// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2011 Fujitsu.  All rights reserved.
 * Written by Miao Xie <miaox@cn.fujitsu.com>
 */

#include <linux/slab.h>
#include <linux/iversion.h>
#include "ctree.h"
#include "fs.h"
#include "messages.h"
#include "misc.h"
#include "delayed-inode.h"
#include "disk-io.h"
#include "transaction.h"
#include "qgroup.h"
#include "locking.h"
#include "inode-item.h"
#include "space-info.h"
#include "accessors.h"
#include "file-item.h"

#define BTRFS_DELAYED_WRITEBACK         512
#define BTRFS_DELAYED_BACKGROUND        128
#define BTRFS_DELAYED_BATCH             16

static struct kmem_cache *delayed_node_cache;

int __init btrfs_delayed_inode_init(void)
{
        delayed_node_cache = KMEM_CACHE(btrfs_delayed_node, 0);
        if (!delayed_node_cache)
                return -ENOMEM;
        return 0;
}

void __cold btrfs_delayed_inode_exit(void)
{
        kmem_cache_destroy(delayed_node_cache);
}

void btrfs_init_delayed_root(struct btrfs_delayed_root *delayed_root)
{
        atomic_set(&delayed_root->items, 0);
        atomic_set(&delayed_root->items_seq, 0);
        delayed_root->nodes = 0;
        spin_lock_init(&delayed_root->lock);
        init_waitqueue_head(&delayed_root->wait);
        INIT_LIST_HEAD(&delayed_root->node_list);
        INIT_LIST_HEAD(&delayed_root->prepare_list);
}

static inline void btrfs_init_delayed_node(
                                struct btrfs_delayed_node *delayed_node,
                                struct btrfs_root *root, u64 inode_id)
{
        delayed_node->root = root;
        delayed_node->inode_id = inode_id;
        refcount_set(&delayed_node->refs, 0);
        btrfs_delayed_node_ref_tracker_dir_init(delayed_node);
        delayed_node->ins_root = RB_ROOT_CACHED;
        delayed_node->del_root = RB_ROOT_CACHED;
        mutex_init(&delayed_node->mutex);
        INIT_LIST_HEAD(&delayed_node->n_list);
        INIT_LIST_HEAD(&delayed_node->p_list);
}

static struct btrfs_delayed_node *btrfs_get_delayed_node(
                struct btrfs_inode *btrfs_inode,
                struct btrfs_ref_tracker *tracker)
{
        struct btrfs_root *root = btrfs_inode->root;
        u64 ino = btrfs_ino(btrfs_inode);
        struct btrfs_delayed_node *node;

        node = READ_ONCE(btrfs_inode->delayed_node);
        if (node) {
                refcount_inc(&node->refs);
                btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_NOFS);
                return node;
        }

        xa_lock(&root->delayed_nodes);
        node = xa_load(&root->delayed_nodes, ino);

        if (node) {
                if (btrfs_inode->delayed_node) {
                        refcount_inc(&node->refs);      /* can be accessed */
                        btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_ATOMIC);
                        BUG_ON(btrfs_inode->delayed_node != node);
                        xa_unlock(&root->delayed_nodes);
                        return node;
                }

                /*
                 * It's possible that we're racing into the middle of removing
                 * this node from the xarray.  In this case, the refcount
                 * was zero and it should never go back to one.  Just return
                 * NULL like it was never in the xarray at all; our release
                 * function is in the process of removing it.
                 *
                 * Some implementations of refcount_inc refuse to bump the
                 * refcount once it has hit zero.  If we don't do this dance
                 * here, refcount_inc() may decide to just WARN_ONCE() instead
                 * of actually bumping the refcount.
                 *
                 * If this node is properly in the xarray, we want to bump the
                 * refcount twice, once for the inode and once for this get
                 * operation.
                 */
                if (refcount_inc_not_zero(&node->refs)) {
                        refcount_inc(&node->refs);
                        btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_ATOMIC);
                        btrfs_delayed_node_ref_tracker_alloc(node, &node->inode_cache_tracker,
                                                             GFP_ATOMIC);
                        btrfs_inode->delayed_node = node;
                } else {
                        node = NULL;
                }

                xa_unlock(&root->delayed_nodes);
                return node;
        }
        xa_unlock(&root->delayed_nodes);

        return NULL;
}

/*
 * Look up an existing delayed node associated with @btrfs_inode or create a new
 * one and insert it to the delayed nodes of the root.
 *
 * Return the delayed node, or error pointer on failure.
 */
static struct btrfs_delayed_node *btrfs_get_or_create_delayed_node(
                struct btrfs_inode *btrfs_inode,
                struct btrfs_ref_tracker *tracker)
{
        struct btrfs_delayed_node *node;
        struct btrfs_root *root = btrfs_inode->root;
        u64 ino = btrfs_ino(btrfs_inode);
        int ret;
        void *ptr;

again:
        node = btrfs_get_delayed_node(btrfs_inode, tracker);
        if (node)
                return node;

        node = kmem_cache_zalloc(delayed_node_cache, GFP_NOFS);
        if (!node)
                return ERR_PTR(-ENOMEM);
        btrfs_init_delayed_node(node, root, ino);

        /* Cached in the inode and can be accessed. */
        refcount_set(&node->refs, 2);
        btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_NOFS);
        btrfs_delayed_node_ref_tracker_alloc(node, &node->inode_cache_tracker, GFP_NOFS);

        /* Allocate and reserve the slot, from now it can return a NULL from xa_load(). */
        ret = xa_reserve(&root->delayed_nodes, ino, GFP_NOFS);
        if (ret == -ENOMEM)
                goto cleanup;

        xa_lock(&root->delayed_nodes);
        ptr = xa_load(&root->delayed_nodes, ino);
        if (ptr) {
                /* Somebody inserted it, go back and read it. */
                xa_unlock(&root->delayed_nodes);
                goto cleanup;
        }
        ptr = __xa_store(&root->delayed_nodes, ino, node, GFP_ATOMIC);
        ASSERT(xa_err(ptr) != -EINVAL);
        ASSERT(xa_err(ptr) != -ENOMEM);
        ASSERT(ptr == NULL);
        btrfs_inode->delayed_node = node;
        xa_unlock(&root->delayed_nodes);

        return node;
cleanup:
        btrfs_delayed_node_ref_tracker_free(node, tracker);
        btrfs_delayed_node_ref_tracker_free(node, &node->inode_cache_tracker);
        btrfs_delayed_node_ref_tracker_dir_exit(node);
        kmem_cache_free(delayed_node_cache, node);
        if (ret)
                return ERR_PTR(ret);
        goto again;
}

