]> git.ipfire.org Git - thirdparty/systemd.git/blobdiff - src/basic/btrfs-util.c
nss-myhostname: don't fill scopeid for non-link-local addresses
[thirdparty/systemd.git] / src / basic / btrfs-util.c
index 074deeccdaa2154138b808dba138fbec574d51dd..5f9e21dcbafecb6c10f986098e36187eea511678 100644 (file)
@@ -1,5 +1,3 @@
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
 /***
   This file is part of systemd.
 
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/fs.h>
+#include <linux/loop.h>
+#include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
-#include <sys/vfs.h>
+#include <string.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
 
 #ifdef HAVE_LINUX_BTRFS_H
 #include <linux/btrfs.h>
 #endif
 
+#include "alloc-util.h"
+#include "btrfs-ctree.h"
+#include "btrfs-util.h"
+#include "chattr-util.h"
+#include "copy.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "io-util.h"
+#include "macro.h"
 #include "missing.h"
-#include "util.h"
 #include "path-util.h"
-#include "macro.h"
-#include "copy.h"
+#include "rm-rf.h"
 #include "selinux-util.h"
 #include "smack-util.h"
-#include "fileio.h"
-#include "btrfs-ctree.h"
-#include "btrfs-util.h"
+#include "sparse-endian.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "time-util.h"
+#include "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
@@ -59,13 +77,13 @@ static int validate_subvolume_name(const char *name) {
 
 static int open_parent(const char *path, int flags) {
         _cleanup_free_ char *parent = NULL;
-        int r, fd;
+        int fd;
 
         assert(path);
 
-        r = path_get_parent(path, &parent);
-        if (r < 0)
-                return r;
+        parent = dirname_malloc(path);
+        if (!parent)
+                return -ENOMEM;
 
         fd = open(parent, flags);
         if (fd < 0)
@@ -102,7 +120,7 @@ int btrfs_is_filesystem(int fd) {
         return F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC);
 }
 
-int btrfs_is_subvol(int fd) {
+int btrfs_is_subvol_fd(int fd) {
         struct stat st;
 
         assert(fd >= 0);
@@ -118,6 +136,18 @@ int btrfs_is_subvol(int fd) {
         return btrfs_is_filesystem(fd);
 }
 
+int btrfs_is_subvol(const char *path) {
+        _cleanup_close_ int fd = -1;
+
+        assert(path);
+
+        fd = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (fd < 0)
+                return -errno;
+
+        return btrfs_is_subvol_fd(fd);
+}
+
 int btrfs_subvol_make(const char *path) {
         struct btrfs_ioctl_vol_args args = {};
         _cleanup_close_ int fd = -1;
@@ -436,7 +466,7 @@ static int btrfs_ioctl_search_args_compare(const struct btrfs_ioctl_search_args
 #define BTRFS_IOCTL_SEARCH_HEADER_BODY(sh)                              \
         ((void*) ((uint8_t*) sh + sizeof(struct btrfs_ioctl_search_header)))
 
-int btrfs_subvol_get_info_fd(int fd, BtrfsSubvolInfo *ret) {
+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,
@@ -453,16 +483,23 @@ int btrfs_subvol_get_info_fd(int fd, BtrfsSubvolInfo *ret) {
                 .key.max_transid = (uint64_t) -1,
         };
 
-        uint64_t subvol_id;
         bool found = false;
         int r;
 
         assert(fd >= 0);
         assert(ret);
 
-        r = btrfs_subvol_get_id_fd(fd, &subvol_id);
-        if (r < 0)
-                return r;
+        if (subvol_id == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &subvol_id);
+                if (r < 0)
+                        return r;
+        } else {
+                r = btrfs_is_filesystem(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+        }
 
         args.key.min_objectid = args.key.max_objectid = subvol_id;
 
@@ -521,7 +558,7 @@ finish:
         return 0;
 }
 
-int btrfs_subvol_get_quota_fd(int fd, BtrfsQuotaInfo *ret) {
+int btrfs_qgroup_get_quota_fd(int fd, uint64_t qgroupid, BtrfsQuotaInfo *ret) {
 
         struct btrfs_ioctl_search_args args = {
                 /* Tree of quota items */
@@ -540,26 +577,37 @@ int btrfs_subvol_get_quota_fd(int fd, BtrfsQuotaInfo *ret) {
                 .key.max_transid = (uint64_t) -1,
         };
 
