Merge branches 'for-3.18/upstream-fixes' and 'for-3.19/upstream' into for-linus

[mirror_ubuntu-artful-kernel.git] / fs / btrfs / qgroup.c

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

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

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

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

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

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

        /*
         * reservation tracking
         */
        u64 reserved;

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

        /*
         * temp variables for accounting operations
         */
        u64 old_refcnt;
        u64 new_refcnt;
};

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

#define ptr_to_u64(x) ((u64)(uintptr_t)x)
#define u64_to_ptr(x) ((struct btrfs_qgroup *)(uintptr_t)x)

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

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

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

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

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

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

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

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

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

        return qgroup;
}

static void __del_qgroup_rb(struct btrfs_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);
        }
        kfree(qgroup);
}

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

        if (!qgroup)
                return -ENOENT;

        rb_erase(&qgroup->node, &fs_info->qgroup_tree);
        __del_qgroup_rb(qgroup);
        return 0;
}

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

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

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

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

        return 0;
}

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

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

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

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

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

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

        if (!fs_info->quota_enabled)
                return 0;

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

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

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

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

        while (1) {
                struct btrfs_qgroup *qgroup;

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

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

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

                        if (btrfs_qgroup_status_version(l, ptr) !=
                            BTRFS_QGROUP_STATUS_VERSION) {
                                btrfs_err(fs_info,
                                 "old qgroup version, quota disabled");
                                goto out;
                        }
                        if (btrfs_qgroup_status_generation(l, ptr) !=
                            fs_info->generation) {
                                flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                                btrfs_err(fs_info,
                                        "qgroup generation mismatch, "
                                        "marked as inconsistent");
                        }
                        fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
                                                                          ptr);
                        rescan_progress = btrfs_qgroup_status_rescan(l, ptr);
                        goto next1;
                }

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

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

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

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

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

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

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

                ret = add_relation_rb(fs_info, found_key.objectid,
                                      found_key.offset);
                if (ret == -ENOENT) {
                        btrfs_warn(fs_info,
                                "orphan qgroup relation 0x%llx->0x%llx",
                                found_key.objectid, found_key.offset);
                        ret = 0;        /* ignore the error */
                }
                if (ret)
                        goto out;
next2:
                ret = btrfs_next_item(quota_root, path);
                if (ret < 0)
                        goto out;
                if (ret)
                        break;
        }
out:
        fs_info->qgroup_flags |= flags;
        if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON)) {
                fs_info->quota_enabled = 0;
                fs_info->pending_quota_state = 0;
        } else if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN &&
                   ret >= 0) {
                ret = qgroup_rescan_init(fs_info, rescan_progress, 0);
        }
        btrfs_free_path(path);

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

        return ret < 0 ? ret : 0;
}

/*
 * 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(qgroup);
        }
        /*
         * we call btrfs_free_qgroup_config() when umounting
         * filesystem and disabling quota, so we set qgroup_ulit
         * to be null here to avoid double free.
         */
        ulist_free(fs_info->qgroup_ulist);
        fs_info->qgroup_ulist = NULL;
}

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

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

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

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

        btrfs_mark_buffer_dirty(path->nodes[0]);

        btrfs_free_path(path);
        return ret;
}

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

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

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

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

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

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

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

        if (btrfs_test_is_dummy_root(quota_root))
                return 0;

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

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

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

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

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

        btrfs_mark_buffer_dirty(leaf);

        btrfs_release_path(path);

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

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

        btrfs_mark_buffer_dirty(leaf);

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

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

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

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

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

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

        btrfs_release_path(path);

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

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

        ret = btrfs_del_item(trans, quota_root, path);

out:
        btrfs_free_path(path);
        return ret;
}

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

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

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

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

        if (ret)
                goto out;

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

        btrfs_mark_buffer_dirty(l);

out:
        btrfs_free_path(path);
        return ret;
}

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

        if (btrfs_test_is_dummy_root(root))
                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, root, &key, path, 0, 1);
        if (ret > 0)
                ret = -ENOENT;

        if (ret)
                goto out;

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

        btrfs_mark_buffer_dirty(l);

out:
        btrfs_free_path(path);
        return ret;
}

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

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

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

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

        if (ret)
                goto out;

        l = path->nodes[0];
        slot = path->slots[0];
        ptr = btrfs_item_ptr(l, slot, struct btrfs_qgroup_status_item);
        btrfs_set_qgroup_status_flags(l, ptr, fs_info->qgroup_flags);
        btrfs_set_qgroup_status_generation(l, ptr, trans->transid);
        btrfs_set_qgroup_status_rescan(l, ptr,
                                fs_info->qgroup_rescan_progress.objectid);

        btrfs_mark_buffer_dirty(l);

out:
        btrfs_free_path(path);
        return ret;
}

/*
 * called with qgroup_lock held
 */
static int btrfs_clean_quota_tree(struct btrfs_trans_handle *trans,
                                  struct btrfs_root *root)
{
        struct btrfs_path *path;
        struct btrfs_key key;
        struct extent_buffer *leaf = NULL;
        int ret;
        int nr = 0;

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

        path->leave_spinning = 1;

        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:
        root->fs_info->pending_quota_state = 0;
        btrfs_free_path(path);
        return ret;
}

int btrfs_quota_enable(struct btrfs_trans_handle *trans,
                       struct btrfs_fs_info *fs_info)
{
        struct btrfs_root *quota_root;
        struct btrfs_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;
        int ret = 0;
        int slot;

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (fs_info->quota_root) {
                fs_info->pending_quota_state = 1;
                goto out;
        }

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

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

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

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

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

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

        btrfs_mark_buffer_dirty(leaf);

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

        btrfs_release_path(path);
        ret = btrfs_search_slot_for_read(tree_root, &key, path, 1, 0);
        if (ret > 0)
                goto out_add_root;
        if (ret < 0)
                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) {
                        ret = add_qgroup_item(trans, quota_root,
                                              found_key.offset);
                        if (ret)
                                goto out_free_path;