/*
 * Call it when holding delayed_node->mutex
 *
 * If mod = 1, add this node into the prepared list.
 */
static void btrfs_queue_delayed_node(struct btrfs_delayed_root *root,
                                     struct btrfs_delayed_node *node,
                                     int mod)
{
        spin_lock(&root->lock);
        if (test_bit(BTRFS_DELAYED_NODE_IN_LIST, &node->flags)) {
                if (!list_empty(&node->p_list))
                        list_move_tail(&node->p_list, &root->prepare_list);
                else if (mod)
                        list_add_tail(&node->p_list, &root->prepare_list);
        } else {
                list_add_tail(&node->n_list, &root->node_list);
                list_add_tail(&node->p_list, &root->prepare_list);
                refcount_inc(&node->refs);      /* inserted into list */
                btrfs_delayed_node_ref_tracker_alloc(node, &node->node_list_tracker,
                                                     GFP_ATOMIC);
                root->nodes++;
                set_bit(BTRFS_DELAYED_NODE_IN_LIST, &node->flags);
        }
        spin_unlock(&root->lock);
}

/* Call it when holding delayed_node->mutex */
static void btrfs_dequeue_delayed_node(struct btrfs_delayed_root *root,
                                       struct btrfs_delayed_node *node)
{
        spin_lock(&root->lock);
        if (test_bit(BTRFS_DELAYED_NODE_IN_LIST, &node->flags)) {
                root->nodes--;
                btrfs_delayed_node_ref_tracker_free(node, &node->node_list_tracker);
                refcount_dec(&node->refs);      /* not in the list */
                list_del_init(&node->n_list);
                if (!list_empty(&node->p_list))
                        list_del_init(&node->p_list);
                clear_bit(BTRFS_DELAYED_NODE_IN_LIST, &node->flags);
        }
        spin_unlock(&root->lock);
}

static struct btrfs_delayed_node *btrfs_first_delayed_node(
                        struct btrfs_fs_info *fs_info,
                        struct btrfs_ref_tracker *tracker)
{
        struct btrfs_delayed_node *node;

        spin_lock(&fs_info->delayed_root.lock);
        node = list_first_entry_or_null(&fs_info->delayed_root.node_list,
                                        struct btrfs_delayed_node, n_list);
        if (node) {
                refcount_inc(&node->refs);
                btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_ATOMIC);
        }
        spin_unlock(&fs_info->delayed_root.lock);

        return node;
}

static struct btrfs_delayed_node *btrfs_next_delayed_node(
                                                struct btrfs_delayed_node *node,
                                                struct btrfs_ref_tracker *tracker)
{
        struct btrfs_delayed_root *delayed_root;
        struct list_head *p;
        struct btrfs_delayed_node *next = NULL;

        delayed_root = &node->root->fs_info->delayed_root;
        spin_lock(&delayed_root->lock);
        if (!test_bit(BTRFS_DELAYED_NODE_IN_LIST, &node->flags)) {
                /* not in the list */
                if (list_empty(&delayed_root->node_list))
                        goto out;
                p = delayed_root->node_list.next;
        } else if (list_is_last(&node->n_list, &delayed_root->node_list))
                goto out;
        else
                p = node->n_list.next;

        next = list_entry(p, struct btrfs_delayed_node, n_list);
        refcount_inc(&next->refs);
        btrfs_delayed_node_ref_tracker_alloc(next, tracker, GFP_ATOMIC);
out:
        spin_unlock(&delayed_root->lock);

        return next;
}

static void __btrfs_release_delayed_node(
                                struct btrfs_delayed_node *delayed_node,
                                int mod, struct btrfs_ref_tracker *tracker)
{
        struct btrfs_delayed_root *delayed_root;

        if (!delayed_node)
                return;

        delayed_root = &delayed_node->root->fs_info->delayed_root;

        mutex_lock(&delayed_node->mutex);
        if (delayed_node->count)
                btrfs_queue_delayed_node(delayed_root, delayed_node, mod);
        else
                btrfs_dequeue_delayed_node(delayed_root, delayed_node);
        mutex_unlock(&delayed_node->mutex);

        btrfs_delayed_node_ref_tracker_free(delayed_node, tracker);
        if (refcount_dec_and_test(&delayed_node->refs)) {
                struct btrfs_root *root = delayed_node->root;

                xa_erase(&root->delayed_nodes, delayed_node->inode_id);
                /*
                 * Once our refcount goes to zero, nobody is allowed to bump it
                 * back up.  We can delete it now.
                 */
                ASSERT(refcount_read(&delayed_node->refs) == 0);
                btrfs_delayed_node_ref_tracker_dir_exit(delayed_node);
                kmem_cache_free(delayed_node_cache, delayed_node);
        }
}

static inline void btrfs_release_delayed_node(struct btrfs_delayed_node *node,
                                              struct btrfs_ref_tracker *tracker)
{
        __btrfs_release_delayed_node(node, 0, tracker);
}

static struct btrfs_delayed_node *btrfs_first_prepared_delayed_node(
                                        struct btrfs_delayed_root *delayed_root,
                                        struct btrfs_ref_tracker *tracker)
{
        struct btrfs_delayed_node *node;

        spin_lock(&delayed_root->lock);
        node = list_first_entry_or_null(&delayed_root->prepare_list,
                                        struct btrfs_delayed_node, p_list);
        if (node) {
                list_del_init(&node->p_list);
                refcount_inc(&node->refs);
                btrfs_delayed_node_ref_tracker_alloc(node, tracker, GFP_ATOMIC);
        }
        spin_unlock(&delayed_root->lock);

        return node;
}

static inline void btrfs_release_prepared_delayed_node(
                                        struct btrfs_delayed_node *node,
                                        struct btrfs_ref_tracker *tracker)
{
        __btrfs_release_delayed_node(node, 1, tracker);
}

static struct btrfs_delayed_item *btrfs_alloc_delayed_item(u16 data_len,
                                           struct btrfs_delayed_node *node,
                                           enum btrfs_delayed_item_type type)
{
        struct btrfs_delayed_item *item;

        item = kmalloc_flex(*item, data, data_len, GFP_NOFS);
        if (item) {
                item->data_len = data_len;
                item->type = type;
                item->bytes_reserved = 0;
                item->delayed_node = node;
                RB_CLEAR_NODE(&item->rb_node);
                INIT_LIST_HEAD(&item->log_list);
                item->logged = false;
                refcount_set(&item->refs, 1);
        }
        return item;
}

static int delayed_item_index_cmp(const void *key, const struct rb_node *node)
{
        const u64 *index = key;
        const struct btrfs_delayed_item *delayed_item = rb_entry(node,
                                                 struct btrfs_delayed_item, rb_node);

        if (delayed_item->index < *index)
                return 1;
        else if (delayed_item->index > *index)
                return -1;

        return 0;
}

/*
 * Look up the delayed item by key.
 *
 * @delayed_node: pointer to the delayed node
 * @index:        the dir index value to lookup (offset of a dir index key)
 *
 * Note: if we don't find the right item, we will return the prev item and
 * the next item.
 */
static struct btrfs_delayed_item *__btrfs_lookup_delayed_item(
                                struct rb_root *root,
                                u64 index)
{
        struct rb_node *node;

