// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2011 STRATO.  All rights reserved.
 */

#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 <linux/btrfs.h>
#include <linux/sched/mm.h>

#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "locking.h"
#include "ulist.h"
#include "backref.h"
#include "extent_io.h"
#include "qgroup.h"
#include "block-group.h"
#include "sysfs.h"
#include "tree-mod-log.h"

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

/*
 * Helpers to access qgroup reservation
 *
 * Callers should ensure the lock context and type are valid
 */

static u64 qgroup_rsv_total(const struct btrfs_qgroup *qgroup)
{
        u64 ret = 0;
        int i;

        for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
                ret += qgroup->rsv.values[i];

        return ret;
}

#ifdef CONFIG_BTRFS_DEBUG
static const char *qgroup_rsv_type_str(enum btrfs_qgroup_rsv_type type)
{
        if (type == BTRFS_QGROUP_RSV_DATA)
                return "data";
        if (type == BTRFS_QGROUP_RSV_META_PERTRANS)
                return "meta_pertrans";
        if (type == BTRFS_QGROUP_RSV_META_PREALLOC)
                return "meta_prealloc";
        return NULL;
}
#endif

static void qgroup_rsv_add(struct btrfs_fs_info *fs_info,
                           struct btrfs_qgroup *qgroup, u64 num_bytes,
                           enum btrfs_qgroup_rsv_type type)
{
        trace_qgroup_update_reserve(fs_info, qgroup, num_bytes, type);
        qgroup->rsv.values[type] += num_bytes;
}

static void qgroup_rsv_release(struct btrfs_fs_info *fs_info,
                               struct btrfs_qgroup *qgroup, u64 num_bytes,
                               enum btrfs_qgroup_rsv_type type)
{
        trace_qgroup_update_reserve(fs_info, qgroup, -(s64)num_bytes, type);
        if (qgroup->rsv.values[type] >= num_bytes) {
                qgroup->rsv.values[type] -= num_bytes;
                return;
        }
#ifdef CONFIG_BTRFS_DEBUG
        WARN_RATELIMIT(1,
                "qgroup %llu %s reserved space underflow, have %llu to free %llu",
                qgroup->qgroupid, qgroup_rsv_type_str(type),
                qgroup->rsv.values[type], num_bytes);
#endif
        qgroup->rsv.values[type] = 0;
}

static void qgroup_rsv_add_by_qgroup(struct btrfs_fs_info *fs_info,
                                     struct btrfs_qgroup *dest,
                                     struct btrfs_qgroup *src)
{
        int i;

        for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
                qgroup_rsv_add(fs_info, dest, src->rsv.values[i], i);
}

static void qgroup_rsv_release_by_qgroup(struct btrfs_fs_info *fs_info,
                                         struct btrfs_qgroup *dest,
                                          struct btrfs_qgroup *src)
{
        int i;

        for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++)
                qgroup_rsv_release(fs_info, dest, src->rsv.values[i], i);
}

static void btrfs_qgroup_update_old_refcnt(struct btrfs_qgroup *qg, u64 seq,
                                           int mod)
{
        if (qg->old_refcnt < seq)
                qg->old_refcnt = seq;
        qg->old_refcnt += mod;
}

static void btrfs_qgroup_update_new_refcnt(struct btrfs_qgroup *qg, u64 seq,
                                           int mod)
{
        if (qg->new_refcnt < seq)
                qg->new_refcnt = seq;
        qg->new_refcnt += mod;
}

static inline u64 btrfs_qgroup_get_old_refcnt(struct btrfs_qgroup *qg, u64 seq)
{
        if (qg->old_refcnt < seq)
                return 0;
        return qg->old_refcnt - seq;
}

static inline u64 btrfs_qgroup_get_new_refcnt(struct btrfs_qgroup *qg, u64 seq)
{
        if (qg->new_refcnt < seq)
                return 0;
        return qg->new_refcnt - seq;
}

/*
 * 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;
};

static inline u64 qgroup_to_aux(struct btrfs_qgroup *qg)
{
        return (u64)(uintptr_t)qg;
}

static inline struct btrfs_qgroup* unode_aux_to_qgroup(struct ulist_node *n)
{
        return (struct btrfs_qgroup *)(uintptr_t)n->aux;
}

static int
qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
                   int init_flags);
static void qgroup_rescan_zero_tracking(struct btrfs_fs_info *fs_info);

/* must be called with qgroup_ioctl_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;
}

static void __del_qgroup_rb(struct btrfs_fs_info *fs_info,
                            struct btrfs_qgroup *qgroup)
{
        struct btrfs_qgroup_list *list;

        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);
        }
}

/* 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);

        if (!qgroup)
                return -ENOENT;

        rb_erase(&qgroup->node, &fs_info->qgroup_tree);
        __del_qgroup_rb(fs_info, 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;
}

#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
                               u64 rfer, u64 excl)
{
        struct btrfs_qgroup *qgroup;

        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup)
                return -EINVAL;
        if (qgroup->rfer != rfer || qgroup->excl != excl)
                return -EINVAL;
        return 0;
}
#endif

/*
 * 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;
        u64 rescan_progress = 0;

        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return 0;

        fs_info->qgroup_ulist = ulist_alloc(GFP_KERNEL);
        if (!fs_info->qgroup_ulist) {
                ret = -ENOMEM;
                goto out;
        }

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

        ret = btrfs_sysfs_add_qgroups(fs_info);
        if (ret < 0)
                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) {
                                btrfs_err(fs_info,
                                 "old qgroup version, quota disabled");
                                goto out;
                        }
                        if (btrfs_qgroup_status_generation(l, ptr) !=
                            fs_info->generation) {
                                flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                                btrfs_err(fs_info,
                                        "qgroup generation mismatch, marked as inconsistent");
                        }
                        fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
                                                                          ptr);
                        rescan_progress = btrfs_qgroup_status_rescan(l, ptr);
                        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)) {
                        btrfs_err(fs_info, "inconsistent qgroup config");
                        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;
                        }
                }
                ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
                if (ret < 0)
                        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 == -ENOENT) {
                        btrfs_warn(fs_info,
                                "orphan qgroup relation 0x%llx->0x%llx",
                                found_key.objectid, found_key.offset);
                        ret = 0;        /* ignore the error */
                }
                if (ret)
                        goto out;
next2:
                ret = btrfs_next_item(quota_root, path);
                if (ret < 0)
                        goto out;
                if (ret)
                        break;
        }
out:
        btrfs_free_path(path);
        fs_info->qgroup_flags |= flags;
        if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
                clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
        else if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN &&
                 ret >= 0)
                ret = qgroup_rescan_init(fs_info, rescan_progress, 0);

        if (ret < 0) {
                ulist_free(fs_info->qgroup_ulist);
                fs_info->qgroup_ulist = NULL;
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
                btrfs_sysfs_del_qgroups(fs_info);
        }

        return ret < 0 ? ret : 0;
}

/*
 * Called in close_ctree() when quota is still enabled.  This verifies we don't
 * leak some reserved space.
 *
 * Return false if no reserved space is left.
 * Return true if some reserved space is leaked.
 */
bool btrfs_check_quota_leak(struct btrfs_fs_info *fs_info)
{
        struct rb_node *node;
        bool ret = false;

        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return ret;
        /*
         * Since we're unmounting, there is no race and no need to grab qgroup
         * lock.  And here we don't go post-order to provide a more user
         * friendly sorted result.
         */
        for (node = rb_first(&fs_info->qgroup_tree); node; node = rb_next(node)) {
                struct btrfs_qgroup *qgroup;
                int i;

                qgroup = rb_entry(node, struct btrfs_qgroup, node);
                for (i = 0; i < BTRFS_QGROUP_RSV_LAST; i++) {
                        if (qgroup->rsv.values[i]) {
                                ret = true;
                                btrfs_warn(fs_info,
                "qgroup %hu/%llu has unreleased space, type %d rsv %llu",
                                   btrfs_qgroup_level(qgroup->qgroupid),
                                   btrfs_qgroup_subvolid(qgroup->qgroupid),
                                   i, qgroup->rsv.values[i]);
                        }
                }
        }
        return ret;
}