                        qgroup = add_qgroup_rb(fs_info, found_key.offset);
                        if (IS_ERR(qgroup)) {
                                ret = PTR_ERR(qgroup);
                                goto out_free_path;
                        }
                }
                ret = btrfs_next_item(tree_root, path);
                if (ret < 0)
                        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)
                goto out_free_path;

        qgroup = add_qgroup_rb(fs_info, BTRFS_FS_TREE_OBJECTID);
        if (IS_ERR(qgroup)) {
                ret = PTR_ERR(qgroup);
                goto out_free_path;
        }
        spin_lock(&fs_info->qgroup_lock);
        fs_info->quota_root = quota_root;
        fs_info->pending_quota_state = 1;
        spin_unlock(&fs_info->qgroup_lock);
out_free_path:
        btrfs_free_path(path);
out_free_root:
        if (ret) {
                free_extent_buffer(quota_root->node);
                free_extent_buffer(quota_root->commit_root);
                kfree(quota_root);
        }
out:
        if (ret) {
                ulist_free(fs_info->qgroup_ulist);
                fs_info->qgroup_ulist = NULL;
        }
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_root)
                goto out;
        spin_lock(&fs_info->qgroup_lock);
        fs_info->quota_enabled = 0;
        fs_info->pending_quota_state = 0;
        quota_root = fs_info->quota_root;
        fs_info->quota_root = NULL;
        spin_unlock(&fs_info->qgroup_lock);

        btrfs_free_qgroup_config(fs_info);

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

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

        list_del(&quota_root->dirty_list);

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

        free_extent_buffer(quota_root->node);
        free_extent_buffer(quota_root->commit_root);
        kfree(quota_root);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

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

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

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

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

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

        spin_lock(&fs_info->qgroup_lock);
        ret = add_relation_rb(quota_root->fs_info, src, dst);
        spin_unlock(&fs_info->qgroup_lock);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

        mutex_lock(&fs_info->qgroup_ioctl_lock);
        quota_root = fs_info->quota_root;
        if (!quota_root) {
                ret = -EINVAL;
                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)
                        goto exist;
        }
        ret = -ENOENT;
        goto out;
exist:
        ret = del_qgroup_relation_item(trans, quota_root, src, dst);
        err = del_qgroup_relation_item(trans, quota_root, dst, src);
        if (err && !ret)
                ret = err;

        spin_lock(&fs_info->qgroup_lock);
        del_relation_rb(fs_info, src, dst);
        spin_unlock(&fs_info->qgroup_lock);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

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

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

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

        if (IS_ERR(qgroup))
                ret = PTR_ERR(qgroup);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

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

        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup) {
                ret = -ENOENT;
                goto out;
        } else {
                /* check if there are no relations to this qgroup */
                if (!list_empty(&qgroup->groups) ||
                    !list_empty(&qgroup->members)) {
                        ret = -EBUSY;
                        goto out;
                }
        }
        ret = del_qgroup_item(trans, quota_root, qgroupid);

        spin_lock(&fs_info->qgroup_lock);
        del_qgroup_rb(quota_root->fs_info, qgroupid);
        spin_unlock(&fs_info->qgroup_lock);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

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

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

        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup) {
                ret = -ENOENT;
                goto out;
        }
        ret = update_qgroup_limit_item(trans, quota_root, qgroupid,
                                       limit->flags, limit->max_rfer,
                                       limit->max_excl, limit->rsv_rfer,
                                       limit->rsv_excl);
        if (ret) {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
                btrfs_info(fs_info, "unable to update quota limit for %llu",
                       qgroupid);
        }

        spin_lock(&fs_info->qgroup_lock);
        qgroup->lim_flags = limit->flags;
        qgroup->max_rfer = limit->max_rfer;
        qgroup->max_excl = limit->max_excl;
        qgroup->rsv_rfer = limit->rsv_rfer;
        qgroup->rsv_excl = limit->rsv_excl;
        spin_unlock(&fs_info->qgroup_lock);
out:
        mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
}

static int comp_oper_exist(struct btrfs_qgroup_operation *oper1,
                           struct btrfs_qgroup_operation *oper2)
{
        /*
         * Ignore seq and type here, we're looking for any operation
         * at all related to this extent on that root.
         */
        if (oper1->bytenr < oper2->bytenr)
                return -1;
        if (oper1->bytenr > oper2->bytenr)
                return 1;
        if (oper1->ref_root < oper2->ref_root)
                return -1;
        if (oper1->ref_root > oper2->ref_root)
                return 1;
        return 0;
}

static int qgroup_oper_exists(struct btrfs_fs_info *fs_info,
                              struct btrfs_qgroup_operation *oper)
{
        struct rb_node *n;
        struct btrfs_qgroup_operation *cur;
        int cmp;

        spin_lock(&fs_info->qgroup_op_lock);
        n = fs_info->qgroup_op_tree.rb_node;
        while (n) {
                cur = rb_entry(n, struct btrfs_qgroup_operation, n);
                cmp = comp_oper_exist(cur, oper);
                if (cmp < 0) {
                        n = n->rb_right;
                } else if (cmp) {
                        n = n->rb_left;
                } else {
                        spin_unlock(&fs_info->qgroup_op_lock);
                        return -EEXIST;
                }
        }
        spin_unlock(&fs_info->qgroup_op_lock);
        return 0;
}

static int comp_oper(struct btrfs_qgroup_operation *oper1,
                     struct btrfs_qgroup_operation *oper2)
{
        if (oper1->bytenr < oper2->bytenr)
                return -1;
        if (oper1->bytenr > oper2->bytenr)
                return 1;
        if (oper1->seq < oper2->seq)
                return -1;
        if (oper1->seq > oper2->seq)
                return -1;
        if (oper1->ref_root < oper2->ref_root)
                return -1;
        if (oper1->ref_root > oper2->ref_root)
                return 1;
        if (oper1->type < oper2->type)
                return -1;
        if (oper1->type > oper2->type)
                return 1;
        return 0;
}

static int insert_qgroup_oper(struct btrfs_fs_info *fs_info,
                              struct btrfs_qgroup_operation *oper)
{
        struct rb_node **p;
        struct rb_node *parent = NULL;
        struct btrfs_qgroup_operation *cur;
        int cmp;

        spin_lock(&fs_info->qgroup_op_lock);
        p = &fs_info->qgroup_op_tree.rb_node;
        while (*p) {
                parent = *p;
                cur = rb_entry(parent, struct btrfs_qgroup_operation, n);
                cmp = comp_oper(cur, oper);
                if (cmp < 0) {
                        p = &(*p)->rb_right;
                } else if (cmp) {
                        p = &(*p)->rb_left;
                } else {
                        spin_unlock(&fs_info->qgroup_op_lock);
                        return -EEXIST;
                }
        }
        rb_link_node(&oper->n, parent, p);
        rb_insert_color(&oper->n, &fs_info->qgroup_op_tree);
        spin_unlock(&fs_info->qgroup_op_lock);
        return 0;
}