-        uint64_t subvol_id;
         bool found_info = false, found_limit = false;
         int r;
 
         assert(fd >= 0);
         assert(ret);
 
-        r = btrfs_subvol_get_id_fd(fd, &subvol_id);
-        if (r < 0)
-                return r;
+        if (qgroupid == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &qgroupid);
+                if (r < 0)
+                        return r;
+        } else {
+                r = btrfs_is_filesystem(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+        }
 
-        args.key.min_offset = args.key.max_offset = subvol_id;
+        args.key.min_offset = args.key.max_offset = qgroupid;
 
         while (btrfs_ioctl_search_args_compare(&args) <= 0) {
                 const struct btrfs_ioctl_search_header *sh;
                 unsigned i;
 
                 args.key.nr_items = 256;
-                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
+                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;
@@ -571,7 +619,7 @@ int btrfs_subvol_get_quota_fd(int fd, BtrfsQuotaInfo *ret) {
 
                         if (sh->objectid != 0)
                                 continue;
-                        if (sh->offset != subvol_id)
+                        if (sh->offset != qgroupid)
                                 continue;
 
                         if (sh->type == BTRFS_QGROUP_INFO_KEY) {
@@ -585,12 +633,14 @@ int btrfs_subvol_get_quota_fd(int fd, BtrfsQuotaInfo *ret) {
                         } else if (sh->type == BTRFS_QGROUP_LIMIT_KEY) {
                                 const struct btrfs_qgroup_limit_item *qli = BTRFS_IOCTL_SEARCH_HEADER_BODY(sh);
 
-                                ret->referenced_max = le64toh(qli->max_rfer);
-                                ret->exclusive_max = le64toh(qli->max_excl);
-
-                                if (ret->referenced_max == 0)
+                                if (le64toh(qli->flags) & BTRFS_QGROUP_LIMIT_MAX_RFER)
+                                        ret->referenced_max = le64toh(qli->max_rfer);
+                                else
                                         ret->referenced_max = (uint64_t) -1;
-                                if (ret->exclusive_max == 0)
+
+                                if (le64toh(qli->flags) & BTRFS_QGROUP_LIMIT_MAX_EXCL)
+                                        ret->exclusive_max = le64toh(qli->max_excl);
+                                else
                                         ret->exclusive_max = (uint64_t) -1;
 
                                 found_limit = true;
@@ -622,6 +672,109 @@ finish:
         return 0;
 }
 
+int btrfs_qgroup_get_quota(const char *path, uint64_t qgroupid, BtrfsQuotaInfo *ret) {
+        _cleanup_close_ int fd = -1;
+
+        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_t) -1, lowest_qgroupid = 0;
+        _cleanup_free_ uint64_t *qgroups = NULL;
+        int r, n, i;
+
+        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 distuingished 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 (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_t) -1 || level < lowest) {
+                        lowest_qgroupid = qgroups[i];
+                        lowest = level;
+                }
+        }
+
+        if (lowest == (uint64_t) -1) {
+                /* 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 = -1;
+
+        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) {
         struct stat st;
 
@@ -679,37 +832,79 @@ int btrfs_quota_enable(const char *path, bool b) {
         return btrfs_quota_enable_fd(fd, b);
 }
 
-int btrfs_quota_limit_fd(int fd, uint64_t referenced_max) {
+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 == (uint64_t) -1 ? 0 :
-                        referenced_max == 0 ? 1 : referenced_max,
+                .lim.max_rfer = referenced_max,
                 .lim.flags = BTRFS_QGROUP_LIMIT_MAX_RFER,
         };
+        unsigned c;
         int r;
 
         assert(fd >= 0);
 
-        r = btrfs_is_filesystem(fd);
-        if (r < 0)
-                return r;
-        if (!r)
-                return -ENOTTY;
+        if (qgroupid == 0) {
+                r = btrfs_subvol_get_id_fd(fd, &qgroupid);
+                if (r < 0)
+                        return r;
+        } else {
+                r = btrfs_is_filesystem(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+        }
 