/*
 * This is called from close_ctree() or open_ctree() or btrfs_quota_disable(),
 * first two are in single-threaded paths.And for the third one, we have set
 * quota_root to be null with qgroup_lock held before, so it is safe to clean
 * up the in-memory structures without qgroup_lock held.
 */
void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info)
{
        struct rb_node *n;
        struct btrfs_qgroup *qgroup;

        while ((n = rb_first(&fs_info->qgroup_tree))) {
                qgroup = rb_entry(n, struct btrfs_qgroup, node);
                rb_erase(n, &fs_info->qgroup_tree);
                __del_qgroup_rb(fs_info, qgroup);
                btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
                kfree(qgroup);
        }
        /*
         * We call btrfs_free_qgroup_config() when unmounting
         * filesystem and disabling quota, so we set qgroup_ulist
         * to be null here to avoid double free.
         */
        ulist_free(fs_info->qgroup_ulist);
        fs_info->qgroup_ulist = NULL;
        btrfs_sysfs_del_qgroups(fs_info);
}

static int add_qgroup_relation_item(struct btrfs_trans_handle *trans, u64 src,
                                    u64 dst)
{
        int ret;
        struct btrfs_root *quota_root = trans->fs_info->quota_root;
        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, u64 src,
                                    u64 dst)
{
        int ret;
        struct btrfs_root *quota_root = trans->fs_info->quota_root;
        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;

        if (btrfs_is_testing(quota_root->fs_info))
                return 0;

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

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

        /*
         * Avoid a transaction abort by catching -EEXIST here. In that
         * case, we proceed by re-initializing the existing structure
         * on disk.
         */

        ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
                                      sizeof(*qgroup_info));
        if (ret && ret != -EEXIST)
                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 && ret != -EEXIST)
                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, u64 qgroupid)
{
        int ret;
        struct btrfs_root *quota_root = trans->fs_info->quota_root;
        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_qgroup *qgroup)
{
        struct btrfs_root *quota_root = trans->fs_info->quota_root;
        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 = qgroup->qgroupid;

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

        ret = btrfs_search_slot(trans, quota_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, slot, struct btrfs_qgroup_limit_item);
        btrfs_set_qgroup_limit_flags(l, qgroup_limit, qgroup->lim_flags);
        btrfs_set_qgroup_limit_max_rfer(l, qgroup_limit, qgroup->max_rfer);
        btrfs_set_qgroup_limit_max_excl(l, qgroup_limit, qgroup->max_excl);
        btrfs_set_qgroup_limit_rsv_rfer(l, qgroup_limit, qgroup->rsv_rfer);
        btrfs_set_qgroup_limit_rsv_excl(l, qgroup_limit, qgroup->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_qgroup *qgroup)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_root *quota_root = fs_info->quota_root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct extent_buffer *l;
        struct btrfs_qgroup_info_item *qgroup_info;
        int ret;
        int slot;

        if (btrfs_is_testing(fs_info))
                return 0;

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

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

        ret = btrfs_search_slot(trans, quota_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, slot, 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 = trans->fs_info;
        struct btrfs_root *quota_root = fs_info->quota_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();
        if (!path)
                return -ENOMEM;

        ret = btrfs_search_slot(trans, quota_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);
        btrfs_set_qgroup_status_rescan(l, ptr,
                                fs_info->qgroup_rescan_progress.objectid);

        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;
        struct extent_buffer *leaf = NULL;
        int ret;
        int nr = 0;

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

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

        while (1) {
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (ret < 0)
                        goto out;
                leaf = path->nodes[0];
                nr = btrfs_header_nritems(leaf);
                if (!nr)
                        break;
                /*
                 * delete the leaf one by one
                 * since the whole tree is going
                 * to be deleted.
                 */
                path->slots[0] = 0;
                ret = btrfs_del_items(trans, root, path, 0, nr);
                if (ret)
                        goto out;

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

int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *quota_root;
        struct btrfs_root *tree_root = fs_info->tree_root;
        struct btrfs_path *path = NULL;
        struct btrfs_qgroup_status_item *ptr;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_qgroup *qgroup = NULL;
        struct btrfs_trans_handle *trans = NULL;
        struct ulist *ulist = NULL;
        int ret = 0;
        int slot;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (fs_info->quota_root)
                goto out;

        ulist = ulist_alloc(GFP_KERNEL);
        if (!ulist) {
                ret = -ENOMEM;
                goto out;
        }

        ret = btrfs_sysfs_add_qgroups(fs_info);
        if (ret < 0)
                goto out;

        /*
         * Unlock qgroup_ioctl_lock before starting the transaction. This is to
         * avoid lock acquisition inversion problems (reported by lockdep) between
         * qgroup_ioctl_lock and the vfs freeze semaphores, acquired when we
         * start a transaction.
         * After we started the transaction lock qgroup_ioctl_lock again and
         * check if someone else created the quota root in the meanwhile. If so,
         * just return success and release the transaction handle.
         *
         * Also we don't need to worry about someone else calling
         * btrfs_sysfs_add_qgroups() after we unlock and getting an error because
         * that function returns 0 (success) when the sysfs entries already exist.
         */
        mutex_unlock(&fs_info->qgroup_ioctl_lock);

        /*
         * 1 for quota root item
         * 1 for BTRFS_QGROUP_STATUS item
         *
         * Yet we also need 2*n items for a QGROUP_INFO/QGROUP_LIMIT items
         * per subvolume. However those are not currently reserved since it
         * would be a lot of overkill.
         */
        trans = btrfs_start_transaction(tree_root, 2);

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                trans = NULL;
                goto out;
        }

        if (fs_info->quota_root)
                goto out;

        fs_info->qgroup_ulist = ulist;
        ulist = NULL;

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

                btrfs_abort_transaction(trans, ret);
                goto out;
        }

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                btrfs_abort_transaction(trans, ret);
                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) {
                btrfs_abort_transaction(trans, 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_rescan(leaf, ptr, 0);

        btrfs_mark_buffer_dirty(leaf);

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

        btrfs_release_path(path);
        ret = btrfs_search_slot_for_read(tree_root, &key, path, 1, 0);
        if (ret > 0)
                goto out_add_root;
        if (ret < 0) {
                btrfs_abort_transaction(trans, ret);
                goto out_free_path;
        }

        while (1) {
                slot = path->slots[0];
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.type == BTRFS_ROOT_REF_KEY) {

                        /* Release locks on tree_root before we access quota_root */
                        btrfs_release_path(path);

                        ret = add_qgroup_item(trans, quota_root,
                                              found_key.offset);
                        if (ret) {
                                btrfs_abort_transaction(trans, ret);
                                goto out_free_path;
                        }

                        qgroup = add_qgroup_rb(fs_info, found_key.offset);
                        if (IS_ERR(qgroup)) {
                                ret = PTR_ERR(qgroup);
                                btrfs_abort_transaction(trans, ret);
                                goto out_free_path;
                        }
                        ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
                        if (ret < 0) {
                                btrfs_abort_transaction(trans, ret);
                                goto out_free_path;
                        }
                        ret = btrfs_search_slot_for_read(tree_root, &found_key,
                                                         path, 1, 0);
                        if (ret < 0) {
                                btrfs_abort_transaction(trans, ret);
                                goto out_free_path;
                        }
                        if (ret > 0) {
                                /*
                                 * Shouldn't happen, but in case it does we
                                 * don't need to do the btrfs_next_item, just
                                 * continue.
                                 */
                                continue;
                        }
                }
                ret = btrfs_next_item(tree_root, path);
                if (ret < 0) {
                        btrfs_abort_transaction(trans, ret);
                        goto out_free_path;
                }
                if (ret)
                        break;
        }

out_add_root:
        btrfs_release_path(path);
        ret = add_qgroup_item(trans, quota_root, BTRFS_FS_TREE_OBJECTID);
        if (ret) {
                btrfs_abort_transaction(trans, ret);
                goto out_free_path;
        }

        qgroup = add_qgroup_rb(fs_info, BTRFS_FS_TREE_OBJECTID);
        if (IS_ERR(qgroup)) {
                ret = PTR_ERR(qgroup);
                btrfs_abort_transaction(trans, ret);
                goto out_free_path;
        }
        ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
        if (ret < 0) {
                btrfs_abort_transaction(trans, ret);
                goto out_free_path;
        }

        ret = btrfs_commit_transaction(trans);
        trans = NULL;
        if (ret)
                goto out_free_path;

        /*
         * Set quota enabled flag after committing the transaction, to avoid
         * deadlocks on fs_info->qgroup_ioctl_lock with concurrent snapshot
         * creation.
         */
        spin_lock(&fs_info->qgroup_lock);
        fs_info->quota_root = quota_root;
        set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
        spin_unlock(&fs_info->qgroup_lock);

        ret = qgroup_rescan_init(fs_info, 0, 1);
        if (!ret) {
                qgroup_rescan_zero_tracking(fs_info);
                fs_info->qgroup_rescan_running = true;
                btrfs_queue_work(fs_info->qgroup_rescan_workers,
                                 &fs_info->qgroup_rescan_work);
        }

out_free_path:
        btrfs_free_path(path);
out_free_root:
        if (ret)
                btrfs_put_root(quota_root);
out:
        if (ret) {
                ulist_free(fs_info->qgroup_ulist);
                fs_info->qgroup_ulist = NULL;
                btrfs_sysfs_del_qgroups(fs_info);
        }
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        if (ret && trans)
                btrfs_end_transaction(trans);
        else if (trans)
                ret = btrfs_end_transaction(trans);
        ulist_free(ulist);
        return ret;
}

int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *quota_root;
        struct btrfs_trans_handle *trans = NULL;
        int ret = 0;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root)
                goto out;
        mutex_unlock(&fs_info->qgroup_ioctl_lock);

