btrfs: qgroup: validate btrfs_qgroup_inherit parameter

[linux-2.6-microblaze.git] / fs / btrfs / qgroup.c

// 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"
#include "fs.h"
#include "accessors.h"
#include "extent-tree.h"
#include "root-tree.h"
#include "tree-checker.h"

enum btrfs_qgroup_mode btrfs_qgroup_mode(struct btrfs_fs_info *fs_info)
{
        if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
                return BTRFS_QGROUP_MODE_DISABLED;
        if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE)
                return BTRFS_QGROUP_MODE_SIMPLE;
        return BTRFS_QGROUP_MODE_FULL;
}

bool btrfs_qgroup_enabled(struct btrfs_fs_info *fs_info)
{
        return btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_DISABLED;
}

bool btrfs_qgroup_full_accounting(struct btrfs_fs_info *fs_info)
{
        return btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_FULL;
}

/*
 * 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 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;
}

/*
 * Add qgroup to the filesystem's qgroup tree.
 *
 * Must be called with qgroup_lock held and @prealloc preallocated.
 *
 * The control on the lifespan of @prealloc would be transferred to this
 * function, thus caller should no longer touch @prealloc.
 */
static struct btrfs_qgroup *add_qgroup_rb(struct btrfs_fs_info *fs_info,
                                          struct btrfs_qgroup *prealloc,
                                          u64 qgroupid)
{
        struct rb_node **p = &fs_info->qgroup_tree.rb_node;
        struct rb_node *parent = NULL;
        struct btrfs_qgroup *qgroup;

        /* Caller must have pre-allocated @prealloc. */
        ASSERT(prealloc);

        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 {
                        kfree(prealloc);
                        return qgroup;
                }
        }

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

        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;
}

/*
 * Add relation specified by two qgroups.
 *
 * Must be called with qgroup_lock held, the ownership of @prealloc is
 * transferred to this function and caller should not touch it anymore.
 *
 * Return: 0        on success
 *         -ENOENT  if one of the qgroups is NULL
 *         <0       other errors
 */
static int __add_relation_rb(struct btrfs_qgroup_list *prealloc,
                             struct btrfs_qgroup *member,
                             struct btrfs_qgroup *parent)
{
        if (!member || !parent) {
                kfree(prealloc);
                return -ENOENT;
        }

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

        return 0;
}

/*
 * Add relation specified by two qgroup ids.
 *
 * Must be called with qgroup_lock held.
 *
 * Return: 0        on success
 *         -ENOENT  if one of the ids does not exist
 *         <0       other errors
 */
static int add_relation_rb(struct btrfs_fs_info *fs_info,
                           struct btrfs_qgroup_list *prealloc,
                           u64 memberid, u64 parentid)
{
        struct btrfs_qgroup *member;
        struct btrfs_qgroup *parent;

        member = find_qgroup_rb(fs_info, memberid);
        parent = find_qgroup_rb(fs_info, parentid);

        return __add_relation_rb(prealloc, member, parent);
}

/* 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

static void qgroup_mark_inconsistent(struct btrfs_fs_info *fs_info)
{
        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)
                return;
        fs_info->qgroup_flags |= (BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT |
                                  BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN |
                                  BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING);
}

static void qgroup_read_enable_gen(struct btrfs_fs_info *fs_info,
                                   struct extent_buffer *leaf, int slot,
                                   struct btrfs_qgroup_status_item *ptr)
{
        ASSERT(btrfs_fs_incompat(fs_info, SIMPLE_QUOTA));
        ASSERT(btrfs_item_size(leaf, slot) >= sizeof(*ptr));
        fs_info->qgroup_enable_gen = btrfs_qgroup_status_enable_gen(leaf, ptr);
}

/*
 * 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 (!fs_info->quota_root)
                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;
                        }
                        fs_info->qgroup_flags = btrfs_qgroup_status_flags(l, ptr);
                        if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE) {
                                qgroup_read_enable_gen(fs_info, l, slot, ptr);
                        } else if (btrfs_qgroup_status_generation(l, ptr) != fs_info->generation) {
                                qgroup_mark_inconsistent(fs_info);
                                btrfs_err(fs_info,
                                        "qgroup generation mismatch, marked as inconsistent");
                        }
                        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");
                        qgroup_mark_inconsistent(fs_info);
                }
                if (!qgroup) {
                        struct btrfs_qgroup *prealloc;

                        prealloc = kzalloc(sizeof(*prealloc), GFP_KERNEL);
                        if (!prealloc) {
                                ret = -ENOMEM;
                                goto out;
                        }
                        qgroup = add_qgroup_rb(fs_info, prealloc, found_key.offset);
                }
                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) {
                struct btrfs_qgroup_list *list = NULL;

                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;
                }

                list = kzalloc(sizeof(*list), GFP_KERNEL);
                if (!list) {
                        ret = -ENOMEM;
                        goto out;
                }
                ret = add_relation_rb(fs_info, list, found_key.objectid,
                                      found_key.offset);
                list = NULL;
                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 (ret >= 0) {
                if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON)
                        set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
                if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
                        ret = qgroup_rescan_init(fs_info, rescan_progress, 0);
        } else {
                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 (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED)
                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(trans, 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(trans, 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(trans, 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(trans, 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(trans, 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_QGROUP_STATUS_FLAGS_MASK);
        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(trans, 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_ioctl_quota_ctl_args *quota_ctl_args)
{
        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_qgroup *prealloc = NULL;
        struct btrfs_trans_handle *trans = NULL;
        struct ulist *ulist = NULL;
        const bool simple = (quota_ctl_args->cmd == BTRFS_QUOTA_CTL_ENABLE_SIMPLE_QUOTA);
        int ret = 0;
        int slot;

        /*
         * We need to have subvol_sem write locked, to prevent races between
         * concurrent tasks trying to enable quotas, because we will unlock
         * and relock qgroup_ioctl_lock before setting fs_info->quota_root
         * and before setting BTRFS_FS_QUOTA_ENABLED.
         */
        lockdep_assert_held_write(&fs_info->subvol_sem);

        if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
                btrfs_err(fs_info,
                          "qgroups are currently unsupported in extent tree v2");
                return -EINVAL;
        }

        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;
        if (simple) {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE;
                btrfs_set_qgroup_status_enable_gen(leaf, ptr, trans->transid);
        } else {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        }
        btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags &
                                      BTRFS_QGROUP_STATUS_FLAGS_MASK);
        btrfs_set_qgroup_status_rescan(leaf, ptr, 0);

        btrfs_mark_buffer_dirty(trans, 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);

                        /* We should not have a stray @prealloc pointer. */
                        ASSERT(prealloc == NULL);
                        prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS);
                        if (!prealloc) {
                                ret = -ENOMEM;
                                btrfs_abort_transaction(trans, ret);
                                goto out_free_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, prealloc, found_key.offset);
                        prealloc = NULL;
                        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;
        }

        ASSERT(prealloc == NULL);
        prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS);
        if (!prealloc) {
                ret = -ENOMEM;
                goto out_free_path;
        }
        qgroup = add_qgroup_rb(fs_info, prealloc, BTRFS_FS_TREE_OBJECTID);
        prealloc = NULL;
        ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
        if (ret < 0) {
                btrfs_abort_transaction(trans, ret);
                goto out_free_path;
        }

        fs_info->qgroup_enable_gen = trans->transid;

        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        /*
         * Commit the transaction while not holding qgroup_ioctl_lock, to avoid
         * a deadlock with tasks concurrently doing other qgroup operations, such
         * adding/removing qgroups or adding/deleting qgroup relations for example,
         * because all qgroup operations first start or join a transaction and then
         * lock the qgroup_ioctl_lock mutex.
         * We are safe from a concurrent task trying to enable quotas, by calling
         * this function, since we are serialized by fs_info->subvol_sem.
         */
        ret = btrfs_commit_transaction(trans);
        trans = NULL;
        mutex_lock(&fs_info->qgroup_ioctl_lock);
        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);
        if (simple)
                btrfs_set_fs_incompat(fs_info, SIMPLE_QUOTA);
        spin_unlock(&fs_info->qgroup_lock);

        /* Skip rescan for simple qgroups. */
        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)
                goto out_free_path;

        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);
        } else {
                /*
                 * We have set both BTRFS_FS_QUOTA_ENABLED and
                 * BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with
                 * -EINPROGRESS. That can happen because someone started the
                 * rescan worker by calling quota rescan ioctl before we
                 * attempted to initialize the rescan worker. Failure due to
                 * quotas disabled in the meanwhile is not possible, because
                 * we are holding a write lock on fs_info->subvol_sem, which
                 * is also acquired when disabling quotas.
                 * Ignore such error, and any other error would need to undo
                 * everything we did in the transaction we just committed.
                 */
                ASSERT(ret == -EINPROGRESS);
                ret = 0;
        }

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);
        kfree(prealloc);
        return ret;
}

/*
 * It is possible to have outstanding ordered extents which reserved bytes
 * before we disabled. We need to fully flush delalloc, ordered extents, and a
 * commit to ensure that we don't leak such reservations, only to have them
 * come back if we re-enable.
 *
 * - enable simple quotas
 * - reserve space
 * - release it, store rsv_bytes in OE
 * - disable quotas
 * - enable simple quotas (qgroup rsv are all 0)
 * - OE finishes
 * - run delayed refs
 * - free rsv_bytes, resulting in miscounting or even underflow
 */
static int flush_reservations(struct btrfs_fs_info *fs_info)
{
        struct btrfs_trans_handle *trans;
        int ret;

        ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
        if (ret)
                return ret;
        btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
        trans = btrfs_join_transaction(fs_info->tree_root);
        if (IS_ERR(trans))
                return PTR_ERR(trans);
        ret = btrfs_commit_transaction(trans);

        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;

        /*
         * We need to have subvol_sem write locked to prevent races with
         * snapshot creation.
         */
        lockdep_assert_held_write(&fs_info->subvol_sem);

        /*
         * Lock the cleaner mutex to prevent races with concurrent relocation,
         * because relocation may be building backrefs for blocks of the quota
         * root while we are deleting the root. This is like dropping fs roots
         * of deleted snapshots/subvolumes, we need the same protection.
         *
         * This also prevents races between concurrent tasks trying to disable
         * quotas, because we will unlock and relock qgroup_ioctl_lock across
         * BTRFS_FS_QUOTA_ENABLED changes.
         */
        mutex_lock(&fs_info->cleaner_mutex);

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

        /*
         * Unlock the qgroup_ioctl_lock mutex before waiting for the rescan worker to
         * complete. Otherwise we can deadlock because btrfs_remove_qgroup() needs
         * to lock that mutex while holding a transaction handle and the rescan
         * worker needs to commit a transaction.
         */
        mutex_unlock(&fs_info->qgroup_ioctl_lock);

        /*
         * Request qgroup rescan worker to complete and wait for it. This wait
         * must be done before transaction start for quota disable since it may
         * deadlock with transaction by the qgroup rescan worker.
         */
        clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
        btrfs_qgroup_wait_for_completion(fs_info, false);

        ret = flush_reservations(fs_info);
        if (ret)
                goto out_unlock_cleaner;

        /*
         * 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;
                set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
                goto out;
        }

        if (!fs_info->quota_root)
                goto out;

        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;
        fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_SIMPLE_MODE;
        fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL;
        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;
        }

        spin_lock(&fs_info->trans_lock);
        list_del(&quota_root->dirty_list);
        spin_unlock(&fs_info->trans_lock);

        btrfs_tree_lock(quota_root->node);
        btrfs_clear_buffer_dirty(trans, quota_root->node);
        btrfs_tree_unlock(quota_root->node);
        btrfs_free_tree_block(trans, btrfs_root_id(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_commit_transaction(trans);
out_unlock_cleaner:
        mutex_unlock(&fs_info->cleaner_mutex);

        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);
}

static void qgroup_iterator_add(struct list_head *head, struct btrfs_qgroup *qgroup)
{
        if (!list_empty(&qgroup->iterator))
                return;

        list_add_tail(&qgroup->iterator, head);
}

static void qgroup_iterator_clean(struct list_head *head)
{
        while (!list_empty(head)) {
                struct btrfs_qgroup *qgroup;

                qgroup = list_first_entry(head, struct btrfs_qgroup, iterator);
                list_del_init(&qgroup->iterator);
        }
}

/*
 * 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, u64 ref_root,
                                    struct btrfs_qgroup *src, int sign)
{
        struct btrfs_qgroup *qgroup;
        struct btrfs_qgroup *cur;
        LIST_HEAD(qgroup_list);
        u64 num_bytes = src->excl;
        int ret = 0;

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

        qgroup_iterator_add(&qgroup_list, qgroup);
        list_for_each_entry(cur, &qgroup_list, iterator) {
                struct btrfs_qgroup_list *glist;

                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);

                /* Append parent qgroups to @qgroup_list. */
                list_for_each_entry(glist, &qgroup->groups, next_group)
                        qgroup_iterator_add(&qgroup_list, glist->group);
        }
        ret = 0;
out:
        qgroup_iterator_clean(&qgroup_list);
        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,
                                   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, 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 btrfs_qgroup_list *prealloc = NULL;
        int ret = 0;

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

        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;
                }
        }

        prealloc = kzalloc(sizeof(*list), GFP_NOFS);
        if (!prealloc) {
                ret = -ENOMEM;
                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(prealloc, member, parent);
        prealloc = NULL;
        if (ret < 0) {
                spin_unlock(&fs_info->qgroup_lock);
                goto out;
        }
        ret = quick_update_accounting(fs_info, src, dst, 1);
        spin_unlock(&fs_info->qgroup_lock);
out:
        kfree(prealloc);
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        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;
        bool found = false;
        int ret = 0;
        int ret2;

        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, src, dst, -1);
                spin_unlock(&fs_info->qgroup_lock);
        }
out:
        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;
        struct btrfs_qgroup *prealloc = NULL;
        int ret = 0;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED)
                return 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;
        }

        prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS);
        if (!prealloc) {
                ret = -ENOMEM;
                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, prealloc, qgroupid);
        spin_unlock(&fs_info->qgroup_lock);
        prealloc = NULL;

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

static bool qgroup_has_usage(struct btrfs_qgroup *qgroup)
{
        return (qgroup->rfer > 0 || qgroup->rfer_cmpr > 0 ||
                qgroup->excl > 0 || qgroup->excl_cmpr > 0 ||
                qgroup->rsv.values[BTRFS_QGROUP_RSV_DATA] > 0 ||
                qgroup->rsv.values[BTRFS_QGROUP_RSV_META_PREALLOC] > 0 ||
                qgroup->rsv.values[BTRFS_QGROUP_RSV_META_PERTRANS] > 0);
}

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;
        }

        if (is_fstree(qgroupid) && qgroup_has_usage(qgroup)) {
                ret = -EBUSY;
                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) {
                qgroup_mark_inconsistent(fs_info);
                btrfs_info(fs_info, "unable to update quota limit for %llu",
                       qgroupid);
        }

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

/*
 * Inform qgroup to trace one dirty extent, its info is recorded in @record.
 * So qgroup can account it at transaction committing time.
 *
 * No lock version, caller must acquire delayed ref lock and allocated memory,
 * then call btrfs_qgroup_trace_extent_post() after exiting lock context.
 *
 * Return 0 for success insert
 * Return >0 for existing record, caller can free @record safely.
 * Error is not possible
 */
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;

        if (!btrfs_qgroup_full_accounting(fs_info))
                return 1;

        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;
}

/*
 * Post handler after qgroup_trace_extent_nolock().
 *
 * NOTE: Current qgroup does the expensive backref walk at transaction
 * committing time with TRANS_STATE_COMMIT_DOING, this blocks incoming
 * new transaction.
 * This is designed to allow btrfs_find_all_roots() to get correct new_roots
 * result.
 *
 * However for old_roots there is no need to do backref walk at that time,
 * since we search commit roots to walk backref and result will always be
 * correct.
 *
 * Due to the nature of no lock version, we can't do backref there.
 * So we must call btrfs_qgroup_trace_extent_post() after exiting
 * spinlock context.
 *
 * TODO: If we can fix and prove btrfs_find_all_roots() can get correct result
 * using current root, then we can move all expensive backref walk out of
 * transaction committing, but not now as qgroup accounting will be wrong again.
 */
int btrfs_qgroup_trace_extent_post(struct btrfs_trans_handle *trans,
                                   struct btrfs_qgroup_extent_record *qrecord)
{
        struct btrfs_backref_walk_ctx ctx = { 0 };
        int ret;

        if (!btrfs_qgroup_full_accounting(trans->fs_info))
                return 0;
        /*
         * 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);

        if (trans->fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING)
                return 0;

        ctx.bytenr = qrecord->bytenr;
        ctx.fs_info = trans->fs_info;

        ret = btrfs_find_all_roots(&ctx, true);
        if (ret < 0) {
                qgroup_mark_inconsistent(trans->fs_info);
                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 = ctx.roots;
        return 0;
}

/*
 * Inform qgroup to trace one dirty extent, specified by @bytenr and
 * @num_bytes.
 * So qgroup can account it at commit trans time.
 *
 * Better encapsulated version, with memory allocation and backref walk for
 * commit roots.
 * So this can sleep.
 *
 * Return 0 if the operation is done.
 * Return <0 for error, like memory allocation failure or invalid parameter
 * (NULL trans)
 */
int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans, u64 bytenr,
                              u64 num_bytes)
{
        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 (!btrfs_qgroup_full_accounting(fs_info) || bytenr == 0 || num_bytes == 0)
                return 0;
        record = kzalloc(sizeof(*record), GFP_NOFS);
        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);
}

/*
 * Inform qgroup to trace all leaf items of data
 *
 * Return 0 for success
 * Return <0 for error(ENOMEM)
 */
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 (!btrfs_qgroup_full_accounting(fs_info))
                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);
                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);
        if (ret < 0)
                goto out;
        ret = btrfs_qgroup_trace_extent(trans, dst_path->nodes[dst_level]->start,
                                        nodesize);
        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 (!btrfs_qgroup_full_accounting(fs_info))
                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)
                qgroup_mark_inconsistent(fs_info);
        return ret;
}

