qgroup.c

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/*
 * Copyright (C) 2011 STRATO.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/workqueue.h>

#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "locking.h"
#include "ulist.h"
#include "ioctl.h"
#include "backref.h"

/* TODO XXX FIXME
 *  - subvol delete -> delete when ref goes to 0? delete limits also?
 *  - reorganize keys
 *  - compressed
 *  - sync
 *  - rescan
 *  - copy also limits on subvol creation
 *  - limit
 *  - caches fuer ulists
 *  - performance benchmarks
 *  - check all ioctl parameters
 */

/*
 * one struct for each qgroup, organized in fs_info->qgroup_tree.
 */
struct btrfs_qgroup {
    u64 qgroupid;

    /*
     * state
     */
    u64 rfer;   /* referenced */
    u64 rfer_cmpr;  /* referenced compressed */
    u64 excl;   /* exclusive */
    u64 excl_cmpr;  /* exclusive compressed */

    /*
     * limits
     */
    u64 lim_flags;  /* which limits are set */
    u64 max_rfer;
    u64 max_excl;
    u64 rsv_rfer;
    u64 rsv_excl;

    /*
     * reservation tracking
     */
    u64 reserved;

    /*
     * lists
     */
    struct list_head groups;  /* groups this group is member of */
    struct list_head members; /* groups that are members of this group */
    struct list_head dirty;   /* dirty groups */
    struct rb_node node;      /* tree of qgroups */

    /*
     * temp variables for accounting operations
     */
    u64 tag;
    u64 refcnt;
};

/*
 * glue structure to represent the relations between qgroups.
 */
struct btrfs_qgroup_list {
    struct list_head next_group;
    struct list_head next_member;
    struct btrfs_qgroup *group;
    struct btrfs_qgroup *member;
};

/* must be called with qgroup_lock held */
static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
                       u64 qgroupid)
{
    struct rb_node *n = fs_info->qgroup_tree.rb_node;
    struct btrfs_qgroup *qgroup;

    while (n) {
        qgroup = rb_entry(n, struct btrfs_qgroup, node);
        if (qgroup->qgroupid < qgroupid)
            n = n->rb_left;
        else if (qgroup->qgroupid > qgroupid)
            n = n->rb_right;
        else
            return qgroup;
    }
    return NULL;
}

/* must be called with qgroup_lock held */
static struct btrfs_qgroup *add_qgroup_rb(struct btrfs_fs_info *fs_info,
                      u64 qgroupid)
{
    struct rb_node **p = &fs_info->qgroup_tree.rb_node;
    struct rb_node *parent = NULL;
    struct btrfs_qgroup *qgroup;

    while (*p) {
        parent = *p;
        qgroup = rb_entry(parent, struct btrfs_qgroup, node);

        if (qgroup->qgroupid < qgroupid)
            p = &(*p)->rb_left;
        else if (qgroup->qgroupid > qgroupid)
            p = &(*p)->rb_right;
        else
            return qgroup;
    }

    qgroup = kzalloc(sizeof(*qgroup), GFP_ATOMIC);
    if (!qgroup)
        return ERR_PTR(-ENOMEM);

    qgroup->qgroupid = qgroupid;
    INIT_LIST_HEAD(&qgroup->groups);
    INIT_LIST_HEAD(&qgroup->members);
    INIT_LIST_HEAD(&qgroup->dirty);

    rb_link_node(&qgroup->node, parent, p);
    rb_insert_color(&qgroup->node, &fs_info->qgroup_tree);

    return qgroup;
}

/* must be called with qgroup_lock held */
static int del_qgroup_rb(struct btrfs_fs_info *fs_info, u64 qgroupid)
{
    struct btrfs_qgroup *qgroup = find_qgroup_rb(fs_info, qgroupid);
    struct btrfs_qgroup_list *list;

    if (!qgroup)
        return -ENOENT;

    rb_erase(&qgroup->node, &fs_info->qgroup_tree);
    list_del(&qgroup->dirty);

    while (!list_empty(&qgroup->groups)) {
        list = list_first_entry(&qgroup->groups,
                    struct btrfs_qgroup_list, next_group);
        list_del(&list->next_group);
        list_del(&list->next_member);
        kfree(list);
    }

    while (!list_empty(&qgroup->members)) {
        list = list_first_entry(&qgroup->members,
                    struct btrfs_qgroup_list, next_member);
        list_del(&list->next_group);
        list_del(&list->next_member);
        kfree(list);
    }
    kfree(qgroup);

    return 0;
}

/* must be called with qgroup_lock held */
static int add_relation_rb(struct btrfs_fs_info *fs_info,
               u64 memberid, u64 parentid)
{
    struct btrfs_qgroup *member;
    struct btrfs_qgroup *parent;
    struct btrfs_qgroup_list *list;

    member = find_qgroup_rb(fs_info, memberid);
    parent = find_qgroup_rb(fs_info, parentid);
    if (!member || !parent)
        return -ENOENT;

    list = kzalloc(sizeof(*list), GFP_ATOMIC);
    if (!list)
        return -ENOMEM;

    list->group = parent;
    list->member = member;
    list_add_tail(&list->next_group, &member->groups);
    list_add_tail(&list->next_member, &parent->members);

    return 0;
}

/* must be called with qgroup_lock held */
static int del_relation_rb(struct btrfs_fs_info *fs_info,
               u64 memberid, u64 parentid)
{
    struct btrfs_qgroup *member;
    struct btrfs_qgroup *parent;
    struct btrfs_qgroup_list *list;

    member = find_qgroup_rb(fs_info, memberid);
    parent = find_qgroup_rb(fs_info, parentid);
    if (!member || !parent)
        return -ENOENT;

    list_for_each_entry(list, &member->groups, next_group) {
        if (list->group == parent) {
            list_del(&list->next_group);
            list_del(&list->next_member);
            kfree(list);
            return 0;
        }
    }
    return -ENOENT;
}