        /*
         * 1 For the root item
         *
         * We should also reserve enough items for the quota tree deletion in
         * btrfs_clean_quota_tree but this is not done.
         *
         * Also, we must always start a transaction without holding the mutex
         * qgroup_ioctl_lock, see btrfs_quota_enable().
         */
        trans = btrfs_start_transaction(fs_info->tree_root, 1);

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                trans = NULL;
                goto out;
        }

        if (!fs_info->quota_root)
                goto out;

        clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
        btrfs_qgroup_wait_for_completion(fs_info, false);
        spin_lock(&fs_info->qgroup_lock);
        quota_root = fs_info->quota_root;
        fs_info->quota_root = NULL;
        fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON;
        spin_unlock(&fs_info->qgroup_lock);

        btrfs_free_qgroup_config(fs_info);

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

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

        list_del(&quota_root->dirty_list);

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

        btrfs_put_root(quota_root);

out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        if (ret && trans)
                btrfs_end_transaction(trans);
        else if (trans)
                ret = btrfs_end_transaction(trans);

        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);
}

/*
 * The easy accounting, we're updating qgroup relationship whose child qgroup
 * only has exclusive extents.
 *
 * In this case, all exclusive extents will also be exclusive for parent, so
 * excl/rfer just get added/removed.
 *
 * So is qgroup reservation space, which should also be added/removed to
 * parent.
 * Or when child tries to release reservation space, parent will underflow its
 * reservation (for relationship adding case).
 *
 * Caller should hold fs_info->qgroup_lock.
 */
static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info,
                                    struct ulist *tmp, u64 ref_root,
                                    struct btrfs_qgroup *src, int sign)
{
        struct btrfs_qgroup *qgroup;
        struct btrfs_qgroup_list *glist;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        u64 num_bytes = src->excl;
        int ret = 0;

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

        qgroup->rfer += sign * num_bytes;
        qgroup->rfer_cmpr += sign * num_bytes;

        WARN_ON(sign < 0 && qgroup->excl < num_bytes);
        qgroup->excl += sign * num_bytes;
        qgroup->excl_cmpr += sign * num_bytes;

        if (sign > 0)
                qgroup_rsv_add_by_qgroup(fs_info, qgroup, src);
        else
                qgroup_rsv_release_by_qgroup(fs_info, qgroup, src);

        qgroup_dirty(fs_info, qgroup);

        /* Get all of the parent groups that contain this qgroup */
        list_for_each_entry(glist, &qgroup->groups, next_group) {
                ret = ulist_add(tmp, glist->group->qgroupid,
                                qgroup_to_aux(glist->group), GFP_ATOMIC);
                if (ret < 0)
                        goto out;
        }

        /* Iterate all of the parents and adjust their reference counts */
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(tmp, &uiter))) {
                qgroup = unode_aux_to_qgroup(unode);
                qgroup->rfer += sign * num_bytes;
                qgroup->rfer_cmpr += sign * num_bytes;
                WARN_ON(sign < 0 && qgroup->excl < num_bytes);
                qgroup->excl += sign * num_bytes;
                if (sign > 0)
                        qgroup_rsv_add_by_qgroup(fs_info, qgroup, src);
                else
                        qgroup_rsv_release_by_qgroup(fs_info, qgroup, src);
                qgroup->excl_cmpr += sign * num_bytes;
                qgroup_dirty(fs_info, qgroup);

                /* Add any parents of the parents */
                list_for_each_entry(glist, &qgroup->groups, next_group) {
                        ret = ulist_add(tmp, glist->group->qgroupid,
                                        qgroup_to_aux(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                goto out;
                }
        }
        ret = 0;
out:
        return ret;
}


/*
 * Quick path for updating qgroup with only excl refs.
 *
 * In that case, just update all parent will be enough.
 * Or we needs to do a full rescan.
 * Caller should also hold fs_info->qgroup_lock.
 *
 * Return 0 for quick update, return >0 for need to full rescan
 * and mark INCONSISTENT flag.
 * Return < 0 for other error.
 */
static int quick_update_accounting(struct btrfs_fs_info *fs_info,
                                   struct ulist *tmp, u64 src, u64 dst,
                                   int sign)
{
        struct btrfs_qgroup *qgroup;
        int ret = 1;
        int err = 0;

        qgroup = find_qgroup_rb(fs_info, src);
        if (!qgroup)
                goto out;
        if (qgroup->excl == qgroup->rfer) {
                ret = 0;
                err = __qgroup_excl_accounting(fs_info, tmp, dst,
                                               qgroup, sign);
                if (err < 0) {
                        ret = err;
                        goto out;
                }
        }
out:
        if (ret)
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        return ret;
}

int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
                              u64 dst)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup *parent;
        struct btrfs_qgroup *member;
        struct btrfs_qgroup_list *list;
        struct ulist *tmp;
        unsigned int nofs_flag;
        int ret = 0;

        /* Check the level of src and dst first */
        if (btrfs_qgroup_level(src) >= btrfs_qgroup_level(dst))
                return -EINVAL;

        /* We hold a transaction handle open, must do a NOFS allocation. */
        nofs_flag = memalloc_nofs_save();
        tmp = ulist_alloc(GFP_KERNEL);
        memalloc_nofs_restore(nofs_flag);
        if (!tmp)
                return -ENOMEM;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root) {
                ret = -ENOTCONN;
                goto out;
        }
        member = find_qgroup_rb(fs_info, src);
        parent = find_qgroup_rb(fs_info, dst);
        if (!member || !parent) {
                ret = -EINVAL;
                goto out;
        }

        /* check if such qgroup relation exist firstly */
        list_for_each_entry(list, &member->groups, next_group) {
                if (list->group == parent) {
                        ret = -EEXIST;
                        goto out;
                }
        }

        ret = add_qgroup_relation_item(trans, src, dst);
        if (ret)
                goto out;

        ret = add_qgroup_relation_item(trans, dst, src);
        if (ret) {
                del_qgroup_relation_item(trans, src, dst);
                goto out;
        }

        spin_lock(&fs_info->qgroup_lock);
        ret = add_relation_rb(fs_info, src, dst);
        if (ret < 0) {
                spin_unlock(&fs_info->qgroup_lock);
                goto out;
        }
        ret = quick_update_accounting(fs_info, tmp, src, dst, 1);
        spin_unlock(&fs_info->qgroup_lock);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        ulist_free(tmp);
        return ret;
}

static int __del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
                                 u64 dst)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup *parent;
        struct btrfs_qgroup *member;
        struct btrfs_qgroup_list *list;
        struct ulist *tmp;
        bool found = false;
        unsigned int nofs_flag;
        int ret = 0;
        int ret2;

        /* We hold a transaction handle open, must do a NOFS allocation. */
        nofs_flag = memalloc_nofs_save();
        tmp = ulist_alloc(GFP_KERNEL);
        memalloc_nofs_restore(nofs_flag);
        if (!tmp)
                return -ENOMEM;

        if (!fs_info->quota_root) {
                ret = -ENOTCONN;
                goto out;
        }

        member = find_qgroup_rb(fs_info, src);
        parent = find_qgroup_rb(fs_info, dst);
        /*
         * The parent/member pair doesn't exist, then try to delete the dead
         * relation items only.
         */
        if (!member || !parent)
                goto delete_item;

        /* check if such qgroup relation exist firstly */
        list_for_each_entry(list, &member->groups, next_group) {
                if (list->group == parent) {
                        found = true;
                        break;
                }
        }

delete_item:
        ret = del_qgroup_relation_item(trans, src, dst);
        if (ret < 0 && ret != -ENOENT)
                goto out;
        ret2 = del_qgroup_relation_item(trans, dst, src);
        if (ret2 < 0 && ret2 != -ENOENT)
                goto out;