        node = rb_find(&index, root, delayed_item_index_cmp);
        return rb_entry_safe(node, struct btrfs_delayed_item, rb_node);
}

static int btrfs_delayed_item_cmp(const struct rb_node *new,
                                  const struct rb_node *exist)
{
        const struct btrfs_delayed_item *new_item =
                rb_entry(new, struct btrfs_delayed_item, rb_node);

        return delayed_item_index_cmp(&new_item->index, exist);
}

static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
                                    struct btrfs_delayed_item *ins)
{
        struct rb_root_cached *root;
        struct rb_node *exist;

        if (ins->type == BTRFS_DELAYED_INSERTION_ITEM)
                root = &delayed_node->ins_root;
        else
                root = &delayed_node->del_root;

        exist = rb_find_add_cached(&ins->rb_node, root, btrfs_delayed_item_cmp);
        if (exist)
                return -EEXIST;

        if (ins->type == BTRFS_DELAYED_INSERTION_ITEM &&
            ins->index >= delayed_node->index_cnt)
                delayed_node->index_cnt = ins->index + 1;

        delayed_node->count++;
        atomic_inc(&delayed_node->root->fs_info->delayed_root.items);
        return 0;
}

static void finish_one_item(struct btrfs_delayed_root *delayed_root)
{
        int seq = atomic_inc_return(&delayed_root->items_seq);

        /* atomic_dec_return implies a barrier */
        if ((atomic_dec_return(&delayed_root->items) <
            BTRFS_DELAYED_BACKGROUND || seq % BTRFS_DELAYED_BATCH == 0))
                cond_wake_up_nomb(&delayed_root->wait);
}

static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
{
        struct btrfs_delayed_node *delayed_node = delayed_item->delayed_node;
        struct rb_root_cached *root;

        /* Not inserted, ignore it. */
        if (RB_EMPTY_NODE(&delayed_item->rb_node))
                return;

        /* If it's in a rbtree, then we need to have delayed node locked. */
        lockdep_assert_held(&delayed_node->mutex);

        if (delayed_item->type == BTRFS_DELAYED_INSERTION_ITEM)
                root = &delayed_node->ins_root;
        else
                root = &delayed_node->del_root;

        rb_erase_cached(&delayed_item->rb_node, root);
        RB_CLEAR_NODE(&delayed_item->rb_node);
        delayed_node->count--;
        finish_one_item(&delayed_node->root->fs_info->delayed_root);
}

static void btrfs_release_delayed_item(struct btrfs_delayed_item *item)
{
        if (item) {
                __btrfs_remove_delayed_item(item);
                if (refcount_dec_and_test(&item->refs))
                        kfree(item);
        }
}

static struct btrfs_delayed_item *__btrfs_first_delayed_insertion_item(
                                        struct btrfs_delayed_node *delayed_node)
{
        struct rb_node *p = rb_first_cached(&delayed_node->ins_root);

        return rb_entry_safe(p, struct btrfs_delayed_item, rb_node);
}

static struct btrfs_delayed_item *__btrfs_first_delayed_deletion_item(
                                        struct btrfs_delayed_node *delayed_node)
{
        struct rb_node *p = rb_first_cached(&delayed_node->del_root);

        return rb_entry_safe(p, struct btrfs_delayed_item, rb_node);
}

static struct btrfs_delayed_item *__btrfs_next_delayed_item(
                                                struct btrfs_delayed_item *item)
{
        struct rb_node *p = rb_next(&item->rb_node);

        return rb_entry_safe(p, struct btrfs_delayed_item, rb_node);
}

static int btrfs_delayed_item_reserve_metadata(struct btrfs_trans_handle *trans,
                                               struct btrfs_delayed_item *item)
{
        struct btrfs_block_rsv *src_rsv;
        struct btrfs_block_rsv *dst_rsv;
        struct btrfs_fs_info *fs_info = trans->fs_info;
        u64 num_bytes;
        int ret;

        if (!trans->bytes_reserved)
                return 0;

        src_rsv = trans->block_rsv;
        dst_rsv = &fs_info->delayed_block_rsv;

        num_bytes = btrfs_calc_insert_metadata_size(fs_info, 1);

        /*
         * Here we migrate space rsv from transaction rsv, since have already
         * reserved space when starting a transaction.  So no need to reserve
         * qgroup space here.
         */
        ret = btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes, true);
        if (!ret) {
                trace_btrfs_space_reservation(fs_info, "delayed_item",
                                              item->delayed_node->inode_id,
                                              num_bytes, 1);
                /*
                 * For insertions we track reserved metadata space by accounting
                 * for the number of leaves that will be used, based on the delayed
                 * node's curr_index_batch_size and index_item_leaves fields.
                 */
                if (item->type == BTRFS_DELAYED_DELETION_ITEM)
                        item->bytes_reserved = num_bytes;
        }

        return ret;
}

static void btrfs_delayed_item_release_metadata(struct btrfs_root *root,
                                                struct btrfs_delayed_item *item)
{
        struct btrfs_block_rsv *rsv;
        struct btrfs_fs_info *fs_info = root->fs_info;

        if (!item->bytes_reserved)
                return;

        rsv = &fs_info->delayed_block_rsv;
        /*
         * Check btrfs_delayed_item_reserve_metadata() to see why we don't need
         * to release/reserve qgroup space.
         */
        trace_btrfs_space_reservation(fs_info, "delayed_item",
                                      item->delayed_node->inode_id,
                                      item->bytes_reserved, 0);
        btrfs_block_rsv_release(fs_info, rsv, item->bytes_reserved, NULL);
}

static void btrfs_delayed_item_release_leaves(struct btrfs_delayed_node *node,
                                              unsigned int num_leaves)
{
        struct btrfs_fs_info *fs_info = node->root->fs_info;
        const u64 bytes = btrfs_calc_insert_metadata_size(fs_info, num_leaves);

        /* There are no space reservations during log replay, bail out. */
        if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
                return;

        trace_btrfs_space_reservation(fs_info, "delayed_item", node->inode_id,
                                      bytes, 0);
        btrfs_block_rsv_release(fs_info, &fs_info->delayed_block_rsv, bytes, NULL);
}

static int btrfs_delayed_inode_reserve_metadata(
                                        struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_delayed_node *node)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_block_rsv *src_rsv;
        struct btrfs_block_rsv *dst_rsv;
        u64 num_bytes;
        int ret;

        src_rsv = trans->block_rsv;
        dst_rsv = &fs_info->delayed_block_rsv;

        num_bytes = btrfs_calc_metadata_size(fs_info, 1);