/*
 * The full config is read in one go, only called from open_ctree()
 * It doesn't use any locking, as at this point we're still single-threaded
 */
int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
{
    struct btrfs_key key;
    struct btrfs_key found_key;
    struct btrfs_root *quota_root = fs_info->quota_root;
    struct btrfs_path *path = NULL;
    struct extent_buffer *l;
    int slot;
    int ret = 0;
    u64 flags = 0;

    if (!fs_info->quota_enabled)
        return 0;

    path = btrfs_alloc_path();
    if (!path) {
        ret = -ENOMEM;
        goto out;
    }

    /* default this to quota off, in case no status key is found */
    fs_info->qgroup_flags = 0;

    /*
     * pass 1: read status, all qgroup infos and limits
     */
    key.objectid = 0;
    key.type = 0;
    key.offset = 0;
    ret = btrfs_search_slot_for_read(quota_root, &key, path, 1, 1);
    if (ret)
        goto out;

    while (1) {
        struct btrfs_qgroup *qgroup;

        slot = path->slots[0];
        l = path->nodes[0];
        btrfs_item_key_to_cpu(l, &found_key, slot);

        if (found_key.type == BTRFS_QGROUP_STATUS_KEY) {
            struct btrfs_qgroup_status_item *ptr;

            ptr = btrfs_item_ptr(l, slot,
                         struct btrfs_qgroup_status_item);

            if (btrfs_qgroup_status_version(l, ptr) !=
                BTRFS_QGROUP_STATUS_VERSION) {
                printk(KERN_ERR
                 "btrfs: old qgroup version, quota disabled\n");
                goto out;
            }
            if (btrfs_qgroup_status_generation(l, ptr) !=
                fs_info->generation) {
                flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                printk(KERN_ERR
                    "btrfs: qgroup generation mismatch, "
                    "marked as inconsistent\n");
            }
            fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
                                      ptr);
            /* FIXME read scan element */
            goto next1;
        }

        if (found_key.type != BTRFS_QGROUP_INFO_KEY &&
            found_key.type != BTRFS_QGROUP_LIMIT_KEY)
            goto next1;

        qgroup = find_qgroup_rb(fs_info, found_key.offset);
        if ((qgroup && found_key.type == BTRFS_QGROUP_INFO_KEY) ||
            (!qgroup && found_key.type == BTRFS_QGROUP_LIMIT_KEY)) {
            printk(KERN_ERR "btrfs: inconsitent qgroup config\n");
            flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        }
        if (!qgroup) {
            qgroup = add_qgroup_rb(fs_info, found_key.offset);
            if (IS_ERR(qgroup)) {
                ret = PTR_ERR(qgroup);
                goto out;
            }
        }
        switch (found_key.type) {
        case BTRFS_QGROUP_INFO_KEY: {
            struct btrfs_qgroup_info_item *ptr;

            ptr = btrfs_item_ptr(l, slot,
                         struct btrfs_qgroup_info_item);
            qgroup->rfer = btrfs_qgroup_info_rfer(l, ptr);
            qgroup->rfer_cmpr = btrfs_qgroup_info_rfer_cmpr(l, ptr);
            qgroup->excl = btrfs_qgroup_info_excl(l, ptr);
            qgroup->excl_cmpr = btrfs_qgroup_info_excl_cmpr(l, ptr);
            /* generation currently unused */
            break;
        }
        case BTRFS_QGROUP_LIMIT_KEY: {
            struct btrfs_qgroup_limit_item *ptr;

            ptr = btrfs_item_ptr(l, slot,
                         struct btrfs_qgroup_limit_item);
            qgroup->lim_flags = btrfs_qgroup_limit_flags(l, ptr);
            qgroup->max_rfer = btrfs_qgroup_limit_max_rfer(l, ptr);
            qgroup->max_excl = btrfs_qgroup_limit_max_excl(l, ptr);
            qgroup->rsv_rfer = btrfs_qgroup_limit_rsv_rfer(l, ptr);
            qgroup->rsv_excl = btrfs_qgroup_limit_rsv_excl(l, ptr);
            break;
        }
        }
next1:
        ret = btrfs_next_item(quota_root, path);
        if (ret < 0)
            goto out;
        if (ret)
            break;
    }
    btrfs_release_path(path);

    /*
     * pass 2: read all qgroup relations
     */
    key.objectid = 0;
    key.type = BTRFS_QGROUP_RELATION_KEY;
    key.offset = 0;
    ret = btrfs_search_slot_for_read(quota_root, &key, path, 1, 0);
    if (ret)
        goto out;
    while (1) {
        slot = path->slots[0];
        l = path->nodes[0];
        btrfs_item_key_to_cpu(l, &found_key, slot);

        if (found_key.type != BTRFS_QGROUP_RELATION_KEY)
            goto next2;

        if (found_key.objectid > found_key.offset) {
            /* parent <- member, not needed to build config */
            /* FIXME should we omit the key completely? */
            goto next2;
        }

        ret = add_relation_rb(fs_info, found_key.objectid,
                      found_key.offset);
        if (ret)
            goto out;
next2:
        ret = btrfs_next_item(quota_root, path);
        if (ret < 0)
            goto out;
        if (ret)
            break;
    }
out:
    fs_info->qgroup_flags |= flags;
    if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON)) {
        fs_info->quota_enabled = 0;
        fs_info->pending_quota_state = 0;
    }
    btrfs_free_path(path);

    return ret < 0 ? ret : 0;
}

/*
 * This is only called from close_ctree() or open_ctree(), both in single-
 * treaded paths. Clean up the in-memory structures. No locking needed.
 */
void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info)
{
    struct rb_node *n;
    struct btrfs_qgroup *qgroup;
    struct btrfs_qgroup_list *list;

    while ((n = rb_first(&fs_info->qgroup_tree))) {
        qgroup = rb_entry(n, struct btrfs_qgroup, node);
        rb_erase(n, &fs_info->qgroup_tree);