/*
 * Record a quota operation for processing later on.
 * @trans: the transaction we are adding the delayed op to.
 * @fs_info: the fs_info for this fs.
 * @ref_root: the root of the reference we are acting on,
 * @bytenr: the bytenr we are acting on.
 * @num_bytes: the number of bytes in the reference.
 * @type: the type of operation this is.
 * @mod_seq: do we need to get a sequence number for looking up roots.
 *
 * We just add it to our trans qgroup_ref_list and carry on and process these
 * operations in order at some later point.  If the reference root isn't a fs
 * root then we don't bother with doing anything.
 *
 * MUST BE HOLDING THE REF LOCK.
 */
int btrfs_qgroup_record_ref(struct btrfs_trans_handle *trans,
                            struct btrfs_fs_info *fs_info, u64 ref_root,
                            u64 bytenr, u64 num_bytes,
                            enum btrfs_qgroup_operation_type type, int mod_seq)
{
        struct btrfs_qgroup_operation *oper;
        int ret;

        if (!is_fstree(ref_root) || !fs_info->quota_enabled)
                return 0;

        oper = kmalloc(sizeof(*oper), GFP_NOFS);
        if (!oper)
                return -ENOMEM;

        oper->ref_root = ref_root;
        oper->bytenr = bytenr;
        oper->num_bytes = num_bytes;
        oper->type = type;
        oper->seq = atomic_inc_return(&fs_info->qgroup_op_seq);
        INIT_LIST_HEAD(&oper->elem.list);
        oper->elem.seq = 0;

        trace_btrfs_qgroup_record_ref(oper);

        if (type == BTRFS_QGROUP_OPER_SUB_SUBTREE) {
                /*
                 * If any operation for this bytenr/ref_root combo
                 * exists, then we know it's not exclusively owned and
                 * shouldn't be queued up.
                 *
                 * This also catches the case where we have a cloned
                 * extent that gets queued up multiple times during
                 * drop snapshot.
                 */
                if (qgroup_oper_exists(fs_info, oper)) {
                        kfree(oper);
                        return 0;
                }
        }

        ret = insert_qgroup_oper(fs_info, oper);
        if (ret) {
                /* Shouldn't happen so have an assert for developers */
                ASSERT(0);
                kfree(oper);
                return ret;
        }
        list_add_tail(&oper->list, &trans->qgroup_ref_list);

        if (mod_seq)
                btrfs_get_tree_mod_seq(fs_info, &oper->elem);

        return 0;
}

/*
 * The easy accounting, if we are adding/removing the only ref for an extent
 * then this qgroup and all of the parent qgroups get their refrence and
 * exclusive counts adjusted.
 */
static int qgroup_excl_accounting(struct btrfs_fs_info *fs_info,
                                  struct btrfs_qgroup_operation *oper)
{
        struct btrfs_qgroup *qgroup;
        struct ulist *tmp;
        struct btrfs_qgroup_list *glist;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        int sign = 0;
        int ret = 0;

        tmp = ulist_alloc(GFP_NOFS);
        if (!tmp)
                return -ENOMEM;

        spin_lock(&fs_info->qgroup_lock);
        if (!fs_info->quota_root)
                goto out;
        qgroup = find_qgroup_rb(fs_info, oper->ref_root);
        if (!qgroup)
                goto out;
        switch (oper->type) {
        case BTRFS_QGROUP_OPER_ADD_EXCL:
                sign = 1;
                break;
        case BTRFS_QGROUP_OPER_SUB_EXCL:
                sign = -1;
                break;
        default:
                ASSERT(0);
        }
        qgroup->rfer += sign * oper->num_bytes;
        qgroup->rfer_cmpr += sign * oper->num_bytes;

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

        qgroup_dirty(fs_info, qgroup);

        /* Get all of the parent groups that contain this qgroup */
        list_for_each_entry(glist, &qgroup->groups, next_group) {
                ret = ulist_add(tmp, glist->group->qgroupid,
                                ptr_to_u64(glist->group), GFP_ATOMIC);
                if (ret < 0)
                        goto out;
        }

        /* Iterate all of the parents and adjust their reference counts */
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(tmp, &uiter))) {
                qgroup = u64_to_ptr(unode->aux);
                qgroup->rfer += sign * oper->num_bytes;
                qgroup->rfer_cmpr += sign * oper->num_bytes;
                qgroup->excl += sign * oper->num_bytes;
                if (sign < 0)
                        WARN_ON(qgroup->excl < oper->num_bytes);
                qgroup->excl_cmpr += sign * oper->num_bytes;
                qgroup_dirty(fs_info, qgroup);

                /* Add any parents of the parents */
                list_for_each_entry(glist, &qgroup->groups, next_group) {
                        ret = ulist_add(tmp, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                goto out;
                }
        }
        ret = 0;
out:
        spin_unlock(&fs_info->qgroup_lock);
        ulist_free(tmp);
        return ret;
}

/*
 * Walk all of the roots that pointed to our bytenr and adjust their refcnts as
 * properly.
 */
static int qgroup_calc_old_refcnt(struct btrfs_fs_info *fs_info,
                                  u64 root_to_skip, struct ulist *tmp,
                                  struct ulist *roots, struct ulist *qgroups,
                                  u64 seq, int *old_roots, int rescan)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct ulist_node *tmp_unode;
        struct ulist_iterator tmp_uiter;
        struct btrfs_qgroup *qg;
        int ret;