        /*
         * btrfs_dirty_inode will update the inode under btrfs_join_transaction
         * which doesn't reserve space for speed.  This is a problem since we
         * still need to reserve space for this update, so try to reserve the
         * space.
         *
         * Now if src_rsv == delalloc_block_rsv we'll let it just steal since
         * we always reserve enough to update the inode item.
         */
        if (!src_rsv || (!trans->bytes_reserved &&
                         src_rsv->type != BTRFS_BLOCK_RSV_DELALLOC)) {
                ret = btrfs_qgroup_reserve_meta(root, num_bytes,
                                          BTRFS_QGROUP_RSV_META_PREALLOC, true);
                if (ret < 0)
                        return ret;
                ret = btrfs_block_rsv_add(fs_info, dst_rsv, num_bytes,
                                          BTRFS_RESERVE_NO_FLUSH);
                /* NO_FLUSH could only fail with -ENOSPC */
                ASSERT(ret == 0 || ret == -ENOSPC);
                if (ret)
                        btrfs_qgroup_free_meta_prealloc(root, num_bytes);
        } else {
                ret = btrfs_block_rsv_migrate(src_rsv, dst_rsv, num_bytes, true);
        }

        if (!ret) {
                trace_btrfs_space_reservation(fs_info, "delayed_inode",
                                              node->inode_id, num_bytes, 1);
                node->bytes_reserved = num_bytes;
        }

        return ret;
}

static void btrfs_delayed_inode_release_metadata(struct btrfs_fs_info *fs_info,
                                                struct btrfs_delayed_node *node,
                                                bool qgroup_free)
{
        struct btrfs_block_rsv *rsv;

        if (!node->bytes_reserved)
                return;

        rsv = &fs_info->delayed_block_rsv;
        trace_btrfs_space_reservation(fs_info, "delayed_inode",
                                      node->inode_id, node->bytes_reserved, 0);
        btrfs_block_rsv_release(fs_info, rsv, node->bytes_reserved, NULL);
        if (qgroup_free)
                btrfs_qgroup_free_meta_prealloc(node->root,
                                node->bytes_reserved);
        else
                btrfs_qgroup_convert_reserved_meta(node->root,
                                node->bytes_reserved);
        node->bytes_reserved = 0;
}

/*
 * Insert a single delayed item or a batch of delayed items, as many as possible
 * that fit in a leaf. The delayed items (dir index keys) are sorted by their key
 * in the rbtree, and if there's a gap between two consecutive dir index items,
 * then it means at some point we had delayed dir indexes to add but they got
 * removed (by btrfs_delete_delayed_dir_index()) before we attempted to flush them
 * into the subvolume tree. Dir index keys also have their offsets coming from a
 * monotonically increasing counter, so we can't get new keys with an offset that
 * fits within a gap between delayed dir index items.
 */
static int btrfs_insert_delayed_item(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct btrfs_path *path,
                                     struct btrfs_delayed_item *first_item)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_delayed_node *node = first_item->delayed_node;
        LIST_HEAD(item_list);
        struct btrfs_delayed_item *curr;
        struct btrfs_delayed_item *next;
        const int max_size = BTRFS_LEAF_DATA_SIZE(fs_info);
        struct btrfs_item_batch batch;
        struct btrfs_key first_key;
        const u32 first_data_size = first_item->data_len;
        int total_size;
        char AUTO_KFREE(ins_data);
        int ret;
        bool continuous_keys_only = false;

        lockdep_assert_held(&node->mutex);

        /*
         * During normal operation the delayed index offset is continuously
         * increasing, so we can batch insert all items as there will not be any
         * overlapping keys in the tree.
         *
         * The exception to this is log replay, where we may have interleaved
         * offsets in the tree, so our batch needs to be continuous keys only in
         * order to ensure we do not end up with out of order items in our leaf.
         */
        if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
                continuous_keys_only = true;

        /*
         * For delayed items to insert, we track reserved metadata bytes based
         * on the number of leaves that we will use.
         * See btrfs_insert_delayed_dir_index() and
         * btrfs_delayed_item_reserve_metadata()).
         */
        ASSERT(first_item->bytes_reserved == 0);

        list_add_tail(&first_item->tree_list, &item_list);
        batch.total_data_size = first_data_size;
        batch.nr = 1;
        total_size = first_data_size + sizeof(struct btrfs_item);
        curr = first_item;

        while (true) {
                int next_size;

                next = __btrfs_next_delayed_item(curr);
                if (!next)
                        break;

                /*
                 * We cannot allow gaps in the key space if we're doing log
                 * replay.
                 */
                if (continuous_keys_only && (next->index != curr->index + 1))
                        break;

                ASSERT(next->bytes_reserved == 0);

                next_size = next->data_len + sizeof(struct btrfs_item);
                if (total_size + next_size > max_size)
                        break;

                list_add_tail(&next->tree_list, &item_list);
                batch.nr++;
                total_size += next_size;
                batch.total_data_size += next->data_len;
                curr = next;
        }

        if (batch.nr == 1) {
                first_key.objectid = node->inode_id;
                first_key.type = BTRFS_DIR_INDEX_KEY;
                first_key.offset = first_item->index;
                batch.keys = &first_key;
                batch.data_sizes = &first_data_size;
        } else {
                struct btrfs_key *ins_keys;
                u32 *ins_sizes;
                int i = 0;

                ins_data = kmalloc_array(batch.nr,
                                         sizeof(u32) + sizeof(struct btrfs_key), GFP_NOFS);
                if (!ins_data)
                        return -ENOMEM;
                ins_sizes = (u32 *)ins_data;
                ins_keys = (struct btrfs_key *)(ins_data + batch.nr * sizeof(u32));
                batch.keys = ins_keys;
                batch.data_sizes = ins_sizes;
                list_for_each_entry(curr, &item_list, tree_list) {
                        ins_keys[i].objectid = node->inode_id;
                        ins_keys[i].type = BTRFS_DIR_INDEX_KEY;
                        ins_keys[i].offset = curr->index;
                        ins_sizes[i] = curr->data_len;
                        i++;
                }
        }

        ret = btrfs_insert_empty_items(trans, root, path, &batch);
        if (ret)
                return ret;

        list_for_each_entry(curr, &item_list, tree_list) {
                char *data_ptr;

                data_ptr = btrfs_item_ptr(path->nodes[0], path->slots[0], char);
                write_extent_buffer(path->nodes[0], &curr->data,
                                    (unsigned long)data_ptr, curr->data_len);
                path->slots[0]++;
        }

        /*
         * Now release our path before releasing the delayed items and their
         * metadata reservations, so that we don't block other tasks for more
         * time than needed.
         */
        btrfs_release_path(path);

        ASSERT(node->index_item_leaves > 0);