        WARN_ON(!list_empty(&qgroup->dirty));

        while (!list_empty(&qgroup->groups)) {
            list = list_first_entry(&qgroup->groups,
                        struct btrfs_qgroup_list,
                        next_group);
            list_del(&list->next_group);
            list_del(&list->next_member);
            kfree(list);
        }

        while (!list_empty(&qgroup->members)) {
            list = list_first_entry(&qgroup->members,
                        struct btrfs_qgroup_list,
                        next_member);
            list_del(&list->next_group);
            list_del(&list->next_member);
            kfree(list);
        }
        kfree(qgroup);
    }
}

static int add_qgroup_relation_item(struct btrfs_trans_handle *trans,
                    struct btrfs_root *quota_root,
                    u64 src, u64 dst)
{
    int ret;
    struct btrfs_path *path;
    struct btrfs_key key;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    key.objectid = src;
    key.type = BTRFS_QGROUP_RELATION_KEY;
    key.offset = dst;

    ret = btrfs_insert_empty_item(trans, quota_root, path, &key, 0);

    btrfs_mark_buffer_dirty(path->nodes[0]);

    btrfs_free_path(path);
    return ret;
}

static int del_qgroup_relation_item(struct btrfs_trans_handle *trans,
                    struct btrfs_root *quota_root,
                    u64 src, u64 dst)
{
    int ret;
    struct btrfs_path *path;
    struct btrfs_key key;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    key.objectid = src;
    key.type = BTRFS_QGROUP_RELATION_KEY;
    key.offset = dst;

    ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
    if (ret < 0)
        goto out;

    if (ret > 0) {
        ret = -ENOENT;
        goto out;
    }

    ret = btrfs_del_item(trans, quota_root, path);
out:
    btrfs_free_path(path);
    return ret;
}

static int add_qgroup_item(struct btrfs_trans_handle *trans,
               struct btrfs_root *quota_root, u64 qgroupid)
{
    int ret;
    struct btrfs_path *path;
    struct btrfs_qgroup_info_item *qgroup_info;
    struct btrfs_qgroup_limit_item *qgroup_limit;
    struct extent_buffer *leaf;
    struct btrfs_key key;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    key.objectid = 0;
    key.type = BTRFS_QGROUP_INFO_KEY;
    key.offset = qgroupid;

    ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
                      sizeof(*qgroup_info));
    if (ret)
        goto out;

    leaf = path->nodes[0];
    qgroup_info = btrfs_item_ptr(leaf, path->slots[0],
                 struct btrfs_qgroup_info_item);
    btrfs_set_qgroup_info_generation(leaf, qgroup_info, trans->transid);
    btrfs_set_qgroup_info_rfer(leaf, qgroup_info, 0);
    btrfs_set_qgroup_info_rfer_cmpr(leaf, qgroup_info, 0);
    btrfs_set_qgroup_info_excl(leaf, qgroup_info, 0);
    btrfs_set_qgroup_info_excl_cmpr(leaf, qgroup_info, 0);

    btrfs_mark_buffer_dirty(leaf);

    btrfs_release_path(path);

    key.type = BTRFS_QGROUP_LIMIT_KEY;
    ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
                      sizeof(*qgroup_limit));
    if (ret)
        goto out;

    leaf = path->nodes[0];
    qgroup_limit = btrfs_item_ptr(leaf, path->slots[0],
                  struct btrfs_qgroup_limit_item);
    btrfs_set_qgroup_limit_flags(leaf, qgroup_limit, 0);
    btrfs_set_qgroup_limit_max_rfer(leaf, qgroup_limit, 0);
    btrfs_set_qgroup_limit_max_excl(leaf, qgroup_limit, 0);
    btrfs_set_qgroup_limit_rsv_rfer(leaf, qgroup_limit, 0);
    btrfs_set_qgroup_limit_rsv_excl(leaf, qgroup_limit, 0);

    btrfs_mark_buffer_dirty(leaf);

    ret = 0;
out:
    btrfs_free_path(path);
    return ret;
}

static int del_qgroup_item(struct btrfs_trans_handle *trans,
               struct btrfs_root *quota_root, u64 qgroupid)
{
    int ret;
    struct btrfs_path *path;
    struct btrfs_key key;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    key.objectid = 0;
    key.type = BTRFS_QGROUP_INFO_KEY;
    key.offset = qgroupid;
    ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
    if (ret < 0)
        goto out;

    if (ret > 0) {
        ret = -ENOENT;
        goto out;
    }

    ret = btrfs_del_item(trans, quota_root, path);
    if (ret)
        goto out;

    btrfs_release_path(path);

    key.type = BTRFS_QGROUP_LIMIT_KEY;
    ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
    if (ret < 0)
        goto out;

    if (ret > 0) {
        ret = -ENOENT;
        goto out;
    }

    ret = btrfs_del_item(trans, quota_root, path);

out:
    btrfs_free_path(path);
    return ret;
}

static int update_qgroup_limit_item(struct btrfs_trans_handle *trans,
                    struct btrfs_root *root, u64 qgroupid,
                    u64 flags, u64 max_rfer, u64 max_excl,
                    u64 rsv_rfer, u64 rsv_excl)
{
    struct btrfs_path *path;
    struct btrfs_key key;
    struct extent_buffer *l;
    struct btrfs_qgroup_limit_item *qgroup_limit;
    int ret;
    int slot;

    key.objectid = 0;
    key.type = BTRFS_QGROUP_LIMIT_KEY;
    key.offset = qgroupid;

    path = btrfs_alloc_path();
    BUG_ON(!path);
    ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
    if (ret > 0)
        ret = -ENOENT;

    if (ret)
        goto out;

