fs/btrfs/qgroup.c - third_party/kernel - Git at Google

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

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

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

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

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

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

 	return ret;
 }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 	return qgroup;
 }

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

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

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

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

 	if (!qgroup)
 		return -ENOENT;

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

 /*
  * Add relation specified by two qgroups.
  *
  * Must be called with qgroup_lock held.
  *
  * Return: 0        on success
  *         -ENOENT  if one of the qgroups is NULL
  *         <0       other errors
  */
 static int __add_relation_rb(struct btrfs_qgroup *member, struct btrfs_qgroup *parent)
 {
 	struct btrfs_qgroup_list *list;

 	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;
 }

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

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

 	return __add_relation_rb(member, parent);
 }

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

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

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

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

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

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

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

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

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

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

 	ret = btrfs_sysfs_add_qgroups(fs_info);
 	if (ret < 0)
 		goto out;
 	/* default this to quota off, in case no status key is found */
 	fs_info->qgroup_flags = 0;

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

 	while (1) {
 		struct btrfs_qgroup *qgroup;

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

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

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

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

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

 		qgroup = find_qgroup_rb(fs_info, found_key.offset);
 		if ((qgroup && found_key.type == BTRFS_QGROUP_INFO_KEY) ||
 		    (!qgroup && found_key.type == BTRFS_QGROUP_LIMIT_KEY)) {
 			btrfs_err(fs_info, "inconsistent qgroup config");
 			qgroup_mark_inconsistent(fs_info);
 		}
 		if (!qgroup) {
 			qgroup = add_qgroup_rb(fs_info, found_key.offset);
 			if (IS_ERR(qgroup)) {
 				ret = PTR_ERR(qgroup);
 				goto out;
 			}
 		}
 		ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
 		if (ret < 0)
 			goto out;

 		switch (found_key.type) {
 		case BTRFS_QGROUP_INFO_KEY: {
 			struct btrfs_qgroup_info_item *ptr;

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

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

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

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

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

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

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

 	return ret < 0 ? ret : 0;
 }

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

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

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

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

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

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

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

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

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

 	btrfs_mark_buffer_dirty(trans, path->nodes[0]);

 	btrfs_free_path(path);
 	return ret;
 }

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

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

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

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

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

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

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

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

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

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

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

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

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

 	btrfs_mark_buffer_dirty(trans, leaf);

 	btrfs_release_path(path);

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

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

 	btrfs_mark_buffer_dirty(trans, leaf);

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

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

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

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

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

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

 	btrfs_release_path(path);

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

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

 	ret = btrfs_del_item(trans, quota_root, path);

 out:
 	btrfs_free_path(path);
 	return ret;
 }

 static int update_qgroup_limit_item(struct btrfs_trans_handle *trans,
 				    struct btrfs_qgroup *qgroup)
 {
 	struct btrfs_root *quota_root = trans->fs_info->quota_root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct extent_buffer *l;
 	struct btrfs_qgroup_limit_item *qgroup_limit;
 	int ret;
 	int slot;

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

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

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

 	if (ret)
 		goto out;

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

 	btrfs_mark_buffer_dirty(trans, l);

 out:
 	btrfs_free_path(path);
 	return ret;
 }

 static int update_qgroup_info_item(struct btrfs_trans_handle *trans,
 				   struct btrfs_qgroup *qgroup)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
 	struct btrfs_root *quota_root = fs_info->quota_root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct extent_buffer *l;
 	struct btrfs_qgroup_info_item *qgroup_info;
 	int ret;
 	int slot;

 	if (btrfs_is_testing(fs_info))
 		return 0;

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

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

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

 	if (ret)
 		goto out;

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

 	btrfs_mark_buffer_dirty(trans, l);

 out:
 	btrfs_free_path(path);
 	return ret;
 }

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

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

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

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

 	if (ret)
 		goto out;

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

 	btrfs_mark_buffer_dirty(trans, l);

 out:
 	btrfs_free_path(path);
 	return ret;
 }

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 	if (fs_info->quota_root)
 		goto out;

 	fs_info->qgroup_ulist = ulist;
 	ulist = NULL;

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

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

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

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

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

 	btrfs_mark_buffer_dirty(trans, leaf);