-        if (ioctl(fd, BTRFS_IOC_QGROUP_LIMIT, &args) < 0)
-                return -errno;
+        args.qgroupid = qgroupid;
+
+        for (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_quota_limit(const char *path, uint64_t referenced_max) {
+int btrfs_qgroup_set_limit(const char *path, uint64_t qgroupid, uint64_t referenced_max) {
         _cleanup_close_ int fd = -1;
 
         fd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
         if (fd < 0)
                 return -errno;
 
-        return btrfs_quota_limit_fd(fd, referenced_max);
+        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 = -1;
+
+        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_resize_loopback_fd(int fd, uint64_t new_size, bool grow_only) {
@@ -720,6 +915,10 @@ int btrfs_resize_loopback_fd(int fd, uint64_t new_size, bool grow_only) {
         dev_t dev = 0;
         int r;
 
+        /* In contrast to btrfs quota ioctls ftruncate() cannot make sense of "infinity" or file sizes > 2^31 */
+        if (!FILE_SIZE_VALID(new_size))
+                return -EINVAL;
+
         /* btrfs cannot handle file systems < 16M, hence use this as minimum */
         if (new_size < 16*1024*1024)
                 new_size = 16*1024*1024;
@@ -799,118 +998,306 @@ int btrfs_resize_loopback(const char *p, uint64_t new_size, bool grow_only) {
         return btrfs_resize_loopback_fd(fd, new_size, grow_only);
 }
 
-static int subvol_remove_children(int fd, const char *subvolume, uint64_t subvol_id, bool recursive) {
-        struct btrfs_ioctl_search_args args = {
-                .key.tree_id = BTRFS_ROOT_TREE_OBJECTID,
+int btrfs_qgroupid_make(uint64_t level, uint64_t id, uint64_t *ret) {
+        assert(ret);
 
-                .key.min_objectid = BTRFS_FIRST_FREE_OBJECTID,
-                .key.max_objectid = BTRFS_LAST_FREE_OBJECTID,
+        if (level >= (UINT64_C(1) << (64 - BTRFS_QGROUP_LEVEL_SHIFT)))
+                return -EINVAL;
 
-                .key.min_type = BTRFS_ROOT_BACKREF_KEY,
-                .key.max_type = BTRFS_ROOT_BACKREF_KEY,
+        if (id >= (UINT64_C(1) << BTRFS_QGROUP_LEVEL_SHIFT))
+                return -EINVAL;
 
-                .key.min_transid = 0,
-                .key.max_transid = (uint64_t) -1,
-        };
+        *ret = (level << BTRFS_QGROUP_LEVEL_SHIFT) | id;
+        return 0;
+}
 
-        struct btrfs_ioctl_vol_args vol_args = {};
-        _cleanup_close_ int subvol_fd = -1;
-        struct stat st;
-        bool made_writable = false;
-        int r;
+int btrfs_qgroupid_split(uint64_t qgroupid, uint64_t *level, uint64_t *id) {
+        assert(level || id);
 
-        assert(fd >= 0);
-        assert(subvolume);
+        if (level)
+                *level = qgroupid >> BTRFS_QGROUP_LEVEL_SHIFT;
 
-        if (fstat(fd, &st) < 0)
-                return -errno;
+        if (id)
+                *id = qgroupid & ((UINT64_C(1) << BTRFS_QGROUP_LEVEL_SHIFT) - 1);
 
-        if (!S_ISDIR(st.st_mode))
-                return -EINVAL;
+        return 0;
+}
 
-        /* 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)
-                return 0;
-        if (!recursive || errno != ENOTEMPTY)
-                return -errno;
+static int qgroup_create_or_destroy(int fd, bool b, uint64_t qgroupid) {
 
-        /* OK, the subvolume is not empty, let's look for child
-         * subvolumes, and remove them, first */
-        subvol_fd = openat(fd, subvolume, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
-        if (subvol_fd < 0)
-                return -errno;
+        struct btrfs_ioctl_qgroup_create_args args = {
+                .create = b,
+                .qgroupid = qgroupid,
+        };
+        unsigned c;
+        int r;
 
-        if (subvol_id == 0) {
-                r = btrfs_subvol_get_id_fd(subvol_fd, &subvol_id);
-                if (r < 0)
-                        return r;
-        }
+        r = btrfs_is_filesystem(fd);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
 