    l = path->nodes[0];
    slot = path->slots[0];
    qgroup_limit = btrfs_item_ptr(l, path->slots[0],
                      struct btrfs_qgroup_limit_item);
    btrfs_set_qgroup_limit_flags(l, qgroup_limit, flags);
    btrfs_set_qgroup_limit_max_rfer(l, qgroup_limit, max_rfer);
    btrfs_set_qgroup_limit_max_excl(l, qgroup_limit, max_excl);
    btrfs_set_qgroup_limit_rsv_rfer(l, qgroup_limit, rsv_rfer);
    btrfs_set_qgroup_limit_rsv_excl(l, qgroup_limit, rsv_excl);

    btrfs_mark_buffer_dirty(l);

out:
    btrfs_free_path(path);
    return ret;
}

static int update_qgroup_info_item(struct btrfs_trans_handle *trans,
                   struct btrfs_root *root,
                   struct btrfs_qgroup *qgroup)
{
    struct btrfs_path *path;
    struct btrfs_key key;
    struct extent_buffer *l;
    struct btrfs_qgroup_info_item *qgroup_info;
    int ret;
    int slot;

    key.objectid = 0;
    key.type = BTRFS_QGROUP_INFO_KEY;
    key.offset = qgroup->qgroupid;

    path = btrfs_alloc_path();
    BUG_ON(!path);
    ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
    if (ret > 0)
        ret = -ENOENT;

    if (ret)
        goto out;

    l = path->nodes[0];
    slot = path->slots[0];
    qgroup_info = btrfs_item_ptr(l, path->slots[0],
                 struct btrfs_qgroup_info_item);
    btrfs_set_qgroup_info_generation(l, qgroup_info, trans->transid);
    btrfs_set_qgroup_info_rfer(l, qgroup_info, qgroup->rfer);
    btrfs_set_qgroup_info_rfer_cmpr(l, qgroup_info, qgroup->rfer_cmpr);
    btrfs_set_qgroup_info_excl(l, qgroup_info, qgroup->excl);
    btrfs_set_qgroup_info_excl_cmpr(l, qgroup_info, qgroup->excl_cmpr);

    btrfs_mark_buffer_dirty(l);

out:
    btrfs_free_path(path);
    return ret;
}

static int update_qgroup_status_item(struct btrfs_trans_handle *trans,
                     struct btrfs_fs_info *fs_info,
                    struct btrfs_root *root)
{
    struct btrfs_path *path;
    struct btrfs_key key;
    struct extent_buffer *l;
    struct btrfs_qgroup_status_item *ptr;
    int ret;
    int slot;

    key.objectid = 0;
    key.type = BTRFS_QGROUP_STATUS_KEY;
    key.offset = 0;

    path = btrfs_alloc_path();
    BUG_ON(!path);
    ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
    if (ret > 0)
        ret = -ENOENT;

    if (ret)
        goto out;

    l = path->nodes[0];
    slot = path->slots[0];
    ptr = btrfs_item_ptr(l, slot, struct btrfs_qgroup_status_item);
    btrfs_set_qgroup_status_flags(l, ptr, fs_info->qgroup_flags);
    btrfs_set_qgroup_status_generation(l, ptr, trans->transid);
    /* XXX scan */

    btrfs_mark_buffer_dirty(l);

out:
    btrfs_free_path(path);
    return ret;
}

/*
 * called with qgroup_lock held
 */
static int btrfs_clean_quota_tree(struct btrfs_trans_handle *trans,
                  struct btrfs_root *root)
{
    struct btrfs_path *path;
    struct btrfs_key key;
    int ret;

    if (!root)
        return -EINVAL;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

    while (1) {
        key.objectid = 0;
        key.offset = 0;
        key.type = 0;

        path->leave_spinning = 1;
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret > 0) {
            if (path->slots[0] == 0)
                break;
            path->slots[0]--;
        } else if (ret < 0) {
            break;
        }

        ret = btrfs_del_item(trans, root, path);
        if (ret)
            goto out;
        btrfs_release_path(path);
    }
    ret = 0;
out:
    root->fs_info->pending_quota_state = 0;
    btrfs_free_path(path);
    return ret;
}

int btrfs_quota_enable(struct btrfs_trans_handle *trans,
               struct btrfs_fs_info *fs_info)
{
    struct btrfs_root *quota_root;
    struct btrfs_path *path = NULL;
    struct btrfs_qgroup_status_item *ptr;
    struct extent_buffer *leaf;
    struct btrfs_key key;
    int ret = 0;

    spin_lock(&fs_info->qgroup_lock);
    if (fs_info->quota_root) {
        fs_info->pending_quota_state = 1;
        spin_unlock(&fs_info->qgroup_lock);
        goto out;
    }
    spin_unlock(&fs_info->qgroup_lock);

    /*
     * initially create the quota tree
     */
    quota_root = btrfs_create_tree(trans, fs_info,
                       BTRFS_QUOTA_TREE_OBJECTID);
    if (IS_ERR(quota_root)) {
        ret =  PTR_ERR(quota_root);
        goto out;
    }

    path = btrfs_alloc_path();
    if (!path) {
        ret = -ENOMEM;
        goto out_free_root;
    }

    key.objectid = 0;
    key.type = BTRFS_QGROUP_STATUS_KEY;
    key.offset = 0;

    ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
                      sizeof(*ptr));
    if (ret)
        goto out_free_path;

    leaf = path->nodes[0];
    ptr = btrfs_item_ptr(leaf, path->slots[0],
                 struct btrfs_qgroup_status_item);
    btrfs_set_qgroup_status_generation(leaf, ptr, trans->transid);
    btrfs_set_qgroup_status_version(leaf, ptr, BTRFS_QGROUP_STATUS_VERSION);
    fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON |
                BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
    btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags);
    btrfs_set_qgroup_status_scan(leaf, ptr, 0);

    btrfs_mark_buffer_dirty(leaf);

    spin_lock(&fs_info->qgroup_lock);
    fs_info->quota_root = quota_root;
    fs_info->pending_quota_state = 1;
    spin_unlock(&fs_info->qgroup_lock);
out_free_path:
    btrfs_free_path(path);
out_free_root:
    if (ret) {
        free_extent_buffer(quota_root->node);
        free_extent_buffer(quota_root->commit_root);
        kfree(quota_root);
    }
out:
    return ret;
}