        /* At least one deletion succeeded, return 0 */
        if (!ret || !ret2)
                ret = 0;

        if (found) {
                spin_lock(&fs_info->qgroup_lock);
                del_relation_rb(fs_info, src, dst);
                ret = quick_update_accounting(fs_info, tmp, src, dst, -1);
                spin_unlock(&fs_info->qgroup_lock);
        }
out:
        ulist_free(tmp);
        return ret;
}

int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans, u64 src,
                              u64 dst)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        int ret = 0;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        ret = __del_qgroup_relation(trans, src, dst);
        mutex_unlock(&fs_info->qgroup_ioctl_lock);

        return ret;
}

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

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root) {
                ret = -ENOTCONN;
                goto out;
        }
        quota_root = fs_info->quota_root;
        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (qgroup) {
                ret = -EEXIST;
                goto out;
        }

        ret = add_qgroup_item(trans, quota_root, qgroupid);
        if (ret)
                goto out;

        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);
                goto out;
        }
        ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

int btrfs_remove_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup *qgroup;
        struct btrfs_qgroup_list *list;
        int ret = 0;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root) {
                ret = -ENOTCONN;
                goto out;
        }

        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup) {
                ret = -ENOENT;
                goto out;
        }

        /* Check if there are no children of this qgroup */
        if (!list_empty(&qgroup->members)) {
                ret = -EBUSY;
                goto out;
        }

        ret = del_qgroup_item(trans, qgroupid);
        if (ret && ret != -ENOENT)
                goto out;

        while (!list_empty(&qgroup->groups)) {
                list = list_first_entry(&qgroup->groups,
                                        struct btrfs_qgroup_list, next_group);
                ret = __del_qgroup_relation(trans, qgroupid,
                                            list->group->qgroupid);
                if (ret)
                        goto out;
        }

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

        /*
         * Remove the qgroup from sysfs now without holding the qgroup_lock
         * spinlock, since the sysfs_remove_group() function needs to take
         * the mutex kernfs_mutex through kernfs_remove_by_name_ns().
         */
        btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
        kfree(qgroup);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

int btrfs_limit_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid,
                       struct btrfs_qgroup_limit *limit)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup *qgroup;
        int ret = 0;
        /* Sometimes we would want to clear the limit on this qgroup.
         * To meet this requirement, we treat the -1 as a special value
         * which tell kernel to clear the limit on this qgroup.
         */
        const u64 CLEAR_VALUE = -1;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root) {
                ret = -ENOTCONN;
                goto out;
        }

        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup) {
                ret = -ENOENT;
                goto out;
        }

        spin_lock(&fs_info->qgroup_lock);
        if (limit->flags & BTRFS_QGROUP_LIMIT_MAX_RFER) {
                if (limit->max_rfer == CLEAR_VALUE) {
                        qgroup->lim_flags &= ~BTRFS_QGROUP_LIMIT_MAX_RFER;
                        limit->flags &= ~BTRFS_QGROUP_LIMIT_MAX_RFER;
                        qgroup->max_rfer = 0;
                } else {
                        qgroup->max_rfer = limit->max_rfer;
                }
        }
        if (limit->flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) {
                if (limit->max_excl == CLEAR_VALUE) {
                        qgroup->lim_flags &= ~BTRFS_QGROUP_LIMIT_MAX_EXCL;
                        limit->flags &= ~BTRFS_QGROUP_LIMIT_MAX_EXCL;
                        qgroup->max_excl = 0;
                } else {
                        qgroup->max_excl = limit->max_excl;
                }
        }
        if (limit->flags & BTRFS_QGROUP_LIMIT_RSV_RFER) {
                if (limit->rsv_rfer == CLEAR_VALUE) {
                        qgroup->lim_flags &= ~BTRFS_QGROUP_LIMIT_RSV_RFER;
                        limit->flags &= ~BTRFS_QGROUP_LIMIT_RSV_RFER;
                        qgroup->rsv_rfer = 0;
                } else {
                        qgroup->rsv_rfer = limit->rsv_rfer;
                }
        }
        if (limit->flags & BTRFS_QGROUP_LIMIT_RSV_EXCL) {
                if (limit->rsv_excl == CLEAR_VALUE) {
                        qgroup->lim_flags &= ~BTRFS_QGROUP_LIMIT_RSV_EXCL;
                        limit->flags &= ~BTRFS_QGROUP_LIMIT_RSV_EXCL;
                        qgroup->rsv_excl = 0;
                } else {
                        qgroup->rsv_excl = limit->rsv_excl;
                }
        }
        qgroup->lim_flags |= limit->flags;

        spin_unlock(&fs_info->qgroup_lock);

        ret = update_qgroup_limit_item(trans, qgroup);
        if (ret) {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                btrfs_info(fs_info, "unable to update quota limit for %llu",
                       qgroupid);
        }

out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

int btrfs_qgroup_trace_extent_nolock(struct btrfs_fs_info *fs_info,
                                struct btrfs_delayed_ref_root *delayed_refs,
                                struct btrfs_qgroup_extent_record *record)
{
        struct rb_node **p = &delayed_refs->dirty_extent_root.rb_node;
        struct rb_node *parent_node = NULL;
        struct btrfs_qgroup_extent_record *entry;
        u64 bytenr = record->bytenr;

        lockdep_assert_held(&delayed_refs->lock);
        trace_btrfs_qgroup_trace_extent(fs_info, record);

        while (*p) {
                parent_node = *p;
                entry = rb_entry(parent_node, struct btrfs_qgroup_extent_record,
                                 node);
                if (bytenr < entry->bytenr) {
                        p = &(*p)->rb_left;
                } else if (bytenr > entry->bytenr) {
                        p = &(*p)->rb_right;
                } else {
                        if (record->data_rsv && !entry->data_rsv) {
                                entry->data_rsv = record->data_rsv;
                                entry->data_rsv_refroot =
                                        record->data_rsv_refroot;
                        }
                        return 1;
                }
        }

        rb_link_node(&record->node, parent_node, p);
        rb_insert_color(&record->node, &delayed_refs->dirty_extent_root);
        return 0;
}

int btrfs_qgroup_trace_extent_post(struct btrfs_trans_handle *trans,
                                   struct btrfs_qgroup_extent_record *qrecord)
{
        struct ulist *old_root;
        u64 bytenr = qrecord->bytenr;
        int ret;

        /*
         * We are always called in a context where we are already holding a
         * transaction handle. Often we are called when adding a data delayed
         * reference from btrfs_truncate_inode_items() (truncating or unlinking),
         * in which case we will be holding a write lock on extent buffer from a
         * subvolume tree. In this case we can't allow btrfs_find_all_roots() to
         * acquire fs_info->commit_root_sem, because that is a higher level lock
         * that must be acquired before locking any extent buffers.
         *
         * So we want btrfs_find_all_roots() to not acquire the commit_root_sem
         * but we can't pass it a non-NULL transaction handle, because otherwise
         * it would not use commit roots and would lock extent buffers, causing
         * a deadlock if it ends up trying to read lock the same extent buffer
         * that was previously write locked at btrfs_truncate_inode_items().
         *
         * So pass a NULL transaction handle to btrfs_find_all_roots() and
         * explicitly tell it to not acquire the commit_root_sem - if we are
         * holding a transaction handle we don't need its protection.
         */
        ASSERT(trans != NULL);

        ret = btrfs_find_all_roots(NULL, trans->fs_info, bytenr, 0, &old_root,
                                   true);
        if (ret < 0) {
                trans->fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                btrfs_warn(trans->fs_info,
"error accounting new delayed refs extent (err code: %d), quota inconsistent",
                        ret);
                return 0;
        }

        /*
         * Here we don't need to get the lock of
         * trans->transaction->delayed_refs, since inserted qrecord won't
         * be deleted, only qrecord->node may be modified (new qrecord insert)
         *
         * So modifying qrecord->old_roots is safe here
         */
        qrecord->old_roots = old_root;
        return 0;
}

int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans, u64 bytenr,
                              u64 num_bytes, gfp_t gfp_flag)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup_extent_record *record;
        struct btrfs_delayed_ref_root *delayed_refs;
        int ret;

        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)
            || bytenr == 0 || num_bytes == 0)
                return 0;
        record = kzalloc(sizeof(*record), gfp_flag);
        if (!record)
                return -ENOMEM;

        delayed_refs = &trans->transaction->delayed_refs;
        record->bytenr = bytenr;
        record->num_bytes = num_bytes;
        record->old_roots = NULL;

        spin_lock(&delayed_refs->lock);
        ret = btrfs_qgroup_trace_extent_nolock(fs_info, delayed_refs, record);
        spin_unlock(&delayed_refs->lock);
        if (ret > 0) {
                kfree(record);
                return 0;
        }
        return btrfs_qgroup_trace_extent_post(trans, record);
}

int btrfs_qgroup_trace_leaf_items(struct btrfs_trans_handle *trans,
                                  struct extent_buffer *eb)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        int nr = btrfs_header_nritems(eb);
        int i, extent_type, ret;
        struct btrfs_key key;
        struct btrfs_file_extent_item *fi;
        u64 bytenr, num_bytes;