        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(roots, &uiter))) {
                /* We don't count our current root here */
                if (unode->val == root_to_skip)
                        continue;
                qg = find_qgroup_rb(fs_info, unode->val);
                if (!qg)
                        continue;
                /*
                 * We could have a pending removal of this same ref so we may
                 * not have actually found our ref root when doing
                 * btrfs_find_all_roots, so we need to keep track of how many
                 * old roots we find in case we removed ours and added a
                 * different one at the same time.  I don't think this could
                 * happen in practice but that sort of thinking leads to pain
                 * and suffering and to the dark side.
                 */
                (*old_roots)++;

                ulist_reinit(tmp);
                ret = ulist_add(qgroups, qg->qgroupid, ptr_to_u64(qg),
                                GFP_ATOMIC);
                if (ret < 0)
                        return ret;
                ret = ulist_add(tmp, qg->qgroupid, ptr_to_u64(qg), GFP_ATOMIC);
                if (ret < 0)
                        return ret;
                ULIST_ITER_INIT(&tmp_uiter);
                while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
                        struct btrfs_qgroup_list *glist;

                        qg = u64_to_ptr(tmp_unode->aux);
                        /*
                         * We use this sequence number to keep from having to
                         * run the whole list and 0 out the refcnt every time.
                         * We basically use sequnce as the known 0 count and
                         * then add 1 everytime we see a qgroup.  This is how we
                         * get how many of the roots actually point up to the
                         * upper level qgroups in order to determine exclusive
                         * counts.
                         *
                         * For rescan we want to set old_refcnt to seq so our
                         * exclusive calculations end up correct.
                         */
                        if (rescan)
                                qg->old_refcnt = seq;
                        else if (qg->old_refcnt < seq)
                                qg->old_refcnt = seq + 1;
                        else
                                qg->old_refcnt++;

                        if (qg->new_refcnt < seq)
                                qg->new_refcnt = seq + 1;
                        else
                                qg->new_refcnt++;
                        list_for_each_entry(glist, &qg->groups, next_group) {
                                ret = ulist_add(qgroups, glist->group->qgroupid,
                                                ptr_to_u64(glist->group),
                                                GFP_ATOMIC);
                                if (ret < 0)
                                        return ret;
                                ret = ulist_add(tmp, glist->group->qgroupid,
                                                ptr_to_u64(glist->group),
                                                GFP_ATOMIC);
                                if (ret < 0)
                                        return ret;
                        }
                }
        }
        return 0;
}

/*
 * We need to walk forward in our operation tree and account for any roots that
 * were deleted after we made this operation.
 */
static int qgroup_account_deleted_refs(struct btrfs_fs_info *fs_info,
                                       struct btrfs_qgroup_operation *oper,
                                       struct ulist *tmp,
                                       struct ulist *qgroups, u64 seq,
                                       int *old_roots)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct btrfs_qgroup *qg;
        struct btrfs_qgroup_operation *tmp_oper;
        struct rb_node *n;
        int ret;

        ulist_reinit(tmp);

        /*
         * We only walk forward in the tree since we're only interested in
         * removals that happened _after_  our operation.
         */
        spin_lock(&fs_info->qgroup_op_lock);
        n = rb_next(&oper->n);
        spin_unlock(&fs_info->qgroup_op_lock);
        if (!n)
                return 0;
        tmp_oper = rb_entry(n, struct btrfs_qgroup_operation, n);
        while (tmp_oper->bytenr == oper->bytenr) {
                /*
                 * If it's not a removal we don't care, additions work out
                 * properly with our refcnt tracking.
                 */
                if (tmp_oper->type != BTRFS_QGROUP_OPER_SUB_SHARED &&
                    tmp_oper->type != BTRFS_QGROUP_OPER_SUB_EXCL)
                        goto next;
                qg = find_qgroup_rb(fs_info, tmp_oper->ref_root);
                if (!qg)
                        goto next;
                ret = ulist_add(qgroups, qg->qgroupid, ptr_to_u64(qg),
                                GFP_ATOMIC);
                if (ret) {
                        if (ret < 0)
                                return ret;
                        /*
                         * We only want to increase old_roots if this qgroup is
                         * not already in the list of qgroups.  If it is already
                         * there then that means it must have been re-added or
                         * the delete will be discarded because we had an
                         * existing ref that we haven't looked up yet.  In this
                         * case we don't want to increase old_roots.  So if ret
                         * == 1 then we know that this is the first time we've
                         * seen this qgroup and we can bump the old_roots.
                         */
                        (*old_roots)++;
                        ret = ulist_add(tmp, qg->qgroupid, ptr_to_u64(qg),
                                        GFP_ATOMIC);
                        if (ret < 0)
                                return ret;
                }
next:
                spin_lock(&fs_info->qgroup_op_lock);
                n = rb_next(&tmp_oper->n);
                spin_unlock(&fs_info->qgroup_op_lock);
                if (!n)
                        break;
                tmp_oper = rb_entry(n, struct btrfs_qgroup_operation, n);
        }

        /* Ok now process the qgroups we found */
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(tmp, &uiter))) {
                struct btrfs_qgroup_list *glist;

                qg = u64_to_ptr(unode->aux);
                if (qg->old_refcnt < seq)
                        qg->old_refcnt = seq + 1;
                else
                        qg->old_refcnt++;
                if (qg->new_refcnt < seq)
                        qg->new_refcnt = seq + 1;
                else
                        qg->new_refcnt++;
                list_for_each_entry(glist, &qg->groups, next_group) {
                        ret = ulist_add(qgroups, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                return ret;
                        ret = ulist_add(tmp, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                return ret;
                }
        }
        return 0;
}

/* Add refcnt for the newly added reference. */
static int qgroup_calc_new_refcnt(struct btrfs_fs_info *fs_info,
                                  struct btrfs_qgroup_operation *oper,
                                  struct btrfs_qgroup *qgroup,
                                  struct ulist *tmp, struct ulist *qgroups,
                                  u64 seq)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct btrfs_qgroup *qg;
        int ret;

        ulist_reinit(tmp);
        ret = ulist_add(qgroups, qgroup->qgroupid, ptr_to_u64(qgroup),
                        GFP_ATOMIC);
        if (ret < 0)
                return ret;
        ret = ulist_add(tmp, qgroup->qgroupid, ptr_to_u64(qgroup),
                        GFP_ATOMIC);
        if (ret < 0)
                return ret;
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(tmp, &uiter))) {
                struct btrfs_qgroup_list *glist;

                qg = u64_to_ptr(unode->aux);
                if (oper->type == BTRFS_QGROUP_OPER_ADD_SHARED) {
                        if (qg->new_refcnt < seq)
                                qg->new_refcnt = seq + 1;
                        else
                                qg->new_refcnt++;
                } else {
                        if (qg->old_refcnt < seq)
                                qg->old_refcnt = seq + 1;
                        else
                                qg->old_refcnt++;
                }
                list_for_each_entry(glist, &qg->groups, next_group) {
                        ret = ulist_add(tmp, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                return ret;
                        ret = ulist_add(qgroups, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (ret < 0)
                                return ret;
                }
        }
        return 0;
}