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

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

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

 		if (found_key.type == BTRFS_ROOT_REF_KEY) {

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

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

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

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

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

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

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

 	ret = qgroup_rescan_init(fs_info, 0, 1);
 	if (!ret) {
 	        qgroup_rescan_zero_tracking(fs_info);
 		fs_info->qgroup_rescan_running = true;
 	        btrfs_queue_work(fs_info->qgroup_rescan_workers,
 	                         &fs_info->qgroup_rescan_work);
 	} else {
 		/*
 		 * We have set both BTRFS_FS_QUOTA_ENABLED and
 		 * BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with
 		 * -EINPROGRESS. That can happen because someone started the
 		 * rescan worker by calling quota rescan ioctl before we
 		 * attempted to initialize the rescan worker. Failure due to
 		 * quotas disabled in the meanwhile is not possible, because
 		 * we are holding a write lock on fs_info->subvol_sem, which
 		 * is also acquired when disabling quotas.
 		 * Ignore such error, and any other error would need to undo
 		 * everything we did in the transaction we just committed.
 		 */
 		ASSERT(ret == -EINPROGRESS);
 		ret = 0;
 	}

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

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

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

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

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

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

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

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

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

 	if (!fs_info->quota_root)
 		goto out;

 	spin_lock(&fs_info->qgroup_lock);
 	quota_root = fs_info->quota_root;
 	fs_info->quota_root = NULL;
 	fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON;
 	fs_info->qgroup_drop_subtree_thres = BTRFS_MAX_LEVEL;
 	spin_unlock(&fs_info->qgroup_lock);

 	btrfs_free_qgroup_config(fs_info);

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

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

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

 	btrfs_tree_lock(quota_root->node);
 	btrfs_clear_buffer_dirty(trans, quota_root->node);
 	btrfs_tree_unlock(quota_root->node);
 	ret = btrfs_free_tree_block(trans, btrfs_root_id(quota_root),
 				    quota_root->node, 0, 1);

 	if (ret < 0)
 		btrfs_abort_transaction(trans, ret);

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

 	return ret;
 }

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

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

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

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

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

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

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

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

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

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

 	qgroup_dirty(fs_info, qgroup);

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

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 	return ret;
 }

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

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

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

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

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

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

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

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

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

 	if (is_fstree(qgroupid) && qgroup_has_usage(qgroup)) {
 		ret = -EBUSY;
 		goto out;
 	}

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

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

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

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

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

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

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

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

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

 	spin_unlock(&fs_info->qgroup_lock);

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

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

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

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

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

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

 int btrfs_qgroup_trace_extent_post(struct btrfs_trans_handle *trans,
 				   struct btrfs_qgroup_extent_record *qrecord)
 {
 	struct btrfs_backref_walk_ctx ctx = { 0 };
 	int ret;

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

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

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

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

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

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

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

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

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

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

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

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

 		if (key.type != BTRFS_EXTENT_DATA_KEY)
 			continue;

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

 		if (extent_type == BTRFS_FILE_EXTENT_INLINE)
 			continue;

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

 		num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);

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

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

 	if (root_level == 0)
 		return 1;

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

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

 		level++;
 	}

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

 	return 0;
 }

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

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

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

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

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

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

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

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

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

 			src_path->nodes[cur_level] = eb;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 	eb = dst_path->nodes[cur_level];

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

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

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

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

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

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

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

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

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

 out:
 	btrfs_free_path(dst_path);
 	if (ret < 0)
 		qgroup_mark_inconsistent(fs_info);
 	return ret;
 }

 int btrfs_qgroup_trace_subtree(struct btrfs_trans_handle *trans,
 			       struct extent_buffer *root_eb,
 			       u64 root_gen, int root_level)
 {
 	struct btrfs_fs_info *fs_info = trans->fs_info;
 	int ret = 0;
 	int level;
 	u8 drop_subptree_thres;
 	struct extent_buffer *eb = root_eb;
 	struct btrfs_path *path = NULL;

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

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

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

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

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

 		ret = btrfs_read_extent_buffer(root_eb, &check);
 		if (ret)
 			goto out;
 	}

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

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

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

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

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

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

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

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

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

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

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

 		level--;
 	}

 	ret = 0;
 out:
 	btrfs_free_path(path);

 	return ret;
 }

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

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

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

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

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

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

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

 		trace_qgroup_update_counters(fs_info, qg, cur_old_count,
 					     cur_new_count);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 		num_dirty_extents++;
 		trace_btrfs_qgroup_account_extents(fs_info, record);

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

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

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

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

 	}
 	trace_qgroup_num_dirty_extents(fs_info, trans->transid,
 				       num_dirty_extents);
 	return ret;
 }

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

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

 	if (!fs_info->quota_root)
 		return ret;