        /* We can be called directly from walk_up_proc() */
        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return 0;

        for (i = 0; i < nr; i++) {
                btrfs_item_key_to_cpu(eb, &key, i);

                if (key.type != BTRFS_EXTENT_DATA_KEY)
                        continue;

                fi = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
                /* filter out non qgroup-accountable extents  */
                extent_type = btrfs_file_extent_type(eb, fi);

                if (extent_type == BTRFS_FILE_EXTENT_INLINE)
                        continue;

                bytenr = btrfs_file_extent_disk_bytenr(eb, fi);
                if (!bytenr)
                        continue;

                num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);

                ret = btrfs_qgroup_trace_extent(trans, bytenr, num_bytes,
                                                GFP_NOFS);
                if (ret)
                        return ret;
        }
        cond_resched();
        return 0;
}

/*
 * Walk up the tree from the bottom, freeing leaves and any interior
 * nodes which have had all slots visited. If a node (leaf or
 * interior) is freed, the node above it will have it's slot
 * incremented. The root node will never be freed.
 *
 * At the end of this function, we should have a path which has all
 * slots incremented to the next position for a search. If we need to
 * read a new node it will be NULL and the node above it will have the
 * correct slot selected for a later read.
 *
 * If we increment the root nodes slot counter past the number of
 * elements, 1 is returned to signal completion of the search.
 */
static int adjust_slots_upwards(struct btrfs_path *path, int root_level)
{
        int level = 0;
        int nr, slot;
        struct extent_buffer *eb;

        if (root_level == 0)
                return 1;

        while (level <= root_level) {
                eb = path->nodes[level];
                nr = btrfs_header_nritems(eb);
                path->slots[level]++;
                slot = path->slots[level];
                if (slot >= nr || level == 0) {
                        /*
                         * Don't free the root -  we will detect this
                         * condition after our loop and return a
                         * positive value for caller to stop walking the tree.
                         */
                        if (level != root_level) {
                                btrfs_tree_unlock_rw(eb, path->locks[level]);
                                path->locks[level] = 0;

                                free_extent_buffer(eb);
                                path->nodes[level] = NULL;
                                path->slots[level] = 0;
                        }
                } else {
                        /*
                         * We have a valid slot to walk back down
                         * from. Stop here so caller can process these
                         * new nodes.
                         */
                        break;
                }

                level++;
        }

        eb = path->nodes[root_level];
        if (path->slots[root_level] >= btrfs_header_nritems(eb))
                return 1;

        return 0;
}

/*
 * Helper function to trace a subtree tree block swap.
 *
 * The swap will happen in highest tree block, but there may be a lot of
 * tree blocks involved.
 *
 * For example:
 *  OO = Old tree blocks
 *  NN = New tree blocks allocated during balance
 *
 *           File tree (257)                  Reloc tree for 257
 * L2              OO                                NN
 *               /    \                            /    \
 * L1          OO      OO (a)                    OO      NN (a)
 *            / \     / \                       / \     / \
 * L0       OO   OO OO   OO                   OO   OO NN   NN
 *                  (b)  (c)                          (b)  (c)
 *
 * When calling qgroup_trace_extent_swap(), we will pass:
 * @src_eb = OO(a)
 * @dst_path = [ nodes[1] = NN(a), nodes[0] = NN(c) ]
 * @dst_level = 0
 * @root_level = 1
 *
 * In that case, qgroup_trace_extent_swap() will search from OO(a) to
 * reach OO(c), then mark both OO(c) and NN(c) as qgroup dirty.
 *
 * The main work of qgroup_trace_extent_swap() can be split into 3 parts:
 *
 * 1) Tree search from @src_eb
 *    It should acts as a simplified btrfs_search_slot().
 *    The key for search can be extracted from @dst_path->nodes[dst_level]
 *    (first key).
 *
 * 2) Mark the final tree blocks in @src_path and @dst_path qgroup dirty
 *    NOTE: In above case, OO(a) and NN(a) won't be marked qgroup dirty.
 *    They should be marked during previous (@dst_level = 1) iteration.
 *
 * 3) Mark file extents in leaves dirty
 *    We don't have good way to pick out new file extents only.
 *    So we still follow the old method by scanning all file extents in
 *    the leave.
 *
 * This function can free us from keeping two paths, thus later we only need
 * to care about how to iterate all new tree blocks in reloc tree.
 */
static int qgroup_trace_extent_swap(struct btrfs_trans_handle* trans,
                                    struct extent_buffer *src_eb,
                                    struct btrfs_path *dst_path,
                                    int dst_level, int root_level,
                                    bool trace_leaf)
{
        struct btrfs_key key;
        struct btrfs_path *src_path;
        struct btrfs_fs_info *fs_info = trans->fs_info;
        u32 nodesize = fs_info->nodesize;
        int cur_level = root_level;
        int ret;

        BUG_ON(dst_level > root_level);
        /* Level mismatch */
        if (btrfs_header_level(src_eb) != root_level)
                return -EINVAL;

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

        if (dst_level)
                btrfs_node_key_to_cpu(dst_path->nodes[dst_level], &key, 0);
        else
                btrfs_item_key_to_cpu(dst_path->nodes[dst_level], &key, 0);

        /* For src_path */
        atomic_inc(&src_eb->refs);
        src_path->nodes[root_level] = src_eb;
        src_path->slots[root_level] = dst_path->slots[root_level];
        src_path->locks[root_level] = 0;

        /* A simplified version of btrfs_search_slot() */
        while (cur_level >= dst_level) {
                struct btrfs_key src_key;
                struct btrfs_key dst_key;

                if (src_path->nodes[cur_level] == NULL) {
                        struct extent_buffer *eb;
                        int parent_slot;

                        eb = src_path->nodes[cur_level + 1];
                        parent_slot = src_path->slots[cur_level + 1];

                        eb = btrfs_read_node_slot(eb, parent_slot);
                        if (IS_ERR(eb)) {
                                ret = PTR_ERR(eb);
                                goto out;
                        }

                        src_path->nodes[cur_level] = eb;

                        btrfs_tree_read_lock(eb);
                        src_path->locks[cur_level] = BTRFS_READ_LOCK;
                }

                src_path->slots[cur_level] = dst_path->slots[cur_level];
                if (cur_level) {
                        btrfs_node_key_to_cpu(dst_path->nodes[cur_level],
                                        &dst_key, dst_path->slots[cur_level]);
                        btrfs_node_key_to_cpu(src_path->nodes[cur_level],
                                        &src_key, src_path->slots[cur_level]);
                } else {

                        btrfs_item_key_to_cpu(dst_path->nodes[cur_level],
                                        &dst_key, dst_path->slots[cur_level]);
                        btrfs_item_key_to_cpu(src_path->nodes[cur_level],
                                        &src_key, src_path->slots[cur_level]);
                }
                /* Content mismatch, something went wrong */
                if (btrfs_comp_cpu_keys(&dst_key, &src_key)) {
                        ret = -ENOENT;
                        goto out;
                }
                cur_level--;
        }

        /*
         * Now both @dst_path and @src_path have been populated, record the tree
         * blocks for qgroup accounting.
         */
        ret = btrfs_qgroup_trace_extent(trans, src_path->nodes[dst_level]->start,
                        nodesize, GFP_NOFS);
        if (ret < 0)
                goto out;
        ret = btrfs_qgroup_trace_extent(trans,
                        dst_path->nodes[dst_level]->start,
                        nodesize, GFP_NOFS);
        if (ret < 0)
                goto out;

        /* Record leaf file extents */
        if (dst_level == 0 && trace_leaf) {
                ret = btrfs_qgroup_trace_leaf_items(trans, src_path->nodes[0]);
                if (ret < 0)
                        goto out;
                ret = btrfs_qgroup_trace_leaf_items(trans, dst_path->nodes[0]);
        }
out:
        btrfs_free_path(src_path);
        return ret;
}

/*
 * Helper function to do recursive generation-aware depth-first search, to
 * locate all new tree blocks in a subtree of reloc tree.
 *
 * E.g. (OO = Old tree blocks, NN = New tree blocks, whose gen == last_snapshot)
 *         reloc tree
 * L2         NN (a)
 *          /    \
 * L1    OO        NN (b)
 *      /  \      /  \
 * L0  OO  OO    OO  NN
 *               (c) (d)
 * If we pass:
 * @dst_path = [ nodes[1] = NN(b), nodes[0] = NULL ],
 * @cur_level = 1
 * @root_level = 1
 *
 * We will iterate through tree blocks NN(b), NN(d) and info qgroup to trace
 * above tree blocks along with their counter parts in file tree.
 * While during search, old tree blocks OO(c) will be skipped as tree block swap
 * won't affect OO(c).
 */
static int qgroup_trace_new_subtree_blocks(struct btrfs_trans_handle* trans,
                                           struct extent_buffer *src_eb,
                                           struct btrfs_path *dst_path,
                                           int cur_level, int root_level,
                                           u64 last_snapshot, bool trace_leaf)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct extent_buffer *eb;
        bool need_cleanup = false;
        int ret = 0;
        int i;