int btrfs_quota_disable(struct btrfs_trans_handle *trans,
            struct btrfs_fs_info *fs_info)
{
    struct btrfs_root *tree_root = fs_info->tree_root;
    struct btrfs_root *quota_root;
    int ret = 0;

    spin_lock(&fs_info->qgroup_lock);
    fs_info->quota_enabled = 0;
    fs_info->pending_quota_state = 0;
    quota_root = fs_info->quota_root;
    fs_info->quota_root = NULL;
    btrfs_free_qgroup_config(fs_info);
    spin_unlock(&fs_info->qgroup_lock);

    if (!quota_root)
        return -EINVAL;

    ret = btrfs_clean_quota_tree(trans, quota_root);
    if (ret)
        goto out;

    ret = btrfs_del_root(trans, tree_root, &quota_root->root_key);
    if (ret)
        goto out;

    list_del(&quota_root->dirty_list);

    btrfs_tree_lock(quota_root->node);
    clean_tree_block(trans, tree_root, quota_root->node);
    btrfs_tree_unlock(quota_root->node);
    btrfs_free_tree_block(trans, quota_root, quota_root->node, 0, 1);

    free_extent_buffer(quota_root->node);
    free_extent_buffer(quota_root->commit_root);
    kfree(quota_root);
out:
    return ret;
}

int btrfs_quota_rescan(struct btrfs_fs_info *fs_info)
{
    /* FIXME */
    return 0;
}

int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
                  struct btrfs_fs_info *fs_info, u64 src, u64 dst)
{
    struct btrfs_root *quota_root;
    int ret = 0;

    quota_root = fs_info->quota_root;
    if (!quota_root)
        return -EINVAL;

    ret = add_qgroup_relation_item(trans, quota_root, src, dst);
    if (ret)
        return ret;

    ret = add_qgroup_relation_item(trans, quota_root, dst, src);
    if (ret) {
        del_qgroup_relation_item(trans, quota_root, src, dst);
        return ret;
    }

    spin_lock(&fs_info->qgroup_lock);
    ret = add_relation_rb(quota_root->fs_info, src, dst);
    spin_unlock(&fs_info->qgroup_lock);

    return ret;
}

int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
                  struct btrfs_fs_info *fs_info, u64 src, u64 dst)
{
    struct btrfs_root *quota_root;
    int ret = 0;
    int err;

    quota_root = fs_info->quota_root;
    if (!quota_root)
        return -EINVAL;

    ret = del_qgroup_relation_item(trans, quota_root, src, dst);
    err = del_qgroup_relation_item(trans, quota_root, dst, src);
    if (err && !ret)
        ret = err;

    spin_lock(&fs_info->qgroup_lock);
    del_relation_rb(fs_info, src, dst);

    spin_unlock(&fs_info->qgroup_lock);

    return ret;
}

int btrfs_create_qgroup(struct btrfs_trans_handle *trans,
            struct btrfs_fs_info *fs_info, u64 qgroupid, char *name)
{
    struct btrfs_root *quota_root;
    struct btrfs_qgroup *qgroup;
    int ret = 0;

    quota_root = fs_info->quota_root;
    if (!quota_root)
        return -EINVAL;

    ret = add_qgroup_item(trans, quota_root, qgroupid);

    spin_lock(&fs_info->qgroup_lock);
    qgroup = add_qgroup_rb(fs_info, qgroupid);
    spin_unlock(&fs_info->qgroup_lock);

    if (IS_ERR(qgroup))
        ret = PTR_ERR(qgroup);

    return ret;
}

int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
            struct btrfs_fs_info *fs_info, u64 qgroupid)
{
    struct btrfs_root *quota_root;
    int ret = 0;

    quota_root = fs_info->quota_root;
    if (!quota_root)
        return -EINVAL;

    ret = del_qgroup_item(trans, quota_root, qgroupid);

    spin_lock(&fs_info->qgroup_lock);
    del_qgroup_rb(quota_root->fs_info, qgroupid);

    spin_unlock(&fs_info->qgroup_lock);

    return ret;
}

int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
               struct btrfs_fs_info *fs_info, u64 qgroupid,
               struct btrfs_qgroup_limit *limit)
{
    struct btrfs_root *quota_root = fs_info->quota_root;
    struct btrfs_qgroup *qgroup;
    int ret = 0;

    if (!quota_root)
        return -EINVAL;

    ret = update_qgroup_limit_item(trans, quota_root, qgroupid,
                       limit->flags, limit->max_rfer,
                       limit->max_excl, limit->rsv_rfer,
                       limit->rsv_excl);
    if (ret) {
        fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        printk(KERN_INFO "unable to update quota limit for %llu\n",
               (unsigned long long)qgroupid);
    }

    spin_lock(&fs_info->qgroup_lock);

    qgroup = find_qgroup_rb(fs_info, qgroupid);
    if (!qgroup) {
        ret = -ENOENT;
        goto unlock;
    }
    qgroup->lim_flags = limit->flags;
    qgroup->max_rfer = limit->max_rfer;
    qgroup->max_excl = limit->max_excl;
    qgroup->rsv_rfer = limit->rsv_rfer;
    qgroup->rsv_excl = limit->rsv_excl;

unlock:
    spin_unlock(&fs_info->qgroup_lock);

    return ret;
}

static void qgroup_dirty(struct btrfs_fs_info *fs_info,
             struct btrfs_qgroup *qgroup)
{
    if (list_empty(&qgroup->dirty))
        list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
}

/*
 * btrfs_qgroup_record_ref is called when the ref is added or deleted. it puts
 * the modification into a list that's later used by btrfs_end_transaction to
 * pass the recorded modifications on to btrfs_qgroup_account_ref.
 */
int btrfs_qgroup_record_ref(struct btrfs_trans_handle *trans,
                struct btrfs_delayed_ref_node *node,
                struct btrfs_delayed_extent_op *extent_op)
{
    struct qgroup_update *u;