        /*
         * For normal operations we will batch an entire leaf's worth of delayed
         * items, so if there are more items to process we can decrement
         * index_item_leaves by 1 as we inserted 1 leaf's worth of items.
         *
         * However for log replay we may not have inserted an entire leaf's
         * worth of items, we may have not had continuous items, so decrementing
         * here would mess up the index_item_leaves accounting.  For this case
         * only clean up the accounting when there are no items left.
         */
        if (next && !continuous_keys_only) {
                /*
                 * We inserted one batch of items into a leaf a there are more
                 * items to flush in a future batch, now release one unit of
                 * metadata space from the delayed block reserve, corresponding
                 * the leaf we just flushed to.
                 */
                btrfs_delayed_item_release_leaves(node, 1);
                node->index_item_leaves--;
        } else if (!next) {
                /*
                 * There are no more items to insert. We can have a number of
                 * reserved leaves > 1 here - this happens when many dir index
                 * items are added and then removed before they are flushed (file
                 * names with a very short life, never span a transaction). So
                 * release all remaining leaves.
                 */
                btrfs_delayed_item_release_leaves(node, node->index_item_leaves);
                node->index_item_leaves = 0;
        }

        list_for_each_entry_safe(curr, next, &item_list, tree_list) {
                list_del(&curr->tree_list);
                btrfs_release_delayed_item(curr);
        }

        return 0;
}

static int btrfs_insert_delayed_items(struct btrfs_trans_handle *trans,
                                      struct btrfs_path *path,
                                      struct btrfs_root *root,
                                      struct btrfs_delayed_node *node)
{
        int ret = 0;

        while (ret == 0) {
                struct btrfs_delayed_item *curr;

                mutex_lock(&node->mutex);
                curr = __btrfs_first_delayed_insertion_item(node);
                if (!curr) {
                        mutex_unlock(&node->mutex);
                        break;
                }
                ret = btrfs_insert_delayed_item(trans, root, path, curr);
                mutex_unlock(&node->mutex);
        }

        return ret;
}

static int btrfs_batch_delete_items(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root,
                                    struct btrfs_path *path,
                                    struct btrfs_delayed_item *item)
{
        const u64 ino = item->delayed_node->inode_id;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_delayed_item *curr, *next;
        struct extent_buffer *leaf = path->nodes[0];
        LIST_HEAD(batch_list);
        int nitems, slot, last_slot;
        int ret;
        u64 total_reserved_size = item->bytes_reserved;

        ASSERT(leaf != NULL);

        slot = path->slots[0];
        last_slot = btrfs_header_nritems(leaf) - 1;
        /*
         * Our caller always gives us a path pointing to an existing item, so
         * this can not happen.
         */
        ASSERT(slot <= last_slot);
        if (WARN_ON(slot > last_slot))
                return -ENOENT;

        nitems = 1;
        curr = item;
        list_add_tail(&curr->tree_list, &batch_list);

        /*
         * Keep checking if the next delayed item matches the next item in the
         * leaf - if so, we can add it to the batch of items to delete from the
         * leaf.
         */
        while (slot < last_slot) {
                struct btrfs_key key;

                next = __btrfs_next_delayed_item(curr);
                if (!next)
                        break;

                slot++;
                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (key.objectid != ino ||
                    key.type != BTRFS_DIR_INDEX_KEY ||
                    key.offset != next->index)
                        break;
                nitems++;
                curr = next;
                list_add_tail(&curr->tree_list, &batch_list);
                total_reserved_size += curr->bytes_reserved;
        }

        ret = btrfs_del_items(trans, root, path, path->slots[0], nitems);
        if (ret)
                return ret;

        /* In case of BTRFS_FS_LOG_RECOVERING items won't have reserved space */
        if (total_reserved_size > 0) {
                /*
                 * Check btrfs_delayed_item_reserve_metadata() to see why we
                 * don't need to release/reserve qgroup space.
                 */
                trace_btrfs_space_reservation(fs_info, "delayed_item", ino,
                                              total_reserved_size, 0);
                btrfs_block_rsv_release(fs_info, &fs_info->delayed_block_rsv,
                                        total_reserved_size, NULL);
        }

        list_for_each_entry_safe(curr, next, &batch_list, tree_list) {
                list_del(&curr->tree_list);
                btrfs_release_delayed_item(curr);
        }

        return 0;
}

static int btrfs_delete_delayed_items(struct btrfs_trans_handle *trans,
                                      struct btrfs_path *path,
                                      struct btrfs_root *root,
                                      struct btrfs_delayed_node *node)
{
        struct btrfs_key key;
        int ret = 0;

        key.objectid = node->inode_id;
        key.type = BTRFS_DIR_INDEX_KEY;

        while (ret == 0) {
                struct btrfs_delayed_item *item;

                mutex_lock(&node->mutex);
                item = __btrfs_first_delayed_deletion_item(node);
                if (!item) {
                        mutex_unlock(&node->mutex);
                        break;
                }

                key.offset = item->index;
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (ret > 0) {
                        /*
                         * There's no matching item in the leaf. This means we
                         * have already deleted this item in a past run of the
                         * delayed items. We ignore errors when running delayed
                         * items from an async context, through a work queue job
                         * running btrfs_async_run_delayed_root(), and don't
                         * release delayed items that failed to complete. This
                         * is because we will retry later, and at transaction
                         * commit time we always run delayed items and will
                         * then deal with errors if they fail to run again.
                         *
                         * So just release delayed items for which we can't find
                         * an item in the tree, and move to the next item.
                         */
                        btrfs_release_path(path);
                        btrfs_release_delayed_item(item);
                        ret = 0;
                } else if (ret == 0) {
                        ret = btrfs_batch_delete_items(trans, root, path, item);
                        btrfs_release_path(path);
                }

                /*
                 * We unlock and relock on each iteration, this is to prevent
                 * blocking other tasks for too long while we are being run from
                 * the async context (work queue job). Those tasks are typically
                 * running system calls like creat/mkdir/rename/unlink/etc which
                 * need to add delayed items to this delayed node.
                 */
                mutex_unlock(&node->mutex);
        }

        return ret;
}

static void btrfs_release_delayed_inode(struct btrfs_delayed_node *delayed_node)
{
        if (delayed_node &&
            test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                ASSERT(delayed_node->root);
                clear_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags);
                delayed_node->count--;
                finish_one_item(&delayed_node->root->fs_info->delayed_root);
        }
}

static void btrfs_release_delayed_iref(struct btrfs_delayed_node *delayed_node)
{
        if (test_and_clear_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags)) {
                ASSERT(delayed_node->root);
                delayed_node->count--;
                finish_one_item(&delayed_node->root->fs_info->delayed_root);
        }
}

static int __btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
                                        struct btrfs_root *root,
                                        struct btrfs_path *path,
                                        struct btrfs_delayed_node *node)
{
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_key key;
        struct btrfs_inode_item *inode_item;
        struct extent_buffer *leaf;
        int mod;
        int ret;

        key.objectid = node->inode_id;
        key.type = BTRFS_INODE_ITEM_KEY;
        key.offset = 0;

        if (test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &node->flags))
                mod = -1;
        else
                mod = 1;

        ret = btrfs_lookup_inode(trans, root, path, &key, mod);
        if (ret > 0)
                ret = -ENOENT;
        if (ret < 0) {
                /*
                 * If we fail to update the delayed inode we need to abort the
                 * transaction, because we could leave the inode with the
                 * improper counts behind.
                 */
                if (unlikely(ret != -ENOENT))
                        btrfs_abort_transaction(trans, ret);
                goto out;
        }