-        args.key.min_offset = args.key.max_offset = subvol_id;
+        for (c = 0;; c++) {
+                if (ioctl(fd, BTRFS_IOC_QGROUP_CREATE, &args) < 0) {
 
-        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
-                const struct btrfs_ioctl_search_header *sh;
-                unsigned i;
+                        /* If quota is not enabled, we get EINVAL. Turn this into a recognizable error */
+                        if (errno == EINVAL)
+                                return -ENOPROTOOPT;
+
+                        if (errno == EBUSY && c < 10) {
+                                (void) btrfs_quota_scan_wait(fd);
+                                continue;
+                        }
 
-                args.key.nr_items = 256;
-                if (ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args) < 0)
                         return -errno;
+                }
 
-                if (args.key.nr_items <= 0)
-                        break;
+                break;
+        }
 
-                FOREACH_BTRFS_IOCTL_SEARCH_HEADER(i, sh, args) {
-                        _cleanup_free_ char *p = NULL;
-                        const struct btrfs_root_ref *ref;
-                        struct btrfs_ioctl_ino_lookup_args ino_args;
+        return 0;
+}
 
-                        btrfs_ioctl_search_args_set(&args, sh);
+int btrfs_qgroup_create(int fd, uint64_t qgroupid) {
+        return qgroup_create_or_destroy(fd, true, qgroupid);
+}
 
-                        if (sh->type != BTRFS_ROOT_BACKREF_KEY)
-                                continue;
-                        if (sh->offset != subvol_id)
-                                continue;
+int btrfs_qgroup_destroy(int fd, uint64_t qgroupid) {
+        return qgroup_create_or_destroy(fd, false, qgroupid);
+}
 
-                        ref = BTRFS_IOCTL_SEARCH_HEADER_BODY(sh);
+int btrfs_qgroup_destroy_recursive(int fd, uint64_t qgroupid) {
+        _cleanup_free_ uint64_t *qgroups = NULL;
+        uint64_t subvol_id;
+        int i, n, r;
 
-                        p = strndup((char*) ref + sizeof(struct btrfs_root_ref), le64toh(ref->name_len));
-                        if (!p)
-                                return -ENOMEM;
+        /* Destroys the specified qgroup, but unassigns it from all
+         * its parents first. Also, it recursively destroys all
+         * qgroups it is assgined to that have the same id part of the
+         * qgroupid as the specified group. */
 
-                        zero(ino_args);
-                        ino_args.treeid = subvol_id;
-                        ino_args.objectid = htole64(ref->dirid);
+        r = btrfs_qgroupid_split(qgroupid, NULL, &subvol_id);
+        if (r < 0)
+                return r;
 
-                        if (ioctl(fd, BTRFS_IOC_INO_LOOKUP, &ino_args) < 0)
-                                return -errno;
+        n = btrfs_qgroup_find_parents(fd, qgroupid, &qgroups);
+        if (n < 0)
+                return n;
 
-                        if (!made_writable) {
-                                r = btrfs_subvol_set_read_only_fd(subvol_fd, false);
-                                if (r < 0)
-                                        return r;
+        for (i = 0; i < n; i++) {
+                uint64_t id;
 
-                                made_writable = true;
-                        }
+                r = btrfs_qgroupid_split(qgroups[i], NULL, &id);
+                if (r < 0)
+                        return r;
 
-                        if (isempty(ino_args.name))
-                                /* Subvolume is in the top-level
-                                 * directory of the subvolume. */
-                                r = subvol_remove_children(subvol_fd, p, sh->objectid, recursive);
-                        else {
-                                _cleanup_close_ int child_fd = -1;
+                r = btrfs_qgroup_unassign(fd, qgroupid, qgroups[i]);
+                if (r < 0)
+                        return r;
 
-                                /* Subvolume is somewhere further down,
-                                 * hence we need to open the
-                                 * containing directory first */
+                if (id != subvol_id)
+                        continue;
 
-                                child_fd = openat(subvol_fd, ino_args.name, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
-                                if (child_fd < 0)
-                                        return -errno;
+                /* The parent qgroupid shares the same id part with
+                 * us? If so, destroy it too. */
 