    BUG_ON(!trans->delayed_ref_elem.seq);
    u = kmalloc(sizeof(*u), GFP_NOFS);
    if (!u)
        return -ENOMEM;

    u->node = node;
    u->extent_op = extent_op;
    list_add_tail(&u->list, &trans->qgroup_ref_list);

    return 0;
}

/*
 * btrfs_qgroup_account_ref is called for every ref that is added to or deleted
 * from the fs. First, all roots referencing the extent are searched, and
 * then the space is accounted accordingly to the different roots. The
 * accounting algorithm works in 3 steps documented inline.
 */
int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
                 struct btrfs_fs_info *fs_info,
                 struct btrfs_delayed_ref_node *node,
                 struct btrfs_delayed_extent_op *extent_op)
{
    struct btrfs_key ins;
    struct btrfs_root *quota_root;
    u64 ref_root;
    struct btrfs_qgroup *qgroup;
    struct ulist_node *unode;
    struct ulist *roots = NULL;
    struct ulist *tmp = NULL;
    struct ulist_iterator uiter;
    u64 seq;
    int ret = 0;
    int sgn;

    if (!fs_info->quota_enabled)
        return 0;

    BUG_ON(!fs_info->quota_root);

    ins.objectid = node->bytenr;
    ins.offset = node->num_bytes;
    ins.type = BTRFS_EXTENT_ITEM_KEY;

    if (node->type == BTRFS_TREE_BLOCK_REF_KEY ||
        node->type == BTRFS_SHARED_BLOCK_REF_KEY) {
        struct btrfs_delayed_tree_ref *ref;
        ref = btrfs_delayed_node_to_tree_ref(node);
        ref_root = ref->root;
    } else if (node->type == BTRFS_EXTENT_DATA_REF_KEY ||
           node->type == BTRFS_SHARED_DATA_REF_KEY) {
        struct btrfs_delayed_data_ref *ref;
        ref = btrfs_delayed_node_to_data_ref(node);
        ref_root = ref->root;
    } else {
        BUG();
    }

    if (!is_fstree(ref_root)) {
        /*
         * non-fs-trees are not being accounted
         */
        return 0;
    }

    switch (node->action) {
    case BTRFS_ADD_DELAYED_REF:
    case BTRFS_ADD_DELAYED_EXTENT:
        sgn = 1;
        break;
    case BTRFS_DROP_DELAYED_REF:
        sgn = -1;
        break;
    case BTRFS_UPDATE_DELAYED_HEAD:
        return 0;
    default:
        BUG();
    }

    /*
     * the delayed ref sequence number we pass depends on the direction of
     * the operation. for add operations, we pass (node->seq - 1) to skip
     * the delayed ref's current sequence number, because we need the state
     * of the tree before the add operation. for delete operations, we pass
     * (node->seq) to include the delayed ref's current sequence number,
     * because we need the state of the tree after the delete operation.
     */
    ret = btrfs_find_all_roots(trans, fs_info, node->bytenr,
                   sgn > 0 ? node->seq - 1 : node->seq, &roots);
    if (ret < 0)
        goto out;

    spin_lock(&fs_info->qgroup_lock);
    quota_root = fs_info->quota_root;
    if (!quota_root)
        goto unlock;

    qgroup = find_qgroup_rb(fs_info, ref_root);
    if (!qgroup)
        goto unlock;

    /*
     * step 1: for each old ref, visit all nodes once and inc refcnt
     */
    tmp = ulist_alloc(GFP_ATOMIC);
    if (!tmp) {
        ret = -ENOMEM;
        goto unlock;
    }
    seq = fs_info->qgroup_seq;
    fs_info->qgroup_seq += roots->nnodes + 1; /* max refcnt */

    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(roots, &uiter))) {
        struct ulist_node *tmp_unode;
        struct ulist_iterator tmp_uiter;
        struct btrfs_qgroup *qg;

        qg = find_qgroup_rb(fs_info, unode->val);
        if (!qg)
            continue;

        ulist_reinit(tmp);
                        /* XXX id not needed */
        ulist_add(tmp, qg->qgroupid, (u64)(uintptr_t)qg, GFP_ATOMIC);
        ULIST_ITER_INIT(&tmp_uiter);
        while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
            struct btrfs_qgroup_list *glist;

            qg = (struct btrfs_qgroup *)(uintptr_t)tmp_unode->aux;
            if (qg->refcnt < seq)
                qg->refcnt = seq + 1;
            else
                ++qg->refcnt;

            list_for_each_entry(glist, &qg->groups, next_group) {
                ulist_add(tmp, glist->group->qgroupid,
                      (u64)(uintptr_t)glist->group,
                      GFP_ATOMIC);
            }
        }
    }

    /*
     * step 2: walk from the new root
     */
    ulist_reinit(tmp);
    ulist_add(tmp, qgroup->qgroupid, (uintptr_t)qgroup, GFP_ATOMIC);
    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(tmp, &uiter))) {
        struct btrfs_qgroup *qg;
        struct btrfs_qgroup_list *glist;

        qg = (struct btrfs_qgroup *)(uintptr_t)unode->aux;
        if (qg->refcnt < seq) {
            /* not visited by step 1 */
            qg->rfer += sgn * node->num_bytes;
            qg->rfer_cmpr += sgn * node->num_bytes;
            if (roots->nnodes == 0) {
                qg->excl += sgn * node->num_bytes;
                qg->excl_cmpr += sgn * node->num_bytes;
            }
            qgroup_dirty(fs_info, qg);
        }
        WARN_ON(qg->tag >= seq);
        qg->tag = seq;

        list_for_each_entry(glist, &qg->groups, next_group) {
            ulist_add(tmp, glist->group->qgroupid,
                  (uintptr_t)glist->group, GFP_ATOMIC);
        }
    }