        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);
        write_extent_buffer(leaf, &node->inode_item, (unsigned long)inode_item,
                            sizeof(struct btrfs_inode_item));

        if (!test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &node->flags))
                goto out;

        /*
         * Now we're going to delete the INODE_REF/EXTREF, which should be the
         * only one ref left.  Check if the next item is an INODE_REF/EXTREF.
         *
         * But if we're the last item already, release and search for the last
         * INODE_REF/EXTREF.
         */
        if (path->slots[0] + 1 >= btrfs_header_nritems(leaf)) {
                key.objectid = node->inode_id;
                key.type = BTRFS_INODE_EXTREF_KEY;
                key.offset = (u64)-1;

                btrfs_release_path(path);
                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
                if (unlikely(ret < 0)) {
                        btrfs_abort_transaction(trans, ret);
                        goto err_out;
                }
                ASSERT(ret > 0);
                ASSERT(path->slots[0] > 0);
                ret = 0;
                path->slots[0]--;
                leaf = path->nodes[0];
        } else {
                path->slots[0]++;
        }
        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
        if (key.objectid != node->inode_id)
                goto out;
        if (key.type != BTRFS_INODE_REF_KEY &&
            key.type != BTRFS_INODE_EXTREF_KEY)
                goto out;

        /*
         * Delayed iref deletion is for the inode who has only one link,
         * so there is only one iref. The case that several irefs are
         * in the same item doesn't exist.
         */
        ret = btrfs_del_item(trans, root, path);
        if (ret < 0)
                btrfs_abort_transaction(trans, ret);
out:
        btrfs_release_delayed_iref(node);
        btrfs_release_path(path);
err_out:
        btrfs_delayed_inode_release_metadata(fs_info, node, (ret < 0));
        btrfs_release_delayed_inode(node);
        return ret;
}

static inline int btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
                                             struct btrfs_root *root,
                                             struct btrfs_path *path,
                                             struct btrfs_delayed_node *node)
{
        int ret;

        mutex_lock(&node->mutex);
        if (!test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &node->flags)) {
                mutex_unlock(&node->mutex);
                return 0;
        }

        ret = __btrfs_update_delayed_inode(trans, root, path, node);
        mutex_unlock(&node->mutex);
        return ret;
}

static inline int
__btrfs_commit_inode_delayed_items(struct btrfs_trans_handle *trans,
                                   struct btrfs_path *path,
                                   struct btrfs_delayed_node *node)
{
        int ret;

        ret = btrfs_insert_delayed_items(trans, path, node->root, node);
        if (ret)
                return ret;

        ret = btrfs_delete_delayed_items(trans, path, node->root, node);
        if (ret)
                return ret;

        ret = btrfs_record_root_in_trans(trans, node->root);
        if (ret)
                return ret;

        return btrfs_update_delayed_inode(trans, node->root, path, node);
}

/*
 * Called when committing the transaction.
 * Returns 0 on success.
 * Returns < 0 on error and returns with an aborted transaction with any
 * outstanding delayed items cleaned up.
 */
static int __btrfs_run_delayed_items(struct btrfs_trans_handle *trans, int nr)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        struct btrfs_delayed_node *curr_node, *prev_node;
        struct btrfs_ref_tracker curr_delayed_node_tracker, prev_delayed_node_tracker;
        struct btrfs_path *path;
        struct btrfs_block_rsv *block_rsv;
        int ret = 0;
        bool count = (nr > 0);

        if (TRANS_ABORTED(trans))
                return -EIO;

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

        block_rsv = trans->block_rsv;
        trans->block_rsv = &fs_info->delayed_block_rsv;

        curr_node = btrfs_first_delayed_node(fs_info, &curr_delayed_node_tracker);
        while (curr_node && (!count || nr--)) {
                ret = __btrfs_commit_inode_delayed_items(trans, path,
                                                         curr_node);
                if (unlikely(ret)) {
                        btrfs_abort_transaction(trans, ret);
                        break;
                }

                prev_node = curr_node;
                prev_delayed_node_tracker = curr_delayed_node_tracker;
                curr_node = btrfs_next_delayed_node(curr_node, &curr_delayed_node_tracker);
                /*
                 * See the comment below about releasing path before releasing
                 * node. If the commit of delayed items was successful the path
                 * should always be released, but in case of an error, it may
                 * point to locked extent buffers (a leaf at the very least).
                 */
                ASSERT(path->nodes[0] == NULL);
                btrfs_release_delayed_node(prev_node, &prev_delayed_node_tracker);
        }

        /*
         * Release the path to avoid a potential deadlock and lockdep splat when
         * releasing the delayed node, as that requires taking the delayed node's
         * mutex. If another task starts running delayed items before we take
         * the mutex, it will first lock the mutex and then it may try to lock
         * the same btree path (leaf).
         */
        btrfs_free_path(path);

        if (curr_node)
                btrfs_release_delayed_node(curr_node, &curr_delayed_node_tracker);
        trans->block_rsv = block_rsv;

        return ret;
}

int btrfs_run_delayed_items(struct btrfs_trans_handle *trans)
{
        return __btrfs_run_delayed_items(trans, -1);
}

int btrfs_run_delayed_items_nr(struct btrfs_trans_handle *trans, int nr)
{
        return __btrfs_run_delayed_items(trans, nr);
}

int btrfs_commit_inode_delayed_items(struct btrfs_trans_handle *trans,
                                     struct btrfs_inode *inode)
{
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_node *delayed_node =
                btrfs_get_delayed_node(inode, &delayed_node_tracker);
        BTRFS_PATH_AUTO_FREE(path);
        struct btrfs_block_rsv *block_rsv;
        int ret;

        if (!delayed_node)
                return 0;

        mutex_lock(&delayed_node->mutex);
        if (!delayed_node->count) {
                mutex_unlock(&delayed_node->mutex);
                btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
                return 0;
        }
        mutex_unlock(&delayed_node->mutex);

        path = btrfs_alloc_path();
        if (!path) {
                btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
                return -ENOMEM;
        }

        block_rsv = trans->block_rsv;
        trans->block_rsv = &delayed_node->root->fs_info->delayed_block_rsv;

        ret = __btrfs_commit_inode_delayed_items(trans, path, delayed_node);

        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        trans->block_rsv = block_rsv;

        return ret;
}

int btrfs_commit_inode_delayed_inode(struct btrfs_inode *inode)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_trans_handle *trans;
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_path *path;
        struct btrfs_block_rsv *block_rsv;
        int ret;

        delayed_node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!delayed_node)
                return 0;

        mutex_lock(&delayed_node->mutex);
        if (!test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                mutex_unlock(&delayed_node->mutex);
                btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
                return 0;
        }
        mutex_unlock(&delayed_node->mutex);

        trans = btrfs_join_transaction(delayed_node->root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out;
        }