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

 	ret = update_qgroup_status_item(trans);
 	if (ret)
 		qgroup_mark_inconsistent(fs_info);

 	return ret;
 }

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

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

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

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

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

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

 			++i_qgroups;
 		}
 	}

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

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


 	spin_lock(&fs_info->qgroup_lock);

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

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

 		qgroup_dirty(fs_info, dstgroup);
 	}

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

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

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

 		qgroup_dirty(fs_info, dstgroup);
 		qgroup_dirty(fs_info, srcgroup);
 	}

 	if (!inherit)
 		goto unlock;

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

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

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

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

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

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

 		dst->rfer = src->rfer - level_size;
 		dst->rfer_cmpr = src->rfer_cmpr - level_size;

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

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

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

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

 		dst->excl = src->excl + level_size;
 		dst->excl_cmpr = src->excl_cmpr + level_size;
 		need_rescan = true;
 	}

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

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

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

 	return true;
 }

 static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes, bool enforce,
 			  enum btrfs_qgroup_rsv_type type)
 {
 	struct btrfs_qgroup *qgroup;
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	u64 ref_root = root->root_key.objectid;
 	int ret = 0;
 	LIST_HEAD(qgroup_list);

 	if (!is_fstree(ref_root))
 		return 0;

 	if (num_bytes == 0)
 		return 0;

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

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

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

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

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

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

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

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

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

 	if (!is_fstree(ref_root))
 		return;

 	if (num_bytes == 0)
 		return;

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

 	if (!fs_info->quota_root)
 		goto out;

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

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

 	ulist_reinit(fs_info->qgroup_ulist);
 	ret = ulist_add(fs_info->qgroup_ulist, qgroup->qgroupid,
 			qgroup_to_aux(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 = unode_aux_to_qgroup(unode);

 		qgroup_rsv_release(fs_info, qg, num_bytes, type);

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

 static bool rescan_should_stop(struct btrfs_fs_info *fs_info)
 {
 	return btrfs_fs_closing(fs_info) ||
 		test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state) ||
 		!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) ||
 			  fs_info->qgroup_flags & BTRFS_QGROUP_RUNTIME_FLAG_CANCEL_RESCAN;
 }

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

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

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

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

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

 out:
 	btrfs_free_path(path);

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

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

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

 	if (!trans)
 		return;

 	btrfs_end_transaction(trans);

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

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

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

 		if (ret)
 			return ret;
 	}

 	mutex_lock(&fs_info->qgroup_rescan_lock);

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

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

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

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

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

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

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

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

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

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

 	qgroup_rescan_zero_tracking(fs_info);

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

 	return 0;
 }

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

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

 	if (!running)
 		return 0;

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

 	return ret;
 }

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

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

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

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

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

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

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

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

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

 	return ret;
 }

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

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

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

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

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

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

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

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &root->fs_info->flags) ||
 	    !is_fstree(root->root_key.objectid) || len == 0)
 		return 0;

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

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

 	return ret;

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

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

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

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

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

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

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

 		extent_changeset_release(&changeset);

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

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

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

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

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

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

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

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

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

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

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

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

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) ||
 	    !is_fstree(root->root_key.objectid) || num_bytes == 0)
 		return 0;

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

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

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

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

 void btrfs_qgroup_free_meta_all_pertrans(struct btrfs_root *root)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) ||
 	    !is_fstree(root->root_key.objectid))
 		return;

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

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

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) ||
 	    !is_fstree(root->root_key.objectid))
 		return;

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

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

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

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

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

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

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

 void btrfs_qgroup_convert_reserved_meta(struct btrfs_root *root, int num_bytes)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) ||
 	    !is_fstree(root->root_key.objectid))
 		return;
 	/* Same as btrfs_qgroup_free_meta_prealloc() */
 	num_bytes = sub_root_meta_rsv(root, num_bytes,
 				      BTRFS_QGROUP_RSV_META_PREALLOC);
 	trace_qgroup_meta_convert(root, num_bytes);
 	qgroup_convert_meta(fs_info, root->root_key.objectid, num_bytes);
 	if (!sb_rdonly(fs_info->sb))
 		add_root_meta_rsv(root, num_bytes, BTRFS_QGROUP_RSV_META_PERTRANS);
 }

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

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

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

 	}
 	extent_changeset_release(&changeset);
 }

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

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

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

 	swapped_blocks = &root->swapped_blocks;

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

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

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

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

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

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

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

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

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

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

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

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

 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
 		return 0;
 	if (!is_fstree(root->root_key.objectid) || !root->reloc_root)
 		return 0;

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

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

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

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

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

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

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