/*
 * Inform qgroup to trace a whole subtree, including all its child tree
 * blocks and data.
 * The root tree block is specified by @root_eb.
 *
 * Normally used by relocation(tree block swap) and subvolume deletion.
 *
 * Return 0 for success
 * Return <0 for error(ENOMEM or tree search error)
 */
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;
        u8 drop_subptree_thres;
        struct extent_buffer *eb = root_eb;
        struct btrfs_path *path = NULL;

        ASSERT(0 <= root_level && root_level < BTRFS_MAX_LEVEL);
        ASSERT(root_eb != NULL);

        if (!btrfs_qgroup_full_accounting(fs_info))
                return 0;

        spin_lock(&fs_info->qgroup_lock);
        drop_subptree_thres = fs_info->qgroup_drop_subtree_thres;
        spin_unlock(&fs_info->qgroup_lock);

        /*
         * This function only gets called for snapshot drop, if we hit a high
         * node here, it means we are going to change ownership for quite a lot
         * of extents, which will greatly slow down btrfs_commit_transaction().
         *
         * So here if we find a high tree here, we just skip the accounting and
         * mark qgroup inconsistent.
         */
        if (root_level >= drop_subptree_thres) {
                qgroup_mark_inconsistent(fs_info);
                return 0;
        }

        if (!extent_buffer_uptodate(root_eb)) {
                struct btrfs_tree_parent_check check = {
                        .has_first_key = false,
                        .transid = root_gen,
                        .level = root_level
                };

                ret = btrfs_read_extent_buffer(root_eb, &check);
                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);
                        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;
}

static void qgroup_iterator_nested_add(struct list_head *head, struct btrfs_qgroup *qgroup)
{
        if (!list_empty(&qgroup->nested_iterator))
                return;

        list_add_tail(&qgroup->nested_iterator, head);
}

static void qgroup_iterator_nested_clean(struct list_head *head)
{
        while (!list_empty(head)) {
                struct btrfs_qgroup *qgroup;

                qgroup = list_first_entry(head, struct btrfs_qgroup, nested_iterator);
                list_del_init(&qgroup->nested_iterator);
        }
}

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

        if (!roots)
                return;
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(roots, &uiter))) {
                LIST_HEAD(tmp);

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

                qgroup_iterator_nested_add(qgroups, qg);
                qgroup_iterator_add(&tmp, qg);
                list_for_each_entry(qg, &tmp, iterator) {
                        struct btrfs_qgroup_list *glist;

                        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) {
                                qgroup_iterator_nested_add(qgroups, glist->group);
                                qgroup_iterator_add(&tmp, glist->group);
                        }
                }
                qgroup_iterator_clean(&tmp);
        }
}

/*
 * 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 void qgroup_update_counters(struct btrfs_fs_info *fs_info,
                                   struct list_head *qgroups, u64 nr_old_roots,
                                   u64 nr_new_roots, u64 num_bytes, u64 seq)
{
        struct btrfs_qgroup *qg;

        list_for_each_entry(qg, qgroups, nested_iterator) {
                u64 cur_new_count, cur_old_count;
                bool dirty = false;

                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);
        }
}

/*
 * 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;
        LIST_HEAD(qgroups);
        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 (!btrfs_qgroup_full_accounting(fs_info) ||
            fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING)
                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;

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

        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 */
        qgroup_update_refcnt(fs_info, old_roots, &qgroups, seq, UPDATE_OLD);

        /* Update new refcnts using new_roots */
        qgroup_update_refcnt(fs_info, new_roots, &qgroups, seq, UPDATE_NEW);

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

        /*
         * We're done using the iterator, release all its qgroups while holding
         * fs_info->qgroup_lock so that we don't race with btrfs_remove_qgroup()
         * and trigger use-after-free accesses to qgroups.
         */
        qgroup_iterator_nested_clean(&qgroups);

        /*
         * Bump qgroup_seq to avoid seq overlap
         */
        fs_info->qgroup_seq += max(nr_old_roots, nr_new_roots) + 1;
        spin_unlock(&fs_info->qgroup_lock);
out_free:
        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;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)
                return 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 && !(fs_info->qgroup_flags &
                              BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING)) {
                        struct btrfs_backref_walk_ctx ctx = { 0 };

                        ctx.bytenr = record->bytenr;
                        ctx.fs_info = fs_info;

                        /*
                         * Old roots should be searched when inserting qgroup
                         * extent record.
                         *
                         * But for INCONSISTENT (NO_ACCOUNTING) -> rescan case,
                         * we may have some record inserted during
                         * NO_ACCOUNTING (thus no old_roots populated), but
                         * later we start rescan, which clears NO_ACCOUNTING,
                         * leaving some inserted records without old_roots
                         * populated.
                         *
                         * Those cases are rare and should not cause too much
                         * time spent during commit_transaction().
                         */
                        if (!record->old_roots) {
                                /* Search commit root to find old_roots */
                                ret = btrfs_find_all_roots(&ctx, false);
                                if (ret < 0)
                                        goto cleanup;
                                record->old_roots = ctx.roots;
                                ctx.roots = NULL;
                        }

                        /*
                         * 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().
                         */
                        ctx.trans = trans;
                        ctx.time_seq = BTRFS_SEQ_LAST;
                        ret = btrfs_find_all_roots(&ctx, false);
                        if (ret < 0)
                                goto cleanup;
                        new_roots = ctx.roots;
                        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;
                }
                /* Free the reserved data space */
                btrfs_qgroup_free_refroot(fs_info,
                                record->data_rsv_refroot,
                                record->data_rsv,
                                BTRFS_QGROUP_RSV_DATA);
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;
}

/*
 * Writes all changed qgroups to disk.
 * Called by the transaction commit path and the qgroup assign ioctl.
 */
int btrfs_run_qgroups(struct btrfs_trans_handle *trans)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        int ret = 0;

        /*
         * In case we are called from the qgroup assign ioctl, assert that we
         * are holding the qgroup_ioctl_lock, otherwise we can race with a quota
         * disable operation (ioctl) and access a freed quota root.
         */
        if (trans->transaction->state != TRANS_STATE_COMMIT_DOING)
                lockdep_assert_held(&fs_info->qgroup_ioctl_lock);

        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)
                        qgroup_mark_inconsistent(fs_info);
                ret = update_qgroup_limit_item(trans, qgroup);
                if (ret)
                        qgroup_mark_inconsistent(fs_info);
                spin_lock(&fs_info->qgroup_lock);
        }
        if (btrfs_qgroup_enabled(fs_info))
                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)
                qgroup_mark_inconsistent(fs_info);

        return ret;
}

int btrfs_qgroup_check_inherit(struct btrfs_fs_info *fs_info,
                               struct btrfs_qgroup_inherit *inherit,
                               size_t size)
{
        if (inherit->flags & ~BTRFS_QGROUP_INHERIT_FLAGS_SUPP)
                return -EOPNOTSUPP;
        if (size < sizeof(*inherit) || size > PAGE_SIZE)
                return -EINVAL;

        /*
         * In the past we allowed btrfs_qgroup_inherit to specify to copy
         * rfer/excl numbers directly from other qgroups.  This behavior has
         * been disabled in userspace for a very long time, but here we should
         * also disable it in kernel, as this behavior is known to mark qgroup
         * inconsistent, and a rescan would wipe out the changes anyway.
         *
         * Reject any btrfs_qgroup_inherit with num_ref_copies or num_excl_copies.
         */
        if (inherit->num_ref_copies > 0 || inherit->num_excl_copies > 0)
                return -EINVAL;

        if (inherit->num_qgroups > PAGE_SIZE)
                return -EINVAL;

        if (size != struct_size(inherit, qgroups, inherit->num_qgroups))
                return -EINVAL;

        /*
         * Now check all the remaining qgroups, they should all:
         *
         * - Exist
         * - Be higher level qgroups.
         */
        for (int i = 0; i < inherit->num_qgroups; i++) {
                struct btrfs_qgroup *qgroup;
                u64 qgroupid = inherit->qgroups[i];

                if (btrfs_qgroup_level(qgroupid) == 0)
                        return -EINVAL;

                spin_lock(&fs_info->qgroup_lock);
                qgroup = find_qgroup_rb(fs_info, qgroupid);
                if (!qgroup) {
                        spin_unlock(&fs_info->qgroup_lock);
                        return -ENOENT;
                }
                spin_unlock(&fs_info->qgroup_lock);
        }
        return 0;
}

static int qgroup_auto_inherit(struct btrfs_fs_info *fs_info,
                               u64 inode_rootid,
                               struct btrfs_qgroup_inherit **inherit)
{
        int i = 0;
        u64 num_qgroups = 0;
        struct btrfs_qgroup *inode_qg;
        struct btrfs_qgroup_list *qg_list;
        struct btrfs_qgroup_inherit *res;
        size_t struct_sz;
        u64 *qgids;

        if (*inherit)
                return -EEXIST;

        inode_qg = find_qgroup_rb(fs_info, inode_rootid);
        if (!inode_qg)
                return -ENOENT;

        num_qgroups = list_count_nodes(&inode_qg->groups);

        if (!num_qgroups)
                return 0;

        struct_sz = struct_size(res, qgroups, num_qgroups);
        if (struct_sz == SIZE_MAX)
                return -ERANGE;

        res = kzalloc(struct_sz, GFP_NOFS);
        if (!res)
                return -ENOMEM;
        res->num_qgroups = num_qgroups;
        qgids = res->qgroups;

        list_for_each_entry(qg_list, &inode_qg->groups, next_group)
                qgids[i] = qg_list->group->qgroupid;