    /*
     * step 3: walk again from old refs
     */
    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(roots, &uiter))) {
        struct btrfs_qgroup *qg;
        struct ulist_node *tmp_unode;
        struct ulist_iterator tmp_uiter;

        qg = find_qgroup_rb(fs_info, unode->val);
        if (!qg)
            continue;

        ulist_reinit(tmp);
        ulist_add(tmp, qg->qgroupid, (uintptr_t)qg, GFP_ATOMIC);
        ULIST_ITER_INIT(&tmp_uiter);
        while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
            struct btrfs_qgroup_list *glist;

            qg = (struct btrfs_qgroup *)(uintptr_t)tmp_unode->aux;
            if (qg->tag == seq)
                continue;

            if (qg->refcnt - seq == roots->nnodes) {
                qg->excl -= sgn * node->num_bytes;
                qg->excl_cmpr -= sgn * node->num_bytes;
                qgroup_dirty(fs_info, qg);
            }

            list_for_each_entry(glist, &qg->groups, next_group) {
                ulist_add(tmp, glist->group->qgroupid,
                      (uintptr_t)glist->group,
                      GFP_ATOMIC);
            }
        }
    }
    ret = 0;
unlock:
    spin_unlock(&fs_info->qgroup_lock);
out:
    ulist_free(roots);
    ulist_free(tmp);

    return ret;
}

/*
 * called from commit_transaction. Writes all changed qgroups to disk.
 */
int btrfs_run_qgroups(struct btrfs_trans_handle *trans,
              struct btrfs_fs_info *fs_info)
{
    struct btrfs_root *quota_root = fs_info->quota_root;
    int ret = 0;

    if (!quota_root)
        goto out;

    fs_info->quota_enabled = fs_info->pending_quota_state;

    spin_lock(&fs_info->qgroup_lock);
    while (!list_empty(&fs_info->dirty_qgroups)) {
        struct btrfs_qgroup *qgroup;
        qgroup = list_first_entry(&fs_info->dirty_qgroups,
                      struct btrfs_qgroup, dirty);
        list_del_init(&qgroup->dirty);
        spin_unlock(&fs_info->qgroup_lock);
        ret = update_qgroup_info_item(trans, quota_root, qgroup);
        if (ret)
            fs_info->qgroup_flags |=
                    BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        spin_lock(&fs_info->qgroup_lock);
    }
    if (fs_info->quota_enabled)
        fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_ON;
    else
        fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON;
    spin_unlock(&fs_info->qgroup_lock);

    ret = update_qgroup_status_item(trans, fs_info, quota_root);
    if (ret)
        fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;

out:

    return ret;
}

/*
 * copy the acounting information between qgroups. This is necessary when a
 * snapshot or a subvolume is created
 */
int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
             struct btrfs_fs_info *fs_info, u64 srcid, u64 objectid,
             struct btrfs_qgroup_inherit *inherit)
{
    int ret = 0;
    int i;
    u64 *i_qgroups;
    struct btrfs_root *quota_root = fs_info->quota_root;
    struct btrfs_qgroup *srcgroup;
    struct btrfs_qgroup *dstgroup;
    u32 level_size = 0;

    if (!fs_info->quota_enabled)
        return 0;

    if (!quota_root)
        return -EINVAL;

    /*
     * create a tracking group for the subvol itself
     */
    ret = add_qgroup_item(trans, quota_root, objectid);
    if (ret)
        goto out;

    if (inherit && inherit->flags & BTRFS_QGROUP_INHERIT_SET_LIMITS) {
        ret = update_qgroup_limit_item(trans, quota_root, objectid,
                           inherit->lim.flags,
                           inherit->lim.max_rfer,
                           inherit->lim.max_excl,
                           inherit->lim.rsv_rfer,
                           inherit->lim.rsv_excl);
        if (ret)
            goto out;
    }

    if (srcid) {
        struct btrfs_root *srcroot;
        struct btrfs_key srckey;
        int srcroot_level;

        srckey.objectid = srcid;
        srckey.type = BTRFS_ROOT_ITEM_KEY;
        srckey.offset = (u64)-1;
        srcroot = btrfs_read_fs_root_no_name(fs_info, &srckey);
        if (IS_ERR(srcroot)) {
            ret = PTR_ERR(srcroot);
            goto out;
        }

        rcu_read_lock();
        srcroot_level = btrfs_header_level(srcroot->node);
        level_size = btrfs_level_size(srcroot, srcroot_level);
        rcu_read_unlock();
    }

    /*
     * add qgroup to all inherited groups
     */
    if (inherit) {
        i_qgroups = (u64 *)(inherit + 1);
        for (i = 0; i < inherit->num_qgroups; ++i) {
            ret = add_qgroup_relation_item(trans, quota_root,
                               objectid, *i_qgroups);
            if (ret)
                goto out;
            ret = add_qgroup_relation_item(trans, quota_root,
                               *i_qgroups, objectid);
            if (ret)
                goto out;
            ++i_qgroups;
        }
    }


    spin_lock(&fs_info->qgroup_lock);

    dstgroup = add_qgroup_rb(fs_info, objectid);
    if (IS_ERR(dstgroup)) {
        ret = PTR_ERR(dstgroup);
        goto unlock;
    }

    if (srcid) {
        srcgroup = find_qgroup_rb(fs_info, srcid);
        if (!srcgroup)
            goto unlock;
        dstgroup->rfer = srcgroup->rfer - level_size;
        dstgroup->rfer_cmpr = srcgroup->rfer_cmpr - level_size;
        srcgroup->excl = level_size;
        srcgroup->excl_cmpr = level_size;
        qgroup_dirty(fs_info, dstgroup);
        qgroup_dirty(fs_info, srcgroup);
    }

    if (!inherit)
        goto unlock;