        /* Level sanity check */
        if (cur_level < 0 || cur_level >= BTRFS_MAX_LEVEL - 1 ||
            root_level < 0 || root_level >= BTRFS_MAX_LEVEL - 1 ||
            root_level < cur_level) {
                btrfs_err_rl(fs_info,
                        "%s: bad levels, cur_level=%d root_level=%d",
                        __func__, cur_level, root_level);
                return -EUCLEAN;
        }

        /* Read the tree block if needed */
        if (dst_path->nodes[cur_level] == NULL) {
                int parent_slot;
                u64 child_gen;

                /*
                 * dst_path->nodes[root_level] must be initialized before
                 * calling this function.
                 */
                if (cur_level == root_level) {
                        btrfs_err_rl(fs_info,
        "%s: dst_path->nodes[%d] not initialized, root_level=%d cur_level=%d",
                                __func__, root_level, root_level, cur_level);
                        return -EUCLEAN;
                }

                /*
                 * We need to get child blockptr/gen from parent before we can
                 * read it.
                  */
                eb = dst_path->nodes[cur_level + 1];
                parent_slot = dst_path->slots[cur_level + 1];
                child_gen = btrfs_node_ptr_generation(eb, parent_slot);

                /* This node is old, no need to trace */
                if (child_gen < last_snapshot)
                        goto out;

                eb = btrfs_read_node_slot(eb, parent_slot);
                if (IS_ERR(eb)) {
                        ret = PTR_ERR(eb);
                        goto out;
                }

                dst_path->nodes[cur_level] = eb;
                dst_path->slots[cur_level] = 0;

                btrfs_tree_read_lock(eb);
                dst_path->locks[cur_level] = BTRFS_READ_LOCK;
                need_cleanup = true;
        }

        /* Now record this tree block and its counter part for qgroups */
        ret = qgroup_trace_extent_swap(trans, src_eb, dst_path, cur_level,
                                       root_level, trace_leaf);
        if (ret < 0)
                goto cleanup;

        eb = dst_path->nodes[cur_level];

        if (cur_level > 0) {
                /* Iterate all child tree blocks */
                for (i = 0; i < btrfs_header_nritems(eb); i++) {
                        /* Skip old tree blocks as they won't be swapped */
                        if (btrfs_node_ptr_generation(eb, i) < last_snapshot)
                                continue;
                        dst_path->slots[cur_level] = i;

                        /* Recursive call (at most 7 times) */
                        ret = qgroup_trace_new_subtree_blocks(trans, src_eb,
                                        dst_path, cur_level - 1, root_level,
                                        last_snapshot, trace_leaf);
                        if (ret < 0)
                                goto cleanup;
                }
        }

cleanup:
        if (need_cleanup) {
                /* Clean up */
                btrfs_tree_unlock_rw(dst_path->nodes[cur_level],
                                     dst_path->locks[cur_level]);
                free_extent_buffer(dst_path->nodes[cur_level]);
                dst_path->nodes[cur_level] = NULL;
                dst_path->slots[cur_level] = 0;
                dst_path->locks[cur_level] = 0;
        }
out:
        return ret;
}

static int qgroup_trace_subtree_swap(struct btrfs_trans_handle *trans,
                                struct extent_buffer *src_eb,
                                struct extent_buffer *dst_eb,
                                u64 last_snapshot, bool trace_leaf)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_path *dst_path = NULL;
        int level;
        int ret;

        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return 0;

        /* Wrong parameter order */
        if (btrfs_header_generation(src_eb) > btrfs_header_generation(dst_eb)) {
                btrfs_err_rl(fs_info,
                "%s: bad parameter order, src_gen=%llu dst_gen=%llu", __func__,
                             btrfs_header_generation(src_eb),
                             btrfs_header_generation(dst_eb));
                return -EUCLEAN;
        }

        if (!extent_buffer_uptodate(src_eb) || !extent_buffer_uptodate(dst_eb)) {
                ret = -EIO;
                goto out;
        }

        level = btrfs_header_level(dst_eb);
        dst_path = btrfs_alloc_path();
        if (!dst_path) {
                ret = -ENOMEM;
                goto out;
        }
        /* For dst_path */
        atomic_inc(&dst_eb->refs);
        dst_path->nodes[level] = dst_eb;
        dst_path->slots[level] = 0;
        dst_path->locks[level] = 0;

        /* Do the generation aware breadth-first search */
        ret = qgroup_trace_new_subtree_blocks(trans, src_eb, dst_path, level,
                                              level, last_snapshot, trace_leaf);
        if (ret < 0)
                goto out;
        ret = 0;

out:
        btrfs_free_path(dst_path);
        if (ret < 0)
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        return ret;
}

int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans,
                               struct extent_buffer *root_eb,
                               u64 root_gen, int root_level)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        int ret = 0;
        int level;
        struct extent_buffer *eb = root_eb;
        struct btrfs_path *path = NULL;

        BUG_ON(root_level < 0 || root_level >= BTRFS_MAX_LEVEL);
        BUG_ON(root_eb == NULL);

        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return 0;

        if (!extent_buffer_uptodate(root_eb)) {
                ret = btrfs_read_buffer(root_eb, root_gen, root_level, NULL);
                if (ret)
                        goto out;
        }

        if (root_level == 0) {
                ret = btrfs_qgroup_trace_leaf_items(trans, root_eb);
                goto out;
        }

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

        /*
         * Walk down the tree.  Missing extent blocks are filled in as
         * we go. Metadata is accounted every time we read a new
         * extent block.
         *
         * When we reach a leaf, we account for file extent items in it,
         * walk back up the tree (adjusting slot pointers as we go)
         * and restart the search process.
         */
        atomic_inc(&root_eb->refs);     /* For path */
        path->nodes[root_level] = root_eb;
        path->slots[root_level] = 0;
        path->locks[root_level] = 0; /* so release_path doesn't try to unlock */
walk_down:
        level = root_level;
        while (level >= 0) {
                if (path->nodes[level] == NULL) {
                        int parent_slot;
                        u64 child_bytenr;

                        /*
                         * We need to get child blockptr from parent before we
                         * can read it.
                          */
                        eb = path->nodes[level + 1];
                        parent_slot = path->slots[level + 1];
                        child_bytenr = btrfs_node_blockptr(eb, parent_slot);

                        eb = btrfs_read_node_slot(eb, parent_slot);
                        if (IS_ERR(eb)) {
                                ret = PTR_ERR(eb);
                                goto out;
                        }

                        path->nodes[level] = eb;
                        path->slots[level] = 0;

                        btrfs_tree_read_lock(eb);
                        path->locks[level] = BTRFS_READ_LOCK;

                        ret = btrfs_qgroup_trace_extent(trans, child_bytenr,
                                                        fs_info->nodesize,
                                                        GFP_NOFS);
                        if (ret)
                                goto out;
                }

                if (level == 0) {
                        ret = btrfs_qgroup_trace_leaf_items(trans,
                                                            path->nodes[level]);
                        if (ret)
                                goto out;

                        /* Nonzero return here means we completed our search */
                        ret = adjust_slots_upwards(path, root_level);
                        if (ret)
                                break;

                        /* Restart search with new slots */
                        goto walk_down;
                }

                level--;
        }

        ret = 0;
out:
        btrfs_free_path(path);

        return ret;
}

#define UPDATE_NEW      0
#define UPDATE_OLD      1
/*
 * Walk all of the roots that points to the bytenr and adjust their refcnts.
 */
static int qgroup_update_refcnt(struct btrfs_fs_info *fs_info,
                                struct ulist *roots, struct ulist *tmp,
                                struct ulist *qgroups, u64 seq, int update_old)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct ulist_node *tmp_unode;
        struct ulist_iterator tmp_uiter;
        struct btrfs_qgroup *qg;
        int ret = 0;

        if (!roots)
                return 0;
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(roots, &uiter))) {
                qg = find_qgroup_rb(fs_info, unode->val);
                if (!qg)
                        continue;

                ulist_reinit(tmp);
                ret = ulist_add(qgroups, qg->qgroupid, qgroup_to_aux(qg),
                                GFP_ATOMIC);
                if (ret < 0)
                        return ret;
                ret = ulist_add(tmp, qg->qgroupid, qgroup_to_aux(qg), GFP_ATOMIC);
                if (ret < 0)
                        return ret;
                ULIST_ITER_INIT(&tmp_uiter);
                while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
                        struct btrfs_qgroup_list *glist;