        *inherit = res;
        return 0;
}

/*
 * 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, u64 inode_rootid,
                         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;
        struct btrfs_qgroup *prealloc;
        struct btrfs_qgroup_list **qlist_prealloc = NULL;
        bool free_inherit = false;
        bool need_rescan = false;
        u32 level_size = 0;
        u64 nums;

        prealloc = kzalloc(sizeof(*prealloc), GFP_NOFS);
        if (!prealloc)
                return -ENOMEM;

        /*
         * 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 (!btrfs_qgroup_enabled(fs_info))
                goto out;

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

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE && !inherit) {
                ret = qgroup_auto_inherit(fs_info, inode_rootid, &inherit);
                if (ret)
                        goto out;
                free_inherit = true;
        }

        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;

                qlist_prealloc = kcalloc(inherit->num_qgroups,
                                         sizeof(struct btrfs_qgroup_list *),
                                         GFP_NOFS);
                if (!qlist_prealloc) {
                        ret = -ENOMEM;
                        goto out;
                }
                for (int i = 0; i < inherit->num_qgroups; i++) {
                        qlist_prealloc[i] = kzalloc(sizeof(struct btrfs_qgroup_list),
                                                    GFP_NOFS);
                        if (!qlist_prealloc[i]) {
                                ret = -ENOMEM;
                                goto out;
                        }
                }
        }

        spin_lock(&fs_info->qgroup_lock);

        dstgroup = add_qgroup_rb(fs_info, prealloc, objectid);
        prealloc = NULL;

        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;

                qgroup_dirty(fs_info, dstgroup);
        }

        if (srcid && btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_FULL) {
                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, qlist_prealloc[i], objectid,
                                              *i_qgroups);
                        qlist_prealloc[i] = NULL;
                        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)
                qgroup_mark_inconsistent(fs_info);
        if (qlist_prealloc) {
                for (int i = 0; i < inherit->num_qgroups; i++)
                        kfree(qlist_prealloc[i]);
                kfree(qlist_prealloc);
        }
        if (free_inherit)
                kfree(inherit);
        kfree(prealloc);
        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;
        LIST_HEAD(qgroup_list);

        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)
                goto out;

        qgroup_iterator_add(&qgroup_list, qgroup);
        list_for_each_entry(qgroup, &qgroup_list, iterator) {
                struct btrfs_qgroup_list *glist;

                if (enforce && !qgroup_check_limits(qgroup, num_bytes)) {
                        ret = -EDQUOT;
                        goto out;
                }

                list_for_each_entry(glist, &qgroup->groups, next_group)
                        qgroup_iterator_add(&qgroup_list, glist->group);
        }

        ret = 0;
        /*
         * no limits exceeded, now record the reservation into all qgroups
         */
        list_for_each_entry(qgroup, &qgroup_list, iterator)
                qgroup_rsv_add(fs_info, qgroup, num_bytes, type);

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

/*
 * Free @num_bytes of reserved space with @type for qgroup.  (Normally level 0
 * qgroup).
 *
 * Will handle all higher level qgroup too.
 *
 * NOTE: If @num_bytes is (u64)-1, this means to free all bytes of this qgroup.
 * This special case is only used for META_PERTRANS type.
 */
void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
                               u64 ref_root, u64 num_bytes,
                               enum btrfs_qgroup_rsv_type type)
{
        struct btrfs_qgroup *qgroup;
        LIST_HEAD(qgroup_list);

        if (!is_fstree(ref_root))
                return;

        if (num_bytes == 0)
                return;

        if (num_bytes == (u64)-1 && type != BTRFS_QGROUP_RSV_META_PERTRANS) {
                WARN(1, "%s: Invalid type to free", __func__);
                return;
        }
        spin_lock(&fs_info->qgroup_lock);

        if (!fs_info->quota_root)
                goto out;

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

        if (num_bytes == (u64)-1)
                /*
                 * We're freeing all pertrans rsv, get reserved value from
                 * level 0 qgroup as real num_bytes to free.
                 */
                num_bytes = qgroup->rsv.values[type];

        qgroup_iterator_add(&qgroup_list, qgroup);
        list_for_each_entry(qgroup, &qgroup_list, iterator) {
                struct btrfs_qgroup_list *glist;

                qgroup_rsv_release(fs_info, qgroup, num_bytes, type);
                list_for_each_entry(glist, &qgroup->groups, next_group) {
                        qgroup_iterator_add(&qgroup_list, glist->group);
                }
        }
out:
        qgroup_iterator_clean(&qgroup_list);
        spin_unlock(&fs_info->qgroup_lock);
}

/*
 * Check if the leaf is the last leaf. Which means all node pointers
 * are at their last position.
 */
static bool is_last_leaf(struct btrfs_path *path)
{
        int i;

        for (i = 1; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
                if (path->slots[i] != btrfs_header_nritems(path->nodes[i]) - 1)
                        return false;
        }
        return true;
}

/*
 * returns < 0 on error, 0 when more leafs are to be scanned.
 * returns 1 when done.
 */
static int qgroup_rescan_leaf(struct btrfs_trans_handle *trans,
                              struct btrfs_path *path)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_root *extent_root;
        struct btrfs_key found;
        struct extent_buffer *scratch_leaf = NULL;
        u64 num_bytes;
        bool done;
        int slot;
        int ret;

        if (!btrfs_qgroup_full_accounting(fs_info))
                return 1;

        mutex_lock(&fs_info->qgroup_rescan_lock);
        extent_root = btrfs_extent_root(fs_info,
                                fs_info->qgroup_rescan_progress.objectid);
        ret = btrfs_search_slot_for_read(extent_root,
                                         &fs_info->qgroup_rescan_progress,
                                         path, 1, 0);

        btrfs_debug(fs_info,
                "current progress key (%llu %u %llu), search_slot ret %d",
                fs_info->qgroup_rescan_progress.objectid,
                fs_info->qgroup_rescan_progress.type,
                fs_info->qgroup_rescan_progress.offset, ret);

        if (ret) {
                /*
                 * The rescan is about to end, we will not be scanning any
                 * further blocks. We cannot unset the RESCAN flag here, because
                 * we want to commit the transaction if everything went well.
                 * To make the live accounting work in this phase, we set our
                 * scan progress pointer such that every real extent objectid
                 * will be smaller.
                 */
                fs_info->qgroup_rescan_progress.objectid = (u64)-1;
                btrfs_release_path(path);
                mutex_unlock(&fs_info->qgroup_rescan_lock);
                return ret;
        }
        done = is_last_leaf(path);

        btrfs_item_key_to_cpu(path->nodes[0], &found,
                              btrfs_header_nritems(path->nodes[0]) - 1);
        fs_info->qgroup_rescan_progress.objectid = found.objectid + 1;

        scratch_leaf = btrfs_clone_extent_buffer(path->nodes[0]);
        if (!scratch_leaf) {
                ret = -ENOMEM;
                mutex_unlock(&fs_info->qgroup_rescan_lock);
                goto out;
        }
        slot = path->slots[0];
        btrfs_release_path(path);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        for (; slot < btrfs_header_nritems(scratch_leaf); ++slot) {
                struct btrfs_backref_walk_ctx ctx = { 0 };

                btrfs_item_key_to_cpu(scratch_leaf, &found, slot);
                if (found.type != BTRFS_EXTENT_ITEM_KEY &&
                    found.type != BTRFS_METADATA_ITEM_KEY)
                        continue;
                if (found.type == BTRFS_METADATA_ITEM_KEY)
                        num_bytes = fs_info->nodesize;
                else
                        num_bytes = found.offset;

                ctx.bytenr = found.objectid;
                ctx.fs_info = fs_info;

                ret = btrfs_find_all_roots(&ctx, false);
                if (ret < 0)
                        goto out;
                /* For rescan, just pass old_roots as NULL */
                ret = btrfs_qgroup_account_extent(trans, found.objectid,
                                                  num_bytes, NULL, ctx.roots);
                if (ret < 0)
                        goto out;
        }
out:
        if (scratch_leaf)
                free_extent_buffer(scratch_leaf);

        if (done && !ret) {
                ret = 1;
                fs_info->qgroup_rescan_progress.objectid = (u64)-1;
        }
        return ret;
}

static bool rescan_should_stop(struct btrfs_fs_info *fs_info)
{
        if (btrfs_fs_closing(fs_info))
                return true;
        if (test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state))
                return true;
        if (!btrfs_qgroup_enabled(fs_info))
                return true;
        if (fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN)
                return true;
        return false;
}

static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
{
        struct btrfs_fs_info *fs_info = container_of(work, struct btrfs_fs_info,
                                                     qgroup_rescan_work);
        struct btrfs_path *path;
        struct btrfs_trans_handle *trans = NULL;
        int err = -ENOMEM;
        int ret = 0;
        bool stopped = false;
        bool did_leaf_rescans = false;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)
                return;

        path = btrfs_alloc_path();
        if (!path)
                goto out;
        /*
         * Rescan should only search for commit root, and any later difference
         * should be recorded by qgroup
         */
        path->search_commit_root = 1;
        path->skip_locking = 1;