    i_qgroups = (u64 *)(inherit + 1);
    for (i = 0; i < inherit->num_qgroups; ++i) {
        ret = add_relation_rb(quota_root->fs_info, objectid,
                      *i_qgroups);
        if (ret)
            goto unlock;
        ++i_qgroups;
    }

    for (i = 0; i <  inherit->num_ref_copies; ++i) {
        struct btrfs_qgroup *src;
        struct btrfs_qgroup *dst;

        src = find_qgroup_rb(fs_info, i_qgroups[0]);
        dst = find_qgroup_rb(fs_info, i_qgroups[1]);

        if (!src || !dst) {
            ret = -EINVAL;
            goto unlock;
        }

        dst->rfer = src->rfer - level_size;
        dst->rfer_cmpr = src->rfer_cmpr - level_size;
        i_qgroups += 2;
    }
    for (i = 0; i <  inherit->num_excl_copies; ++i) {
        struct btrfs_qgroup *src;
        struct btrfs_qgroup *dst;

        src = find_qgroup_rb(fs_info, i_qgroups[0]);
        dst = find_qgroup_rb(fs_info, i_qgroups[1]);

        if (!src || !dst) {
            ret = -EINVAL;
            goto unlock;
        }

        dst->excl = src->excl + level_size;
        dst->excl_cmpr = src->excl_cmpr + level_size;
        i_qgroups += 2;
    }

unlock:
    spin_unlock(&fs_info->qgroup_lock);
out:
    return ret;
}

/*
 * reserve some space for a qgroup and all its parents. The reservation takes
 * place with start_transaction or dealloc_reserve, similar to ENOSPC
 * accounting. If not enough space is available, EDQUOT is returned.
 * We assume that the requested space is new for all qgroups.
 */
int btrfs_qgroup_reserve(struct btrfs_root *root, u64 num_bytes)
{
    struct btrfs_root *quota_root;
    struct btrfs_qgroup *qgroup;
    struct btrfs_fs_info *fs_info = root->fs_info;
    u64 ref_root = root->root_key.objectid;
    int ret = 0;
    struct ulist *ulist = NULL;
    struct ulist_node *unode;
    struct ulist_iterator uiter;

    if (!is_fstree(ref_root))
        return 0;

    if (num_bytes == 0)
        return 0;

    spin_lock(&fs_info->qgroup_lock);
    quota_root = fs_info->quota_root;
    if (!quota_root)
        goto out;

    qgroup = find_qgroup_rb(fs_info, ref_root);
    if (!qgroup)
        goto out;

    /*
     * in a first step, we check all affected qgroups if any limits would
     * be exceeded
     */
    ulist = ulist_alloc(GFP_ATOMIC);
    if (!ulist) {
        ret = -ENOMEM;
        goto out;
    }
    ulist_add(ulist, qgroup->qgroupid, (uintptr_t)qgroup, GFP_ATOMIC);
    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(ulist, &uiter))) {
        struct btrfs_qgroup *qg;
        struct btrfs_qgroup_list *glist;

        qg = (struct btrfs_qgroup *)(uintptr_t)unode->aux;

        if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_RFER) &&
            qg->reserved + qg->rfer + num_bytes >
            qg->max_rfer)
            ret = -EDQUOT;

        if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) &&
            qg->reserved + qg->excl + num_bytes >
            qg->max_excl)
            ret = -EDQUOT;

        list_for_each_entry(glist, &qg->groups, next_group) {
            ulist_add(ulist, glist->group->qgroupid,
                  (uintptr_t)glist->group, GFP_ATOMIC);
        }
    }
    if (ret)
        goto out;

    /*
     * no limits exceeded, now record the reservation into all qgroups
     */
    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(ulist, &uiter))) {
        struct btrfs_qgroup *qg;

        qg = (struct btrfs_qgroup *)(uintptr_t)unode->aux;

        qg->reserved += num_bytes;
    }

out:
    spin_unlock(&fs_info->qgroup_lock);
    ulist_free(ulist);

    return ret;
}

void btrfs_qgroup_free(struct btrfs_root *root, u64 num_bytes)
{
    struct btrfs_root *quota_root;
    struct btrfs_qgroup *qgroup;
    struct btrfs_fs_info *fs_info = root->fs_info;
    struct ulist *ulist = NULL;
    struct ulist_node *unode;
    struct ulist_iterator uiter;
    u64 ref_root = root->root_key.objectid;

    if (!is_fstree(ref_root))
        return;

    if (num_bytes == 0)
        return;

    spin_lock(&fs_info->qgroup_lock);

    quota_root = fs_info->quota_root;
    if (!quota_root)
        goto out;

    qgroup = find_qgroup_rb(fs_info, ref_root);
    if (!qgroup)
        goto out;

    ulist = ulist_alloc(GFP_ATOMIC);
    if (!ulist) {
        btrfs_std_error(fs_info, -ENOMEM);
        goto out;
    }
    ulist_add(ulist, qgroup->qgroupid, (uintptr_t)qgroup, GFP_ATOMIC);
    ULIST_ITER_INIT(&uiter);
    while ((unode = ulist_next(ulist, &uiter))) {
        struct btrfs_qgroup *qg;
        struct btrfs_qgroup_list *glist;

        qg = (struct btrfs_qgroup *)(uintptr_t)unode->aux;

        qg->reserved -= num_bytes;

        list_for_each_entry(glist, &qg->groups, next_group) {
            ulist_add(ulist, glist->group->qgroupid,
                  (uintptr_t)glist->group, GFP_ATOMIC);
        }
    }

out:
    spin_unlock(&fs_info->qgroup_lock);
    ulist_free(ulist);
}

void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
{
    if (list_empty(&trans->qgroup_ref_list) && !trans->delayed_ref_elem.seq)
        return;
    printk(KERN_ERR "btrfs: qgroups not uptodate in trans handle %p: list is%s empty, seq is %llu\n",
        trans, list_empty(&trans->qgroup_ref_list) ? "" : " not",
        trans->delayed_ref_elem.seq);
    BUG();
}