                        qg = unode_aux_to_qgroup(tmp_unode);
                        if (update_old)
                                btrfs_qgroup_update_old_refcnt(qg, seq, 1);
                        else
                                btrfs_qgroup_update_new_refcnt(qg, seq, 1);
                        list_for_each_entry(glist, &qg->groups, next_group) {
                                ret = ulist_add(qgroups, glist->group->qgroupid,
                                                qgroup_to_aux(glist->group),
                                                GFP_ATOMIC);
                                if (ret < 0)
                                        return ret;
                                ret = ulist_add(tmp, glist->group->qgroupid,
                                                qgroup_to_aux(glist->group),
                                                GFP_ATOMIC);
                                if (ret < 0)
                                        return ret;
                        }
                }
        }
        return 0;
}

/*
 * Update qgroup rfer/excl counters.
 * Rfer update is easy, codes can explain themselves.
 *
 * Excl update is tricky, the update is split into 2 parts.
 * Part 1: Possible exclusive <-> sharing detect:
 *      |       A       |       !A      |
 *  -------------------------------------
 *  B   |       *       |       -       |
 *  -------------------------------------
 *  !B  |       +       |       **      |
 *  -------------------------------------
 *
 * Conditions:
 * A:   cur_old_roots < nr_old_roots    (not exclusive before)
 * !A:  cur_old_roots == nr_old_roots   (possible exclusive before)
 * B:   cur_new_roots < nr_new_roots    (not exclusive now)
 * !B:  cur_new_roots == nr_new_roots   (possible exclusive now)
 *
 * Results:
 * +: Possible sharing -> exclusive     -: Possible exclusive -> sharing
 * *: Definitely not changed.           **: Possible unchanged.
 *
 * For !A and !B condition, the exception is cur_old/new_roots == 0 case.
 *
 * To make the logic clear, we first use condition A and B to split
 * combination into 4 results.
 *
 * Then, for result "+" and "-", check old/new_roots == 0 case, as in them
 * only on variant maybe 0.
 *
 * Lastly, check result **, since there are 2 variants maybe 0, split them
 * again(2x2).
 * But this time we don't need to consider other things, the codes and logic
 * is easy to understand now.
 */
static int qgroup_update_counters(struct btrfs_fs_info *fs_info,
                                  struct ulist *qgroups,
                                  u64 nr_old_roots,
                                  u64 nr_new_roots,
                                  u64 num_bytes, u64 seq)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct btrfs_qgroup *qg;
        u64 cur_new_count, cur_old_count;

        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(qgroups, &uiter))) {
                bool dirty = false;

                qg = unode_aux_to_qgroup(unode);
                cur_old_count = btrfs_qgroup_get_old_refcnt(qg, seq);
                cur_new_count = btrfs_qgroup_get_new_refcnt(qg, seq);

                trace_qgroup_update_counters(fs_info, qg, cur_old_count,
                                             cur_new_count);

                /* Rfer update part */
                if (cur_old_count == 0 && cur_new_count > 0) {
                        qg->rfer += num_bytes;
                        qg->rfer_cmpr += num_bytes;
                        dirty = true;
                }
                if (cur_old_count > 0 && cur_new_count == 0) {
                        qg->rfer -= num_bytes;
                        qg->rfer_cmpr -= num_bytes;
                        dirty = true;
                }

                /* Excl update part */
                /* Exclusive/none -> shared case */
                if (cur_old_count == nr_old_roots &&
                    cur_new_count < nr_new_roots) {
                        /* Exclusive -> shared */
                        if (cur_old_count != 0) {
                                qg->excl -= num_bytes;
                                qg->excl_cmpr -= num_bytes;
                                dirty = true;
                        }
                }

                /* Shared -> exclusive/none case */
                if (cur_old_count < nr_old_roots &&
                    cur_new_count == nr_new_roots) {
                        /* Shared->exclusive */
                        if (cur_new_count != 0) {
                                qg->excl += num_bytes;
                                qg->excl_cmpr += num_bytes;
                                dirty = true;
                        }
                }

                /* Exclusive/none -> exclusive/none case */
                if (cur_old_count == nr_old_roots &&
                    cur_new_count == nr_new_roots) {
                        if (cur_old_count == 0) {
                                /* None -> exclusive/none */

                                if (cur_new_count != 0) {
                                        /* None -> exclusive */
                                        qg->excl += num_bytes;
                                        qg->excl_cmpr += num_bytes;
                                        dirty = true;
                                }
                                /* None -> none, nothing changed */
                        } else {
                                /* Exclusive -> exclusive/none */

                                if (cur_new_count == 0) {
                                        /* Exclusive -> none */
                                        qg->excl -= num_bytes;
                                        qg->excl_cmpr -= num_bytes;
                                        dirty = true;
                                }
                                /* Exclusive -> exclusive, nothing changed */
                        }
                }

                if (dirty)
                        qgroup_dirty(fs_info, qg);
        }
        return 0;
}

/*
 * Check if the @roots potentially is a list of fs tree roots
 *
 * Return 0 for definitely not a fs/subvol tree roots ulist
 * Return 1 for possible fs/subvol tree roots in the list (considering an empty
 *          one as well)
 */
static int maybe_fs_roots(struct ulist *roots)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;

        /* Empty one, still possible for fs roots */
        if (!roots || roots->nnodes == 0)
                return 1;

        ULIST_ITER_INIT(&uiter);
        unode = ulist_next(roots, &uiter);
        if (!unode)
                return 1;

        /*
         * If it contains fs tree roots, then it must belong to fs/subvol
         * trees.
         * If it contains a non-fs tree, it won't be shared with fs/subvol trees.
         */
        return is_fstree(unode->val);
}

int btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans, u64 bytenr,
                                u64 num_bytes, struct ulist *old_roots,
                                struct ulist *new_roots)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct ulist *qgroups = NULL;
        struct ulist *tmp = NULL;
        u64 seq;
        u64 nr_new_roots = 0;
        u64 nr_old_roots = 0;
        int ret = 0;

        /*
         * If quotas get disabled meanwhile, the resources need to be freed and
         * we can't just exit here.
         */
        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                goto out_free;

        if (new_roots) {
                if (!maybe_fs_roots(new_roots))
                        goto out_free;
                nr_new_roots = new_roots->nnodes;
        }
        if (old_roots) {
                if (!maybe_fs_roots(old_roots))
                        goto out_free;
                nr_old_roots = old_roots->nnodes;
        }

        /* Quick exit, either not fs tree roots, or won't affect any qgroup */
        if (nr_old_roots == 0 && nr_new_roots == 0)
                goto out_free;

        BUG_ON(!fs_info->quota_root);

        trace_btrfs_qgroup_account_extent(fs_info, trans->transid, bytenr,
                                        num_bytes, nr_old_roots, nr_new_roots);

        qgroups = ulist_alloc(GFP_NOFS);
        if (!qgroups) {
                ret = -ENOMEM;
                goto out_free;
        }
        tmp = ulist_alloc(GFP_NOFS);
        if (!tmp) {
                ret = -ENOMEM;
                goto out_free;
        }

        mutex_lock(&fs_info->qgroup_rescan_lock);
        if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
                if (fs_info->qgroup_rescan_progress.objectid <= bytenr) {
                        mutex_unlock(&fs_info->qgroup_rescan_lock);
                        ret = 0;
                        goto out_free;
                }
        }
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        spin_lock(&fs_info->qgroup_lock);
        seq = fs_info->qgroup_seq;

        /* Update old refcnts using old_roots */
        ret = qgroup_update_refcnt(fs_info, old_roots, tmp, qgroups, seq,
                                   UPDATE_OLD);
        if (ret < 0)
                goto out;

        /* Update new refcnts using new_roots */
        ret = qgroup_update_refcnt(fs_info, new_roots, tmp, qgroups, seq,
                                   UPDATE_NEW);
        if (ret < 0)
                goto out;

        qgroup_update_counters(fs_info, qgroups, nr_old_roots, nr_new_roots,
                               num_bytes, seq);