        err = 0;
        while (!err && !(stopped = rescan_should_stop(fs_info))) {
                trans = btrfs_start_transaction(fs_info->fs_root, 0);
                if (IS_ERR(trans)) {
                        err = PTR_ERR(trans);
                        break;
                }

                err = qgroup_rescan_leaf(trans, path);
                did_leaf_rescans = true;

                if (err > 0)
                        btrfs_commit_transaction(trans);
                else
                        btrfs_end_transaction(trans);
        }

out:
        btrfs_free_path(path);

        mutex_lock(&fs_info->qgroup_rescan_lock);
        if (err > 0 &&
            fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        } else if (err < 0 || stopped) {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        }
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        /*
         * Only update status, since the previous part has already updated the
         * qgroup info, and only if we did any actual work. This also prevents
         * race with a concurrent quota disable, which has already set
         * fs_info->quota_root to NULL and cleared BTRFS_FS_QUOTA_ENABLED at
         * btrfs_quota_disable().
         */
        if (did_leaf_rescans) {
                trans = btrfs_start_transaction(fs_info->quota_root, 1);
                if (IS_ERR(trans)) {
                        err = PTR_ERR(trans);
                        trans = NULL;
                        btrfs_err(fs_info,
                                  "fail to start transaction for status update: %d",
                                  err);
                }
        } else {
                trans = NULL;
        }

        mutex_lock(&fs_info->qgroup_rescan_lock);
        if (!stopped ||
            fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN)
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
        if (trans) {
                ret = update_qgroup_status_item(trans);
                if (ret < 0) {
                        err = ret;
                        btrfs_err(fs_info, "fail to update qgroup status: %d",
                                  err);
                }
        }
        fs_info->qgroup_rescan_running = false;
        fs_info->qgroup_flags &= ~BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN;
        complete_all(&fs_info->qgroup_rescan_completion);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        if (!trans)
                return;

        btrfs_end_transaction(trans);

        if (stopped) {
                btrfs_info(fs_info, "qgroup scan paused");
        } else if (fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN) {
                btrfs_info(fs_info, "qgroup scan cancelled");
        } else if (err >= 0) {
                btrfs_info(fs_info, "qgroup scan completed%s",
                        err > 0 ? " (inconsistency flag cleared)" : "");
        } else {
                btrfs_err(fs_info, "qgroup scan failed with %d", err);
        }
}

/*
 * Checks that (a) no rescan is running and (b) quota is enabled. Allocates all
 * memory required for the rescan context.
 */
static int
qgroup_rescan_init(struct btrfs_fs_info *fs_info, u64 progress_objectid,
                   int init_flags)
{
        int ret = 0;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE) {
                btrfs_warn(fs_info, "qgroup rescan init failed, running in simple mode");
                return -EINVAL;
        }

        if (!init_flags) {
                /* we're resuming qgroup rescan at mount time */
                if (!(fs_info->qgroup_flags &
                      BTRFS_QGROUP_STATUS_FLAG_RESCAN)) {
                        btrfs_warn(fs_info,
                        "qgroup rescan init failed, qgroup rescan is not queued");
                        ret = -EINVAL;
                } else if (!(fs_info->qgroup_flags &
                             BTRFS_QGROUP_STATUS_FLAG_ON)) {
                        btrfs_warn(fs_info,
                        "qgroup rescan init failed, qgroup is not enabled");
                        ret = -EINVAL;
                }

                if (ret)
                        return ret;
        }

        mutex_lock(&fs_info->qgroup_rescan_lock);

        if (init_flags) {
                if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
                        btrfs_warn(fs_info,
                                   "qgroup rescan is already in progress");
                        ret = -EINPROGRESS;
                } else if (!(fs_info->qgroup_flags &
                             BTRFS_QGROUP_STATUS_FLAG_ON)) {
                        btrfs_warn(fs_info,
                        "qgroup rescan init failed, qgroup is not enabled");
                        ret = -EINVAL;
                } else if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED) {
                        /* Quota disable is in progress */
                        ret = -EBUSY;
                }

                if (ret) {
                        mutex_unlock(&fs_info->qgroup_rescan_lock);
                        return ret;
                }
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
        }

        memset(&fs_info->qgroup_rescan_progress, 0,
                sizeof(fs_info->qgroup_rescan_progress));
        fs_info->qgroup_flags &= ~(BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN |
                                   BTRFS_QGROUP_RUNTIME_FLAG_NO_ACCOUNTING);
        fs_info->qgroup_rescan_progress.objectid = progress_objectid;
        init_completion(&fs_info->qgroup_rescan_completion);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        btrfs_init_work(&fs_info->qgroup_rescan_work,
                        btrfs_qgroup_rescan_worker, NULL);
        return 0;
}

static void
qgroup_rescan_zero_tracking(struct btrfs_fs_info *fs_info)
{
        struct rb_node *n;
        struct btrfs_qgroup *qgroup;

        spin_lock(&fs_info->qgroup_lock);
        /* clear all current qgroup tracking information */
        for (n = rb_first(&fs_info->qgroup_tree); n; n = rb_next(n)) {
                qgroup = rb_entry(n, struct btrfs_qgroup, node);
                qgroup->rfer = 0;
                qgroup->rfer_cmpr = 0;
                qgroup->excl = 0;
                qgroup->excl_cmpr = 0;
                qgroup_dirty(fs_info, qgroup);
        }
        spin_unlock(&fs_info->qgroup_lock);
}

int
btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
{
        int ret = 0;
        struct btrfs_trans_handle *trans;

        ret = qgroup_rescan_init(fs_info, 0, 1);
        if (ret)
                return ret;

        /*
         * We have set the rescan_progress to 0, which means no more
         * delayed refs will be accounted by btrfs_qgroup_account_ref.
         * However, btrfs_qgroup_account_ref may be right after its call
         * to btrfs_find_all_roots, in which case it would still do the
         * accounting.
         * To solve this, we're committing the transaction, which will
         * ensure we run all delayed refs and only after that, we are
         * going to clear all tracking information for a clean start.
         */

        trans = btrfs_attach_transaction_barrier(fs_info->fs_root);
        if (IS_ERR(trans) && trans != ERR_PTR(-ENOENT)) {
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
                return PTR_ERR(trans);
        } else if (trans != ERR_PTR(-ENOENT)) {
                ret = btrfs_commit_transaction(trans);
                if (ret) {
                        fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
                        return ret;
                }
        }

        qgroup_rescan_zero_tracking(fs_info);

        mutex_lock(&fs_info->qgroup_rescan_lock);
        fs_info->qgroup_rescan_running = true;
        btrfs_queue_work(fs_info->qgroup_rescan_workers,
                         &fs_info->qgroup_rescan_work);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        return 0;
}

int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info,
                                     bool interruptible)
{
        int running;
        int ret = 0;

        mutex_lock(&fs_info->qgroup_rescan_lock);
        running = fs_info->qgroup_rescan_running;
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        if (!running)
                return 0;

        if (interruptible)
                ret = wait_for_completion_interruptible(
                                        &fs_info->qgroup_rescan_completion);
        else
                wait_for_completion(&fs_info->qgroup_rescan_completion);

        return ret;
}

/*
 * this is only called from open_ctree where we're still single threaded, thus
 * locking is omitted here.
 */
void
btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info)
{
        if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) {
                mutex_lock(&fs_info->qgroup_rescan_lock);
                fs_info->qgroup_rescan_running = true;
                btrfs_queue_work(fs_info->qgroup_rescan_workers,
                                 &fs_info->qgroup_rescan_work);
                mutex_unlock(&fs_info->qgroup_rescan_lock);
        }
}

#define rbtree_iterate_from_safe(node, next, start)                             \
       for (node = start; node && ({ next = rb_next(node); 1;}); node = next)

static int qgroup_unreserve_range(struct btrfs_inode *inode,
                                  struct extent_changeset *reserved, u64 start,
                                  u64 len)
{
        struct rb_node *node;
        struct rb_node *next;
        struct ulist_node *entry;
        int ret = 0;

        node = reserved->range_changed.root.rb_node;
        if (!node)
                return 0;
        while (node) {
                entry = rb_entry(node, struct ulist_node, rb_node);
                if (entry->val < start)
                        node = node->rb_right;
                else
                        node = node->rb_left;
        }

        if (entry->val > start && rb_prev(&entry->rb_node))
                entry = rb_entry(rb_prev(&entry->rb_node), struct ulist_node,
                                 rb_node);

        rbtree_iterate_from_safe(node, next, &entry->rb_node) {
                u64 entry_start;
                u64 entry_end;
                u64 entry_len;
                int clear_ret;

                entry = rb_entry(node, struct ulist_node, rb_node);
                entry_start = entry->val;
                entry_end = entry->aux;
                entry_len = entry_end - entry_start + 1;

                if (entry_start >= start + len)
                        break;
                if (entry_start + entry_len <= start)
                        continue;
                /*
                 * Now the entry is in [start, start + len), revert the
                 * EXTENT_QGROUP_RESERVED bit.
                 */
                clear_ret = clear_extent_bits(&inode->io_tree, entry_start,
                                              entry_end, EXTENT_QGROUP_RESERVED);
                if (!ret && clear_ret < 0)
                        ret = clear_ret;

                ulist_del(&reserved->range_changed, entry->val, entry->aux);
                if (likely(reserved->bytes_changed >= entry_len)) {
                        reserved->bytes_changed -= entry_len;
                } else {
                        WARN_ON(1);
                        reserved->bytes_changed = 0;
                }
        }

        return ret;
}

/*
 * Try to free some space for qgroup.
 *
 * For qgroup, there are only 3 ways to free qgroup space:
 * - Flush nodatacow write
 *   Any nodatacow write will free its reserved data space at run_delalloc_range().
 *   In theory, we should only flush nodatacow inodes, but it's not yet
 *   possible, so we need to flush the whole root.
 *
 * - Wait for ordered extents
 *   When ordered extents are finished, their reserved metadata is finally
 *   converted to per_trans status, which can be freed by later commit
 *   transaction.
 *
 * - Commit transaction
 *   This would free the meta_per_trans space.
 *   In theory this shouldn't provide much space, but any more qgroup space
 *   is needed.
 */
static int try_flush_qgroup(struct btrfs_root *root)
{
        struct btrfs_trans_handle *trans;
        int ret;