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

        block_rsv = trans->block_rsv;
        trans->block_rsv = &fs_info->delayed_block_rsv;

        mutex_lock(&delayed_node->mutex);
        if (test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags))
                ret = __btrfs_update_delayed_inode(trans, delayed_node->root,
                                                   path, delayed_node);
        else
                ret = 0;
        mutex_unlock(&delayed_node->mutex);

        btrfs_free_path(path);
        trans->block_rsv = block_rsv;
trans_out:
        btrfs_end_transaction(trans);
        btrfs_btree_balance_dirty(fs_info);
out:
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);

        return ret;
}

void btrfs_remove_delayed_node(struct btrfs_inode *inode)
{
        struct btrfs_delayed_node *delayed_node;

        delayed_node = READ_ONCE(inode->delayed_node);
        if (!delayed_node)
                return;

        inode->delayed_node = NULL;

        btrfs_release_delayed_node(delayed_node, &delayed_node->inode_cache_tracker);
}

struct btrfs_async_delayed_work {
        struct btrfs_delayed_root *delayed_root;
        int nr;
        struct btrfs_work work;
};

static void btrfs_async_run_delayed_root(struct btrfs_work *work)
{
        struct btrfs_async_delayed_work *async_work;
        struct btrfs_delayed_root *delayed_root;
        struct btrfs_trans_handle *trans;
        struct btrfs_path *path;
        struct btrfs_delayed_node *delayed_node = NULL;
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_root *root;
        struct btrfs_block_rsv *block_rsv;
        int total_done = 0;

        async_work = container_of(work, struct btrfs_async_delayed_work, work);
        delayed_root = async_work->delayed_root;

        path = btrfs_alloc_path();
        if (!path)
                goto out;

        do {
                if (atomic_read(&delayed_root->items) <
                    BTRFS_DELAYED_BACKGROUND / 2)
                        break;

                delayed_node = btrfs_first_prepared_delayed_node(delayed_root,
                                                                 &delayed_node_tracker);
                if (!delayed_node)
                        break;

                root = delayed_node->root;

                trans = btrfs_join_transaction(root);
                if (IS_ERR(trans)) {
                        btrfs_release_path(path);
                        btrfs_release_prepared_delayed_node(delayed_node,
                                                            &delayed_node_tracker);
                        total_done++;
                        continue;
                }

                block_rsv = trans->block_rsv;
                trans->block_rsv = &root->fs_info->delayed_block_rsv;

                __btrfs_commit_inode_delayed_items(trans, path, delayed_node);

                trans->block_rsv = block_rsv;
                btrfs_end_transaction(trans);
                btrfs_btree_balance_dirty_nodelay(root->fs_info);

                btrfs_release_path(path);
                btrfs_release_prepared_delayed_node(delayed_node,
                                                    &delayed_node_tracker);
                total_done++;

        } while ((async_work->nr == 0 && total_done < BTRFS_DELAYED_WRITEBACK)
                 || total_done < async_work->nr);

        btrfs_free_path(path);
out:
        wake_up(&delayed_root->wait);
        kfree(async_work);
}


static int btrfs_wq_run_delayed_node(struct btrfs_delayed_root *delayed_root,
                                     struct btrfs_fs_info *fs_info, int nr)
{
        struct btrfs_async_delayed_work *async_work;

        async_work = kmalloc_obj(*async_work, GFP_NOFS);
        if (!async_work)
                return -ENOMEM;

        async_work->delayed_root = delayed_root;
        btrfs_init_work(&async_work->work, btrfs_async_run_delayed_root, NULL);
        async_work->nr = nr;

        btrfs_queue_work(fs_info->delayed_workers, &async_work->work);
        return 0;
}

void btrfs_assert_delayed_root_empty(struct btrfs_fs_info *fs_info)
{
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_node *node;

        node = btrfs_first_delayed_node(fs_info, &delayed_node_tracker);
        if (WARN_ON(node)) {
                btrfs_delayed_node_ref_tracker_free(node,
                                                    &delayed_node_tracker);
                refcount_dec(&node->refs);
        }
}

static bool could_end_wait(struct btrfs_delayed_root *delayed_root, int seq)
{
        int val = atomic_read(&delayed_root->items_seq);

        if (val < seq || val >= seq + BTRFS_DELAYED_BATCH)
                return true;

        if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND)
                return true;

        return false;
}

void btrfs_balance_delayed_items(struct btrfs_fs_info *fs_info)
{
        struct btrfs_delayed_root *delayed_root = &fs_info->delayed_root;

        if ((atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND) ||
                btrfs_workqueue_normal_congested(fs_info->delayed_workers))
                return;

        if (atomic_read(&delayed_root->items) >= BTRFS_DELAYED_WRITEBACK) {
                int seq;
                int ret;

                seq = atomic_read(&delayed_root->items_seq);

                ret = btrfs_wq_run_delayed_node(delayed_root, fs_info, 0);
                if (ret)
                        return;

                wait_event_interruptible(delayed_root->wait,
                                         could_end_wait(delayed_root, seq));
                return;
        }

        btrfs_wq_run_delayed_node(delayed_root, fs_info, BTRFS_DELAYED_BATCH);
}

static void btrfs_release_dir_index_item_space(struct btrfs_trans_handle *trans)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        const u64 bytes = btrfs_calc_insert_metadata_size(fs_info, 1);

        if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
                return;

        /*
         * Adding the new dir index item does not require touching another
         * leaf, so we can release 1 unit of metadata that was previously
         * reserved when starting the transaction. This applies only to
         * the case where we had a transaction start and excludes the
         * transaction join case (when replaying log trees).
         */
        trace_btrfs_space_reservation(fs_info, "transaction",
                                      trans->transid, bytes, 0);
        btrfs_block_rsv_release(fs_info, trans->block_rsv, bytes, NULL);
        ASSERT(trans->bytes_reserved >= bytes);
        trans->bytes_reserved -= bytes;
}