-                                r = subvol_remove_children(child_fd, p, sh->objectid, recursive);
-                        }
+                (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);
+
+        if (ioctl(fd, BTRFS_IOC_QUOTA_RESCAN, &args) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_quota_scan_wait(int fd) {
+        assert(fd >= 0);
+
+        if (ioctl(fd, BTRFS_IOC_QUOTA_RESCAN_WAIT) < 0)
+                return -errno;
+
+        return 0;
+}
+
+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,
+        };
+        unsigned c;
+        int r;
+
+        r = btrfs_is_filesystem(fd);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENOTTY;
+
+        for (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_t) -1,
+        };
+
+        struct btrfs_ioctl_vol_args vol_args = {};
+        _cleanup_close_ int subvol_fd = -1;
+        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);
+        if (subvol_fd < 0)
+                return -errno;
+
+        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) {
+                const struct btrfs_ioctl_search_header *sh;
+                unsigned i;
+
+                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(i, sh, args) {
+                        _cleanup_free_ char *p = NULL;
+                        const struct btrfs_root_ref *ref;
+                        struct btrfs_ioctl_ino_lookup_args ino_args;
+
+                        btrfs_ioctl_search_args_set(&args, sh);
+
+                        if (sh->type != BTRFS_ROOT_BACKREF_KEY)
+                                continue;
+                        if (sh->offset != subvol_id)
+                                continue;
+
+                        ref = BTRFS_IOCTL_SEARCH_HEADER_BODY(sh);
+
+                        p = strndup((char*) ref + sizeof(struct btrfs_root_ref), le64toh(ref->name_len));
+                        if (!p)
+                                return -ENOMEM;
+
+                        zero(ino_args);
+                        ino_args.treeid = subvol_id;
+                        ino_args.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 = -1;
+
+                                /* 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);
+                                if (child_fd < 0)
+                                        return -errno;
+
+                                r = subvol_remove_children(child_fd, p, sh->objectid, flags);
+                        }
                         if (r < 0)
                                 return r;
                 }
@@ -925,10 +1312,11 @@ static int subvol_remove_children(int fd, const char *subvolume, uint64_t subvol
         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(const char *path, bool recursive) {
+int btrfs_subvol_remove(const char *path, BtrfsRemoveFlags flags) {
         _cleanup_close_ int fd = -1;
         const char *subvolume;
         int r;
@@ -943,11 +1331,202 @@ int btrfs_subvol_remove(const char *path, bool recursive) {
         if (fd < 0)
                 return fd;
 
-        return subvol_remove_children(fd, subvolume, 0, recursive);
+        return subvol_remove_children(fd, subvolume, 0, flags);
+}
+
+int btrfs_subvol_remove_fd(int fd, const char *subvolume, BtrfsRemoveFlags flags) {
+        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_t) -1,
+        };
+
+        int r;
+
+        r = btrfs_is_filesystem(fd);
+        if (r < 0)
+                return r;
+        if (!r)
+                return -ENOTTY;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                const struct btrfs_ioctl_search_header *sh;
+                unsigned i;
+
+                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(i, sh, args) {
+                        const struct btrfs_qgroup_limit_item *qli = BTRFS_IOCTL_SEARCH_HEADER_BODY(sh);
+                        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. */
+
+                        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;
 }
 
-int btrfs_subvol_remove_fd(int fd, const char *subvolume, bool recursive) {
-        return subvol_remove_children(fd, subvolume, 0, recursive);
+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, i;
+        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 (i = 0; i < n_old_qgroups; i++) {
+                uint64_t id;
+                int j;
+
+                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 (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) {
@@ -978,12 +1557,12 @@ static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolum
         assert(subvolume);
 
         strncpy(vol_args.name, subvolume, sizeof(vol_args.name)-1);
-        vol_args.fd = old_fd;
 
         if (ioctl(new_fd, BTRFS_IOC_SNAP_CREATE_V2, &vol_args) < 0)
                 return -errno;
 
-        if (!(flags & BTRFS_SNAPSHOT_RECURSIVE))
+        if (!(flags & BTRFS_SNAPSHOT_RECURSIVE) &&
+            !(flags & BTRFS_SNAPSHOT_QUOTA))
                 return 0;
 
         if (old_subvol_id == 0) {
@@ -996,6 +1575,17 @@ static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolum
         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 0;
+        }
+
         args.key.min_offset = args.key.max_offset = old_subvol_id;
 
         while (btrfs_ioctl_search_args_compare(&args) <= 0) {
@@ -1055,7 +1645,7 @@ static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolum
                         if (old_child_fd < 0)
                                 return -errno;
 