        /* Can't hold an open transaction or we run the risk of deadlocking. */
        ASSERT(current->journal_info == NULL);
        if (WARN_ON(current->journal_info))
                return 0;

        /*
         * We don't want to run flush again and again, so if there is a running
         * one, we won't try to start a new flush, but exit directly.
         */
        if (test_and_set_bit(BTRFS_ROOT_QGROUP_FLUSHING, &root->state)) {
                wait_event(root->qgroup_flush_wait,
                        !test_bit(BTRFS_ROOT_QGROUP_FLUSHING, &root->state));
                return 0;
        }

        ret = btrfs_start_delalloc_snapshot(root, true);
        if (ret < 0)
                goto out;
        btrfs_wait_ordered_extents(root, U64_MAX, 0, (u64)-1);

        trans = btrfs_attach_transaction_barrier(root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                if (ret == -ENOENT)
                        ret = 0;
                goto out;
        }

        ret = btrfs_commit_transaction(trans);
out:
        clear_bit(BTRFS_ROOT_QGROUP_FLUSHING, &root->state);
        wake_up(&root->qgroup_flush_wait);
        return ret;
}

static int qgroup_reserve_data(struct btrfs_inode *inode,
                        struct extent_changeset **reserved_ret, u64 start,
                        u64 len)
{
        struct btrfs_root *root = inode->root;
        struct extent_changeset *reserved;
        bool new_reserved = false;
        u64 orig_reserved;
        u64 to_reserve;
        int ret;

        if (btrfs_qgroup_mode(root->fs_info) == BTRFS_QGROUP_MODE_DISABLED ||
            !is_fstree(root->root_key.objectid) || len == 0)
                return 0;

        /* @reserved parameter is mandatory for qgroup */
        if (WARN_ON(!reserved_ret))
                return -EINVAL;
        if (!*reserved_ret) {
                new_reserved = true;
                *reserved_ret = extent_changeset_alloc();
                if (!*reserved_ret)
                        return -ENOMEM;
        }
        reserved = *reserved_ret;
        /* Record already reserved space */
        orig_reserved = reserved->bytes_changed;
        ret = set_record_extent_bits(&inode->io_tree, start,
                        start + len -1, EXTENT_QGROUP_RESERVED, reserved);

        /* Newly reserved space */
        to_reserve = reserved->bytes_changed - orig_reserved;
        trace_btrfs_qgroup_reserve_data(&inode->vfs_inode, start, len,
                                        to_reserve, QGROUP_RESERVE);
        if (ret < 0)
                goto out;
        ret = qgroup_reserve(root, to_reserve, true, BTRFS_QGROUP_RSV_DATA);
        if (ret < 0)
                goto cleanup;

        return ret;

cleanup:
        qgroup_unreserve_range(inode, reserved, start, len);
out:
        if (new_reserved) {
                extent_changeset_free(reserved);
                *reserved_ret = NULL;
        }
        return ret;
}

/*
 * Reserve qgroup space for range [start, start + len).
 *
 * This function will either reserve space from related qgroups or do nothing
 * if the range is already reserved.
 *
 * Return 0 for successful reservation
 * Return <0 for error (including -EQUOT)
 *
 * NOTE: This function may sleep for memory allocation, dirty page flushing and
 *       commit transaction. So caller should not hold any dirty page locked.
 */
int btrfs_qgroup_reserve_data(struct btrfs_inode *inode,
                        struct extent_changeset **reserved_ret, u64 start,
                        u64 len)
{
        int ret;

        ret = qgroup_reserve_data(inode, reserved_ret, start, len);
        if (ret <= 0 && ret != -EDQUOT)
                return ret;

        ret = try_flush_qgroup(inode->root);
        if (ret < 0)
                return ret;
        return qgroup_reserve_data(inode, reserved_ret, start, len);
}

/* Free ranges specified by @reserved, normally in error path */
static int qgroup_free_reserved_data(struct btrfs_inode *inode,
                                     struct extent_changeset *reserved,
                                     u64 start, u64 len, u64 *freed_ret)
{
        struct btrfs_root *root = inode->root;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct extent_changeset changeset;
        u64 freed = 0;
        int ret;

        extent_changeset_init(&changeset);
        len = round_up(start + len, root->fs_info->sectorsize);
        start = round_down(start, root->fs_info->sectorsize);

        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(&reserved->range_changed, &uiter))) {
                u64 range_start = unode->val;
                /* unode->aux is the inclusive end */
                u64 range_len = unode->aux - range_start + 1;
                u64 free_start;
                u64 free_len;

                extent_changeset_release(&changeset);

                /* Only free range in range [start, start + len) */
                if (range_start >= start + len ||
                    range_start + range_len <= start)
                        continue;
                free_start = max(range_start, start);
                free_len = min(start + len, range_start + range_len) -
                           free_start;
                /*
                 * TODO: To also modify reserved->ranges_reserved to reflect
                 * the modification.
                 *
                 * However as long as we free qgroup reserved according to
                 * EXTENT_QGROUP_RESERVED, we won't double free.
                 * So not need to rush.
                 */
                ret = clear_record_extent_bits(&inode->io_tree, free_start,
                                free_start + free_len - 1,
                                EXTENT_QGROUP_RESERVED, &changeset);
                if (ret < 0)
                        goto out;
                freed += changeset.bytes_changed;
        }
        btrfs_qgroup_free_refroot(root->fs_info, root->root_key.objectid, freed,
                                  BTRFS_QGROUP_RSV_DATA);
        if (freed_ret)
                *freed_ret = freed;
        ret = 0;
out:
        extent_changeset_release(&changeset);
        return ret;
}

static int __btrfs_qgroup_release_data(struct btrfs_inode *inode,
                        struct extent_changeset *reserved, u64 start, u64 len,
                        u64 *released, int free)
{
        struct extent_changeset changeset;
        int trace_op = QGROUP_RELEASE;
        int ret;

        if (btrfs_qgroup_mode(inode->root->fs_info) == BTRFS_QGROUP_MODE_DISABLED) {
                extent_changeset_init(&changeset);
                return clear_record_extent_bits(&inode->io_tree, start,
                                                start + len - 1,
                                                EXTENT_QGROUP_RESERVED, &changeset);
        }

        /* In release case, we shouldn't have @reserved */
        WARN_ON(!free && reserved);
        if (free && reserved)
                return qgroup_free_reserved_data(inode, reserved, start, len, released);
        extent_changeset_init(&changeset);
        ret = clear_record_extent_bits(&inode->io_tree, start, start + len -1,
                                       EXTENT_QGROUP_RESERVED, &changeset);
        if (ret < 0)
                goto out;

        if (free)
                trace_op = QGROUP_FREE;
        trace_btrfs_qgroup_release_data(&inode->vfs_inode, start, len,
                                        changeset.bytes_changed, trace_op);
        if (free)
                btrfs_qgroup_free_refroot(inode->root->fs_info,
                                inode->root->root_key.objectid,
                                changeset.bytes_changed, BTRFS_QGROUP_RSV_DATA);
        if (released)
                *released = changeset.bytes_changed;
out:
        extent_changeset_release(&changeset);
        return ret;
}

/*
 * Free a reserved space range from io_tree and related qgroups
 *
 * Should be called when a range of pages get invalidated before reaching disk.
 * Or for error cleanup case.
 * if @reserved is given, only reserved range in [@start, @start + @len) will
 * be freed.
 *
 * For data written to disk, use btrfs_qgroup_release_data().
 *
 * NOTE: This function may sleep for memory allocation.
 */
int btrfs_qgroup_free_data(struct btrfs_inode *inode,
                           struct extent_changeset *reserved,
                           u64 start, u64 len, u64 *freed)
{
        return __btrfs_qgroup_release_data(inode, reserved, start, len, freed, 1);
}