/*
 * This adjusts the counters for all referenced qgroups if need be.
 */
static int qgroup_adjust_counters(struct btrfs_fs_info *fs_info,
                                  u64 root_to_skip, u64 num_bytes,
                                  struct ulist *qgroups, u64 seq,
                                  int old_roots, int new_roots, int rescan)
{
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct btrfs_qgroup *qg;
        u64 cur_new_count, cur_old_count;

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

                qg = u64_to_ptr(unode->aux);
                /*
                 * Wasn't referenced before but is now, add to the reference
                 * counters.
                 */
                if (qg->old_refcnt <= seq && qg->new_refcnt > seq) {
                        qg->rfer += num_bytes;
                        qg->rfer_cmpr += num_bytes;
                        dirty = true;
                }

                /*
                 * Was referenced before but isn't now, subtract from the
                 * reference counters.
                 */
                if (qg->old_refcnt > seq && qg->new_refcnt <= seq) {
                        qg->rfer -= num_bytes;
                        qg->rfer_cmpr -= num_bytes;
                        dirty = true;
                }

                if (qg->old_refcnt < seq)
                        cur_old_count = 0;
                else
                        cur_old_count = qg->old_refcnt - seq;
                if (qg->new_refcnt < seq)
                        cur_new_count = 0;
                else
                        cur_new_count = qg->new_refcnt - seq;

                /*
                 * If our refcount was the same as the roots previously but our
                 * new count isn't the same as the number of roots now then we
                 * went from having a exclusive reference on this range to not.
                 */
                if (old_roots && cur_old_count == old_roots &&
                    (cur_new_count != new_roots || new_roots == 0)) {
                        WARN_ON(cur_new_count != new_roots && new_roots == 0);
                        qg->excl -= num_bytes;
                        qg->excl_cmpr -= num_bytes;
                        dirty = true;
                }

                /*
                 * If we didn't reference all the roots before but now we do we
                 * have an exclusive reference to this range.
                 */
                if ((!old_roots || (old_roots && cur_old_count != old_roots))
                    && cur_new_count == new_roots) {
                        qg->excl += num_bytes;
                        qg->excl_cmpr += num_bytes;
                        dirty = true;
                }

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

/*
 * If we removed a data extent and there were other references for that bytenr
 * then we need to lookup all referenced roots to make sure we still don't
 * reference this bytenr.  If we do then we can just discard this operation.
 */
static int check_existing_refs(struct btrfs_trans_handle *trans,
                               struct btrfs_fs_info *fs_info,
                               struct btrfs_qgroup_operation *oper)
{
        struct ulist *roots = NULL;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        int ret = 0;

        ret = btrfs_find_all_roots(trans, fs_info, oper->bytenr,
                                   oper->elem.seq, &roots);
        if (ret < 0)
                return ret;
        ret = 0;

        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(roots, &uiter))) {
                if (unode->val == oper->ref_root) {
                        ret = 1;
                        break;
                }
        }
        ulist_free(roots);
        btrfs_put_tree_mod_seq(fs_info, &oper->elem);

        return ret;
}

/*
 * If we share a reference across multiple roots then we may need to adjust
 * various qgroups referenced and exclusive counters.  The basic premise is this
 *
 * 1) We have seq to represent a 0 count.  Instead of looping through all of the
 * qgroups and resetting their refcount to 0 we just constantly bump this
 * sequence number to act as the base reference count.  This means that if
 * anybody is equal to or below this sequence they were never referenced.  We
 * jack this sequence up by the number of roots we found each time in order to
 * make sure we don't have any overlap.
 *
 * 2) We first search all the roots that reference the area _except_ the root
 * we're acting on currently.  This makes up the old_refcnt of all the qgroups
 * before.
 *
 * 3) We walk all of the qgroups referenced by the root we are currently acting
 * on, and will either adjust old_refcnt in the case of a removal or the
 * new_refcnt in the case of an addition.
 *
 * 4) Finally we walk all the qgroups that are referenced by this range
 * including the root we are acting on currently.  We will adjust the counters
 * based on the number of roots we had and will have after this operation.
 *
 * Take this example as an illustration
 *
 *                      [qgroup 1/0]
 *                   /         |          \
 *              [qg 0/0]   [qg 0/1]     [qg 0/2]
 *                 \          |            /
 *                [        extent           ]
 *
 * Say we are adding a reference that is covered by qg 0/0.  The first step
 * would give a refcnt of 1 to qg 0/1 and 0/2 and a refcnt of 2 to qg 1/0 with
 * old_roots being 2.  Because it is adding new_roots will be 1.  We then go
 * through qg 0/0 which will get the new_refcnt set to 1 and add 1 to qg 1/0's
 * new_refcnt, bringing it to 3.  We then walk through all of the qgroups, we
 * notice that the old refcnt for qg 0/0 < the new refcnt, so we added a
 * reference and thus must add the size to the referenced bytes.  Everything
 * else is the same so nothing else changes.
 */
static int qgroup_shared_accounting(struct btrfs_trans_handle *trans,
                                    struct btrfs_fs_info *fs_info,
                                    struct btrfs_qgroup_operation *oper)
{
        struct ulist *roots = NULL;
        struct ulist *qgroups, *tmp;
        struct btrfs_qgroup *qgroup;
        struct seq_list elem = {};
        u64 seq;
        int old_roots = 0;
        int new_roots = 0;
        int ret = 0;

        if (oper->elem.seq) {
                ret = check_existing_refs(trans, fs_info, oper);
                if (ret < 0)
                        return ret;
                if (ret)
                        return 0;
        }

        qgroups = ulist_alloc(GFP_NOFS);
        if (!qgroups)
                return -ENOMEM;

        tmp = ulist_alloc(GFP_NOFS);
        if (!tmp) {
                ulist_free(qgroups);
                return -ENOMEM;
        }

        btrfs_get_tree_mod_seq(fs_info, &elem);
        ret = btrfs_find_all_roots(trans, fs_info, oper->bytenr, elem.seq,
                                   &roots);
        btrfs_put_tree_mod_seq(fs_info, &elem);
        if (ret < 0) {
                ulist_free(qgroups);
                ulist_free(tmp);
                return ret;
        }
        spin_lock(&fs_info->qgroup_lock);
        qgroup = find_qgroup_rb(fs_info, oper->ref_root);
        if (!qgroup)
                goto out;
        seq = fs_info->qgroup_seq;

