                                if (flags & BTRFS_SNAPSHOT_FALLBACK_IMMUTABLE)
+                                        (void) chattr_at(new_fd, subvolume, FS_IMMUTABLE_FL, FS_IMMUTABLE_FL, NULL);
+                        } else {
+                                r = btrfs_subvol_set_read_only_at(new_fd, subvolume, true);
+                                if (r < 0)
+                                        goto fallback_fail;
+                        }
+                }
+
+                return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
+
+        fallback_fail:
+                (void) rm_rf_at(new_fd, subvolume, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME);
+                return r;
+        }
+
+        return subvol_snapshot_children(old_fd, new_fd, subvolume, 0, flags);
+}
+
+int btrfs_qgroup_find_parents(int fd, uint64_t qgroupid, uint64_t **ret) {
+
+        struct btrfs_ioctl_search_args args = {
+                /* Tree of quota items */
+                .key.tree_id = BTRFS_QUOTA_TREE_OBJECTID,
+
+                /* Look precisely for the quota relation items */
+                .key.min_type = BTRFS_QGROUP_RELATION_KEY,
+                .key.max_type = BTRFS_QGROUP_RELATION_KEY,
+
+                /* No restrictions on the other components */
+                .key.min_offset = 0,
+                .key.max_offset = UINT64_MAX,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        _cleanup_free_ uint64_t *items = NULL;
+        size_t n_items = 0;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (qgroupid == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &qgroupid);
+                if (r < 0)
+                        return r;
+        } else {
+                r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOTTY;
+        }
+
+        args.key.min_objectid = args.key.max_objectid = qgroupid;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                _unused_ const void *body;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0) {
+                        if (errno == ENOENT) /* quota tree missing: quota is disabled */
+                                break;
+
+                        return -errno;
+                }
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+
+                        /* Make sure we start the next search at least from this entry */
+                        btrfs_ioctl_search_args_set(&args, &sh);
+
+                        if (sh.type != BTRFS_QGROUP_RELATION_KEY)
+                                continue;
+                        if (sh.offset < sh.objectid)
+                                continue;
+                        if (sh.objectid != qgroupid)
+                                continue;
+
+                        if (!GREEDY_REALLOC(items, n_items+1))
+                                return -ENOMEM;
+
+                        items[n_items++] = sh.offset;
+                }
+
+                /* Increase search key by one, to read the next item, if we can. */
+                if (!btrfs_ioctl_search_args_inc(&args))
+                        break;
+        }
+
+        if (n_items <= 0) {
+                *ret = NULL;
+                return 0;
+        }
+
+        *ret = TAKE_PTR(items);
+
+        return (int) n_items;
+}
+
+int btrfs_subvol_auto_qgroup_fd(int fd, uint64_t subvol_id, bool insert_intermediary_qgroup) {
+        _cleanup_free_ uint64_t *qgroups = NULL;
+        _cleanup_close_ int real_fd = -EBADF;
+        uint64_t parent_subvol;
+        bool changed = false;
+        int n = 0, r;
+
+        assert(fd >= 0);
+
+        /*
+         * Sets up the specified subvolume's qgroup automatically in
+         * one of two ways:
+         *
+         * If insert_intermediary_qgroup is false, the subvolume's
+         * leaf qgroup will be assigned to the same parent qgroups as
+         * the subvolume's parent subvolume.
+         *
+         * If insert_intermediary_qgroup is true a new intermediary
+         * higher-level qgroup is created, with a higher level number,
+         * but reusing the id of the subvolume. The level number is
+         * picked as one smaller than the lowest level qgroup the
+         * parent subvolume is a member of. If the parent subvolume's
+         * leaf qgroup is assigned to no higher-level qgroup a new
+         * qgroup of level 255 is created instead. Either way, the new
+         * qgroup is then assigned to the parent's higher-level
+         * qgroup, and the subvolume itself is assigned to it.
+         *
+         * If the subvolume is already assigned to a higher level
+         * qgroup, no operation is executed.
+         *
+         * Effectively this means: regardless if
+         * insert_intermediary_qgroup is true or not, after this
+         * function is invoked the subvolume will be accounted within
+         * the same qgroups as the parent. However, if it is true, it
+         * will also get its own higher-level qgroup, which may in
+         * turn be used by subvolumes created beneath this subvolume
+         * later on.
+         *
+         * This hence defines a simple default qgroup setup for
+         * subvolumes, as long as this function is invoked on each
+         * created subvolume: each subvolume is always accounting
+         * together with its immediate parents. Optionally, if
+         * insert_intermediary_qgroup is true, it will also get a
+         * qgroup that then includes all its own child subvolumes.