/*
 * Release a reserved space range from io_tree only.
 *
 * Should be called when a range of pages get written to disk and corresponding
 * FILE_EXTENT is inserted into corresponding root.
 *
 * Since new qgroup accounting framework will only update qgroup numbers at
 * commit_transaction() time, its reserved space shouldn't be freed from
 * related qgroups.
 *
 * But we should release the range from io_tree, to allow further write to be
 * COWed.
 *
 * NOTE: This function may sleep for memory allocation.
 */
int btrfs_qgroup_release_data(struct btrfs_inode *inode, u64 start, u64 len, u64 *released)
{
        return __btrfs_qgroup_release_data(inode, NULL, start, len, released, 0);
}

static void add_root_meta_rsv(struct btrfs_root *root, int num_bytes,
                              enum btrfs_qgroup_rsv_type type)
{
        if (type != BTRFS_QGROUP_RSV_META_PREALLOC &&
            type != BTRFS_QGROUP_RSV_META_PERTRANS)
                return;
        if (num_bytes == 0)
                return;

        spin_lock(&root->qgroup_meta_rsv_lock);
        if (type == BTRFS_QGROUP_RSV_META_PREALLOC)
                root->qgroup_meta_rsv_prealloc += num_bytes;
        else
                root->qgroup_meta_rsv_pertrans += num_bytes;
        spin_unlock(&root->qgroup_meta_rsv_lock);
}

static int sub_root_meta_rsv(struct btrfs_root *root, int num_bytes,
                             enum btrfs_qgroup_rsv_type type)
{
        if (type != BTRFS_QGROUP_RSV_META_PREALLOC &&
            type != BTRFS_QGROUP_RSV_META_PERTRANS)
                return 0;
        if (num_bytes == 0)
                return 0;

        spin_lock(&root->qgroup_meta_rsv_lock);
        if (type == BTRFS_QGROUP_RSV_META_PREALLOC) {
                num_bytes = min_t(u64, root->qgroup_meta_rsv_prealloc,
                                  num_bytes);
                root->qgroup_meta_rsv_prealloc -= num_bytes;
        } else {
                num_bytes = min_t(u64, root->qgroup_meta_rsv_pertrans,
                                  num_bytes);
                root->qgroup_meta_rsv_pertrans -= num_bytes;
        }
        spin_unlock(&root->qgroup_meta_rsv_lock);
        return num_bytes;
}

int btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
                              enum btrfs_qgroup_rsv_type type, bool enforce)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        int ret;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED ||
            !is_fstree(root->root_key.objectid) || num_bytes == 0)
                return 0;

        BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
        trace_qgroup_meta_reserve(root, (s64)num_bytes, type);
        ret = qgroup_reserve(root, num_bytes, enforce, type);
        if (ret < 0)
                return ret;
        /*
         * Record what we have reserved into root.
         *
         * To avoid quota disabled->enabled underflow.
         * In that case, we may try to free space we haven't reserved
         * (since quota was disabled), so record what we reserved into root.
         * And ensure later release won't underflow this number.
         */
        add_root_meta_rsv(root, num_bytes, type);
        return ret;
}

int __btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
                                enum btrfs_qgroup_rsv_type type, bool enforce,
                                bool noflush)
{
        int ret;

        ret = btrfs_qgroup_reserve_meta(root, num_bytes, type, enforce);
        if ((ret <= 0 && ret != -EDQUOT) || noflush)
                return ret;

        ret = try_flush_qgroup(root);
        if (ret < 0)
                return ret;
        return btrfs_qgroup_reserve_meta(root, num_bytes, type, enforce);
}

/*
 * Per-transaction meta reservation should be all freed at transaction commit
 * time
 */
void btrfs_qgroup_free_meta_all_pertrans(struct btrfs_root *root)
{
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED ||
            !is_fstree(root->root_key.objectid))
                return;

        /* TODO: Update trace point to handle such free */
        trace_qgroup_meta_free_all_pertrans(root);
        /* Special value -1 means to free all reserved space */
        btrfs_qgroup_free_refroot(fs_info, root->root_key.objectid, (u64)-1,
                                  BTRFS_QGROUP_RSV_META_PERTRANS);
}

void __btrfs_qgroup_free_meta(struct btrfs_root *root, int num_bytes,
                              enum btrfs_qgroup_rsv_type type)
{
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED ||
            !is_fstree(root->root_key.objectid))
                return;

        /*
         * reservation for META_PREALLOC can happen before quota is enabled,
         * which can lead to underflow.
         * Here ensure we will only free what we really have reserved.
         */
        num_bytes = sub_root_meta_rsv(root, num_bytes, type);
        BUG_ON(num_bytes != round_down(num_bytes, fs_info->nodesize));
        trace_qgroup_meta_reserve(root, -(s64)num_bytes, type);
        btrfs_qgroup_free_refroot(fs_info, root->root_key.objectid,
                                  num_bytes, type);
}

static void qgroup_convert_meta(struct btrfs_fs_info *fs_info, u64 ref_root,
                                int num_bytes)
{
        struct btrfs_qgroup *qgroup;
        LIST_HEAD(qgroup_list);

        if (num_bytes == 0)
                return;
        if (!fs_info->quota_root)
                return;

        spin_lock(&fs_info->qgroup_lock);
        qgroup = find_qgroup_rb(fs_info, ref_root);
        if (!qgroup)
                goto out;

        qgroup_iterator_add(&qgroup_list, qgroup);
        list_for_each_entry(qgroup, &qgroup_list, iterator) {
                struct btrfs_qgroup_list *glist;

                qgroup_rsv_release(fs_info, qgroup, num_bytes,
                                BTRFS_QGROUP_RSV_META_PREALLOC);
                if (!sb_rdonly(fs_info->sb))
                        qgroup_rsv_add(fs_info, qgroup, num_bytes,
                                       BTRFS_QGROUP_RSV_META_PERTRANS);

                list_for_each_entry(glist, &qgroup->groups, next_group)
                        qgroup_iterator_add(&qgroup_list, glist->group);
        }
out:
        qgroup_iterator_clean(&qgroup_list);
        spin_unlock(&fs_info->qgroup_lock);
}

/*
 * Convert @num_bytes of META_PREALLOCATED reservation to META_PERTRANS.
 *
 * This is called when preallocated meta reservation needs to be used.
 * Normally after btrfs_join_transaction() call.
 */
void btrfs_qgroup_convert_reserved_meta(struct btrfs_root *root, int num_bytes)
{
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED ||
            !is_fstree(root->root_key.objectid))
                return;
        /* Same as btrfs_qgroup_free_meta_prealloc() */
        num_bytes = sub_root_meta_rsv(root, num_bytes,
                                      BTRFS_QGROUP_RSV_META_PREALLOC);
        trace_qgroup_meta_convert(root, num_bytes);
        qgroup_convert_meta(fs_info, root->root_key.objectid, num_bytes);
}

/*
 * Check qgroup reserved space leaking, normally at destroy inode
 * time
 */
void btrfs_qgroup_check_reserved_leak(struct btrfs_inode *inode)
{
        struct extent_changeset changeset;
        struct ulist_node *unode;
        struct ulist_iterator iter;
        int ret;

        extent_changeset_init(&changeset);
        ret = clear_record_extent_bits(&inode->io_tree, 0, (u64)-1,
                        EXTENT_QGROUP_RESERVED, &changeset);

        WARN_ON(ret < 0);
        if (WARN_ON(changeset.bytes_changed)) {
                ULIST_ITER_INIT(&iter);
                while ((unode = ulist_next(&changeset.range_changed, &iter))) {
                        btrfs_warn(inode->root->fs_info,
                "leaking qgroup reserved space, ino: %llu, start: %llu, end: %llu",
                                btrfs_ino(inode), unode->val, unode->aux);
                }
                btrfs_qgroup_free_refroot(inode->root->fs_info,
                                inode->root->root_key.objectid,
                                changeset.bytes_changed, BTRFS_QGROUP_RSV_DATA);

        }
        extent_changeset_release(&changeset);
}

void btrfs_qgroup_init_swapped_blocks(
        struct btrfs_qgroup_swapped_blocks *swapped_blocks)
{
        int i;

        spin_lock_init(&swapped_blocks->lock);
        for (i = 0; i < BTRFS_MAX_LEVEL; i++)
                swapped_blocks->blocks[i] = RB_ROOT;
        swapped_blocks->swapped = false;
}

/*
 * Delete all swapped blocks record of @root.
 * Every record here means we skipped a full subtree scan for qgroup.
 *
 * Gets called when committing one transaction.
 */
void btrfs_qgroup_clean_swapped_blocks(struct btrfs_root *root)
{
        struct btrfs_qgroup_swapped_blocks *swapped_blocks;
        int i;

        swapped_blocks = &root->swapped_blocks;

        spin_lock(&swapped_blocks->lock);
        if (!swapped_blocks->swapped)
                goto out;
        for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
                struct rb_root *cur_root = &swapped_blocks->blocks[i];
                struct btrfs_qgroup_swapped_block *entry;
                struct btrfs_qgroup_swapped_block *next;

                rbtree_postorder_for_each_entry_safe(entry, next, cur_root,
                                                     node)
                        kfree(entry);
                swapped_blocks->blocks[i] = RB_ROOT;
        }
        swapped_blocks->swapped = false;
out:
        spin_unlock(&swapped_blocks->lock);
}