        /*
         * So roots is the list of all the roots currently pointing at the
         * bytenr, including the ref we are adding if we are adding, or not if
         * we are removing a ref.  So we pass in the ref_root to skip that root
         * in our calculations.  We set old_refnct and new_refcnt cause who the
         * hell knows what everything looked like before, and it doesn't matter
         * except...
         */
        ret = qgroup_calc_old_refcnt(fs_info, oper->ref_root, tmp, roots, qgroups,
                                     seq, &old_roots, 0);
        if (ret < 0)
                goto out;

        /*
         * Now adjust the refcounts of the qgroups that care about this
         * reference, either the old_count in the case of removal or new_count
         * in the case of an addition.
         */
        ret = qgroup_calc_new_refcnt(fs_info, oper, qgroup, tmp, qgroups,
                                     seq);
        if (ret < 0)
                goto out;

        /*
         * ...in the case of removals.  If we had a removal before we got around
         * to processing this operation then we need to find that guy and count
         * his references as if they really existed so we don't end up screwing
         * up the exclusive counts.  Then whenever we go to process the delete
         * everything will be grand and we can account for whatever exclusive
         * changes need to be made there.  We also have to pass in old_roots so
         * we have an accurate count of the roots as it pertains to this
         * operations view of the world.
         */
        ret = qgroup_account_deleted_refs(fs_info, oper, tmp, qgroups, seq,
                                          &old_roots);
        if (ret < 0)
                goto out;

        /*
         * We are adding our root, need to adjust up the number of roots,
         * otherwise old_roots is the number of roots we want.
         */
        if (oper->type == BTRFS_QGROUP_OPER_ADD_SHARED) {
                new_roots = old_roots + 1;
        } else {
                new_roots = old_roots;
                old_roots++;
        }
        fs_info->qgroup_seq += old_roots + 1;


        /*
         * And now the magic happens, bless Arne for having a pretty elegant
         * solution for this.
         */
        qgroup_adjust_counters(fs_info, oper->ref_root, oper->num_bytes,
                               qgroups, seq, old_roots, new_roots, 0);
out:
        spin_unlock(&fs_info->qgroup_lock);
        ulist_free(qgroups);
        ulist_free(roots);
        ulist_free(tmp);
        return ret;
}

/*
 * Process a reference to a shared subtree. This type of operation is
 * queued during snapshot removal when we encounter extents which are
 * shared between more than one root.
 */
static int qgroup_subtree_accounting(struct btrfs_trans_handle *trans,
                                     struct btrfs_fs_info *fs_info,
                                     struct btrfs_qgroup_operation *oper)
{
        struct ulist *roots = NULL;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        struct btrfs_qgroup_list *glist;
        struct ulist *parents;
        int ret = 0;
        int err;
        struct btrfs_qgroup *qg;
        u64 root_obj = 0;
        struct seq_list elem = {};

        parents = ulist_alloc(GFP_NOFS);
        if (!parents)
                return -ENOMEM;

        btrfs_get_tree_mod_seq(fs_info, &elem);
        ret = btrfs_find_all_roots(trans, fs_info, oper->bytenr,
                                   elem.seq, &roots);
        btrfs_put_tree_mod_seq(fs_info, &elem);
        if (ret < 0)
                goto out;

        if (roots->nnodes != 1)
                goto out;

        ULIST_ITER_INIT(&uiter);
        unode = ulist_next(roots, &uiter); /* Only want 1 so no need to loop */
        /*
         * If we find our ref root then that means all refs
         * this extent has to the root have not yet been
         * deleted. In that case, we do nothing and let the
         * last ref for this bytenr drive our update.
         *
         * This can happen for example if an extent is
         * referenced multiple times in a snapshot (clone,
         * etc). If we are in the middle of snapshot removal,
         * queued updates for such an extent will find the
         * root if we have not yet finished removing the
         * snapshot.
         */
        if (unode->val == oper->ref_root)
                goto out;

        root_obj = unode->val;
        BUG_ON(!root_obj);

        spin_lock(&fs_info->qgroup_lock);
        qg = find_qgroup_rb(fs_info, root_obj);
        if (!qg)
                goto out_unlock;

        qg->excl += oper->num_bytes;
        qg->excl_cmpr += oper->num_bytes;
        qgroup_dirty(fs_info, qg);

        /*
         * Adjust counts for parent groups. First we find all
         * parents, then in the 2nd loop we do the adjustment
         * while adding parents of the parents to our ulist.
         */
        list_for_each_entry(glist, &qg->groups, next_group) {
                err = ulist_add(parents, glist->group->qgroupid,
                                ptr_to_u64(glist->group), GFP_ATOMIC);
                if (err < 0) {
                        ret = err;
                        goto out_unlock;
                }
        }

        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(parents, &uiter))) {
                qg = u64_to_ptr(unode->aux);
                qg->excl += oper->num_bytes;
                qg->excl_cmpr += oper->num_bytes;
                qgroup_dirty(fs_info, qg);

                /* Add any parents of the parents */
                list_for_each_entry(glist, &qg->groups, next_group) {
                        err = ulist_add(parents, glist->group->qgroupid,
                                        ptr_to_u64(glist->group), GFP_ATOMIC);
                        if (err < 0) {
                                ret = err;
                                goto out_unlock;
                        }
                }
        }

out_unlock:
        spin_unlock(&fs_info->qgroup_lock);

out:
        ulist_free(roots);
        ulist_free(parents);
        return ret;
}