+         */
+
+        /* Turn this into a proper fd, if it is currently O_PATH */
+        fd = fd_reopen_condition(fd, O_RDONLY|O_CLOEXEC, O_PATH, &real_fd);
+        if (fd < 0)
+                return fd;
+
+        if (subvol_id == 0) {
+                r = btrfs_is_subvol_fd(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+
+                r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        }
+
+        n = btrfs_qgroup_find_parents(fd, subvol_id, &qgroups);
+        if (n < 0)
+                return n;
+        if (n > 0) /* already parent qgroups set up, let's bail */
+                return 0;
+
+        qgroups = mfree(qgroups);
+
+        r = btrfs_subvol_get_parent(fd, subvol_id, &parent_subvol);
+        if (r == -ENXIO)
+                /* No parent, hence no qgroup memberships */
+                n = 0;
+        else if (r < 0)
+                return r;
+        else {
+                n = btrfs_qgroup_find_parents(fd, parent_subvol, &qgroups);
+                if (n < 0)
+                        return n;
+        }
+
+        if (insert_intermediary_qgroup) {
+                uint64_t lowest = 256, new_qgroupid;
+                bool created = false;
+
+                /* Determine the lowest qgroup that the parent
+                 * subvolume is assigned to. */
+
+                for (int i = 0; i < n; i++) {
+                        uint64_t level;
+
+                        r = btrfs_qgroupid_split(qgroups[i], &level, NULL);
+                        if (r < 0)
+                                return r;
+
+                        if (level < lowest)
+                                lowest = level;
+                }
+
+                if (lowest <= 1) /* There are no levels left we could use insert an intermediary qgroup at */
+                        return -EBUSY;
+
+                r = btrfs_qgroupid_make(lowest - 1, subvol_id, &new_qgroupid);
+                if (r < 0)
+                        return r;
+
+                /* Create the new intermediary group, unless it already exists */
+                r = btrfs_qgroup_create(fd, new_qgroupid);
+                if (r < 0 && r != -EEXIST)
+                        return r;
+                if (r >= 0)
+                        changed = created = true;
+
+                for (int i = 0; i < n; i++) {
+                        r = btrfs_qgroup_assign(fd, new_qgroupid, qgroups[i]);
+                        if (r < 0 && r != -EEXIST) {
+                                if (created)
+                                        (void) btrfs_qgroup_destroy_recursive(fd, new_qgroupid);
+
+                                return r;
+                        }
+                        if (r >= 0)
+                                changed = true;
+                }
+
+                r = btrfs_qgroup_assign(fd, subvol_id, new_qgroupid);
+                if (r < 0 && r != -EEXIST) {
+                        if (created)
+                                (void) btrfs_qgroup_destroy_recursive(fd, new_qgroupid);
+                        return r;
+                }
+                if (r >= 0)
+                        changed = true;
+
+        } else {
+                int i;
+
+                /* Assign our subvolume to all the same qgroups as the parent */
+
+                for (i = 0; i < n; i++) {
+                        r = btrfs_qgroup_assign(fd, subvol_id, qgroups[i]);
+                        if (r < 0 && r != -EEXIST)
+                                return r;
+                        if (r >= 0)
+                                changed = true;
+                }
+        }
+
+        return changed;
+}
+
+int btrfs_subvol_auto_qgroup(const char *path, uint64_t subvol_id, bool create_intermediary_qgroup) {
+        _cleanup_close_ int fd = -EBADF;
+
+        fd = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_subvol_auto_qgroup_fd(fd, subvol_id, create_intermediary_qgroup);
+}
+
+int btrfs_subvol_get_parent(int fd, uint64_t subvol_id, uint64_t *ret) {
+
+        struct btrfs_ioctl_search_args args = {
+                /* Tree of tree roots */
+                .key.tree_id = BTRFS_ROOT_TREE_OBJECTID,
+
+                /* Look precisely for the subvolume items */
+                .key.min_type = BTRFS_ROOT_BACKREF_KEY,
+                .key.max_type = BTRFS_ROOT_BACKREF_KEY,
+
+                /* No restrictions on the other components */
+                .key.min_offset = 0,
+                .key.max_offset = UINT64_MAX,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        } else {
+                r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -ENOTTY;
+        }
+
+        args.key.min_objectid = args.key.max_objectid = subvol_id;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                _unused_ const void *body = NULL;
+
+                args.key.nr_items = 256;
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
+                        return negative_errno();
+
+                if (args.key.nr_items <= 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, args) {
+
+                        if (sh.type != BTRFS_ROOT_BACKREF_KEY)
+                                continue;
+                        if (sh.objectid != subvol_id)
+                                continue;
+