/*
 * Add subtree roots record into @subvol_root.
 *
 * @subvol_root:        tree root of the subvolume tree get swapped
 * @bg:                 block group under balance
 * @subvol_parent/slot: pointer to the subtree root in subvolume tree
 * @reloc_parent/slot:  pointer to the subtree root in reloc tree
 *                      BOTH POINTERS ARE BEFORE TREE SWAP
 * @last_snapshot:      last snapshot generation of the subvolume tree
 */
int btrfs_qgroup_add_swapped_blocks(struct btrfs_trans_handle *trans,
                struct btrfs_root *subvol_root,
                struct btrfs_block_group *bg,
                struct extent_buffer *subvol_parent, int subvol_slot,
                struct extent_buffer *reloc_parent, int reloc_slot,
                u64 last_snapshot)
{
        struct btrfs_fs_info *fs_info = subvol_root->fs_info;
        struct btrfs_qgroup_swapped_blocks *blocks = &subvol_root->swapped_blocks;
        struct btrfs_qgroup_swapped_block *block;
        struct rb_node **cur;
        struct rb_node *parent = NULL;
        int level = btrfs_header_level(subvol_parent) - 1;
        int ret = 0;

        if (!btrfs_qgroup_full_accounting(fs_info))
                return 0;

        if (btrfs_node_ptr_generation(subvol_parent, subvol_slot) >
            btrfs_node_ptr_generation(reloc_parent, reloc_slot)) {
                btrfs_err_rl(fs_info,
                "%s: bad parameter order, subvol_gen=%llu reloc_gen=%llu",
                        __func__,
                        btrfs_node_ptr_generation(subvol_parent, subvol_slot),
                        btrfs_node_ptr_generation(reloc_parent, reloc_slot));
                return -EUCLEAN;
        }

        block = kmalloc(sizeof(*block), GFP_NOFS);
        if (!block) {
                ret = -ENOMEM;
                goto out;
        }

        /*
         * @reloc_parent/slot is still before swap, while @block is going to
         * record the bytenr after swap, so we do the swap here.
         */
        block->subvol_bytenr = btrfs_node_blockptr(reloc_parent, reloc_slot);
        block->subvol_generation = btrfs_node_ptr_generation(reloc_parent,
                                                             reloc_slot);
        block->reloc_bytenr = btrfs_node_blockptr(subvol_parent, subvol_slot);
        block->reloc_generation = btrfs_node_ptr_generation(subvol_parent,
                                                            subvol_slot);
        block->last_snapshot = last_snapshot;
        block->level = level;

        /*
         * If we have bg == NULL, we're called from btrfs_recover_relocation(),
         * no one else can modify tree blocks thus we qgroup will not change
         * no matter the value of trace_leaf.
         */
        if (bg && bg->flags & BTRFS_BLOCK_GROUP_DATA)
                block->trace_leaf = true;
        else
                block->trace_leaf = false;
        btrfs_node_key_to_cpu(reloc_parent, &block->first_key, reloc_slot);

        /* Insert @block into @blocks */
        spin_lock(&blocks->lock);
        cur = &blocks->blocks[level].rb_node;
        while (*cur) {
                struct btrfs_qgroup_swapped_block *entry;

                parent = *cur;
                entry = rb_entry(parent, struct btrfs_qgroup_swapped_block,
                                 node);

                if (entry->subvol_bytenr < block->subvol_bytenr) {
                        cur = &(*cur)->rb_left;
                } else if (entry->subvol_bytenr > block->subvol_bytenr) {
                        cur = &(*cur)->rb_right;
                } else {
                        if (entry->subvol_generation !=
                                        block->subvol_generation ||
                            entry->reloc_bytenr != block->reloc_bytenr ||
                            entry->reloc_generation !=
                                        block->reloc_generation) {
                                /*
                                 * Duplicated but mismatch entry found.
                                 * Shouldn't happen.
                                 *
                                 * Marking qgroup inconsistent should be enough
                                 * for end users.
                                 */
                                WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
                                ret = -EEXIST;
                        }
                        kfree(block);
                        goto out_unlock;
                }
        }
        rb_link_node(&block->node, parent, cur);
        rb_insert_color(&block->node, &blocks->blocks[level]);
        blocks->swapped = true;
out_unlock:
        spin_unlock(&blocks->lock);
out:
        if (ret < 0)
                qgroup_mark_inconsistent(fs_info);
        return ret;
}

/*
 * Check if the tree block is a subtree root, and if so do the needed
 * delayed subtree trace for qgroup.
 *
 * This is called during btrfs_cow_block().
 */
int btrfs_qgroup_trace_subtree_after_cow(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root,
                                         struct extent_buffer *subvol_eb)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_tree_parent_check check = { 0 };
        struct btrfs_qgroup_swapped_blocks *blocks = &root->swapped_blocks;
        struct btrfs_qgroup_swapped_block *block;
        struct extent_buffer *reloc_eb = NULL;
        struct rb_node *node;
        bool found = false;
        bool swapped = false;
        int level = btrfs_header_level(subvol_eb);
        int ret = 0;
        int i;

        if (!btrfs_qgroup_full_accounting(fs_info))
                return 0;
        if (!is_fstree(root->root_key.objectid) || !root->reloc_root)
                return 0;

        spin_lock(&blocks->lock);
        if (!blocks->swapped) {
                spin_unlock(&blocks->lock);
                return 0;
        }
        node = blocks->blocks[level].rb_node;

        while (node) {
                block = rb_entry(node, struct btrfs_qgroup_swapped_block, node);
                if (block->subvol_bytenr < subvol_eb->start) {
                        node = node->rb_left;
                } else if (block->subvol_bytenr > subvol_eb->start) {
                        node = node->rb_right;
                } else {
                        found = true;
                        break;
                }
        }
        if (!found) {
                spin_unlock(&blocks->lock);
                goto out;
        }
        /* Found one, remove it from @blocks first and update blocks->swapped */
        rb_erase(&block->node, &blocks->blocks[level]);
        for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
                if (RB_EMPTY_ROOT(&blocks->blocks[i])) {
                        swapped = true;
                        break;
                }
        }
        blocks->swapped = swapped;
        spin_unlock(&blocks->lock);

        check.level = block->level;
        check.transid = block->reloc_generation;
        check.has_first_key = true;
        memcpy(&check.first_key, &block->first_key, sizeof(check.first_key));

        /* Read out reloc subtree root */
        reloc_eb = read_tree_block(fs_info, block->reloc_bytenr, &check);
        if (IS_ERR(reloc_eb)) {
                ret = PTR_ERR(reloc_eb);
                reloc_eb = NULL;
                goto free_out;
        }
        if (!extent_buffer_uptodate(reloc_eb)) {
                ret = -EIO;
                goto free_out;
        }

        ret = qgroup_trace_subtree_swap(trans, reloc_eb, subvol_eb,
                        block->last_snapshot, block->trace_leaf);
free_out:
        kfree(block);
        free_extent_buffer(reloc_eb);
out:
        if (ret < 0) {
                btrfs_err_rl(fs_info,
                             "failed to account subtree at bytenr %llu: %d",
                             subvol_eb->start, ret);
                qgroup_mark_inconsistent(fs_info);
        }
        return ret;
}

void btrfs_qgroup_destroy_extent_records(struct btrfs_transaction *trans)
{
        struct btrfs_qgroup_extent_record *entry;
        struct btrfs_qgroup_extent_record *next;
        struct rb_root *root;

        root = &trans->delayed_refs.dirty_extent_root;
        rbtree_postorder_for_each_entry_safe(entry, next, root, node) {
                ulist_free(entry->old_roots);
                kfree(entry);
        }
        *root = RB_ROOT;
}

void btrfs_free_squota_rsv(struct btrfs_fs_info *fs_info, u64 root, u64 rsv_bytes)
{
        if (btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_SIMPLE)
                return;

        if (!is_fstree(root))
                return;

        btrfs_qgroup_free_refroot(fs_info, root, rsv_bytes, BTRFS_QGROUP_RSV_DATA);
}

int btrfs_record_squota_delta(struct btrfs_fs_info *fs_info,
                              struct btrfs_squota_delta *delta)
{
        int ret;
        struct btrfs_qgroup *qgroup;
        struct btrfs_qgroup *qg;
        LIST_HEAD(qgroup_list);
        u64 root = delta->root;
        u64 num_bytes = delta->num_bytes;
        const int sign = (delta->is_inc ? 1 : -1);

        if (btrfs_qgroup_mode(fs_info) != BTRFS_QGROUP_MODE_SIMPLE)
                return 0;

        if (!is_fstree(root))
                return 0;

        /* If the extent predates enabling quotas, don't count it. */
        if (delta->generation < fs_info->qgroup_enable_gen)
                return 0;

        spin_lock(&fs_info->qgroup_lock);
        qgroup = find_qgroup_rb(fs_info, root);
        if (!qgroup) {
                ret = -ENOENT;
                goto out;
        }

        ret = 0;
        qgroup_iterator_add(&qgroup_list, qgroup);
        list_for_each_entry(qg, &qgroup_list, iterator) {
                struct btrfs_qgroup_list *glist;

                qg->excl += num_bytes * sign;
                qg->rfer += num_bytes * sign;
                qgroup_dirty(fs_info, qg);

                list_for_each_entry(glist, &qg->groups, next_group)
                        qgroup_iterator_add(&qgroup_list, glist->group);
        }
        qgroup_iterator_clean(&qgroup_list);

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