/*
 * btrfs_qgroup_account_ref is called for every ref that is added to or deleted
 * from the fs. First, all roots referencing the extent are searched, and
 * then the space is accounted accordingly to the different roots. The
 * accounting algorithm works in 3 steps documented inline.
 */
static int btrfs_qgroup_account(struct btrfs_trans_handle *trans,
                                struct btrfs_fs_info *fs_info,
                                struct btrfs_qgroup_operation *oper)
{
        int ret = 0;

        if (!fs_info->quota_enabled)
                return 0;

        BUG_ON(!fs_info->quota_root);

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

        ASSERT(is_fstree(oper->ref_root));

        trace_btrfs_qgroup_account(oper);

        switch (oper->type) {
        case BTRFS_QGROUP_OPER_ADD_EXCL:
        case BTRFS_QGROUP_OPER_SUB_EXCL:
                ret = qgroup_excl_accounting(fs_info, oper);
                break;
        case BTRFS_QGROUP_OPER_ADD_SHARED:
        case BTRFS_QGROUP_OPER_SUB_SHARED:
                ret = qgroup_shared_accounting(trans, fs_info, oper);
                break;
        case BTRFS_QGROUP_OPER_SUB_SUBTREE:
                ret = qgroup_subtree_accounting(trans, fs_info, oper);
                break;
        default:
                ASSERT(0);
        }
        return ret;
}

/*
 * Needs to be called everytime we run delayed refs, even if there is an error
 * in order to cleanup outstanding operations.
 */
int btrfs_delayed_qgroup_accounting(struct btrfs_trans_handle *trans,
                                    struct btrfs_fs_info *fs_info)
{
        struct btrfs_qgroup_operation *oper;
        int ret = 0;

        while (!list_empty(&trans->qgroup_ref_list)) {
                oper = list_first_entry(&trans->qgroup_ref_list,
                                        struct btrfs_qgroup_operation, list);
                list_del_init(&oper->list);
                if (!ret || !trans->aborted)
                        ret = btrfs_qgroup_account(trans, fs_info, oper);
                spin_lock(&fs_info->qgroup_op_lock);
                rb_erase(&oper->n, &fs_info->qgroup_op_tree);
                spin_unlock(&fs_info->qgroup_op_lock);
                btrfs_put_tree_mod_seq(fs_info, &oper->elem);
                kfree(oper);
        }
        return ret;
}

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

        if (!quota_root)
                goto out;

        if (!fs_info->quota_enabled && fs_info->pending_quota_state)
                start_rescan_worker = 1;

        fs_info->quota_enabled = fs_info->pending_quota_state;

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

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

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

out:

        return ret;
}

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

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

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

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

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

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

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

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

                rcu_read_lock();
                level_size = srcroot->nodesize;
                rcu_read_unlock();
        }

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


        spin_lock(&fs_info->qgroup_lock);

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

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

                /*
                 * 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.
                 */
                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;
                qgroup_dirty(fs_info, dstgroup);
                qgroup_dirty(fs_info, srcgroup);
        }

        if (!inherit)
                goto unlock;

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

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

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

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

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

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

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

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

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

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

        if (!is_fstree(ref_root))
                return 0;

        if (num_bytes == 0)
                return 0;

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

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

        /*
         * in a first step, we check all affected qgroups if any limits would
         * be exceeded
         */
        ulist_reinit(fs_info->qgroup_ulist);
        ret = ulist_add(fs_info->qgroup_ulist, qgroup->qgroupid,
                        (uintptr_t)qgroup, GFP_ATOMIC);
        if (ret < 0)
                goto out;
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(fs_info->qgroup_ulist, &uiter))) {
                struct btrfs_qgroup *qg;
                struct btrfs_qgroup_list *glist;

                qg = u64_to_ptr(unode->aux);

                if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_RFER) &&
                    qg->reserved + (s64)qg->rfer + num_bytes >
                    qg->max_rfer) {
                        ret = -EDQUOT;
                        goto out;
                }

                if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) &&
                    qg->reserved + (s64)qg->excl + num_bytes >
                    qg->max_excl) {
                        ret = -EDQUOT;
                        goto out;
                }

                list_for_each_entry(glist, &qg->groups, next_group) {
                        ret = ulist_add(fs_info->qgroup_ulist,
                                        glist->group->qgroupid,
                                        (uintptr_t)glist->group, GFP_ATOMIC);
                        if (ret < 0)
                                goto out;
                }
        }
        ret = 0;
        /*
         * no limits exceeded, now record the reservation into all qgroups
         */
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(fs_info->qgroup_ulist, &uiter))) {
                struct btrfs_qgroup *qg;

                qg = u64_to_ptr(unode->aux);

                qg->reserved += num_bytes;
        }

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

void btrfs_qgroup_free(struct btrfs_root *root, u64 num_bytes)
{
        struct btrfs_root *quota_root;
        struct btrfs_qgroup *qgroup;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct ulist_node *unode;
        struct ulist_iterator uiter;
        u64 ref_root = root->root_key.objectid;
        int ret = 0;

        if (!is_fstree(ref_root))
                return;

        if (num_bytes == 0)
                return;

        spin_lock(&fs_info->qgroup_lock);

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

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

        ulist_reinit(fs_info->qgroup_ulist);
        ret = ulist_add(fs_info->qgroup_ulist, qgroup->qgroupid,
                        (uintptr_t)qgroup, GFP_ATOMIC);
        if (ret < 0)
                goto out;
        ULIST_ITER_INIT(&uiter);
        while ((unode = ulist_next(fs_info->qgroup_ulist, &uiter))) {
                struct btrfs_qgroup *qg;
                struct btrfs_qgroup_list *glist;

                qg = u64_to_ptr(unode->aux);

                qg->reserved -= num_bytes;

                list_for_each_entry(glist, &qg->groups, next_group) {
                        ret = ulist_add(fs_info->qgroup_ulist,
                                        glist->group->qgroupid,
                                        (uintptr_t)glist->group, GFP_ATOMIC);
                        if (ret < 0)
                                goto out;
                }
        }

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

void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
{
        if (list_empty(&trans->qgroup_ref_list) && !trans->delayed_ref_elem.seq)
                return;
        btrfs_err(trans->root->fs_info,
                "qgroups not uptodate in trans handle %p:  list is%s empty, "
                "seq is %#x.%x",
                trans, list_empty(&trans->qgroup_ref_list) ? "" : " not",
                (u32)(trans->delayed_ref_elem.seq >> 32),
                (u32)trans->delayed_ref_elem.seq);
        BUG();
}