+                        *ret = sh.offset;
+                        return 0;
+                }
+        }
+
+        return -ENXIO;
+}
+
+int btrfs_forget_device(const char *path) {
+        _cleanup_close_ int control_fd = -EBADF;
+        struct btrfs_ioctl_vol_args args = {};
+
+        assert(path);
+
+        if (strlen(path) > BTRFS_PATH_NAME_MAX)
+                return -E2BIG;
+
+        strcpy(args.name, path);
+
+        control_fd = open("/dev/btrfs-control", O_RDWR|O_CLOEXEC);
+        if (control_fd < 0)
+                return -errno;
+
+        return RET_NERRNO(ioctl(control_fd, BTRFS_IOC_FORGET_DEV, &args));
+}
+
+typedef struct BtrfsStripe {
+        uint64_t devid;
+        uint64_t offset;
+} BtrfsStripe;
+
+typedef struct BtrfsChunk {
+        uint64_t offset;
+        uint64_t length;
+        uint64_t type;
+
+        BtrfsStripe *stripes;
+        uint16_t n_stripes;
+        uint64_t stripe_len;
+} BtrfsChunk;
+
+typedef struct BtrfsChunkTree {
+        BtrfsChunk **chunks;
+        size_t n_chunks;
+} BtrfsChunkTree;
+
+static BtrfsChunk* btrfs_chunk_free(BtrfsChunk *chunk) {
+        if (!chunk)
+                return NULL;
+
+        free(chunk->stripes);
+
+        return mfree(chunk);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(BtrfsChunk*, btrfs_chunk_free);
+
+static void btrfs_chunk_tree_done(BtrfsChunkTree *tree) {
+        assert(tree);
+
+        FOREACH_ARRAY(i, tree->chunks, tree->n_chunks)
+                btrfs_chunk_free(*i);
+
+        free(tree->chunks);
+}
+
+static int btrfs_read_chunk_tree_fd(int fd, BtrfsChunkTree *ret) {
+
+        struct btrfs_ioctl_search_args search_args = {
+                .key.tree_id = BTRFS_CHUNK_TREE_OBJECTID,
+
+                .key.min_type = BTRFS_CHUNK_ITEM_KEY,
+                .key.max_type = BTRFS_CHUNK_ITEM_KEY,
+
+                .key.min_objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID,
+                .key.max_objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID,
+
+                .key.min_offset = 0,
+                .key.max_offset = UINT64_MAX,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        _cleanup_(btrfs_chunk_tree_done) BtrfsChunkTree tree = {};
+
+        assert(fd >= 0);
+        assert(ret);
+
+        while (btrfs_ioctl_search_args_compare(&search_args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                search_args.key.nr_items = 256;
+
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search_args) < 0)
+                        return -errno;
+
+                if (search_args.key.nr_items == 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, search_args) {
+                        _cleanup_(btrfs_chunk_freep) BtrfsChunk *chunk = NULL;
+
+                        btrfs_ioctl_search_args_set(&search_args, &sh);
+
+                        if (sh.objectid != BTRFS_FIRST_CHUNK_TREE_OBJECTID)
+                                continue;
+                        if (sh.type != BTRFS_CHUNK_ITEM_KEY)
+                                continue;
+
+                        chunk = new(BtrfsChunk, 1);
+                        if (!chunk)
+                                return -ENOMEM;
+
+                        const struct btrfs_chunk *item = body;
+                        *chunk = (BtrfsChunk) {
+                                .offset = sh.offset,
+                                .length = le64toh(item->length),
+                                .type = le64toh(item->type),
+                                .n_stripes = le16toh(item->num_stripes),
+                                .stripe_len = le64toh(item->stripe_len),
+                        };
+
+                        chunk->stripes = new(BtrfsStripe, chunk->n_stripes);
+                        if (!chunk->stripes)
+                                return -ENOMEM;
+
+                        for (size_t j = 0; j < chunk->n_stripes; j++) {
+                                const struct btrfs_stripe *stripe = &item->stripe + j;
+
+                                chunk->stripes[j] = (BtrfsStripe) {
+                                        .devid = le64toh(stripe->devid),
+                                        .offset = le64toh(stripe->offset),
+                                };
+                        }
+
+                        if (!GREEDY_REALLOC(tree.chunks, tree.n_chunks + 1))
+                                return -ENOMEM;
+
+                        tree.chunks[tree.n_chunks++] = TAKE_PTR(chunk);
+                }
+
+                if (!btrfs_ioctl_search_args_inc(&search_args))
+                        break;
+        }
+
+        *ret = TAKE_STRUCT(tree);
+        return 0;
+}
+
+static BtrfsChunk* btrfs_find_chunk_from_logical_address(const BtrfsChunkTree *tree, uint64_t logical) {
+        size_t min_index, max_index;
+
+        assert(tree);
+        assert(tree->chunks || tree->n_chunks == 0);
+
+        if (tree->n_chunks == 0)
+                return NULL;
+
+        /* bisection */
+        min_index = 0;
+        max_index = tree->n_chunks - 1;
+
+        while (min_index <= max_index) {
+                size_t mid = (min_index + max_index) / 2;
+
+                if (logical < tree->chunks[mid]->offset) {
+                        if (mid < 1)
+                                return NULL;