-                        np = strjoin(subvolume, "/", ino_args.name, NULL);
+                        np = strjoin(subvolume, "/", ino_args.name);
                         if (!np)
                                 return -ENOMEM;
 
@@ -1113,6 +1703,9 @@ static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolum
                         break;
         }
 
+        if (flags & BTRFS_SNAPSHOT_QUOTA)
+                (void) copy_subtree_quota_limits(new_fd, old_subvol_id, new_subvol_id);
+
         return 0;
 }
 
@@ -1124,32 +1717,50 @@ int btrfs_subvol_snapshot_fd(int old_fd, const char *new_path, BtrfsSnapshotFlag
         assert(old_fd >= 0);
         assert(new_path);
 
-        r = btrfs_is_subvol(old_fd);
+        r = btrfs_is_subvol_fd(old_fd);
         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_path);
-                if (r < 0)
+                if (r == -ENOTTY && (flags & BTRFS_SNAPSHOT_FALLBACK_DIRECTORY)) {
+                        /* If the destination doesn't support subvolumes, then use a plain directory, if that's requested. */
+                        if (mkdir(new_path, 0755) < 0)
+                                return r;
+
+                        plain_directory = true;
+                } else if (r < 0)
                         return r;
 
                 r = copy_directory_fd(old_fd, new_path, true);
-                if (r < 0) {
-                        btrfs_subvol_remove(new_path, false);
-                        return r;
-                }
+                if (r < 0)
+                        goto fallback_fail;
 
                 if (flags & BTRFS_SNAPSHOT_READ_ONLY) {
-                        r = btrfs_subvol_set_read_only(new_path, true);
-                        if (r < 0) {
-                                btrfs_subvol_remove(new_path, false);
-                                return r;
+
+                        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_path(new_path, FS_IMMUTABLE_FL, FS_IMMUTABLE_FL);
+                        } else {
+                                r = btrfs_subvol_set_read_only(new_path, true);
+                                if (r < 0)
+                                        goto fallback_fail;
                         }
                 }
 
                 return 0;
+
+        fallback_fail:
+                (void) rm_rf(new_path, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME);
+                return r;
         }
 
         r = extract_subvolume_name(new_path, &subvolume);
@@ -1175,3 +1786,311 @@ int btrfs_subvol_snapshot(const char *old_path, const char *new_path, BtrfsSnaps
 
         return btrfs_subvol_snapshot_fd(old_fd, new_path, 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_t) -1,
+
+                .key.min_transid = 0,
+                .key.max_transid = (uint64_t) -1,
+        };
+
+        _cleanup_free_ uint64_t *items = NULL;
+        size_t n_items = 0, n_allocated = 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 = btrfs_is_filesystem(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+        }
+
+        args.key.min_objectid = args.key.max_objectid = qgroupid;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                const struct btrfs_ioctl_search_header *sh;
+                unsigned i;
+
+                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(i, sh, 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_allocated, 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 = items;
+        items = NULL;
+
+        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;
+        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.
+         */
+
+        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;
+                int i;
+
+                /* Determine the lowest qgroup that the parent
+                 * subvolume is assigned to. */
+
+                for (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 (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 = -1;
+
+        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_t) -1,
+
+                .key.min_transid = 0,
+                .key.max_transid = (uint64_t) -1,
+        };
+        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 = btrfs_is_filesystem(fd);
+                if (r < 0)
+                        return r;
+                if (!r)
+                        return -ENOTTY;
+        }
+
+        args.key.min_objectid = args.key.max_objectid = subvol_id;
+
+        while (btrfs_ioctl_search_args_compare(&args) <= 0) {
+                const struct btrfs_ioctl_search_header *sh;
+                unsigned i;
+
+                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(i, sh, args) {
+
+                        if (sh->type != BTRFS_ROOT_BACKREF_KEY)
+                                continue;
+                        if (sh->objectid != subvol_id)
+                                continue;
+
+                        *ret = sh->offset;
+                        return 0;
+                }
+        }
+
+        return -ENXIO;
+}