/*
 * returns < 0 on error, 0 when more leafs are to be scanned.
 * returns 1 when done, 2 when done and FLAG_INCONSISTENT was cleared.
 */
static int
qgroup_rescan_leaf(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
                   struct btrfs_trans_handle *trans, struct ulist *qgroups,
                   struct ulist *tmp, struct extent_buffer *scratch_leaf)
{
        struct btrfs_key found;
        struct ulist *roots = NULL;
        struct seq_list tree_mod_seq_elem = {};
        u64 num_bytes;
        u64 seq;
        int new_roots;
        int slot;
        int ret;

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

        pr_debug("current progress key (%llu %u %llu), search_slot ret %d\n",
                 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;
        }

        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;

        btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
        memcpy(scratch_leaf, path->nodes[0], sizeof(*scratch_leaf));
        slot = path->slots[0];
        btrfs_release_path(path);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        for (; slot < btrfs_header_nritems(scratch_leaf); ++slot) {
                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->extent_root->nodesize;
                else
                        num_bytes = found.offset;

                ulist_reinit(qgroups);
                ret = btrfs_find_all_roots(NULL, fs_info, found.objectid, 0,
                                           &roots);
                if (ret < 0)
                        goto out;
                spin_lock(&fs_info->qgroup_lock);
                seq = fs_info->qgroup_seq;
                fs_info->qgroup_seq += roots->nnodes + 1; /* max refcnt */

                new_roots = 0;
                ret = qgroup_calc_old_refcnt(fs_info, 0, tmp, roots, qgroups,
                                             seq, &new_roots, 1);
                if (ret < 0) {
                        spin_unlock(&fs_info->qgroup_lock);
                        ulist_free(roots);
                        goto out;
                }

                ret = qgroup_adjust_counters(fs_info, 0, num_bytes, qgroups,
                                             seq, 0, new_roots, 1);
                if (ret < 0) {
                        spin_unlock(&fs_info->qgroup_lock);
                        ulist_free(roots);
                        goto out;
                }
                spin_unlock(&fs_info->qgroup_lock);
                ulist_free(roots);
        }
out:
        btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);

        return ret;
}

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;
        struct ulist *tmp = NULL, *qgroups = NULL;
        struct extent_buffer *scratch_leaf = NULL;
        int err = -ENOMEM;

        path = btrfs_alloc_path();
        if (!path)
                goto out;
        qgroups = ulist_alloc(GFP_NOFS);
        if (!qgroups)
                goto out;
        tmp = ulist_alloc(GFP_NOFS);
        if (!tmp)
                goto out;
        scratch_leaf = kmalloc(sizeof(*scratch_leaf), GFP_NOFS);
        if (!scratch_leaf)
                goto out;

        err = 0;
        while (!err) {
                trans = btrfs_start_transaction(fs_info->fs_root, 0);
                if (IS_ERR(trans)) {
                        err = PTR_ERR(trans);
                        break;
                }
                if (!fs_info->quota_enabled) {
                        err = -EINTR;
                } else {
                        err = qgroup_rescan_leaf(fs_info, path, trans,
                                                 qgroups, tmp, scratch_leaf);
                }
                if (err > 0)
                        btrfs_commit_transaction(trans, fs_info->fs_root);
                else
                        btrfs_end_transaction(trans, fs_info->fs_root);
        }

out:
        kfree(scratch_leaf);
        ulist_free(qgroups);
        ulist_free(tmp);
        btrfs_free_path(path);

        mutex_lock(&fs_info->qgroup_rescan_lock);
        fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;

        if (err == 2 &&
            fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        } else if (err < 0) {
                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
        }
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        if (err >= 0) {
                btrfs_info(fs_info, "qgroup scan completed%s",
                        err == 2 ? " (inconsistency flag cleared)" : "");
        } else {
                btrfs_err(fs_info, "qgroup scan failed with %d", err);
        }

        complete_all(&fs_info->qgroup_rescan_completion);
}

/*
 * 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 (!init_flags &&
            (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN) ||
             !(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))) {
                ret = -EINVAL;
                goto err;
        }

        mutex_lock(&fs_info->qgroup_rescan_lock);
        spin_lock(&fs_info->qgroup_lock);

        if (init_flags) {
                if (fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN)
                        ret = -EINPROGRESS;
                else if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON))
                        ret = -EINVAL;

                if (ret) {
                        spin_unlock(&fs_info->qgroup_lock);
                        mutex_unlock(&fs_info->qgroup_rescan_lock);
                        goto err;
                }

                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_rescan_progress.objectid = progress_objectid;

        spin_unlock(&fs_info->qgroup_lock);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        init_completion(&fs_info->qgroup_rescan_completion);

        memset(&fs_info->qgroup_rescan_work, 0,
               sizeof(fs_info->qgroup_rescan_work));
        btrfs_init_work(&fs_info->qgroup_rescan_work,
                        btrfs_qgroup_rescan_helper,
                        btrfs_qgroup_rescan_worker, NULL, NULL);

        if (ret) {
err:
                btrfs_info(fs_info, "qgroup_rescan_init failed with %d", ret);
                return ret;
        }

        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;
        }
        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_join_transaction(fs_info->fs_root);
        if (IS_ERR(trans)) {
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
                return PTR_ERR(trans);
        }
        ret = btrfs_commit_transaction(trans, fs_info->fs_root);
        if (ret) {
                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
                return ret;
        }

        qgroup_rescan_zero_tracking(fs_info);

        btrfs_queue_work(fs_info->qgroup_rescan_workers,
                         &fs_info->qgroup_rescan_work);

        return 0;
}

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

        mutex_lock(&fs_info->qgroup_rescan_lock);
        spin_lock(&fs_info->qgroup_lock);
        running = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN;
        spin_unlock(&fs_info->qgroup_lock);
        mutex_unlock(&fs_info->qgroup_rescan_lock);

        if (running)
                ret = wait_for_completion_interruptible(
                                        &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)
                btrfs_queue_work(fs_info->qgroup_rescan_workers,
                                 &fs_info->qgroup_rescan_work);
}