        /*
         * Bump qgroup_seq to avoid seq overlap
         */
        fs_info->qgroup_seq += max(nr_old_roots, nr_new_roots) + 1;
out:
        spin_unlock(&fs_info->qgroup_lock);
out_free:
        ulist_free(tmp);
        ulist_free(qgroups);
        ulist_free(old_roots);
        ulist_free(new_roots);
        return ret;
}

int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_qgroup_extent_record *record;
        struct btrfs_delayed_ref_root *delayed_refs;
        struct ulist *new_roots = NULL;
        struct rb_node *node;
        u64 num_dirty_extents = 0;
        u64 qgroup_to_skip;
        int ret = 0;

        delayed_refs = &trans->transaction->delayed_refs;
        qgroup_to_skip = delayed_refs->qgroup_to_skip;
        while ((node = rb_first(&delayed_refs->dirty_extent_root))) {
                record = rb_entry(node, struct btrfs_qgroup_extent_record,
                                  node);

                num_dirty_extents++;
                trace_btrfs_qgroup_account_extents(fs_info, record);

                if (!ret) {
                        /*
                         * Old roots should be searched when inserting qgroup
                         * extent record
                         */
                        if (WARN_ON(!record->old_roots)) {
                                /* Search commit root to find old_roots */
                                ret = btrfs_find_all_roots(NULL, fs_info,
                                                record->bytenr, 0,
                                                &record->old_roots, false);
                                if (ret < 0)
                                        goto cleanup;
                        }

                        /* Free the reserved data space */
                        btrfs_qgroup_free_refroot(fs_info,
                                        record->data_rsv_refroot,
                                        record->data_rsv,
                                        BTRFS_QGROUP_RSV_DATA);
                        /*
                         * Use BTRFS_SEQ_LAST as time_seq to do special search,
                         * which doesn't lock tree or delayed_refs and search
                         * current root. It's safe inside commit_transaction().
                         */
                        ret = btrfs_find_all_roots(trans, fs_info,
                           record->bytenr, BTRFS_SEQ_LAST, &new_roots, false);
                        if (ret < 0)
                                goto cleanup;
                        if (qgroup_to_skip) {
                                ulist_del(new_roots, qgroup_to_skip, 0);
                                ulist_del(record->old_roots, qgroup_to_skip,
                                          0);
                        }
                        ret = btrfs_qgroup_account_extent(trans, record->bytenr,
                                                          record->num_bytes,
                                                          record->old_roots,
                                                          new_roots);
                        record->old_roots = NULL;
                        new_roots = NULL;
                }
cleanup:
                ulist_free(record->old_roots);
                ulist_free(new_roots);
                new_roots = NULL;
                rb_erase(node, &delayed_refs->dirty_extent_root);
                kfree(record);

        }
        trace_qgroup_num_dirty_extents(fs_info, trans->transid,
                                       num_dirty_extents);
        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 = trans->fs_info;
        int ret = 0;

        if (!fs_info->quota_root)
                return ret;

        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, qgroup);
                if (ret)
                        fs_info->qgroup_flags |=
                                        BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                ret = update_qgroup_limit_item(trans, qgroup);
                if (ret)
                        fs_info->qgroup_flags |=
                                        BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                spin_lock(&fs_info->qgroup_lock);
        }
        if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                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);
        if (ret)
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;

        return ret;
}

/*
 * Copy the accounting information between qgroups. This is necessary
 * when a snapshot or a subvolume is created. Throwing an error will
 * cause a transaction abort so we take extra care here to only error
 * when a readonly fs is a reasonable outcome.
 */
int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
                         u64 objectid, struct btrfs_qgroup_inherit *inherit)
{
        int ret = 0;
        int i;
        u64 *i_qgroups;
        bool committing = false;
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_root *quota_root;
        struct btrfs_qgroup *srcgroup;
        struct btrfs_qgroup *dstgroup;
        bool need_rescan = false;
        u32 level_size = 0;
        u64 nums;

        /*
         * There are only two callers of this function.
         *
         * One in create_subvol() in the ioctl context, which needs to hold
         * the qgroup_ioctl_lock.
         *
         * The other one in create_pending_snapshot() where no other qgroup
         * code can modify the fs as they all need to either start a new trans
         * or hold a trans handler, thus we don't need to hold
         * qgroup_ioctl_lock.
         * This would avoid long and complex lock chain and make lockdep happy.
         */
        spin_lock(&fs_info->trans_lock);
        if (trans->transaction->state == TRANS_STATE_COMMIT_DOING)
                committing = true;
        spin_unlock(&fs_info->trans_lock);

        if (!committing)
                mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                goto out;

        quota_root = fs_info->quota_root;
        if (!quota_root) {
                ret = -EINVAL;
                goto out;
        }

        if (inherit) {
                i_qgroups = (u64 *)(inherit + 1);
                nums = inherit->num_qgroups + 2 * inherit->num_ref_copies +
                       2 * inherit->num_excl_copies;
                for (i = 0; i < nums; ++i) {
                        srcgroup = find_qgroup_rb(fs_info, *i_qgroups);

                        /*
                         * Zero out invalid groups so we can ignore
                         * them later.
                         */
                        if (!srcgroup ||
                            ((srcgroup->qgroupid >> 48) <= (objectid >> 48)))
                                *i_qgroups = 0ULL;

                        ++i_qgroups;
                }
        }

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

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


        spin_lock(&fs_info->qgroup_lock);

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

        if (inherit && inherit->flags & BTRFS_QGROUP_INHERIT_SET_LIMITS) {
                dstgroup->lim_flags = inherit->lim.flags;
                dstgroup->max_rfer = inherit->lim.max_rfer;
                dstgroup->max_excl = inherit->lim.max_excl;
                dstgroup->rsv_rfer = inherit->lim.rsv_rfer;
                dstgroup->rsv_excl = inherit->lim.rsv_excl;

                ret = update_qgroup_limit_item(trans, dstgroup);
                if (ret) {
                        fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                        btrfs_info(fs_info,
                                   "unable to update quota limit for %llu",
                                   dstgroup->qgroupid);
                        goto unlock;
                }
        }

        if (srcid) {
                srcgroup = find_qgroup_rb(fs_info, srcid);
                if (!srcgroup)
                        goto unlock;

                /*
                 * We call inherit after we clone the root in order to make sure
                 * our counts don't go crazy, so at this point the only
                 * difference between the two roots should be the root node.
                 */
                level_size = fs_info->nodesize;
                dstgroup->rfer = srcgroup->rfer;
                dstgroup->rfer_cmpr = srcgroup->rfer_cmpr;
                dstgroup->excl = level_size;
                dstgroup->excl_cmpr = level_size;
                srcgroup->excl = level_size;
                srcgroup->excl_cmpr = level_size;

                /* inherit the limit info */
                dstgroup->lim_flags = srcgroup->lim_flags;
                dstgroup->max_rfer = srcgroup->max_rfer;
                dstgroup->max_excl = srcgroup->max_excl;
                dstgroup->rsv_rfer = srcgroup->rsv_rfer;
                dstgroup->rsv_excl = srcgroup->rsv_excl;

                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) {
                if (*i_qgroups) {
                        ret = add_relation_rb(fs_info, objectid, *i_qgroups);
                        if (ret)
                                goto unlock;
                }
                ++i_qgroups;

                /*
                 * If we're doing a snapshot, and adding the snapshot to a new
                 * qgroup, the numbers are guaranteed to be incorrect.
                 */
                if (srcid)
                        need_rescan = true;
        }

        for (i = 0; i <  inherit->num_ref_copies; ++i, i_qgroups += 2) {
                struct btrfs_qgroup *src;
                struct btrfs_qgroup *dst;

                if (!i_qgroups[0] || !i_qgroups[1])
                        continue;

                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;

                /* Manually tweaking numbers certainly needs a rescan */
                need_rescan = true;
        }
        for (i = 0; i <  inherit->num_excl_copies; ++i, i_qgroups += 2) {
                struct btrfs_qgroup *src;
                struct btrfs_qgroup *dst;

                if (!i_qgroups[0] || !i_qgroups[1])
                        continue;

                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;
                need_rescan = true;
        }

unlock:
        spin_unlock(&fs_info->qgroup_lock);
        if (!ret)
                ret = btrfs_sysfs_add_one_qgroup(fs_info, dstgroup);
out:
        if (!committing)
                mutex_unlock(&fs_info->qgroup_ioctl_lock);
        if (need_rescan)
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        return ret;
}

static bool qgroup_check_limits(const struct btrfs_qgroup *qg, u64 num_bytes)
{
        if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_RFER) &&
            qgroup_rsv_total(qg) + (s64)qg->rfer + num_bytes > qg->max_rfer)
                return false;

        if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) &&
            qgroup_rsv_total(qg) + (s64)qg->excl + num_bytes > qg->max_excl)
                return false;

        return true;
}

static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes, bool enforce,
                          enum btrfs_qgroup_rsv_type type)
{
        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_node *unode;
        struct ulist_iterator uiter;

        if (!is_fstree(ref_root))
                return 0;

        if (num_bytes == 0)
                return 0;

        if (test_bit(BTRFS_FS_QUOTA_OVERRIDE, &fs_info->flags) &&
            capable(CAP_SYS_RESOURCE))
                enforce = false;

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

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