+
+                        max_index = mid - 1;
+                } else if (logical >= tree->chunks[mid]->offset + tree->chunks[mid]->length)
+                        min_index = mid + 1;
+                else
+                        return tree->chunks[mid];
+        }
+
+        return NULL;
+}
+
+static int btrfs_is_nocow_fd(int fd) {
+        unsigned flags;
+        int r;
+
+        assert(fd >= 0);
+
+        r = fd_is_fs_type(fd, BTRFS_SUPER_MAGIC);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        r = read_attr_fd(fd, &flags);
+        if (r < 0)
+                return r;
+
+        return FLAGS_SET(flags, FS_NOCOW_FL) && !FLAGS_SET(flags, FS_COMPR_FL);
+}
+
+int btrfs_get_file_physical_offset_fd(int fd, uint64_t *ret) {
+
+        struct btrfs_ioctl_search_args search_args = {
+                .key.min_type = BTRFS_EXTENT_DATA_KEY,
+                .key.max_type = BTRFS_EXTENT_DATA_KEY,
+
+                .key.min_offset = 0,
+                .key.max_offset = UINT64_MAX,
+
+                .key.min_transid = 0,
+                .key.max_transid = UINT64_MAX,
+        };
+
+        _cleanup_(btrfs_chunk_tree_done) BtrfsChunkTree tree = {};
+        uint64_t subvol_id;
+        struct stat st;
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        r = stat_verify_regular(&st);
+        if (r < 0)
+                return r;
+
+        r = btrfs_is_nocow_fd(fd);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Cannot get physical address for btrfs extent: CoW enabled");
+
+        r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+        if (r < 0)
+                return r;
+
+        r = btrfs_read_chunk_tree_fd(fd, &tree);
+        if (r < 0)
+                return r;
+
+        search_args.key.tree_id = subvol_id;
+        search_args.key.min_objectid = search_args.key.max_objectid = st.st_ino;
+
+        while (btrfs_ioctl_search_args_compare(&search_args) <= 0) {
+                struct btrfs_ioctl_search_header sh;
+                const void *body;
+
+                search_args.key.nr_items = 256;
+
+                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search_args) < 0)
+                        return -errno;
+
+                if (search_args.key.nr_items == 0)
+                        break;
+
+                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(sh, body, search_args) {
+                        uint64_t logical_offset;
+                        BtrfsChunk *chunk;
+
+                        btrfs_ioctl_search_args_set(&search_args, &sh);
+
+                        if (sh.type != BTRFS_EXTENT_DATA_KEY)
+                                continue;
+
+                        if (sh.objectid != st.st_ino)
+                                continue;
+
+                        const struct btrfs_file_extent_item *item = body;
+                        if (!IN_SET(item->type, BTRFS_FILE_EXTENT_REG, BTRFS_FILE_EXTENT_PREALLOC))
+                                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Cannot get physical address for btrfs extent: invalid type %" PRIu8,
+                                                       item->type);
+
+                        if (item->compression != 0 || item->encryption != 0 || item->other_encoding != 0)
+                                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Cannot get physical address for btrfs extent: has incompatible property");
+
+                        logical_offset = le64toh(item->disk_bytenr);
+                        if (logical_offset == 0)
+                                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Cannot get physical address for btrfs extent: failed to get logical offset");
+
+                        chunk = btrfs_find_chunk_from_logical_address(&tree, logical_offset);
+                        if (!chunk)
+                                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Cannot get physical address for btrfs extent: no matching chunk found");
+
+                        if ((chunk->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) != 0)
+                                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "Cannot get physical address for btrfs extent: unsupported profile");
+
+                        uint64_t relative_chunk, relative_stripe, stripe_nr;
+                        uint16_t stripe_index;
+
+                        assert(logical_offset >= chunk->offset);
+                        assert(chunk->n_stripes > 0);
+                        assert(chunk->stripe_len > 0);
+
+                        relative_chunk = logical_offset - chunk->offset;
+                        stripe_nr = relative_chunk / chunk->stripe_len;
+                        relative_stripe = relative_chunk - stripe_nr * chunk->stripe_len;
+                        stripe_index = stripe_nr % chunk->n_stripes;
+
+                        *ret = chunk->stripes[stripe_index].offset +
+                                stripe_nr / chunk->n_stripes * chunk->stripe_len +
+                                relative_stripe;
+
+                        return 0;
+                }
+
+                if (!btrfs_ioctl_search_args_inc(&search_args))
+                        break;
+        }
+
+        return -ENODATA;
+}