/* Will return 0, -ENOMEM or -EEXIST (index number collision, unexpected). */
int btrfs_insert_delayed_dir_index(struct btrfs_trans_handle *trans,
                                   const char *name, int name_len,
                                   struct btrfs_inode *dir,
                                   const struct btrfs_disk_key *disk_key, u8 flags,
                                   u64 index)
{
        struct btrfs_fs_info *fs_info = trans->fs_info;
        const unsigned int leaf_data_size = BTRFS_LEAF_DATA_SIZE(fs_info);
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_item *delayed_item;
        struct btrfs_dir_item *dir_item;
        bool reserve_leaf_space;
        u32 data_len;
        int ret;

        delayed_node = btrfs_get_or_create_delayed_node(dir, &delayed_node_tracker);
        if (IS_ERR(delayed_node))
                return PTR_ERR(delayed_node);

        delayed_item = btrfs_alloc_delayed_item(sizeof(*dir_item) + name_len,
                                                delayed_node,
                                                BTRFS_DELAYED_INSERTION_ITEM);
        if (!delayed_item) {
                ret = -ENOMEM;
                goto release_node;
        }

        delayed_item->index = index;

        dir_item = (struct btrfs_dir_item *)delayed_item->data;
        dir_item->location = *disk_key;
        btrfs_set_stack_dir_transid(dir_item, trans->transid);
        btrfs_set_stack_dir_data_len(dir_item, 0);
        btrfs_set_stack_dir_name_len(dir_item, name_len);
        btrfs_set_stack_dir_flags(dir_item, flags);
        memcpy((char *)(dir_item + 1), name, name_len);

        data_len = delayed_item->data_len + sizeof(struct btrfs_item);

        mutex_lock(&delayed_node->mutex);

        /*
         * First attempt to insert the delayed item. This is to make the error
         * handling path simpler in case we fail (-EEXIST). There's no risk of
         * any other task coming in and running the delayed item before we do
         * the metadata space reservation below, because we are holding the
         * delayed node's mutex and that mutex must also be locked before the
         * node's delayed items can be run.
         */
        ret = __btrfs_add_delayed_item(delayed_node, delayed_item);
        if (unlikely(ret)) {
                btrfs_err(trans->fs_info,
"error adding delayed dir index item, name: %.*s, index: %llu, root: %llu, dir: %llu, dir->index_cnt: %llu, delayed_node->index_cnt: %llu, error: %d",
                          name_len, name, index, btrfs_root_id(delayed_node->root),
                          delayed_node->inode_id, dir->index_cnt,
                          delayed_node->index_cnt, ret);
                btrfs_release_delayed_item(delayed_item);
                btrfs_release_dir_index_item_space(trans);
                mutex_unlock(&delayed_node->mutex);
                goto release_node;
        }

        if (delayed_node->index_item_leaves == 0 ||
            delayed_node->curr_index_batch_size + data_len > leaf_data_size) {
                delayed_node->curr_index_batch_size = data_len;
                reserve_leaf_space = true;
        } else {
                delayed_node->curr_index_batch_size += data_len;
                reserve_leaf_space = false;
        }

        if (reserve_leaf_space) {
                ret = btrfs_delayed_item_reserve_metadata(trans, delayed_item);
                /*
                 * Space was reserved for a dir index item insertion when we
                 * started the transaction, so getting a failure here should be
                 * impossible.
                 */
                if (WARN_ON(ret)) {
                        btrfs_release_delayed_item(delayed_item);
                        mutex_unlock(&delayed_node->mutex);
                        goto release_node;
                }

                delayed_node->index_item_leaves++;
        } else {
                btrfs_release_dir_index_item_space(trans);
        }
        mutex_unlock(&delayed_node->mutex);

release_node:
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        return ret;
}

static bool btrfs_delete_delayed_insertion_item(struct btrfs_delayed_node *node,
                                                u64 index)
{
        struct btrfs_delayed_item *item;

        mutex_lock(&node->mutex);
        item = __btrfs_lookup_delayed_item(&node->ins_root.rb_root, index);
        if (!item) {
                mutex_unlock(&node->mutex);
                return false;
        }

        /*
         * For delayed items to insert, we track reserved metadata bytes based
         * on the number of leaves that we will use.
         * See btrfs_insert_delayed_dir_index() and
         * btrfs_delayed_item_reserve_metadata()).
         */
        ASSERT(item->bytes_reserved == 0);
        ASSERT(node->index_item_leaves > 0);

        /*
         * If there's only one leaf reserved, we can decrement this item from the
         * current batch, otherwise we can not because we don't know which leaf
         * it belongs to. With the current limit on delayed items, we rarely
         * accumulate enough dir index items to fill more than one leaf (even
         * when using a leaf size of 4K).
         */
        if (node->index_item_leaves == 1) {
                const u32 data_len = item->data_len + sizeof(struct btrfs_item);

                ASSERT(node->curr_index_batch_size >= data_len);
                node->curr_index_batch_size -= data_len;
        }

        btrfs_release_delayed_item(item);

        /* If we now have no more dir index items, we can release all leaves. */
        if (RB_EMPTY_ROOT(&node->ins_root.rb_root)) {
                btrfs_delayed_item_release_leaves(node, node->index_item_leaves);
                node->index_item_leaves = 0;
        }

        mutex_unlock(&node->mutex);
        return true;
}

int btrfs_delete_delayed_dir_index(struct btrfs_trans_handle *trans,
                                   struct btrfs_inode *dir, u64 index)
{
        struct btrfs_delayed_node *node;
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_item *item;
        int ret;

        node = btrfs_get_or_create_delayed_node(dir, &delayed_node_tracker);
        if (IS_ERR(node))
                return PTR_ERR(node);

        if (btrfs_delete_delayed_insertion_item(node, index)) {
                ret = 0;
                goto end;
        }

        item = btrfs_alloc_delayed_item(0, node, BTRFS_DELAYED_DELETION_ITEM);
        if (!item) {
                ret = -ENOMEM;
                goto end;
        }

        item->index = index;

        ret = btrfs_delayed_item_reserve_metadata(trans, item);
        /*
         * we have reserved enough space when we start a new transaction,
         * so reserving metadata failure is impossible.
         */
        if (ret < 0) {
                btrfs_err(trans->fs_info,
"metadata reservation failed for delayed dir item deletion, index: %llu, root: %llu, inode: %llu, error: %d",
                          index, btrfs_root_id(node->root), node->inode_id, ret);
                btrfs_release_delayed_item(item);
                goto end;
        }

        mutex_lock(&node->mutex);
        ret = __btrfs_add_delayed_item(node, item);
        if (unlikely(ret)) {
                btrfs_err(trans->fs_info,
"failed to add delayed dir index item, root: %llu, inode: %llu, index: %llu, error: %d",
                          btrfs_root_id(node->root), node->inode_id, index, ret);
                btrfs_delayed_item_release_metadata(dir->root, item);
                btrfs_release_delayed_item(item);
        }
        mutex_unlock(&node->mutex);
end:
        btrfs_release_delayed_node(node, &delayed_node_tracker);
        return ret;
}

int btrfs_inode_delayed_dir_index_count(struct btrfs_inode *inode)
{
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_delayed_node *delayed_node;

        delayed_node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!delayed_node)
                return -ENOENT;

        /*
         * Since we have held i_mutex of this directory, it is impossible that
         * a new directory index is added into the delayed node and index_cnt
         * is updated now. So we needn't lock the delayed node.
         */
        if (!delayed_node->index_cnt) {
                btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
                return -EINVAL;
        }

        inode->index_cnt = delayed_node->index_cnt;
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        return 0;
}

bool btrfs_readdir_get_delayed_items(struct btrfs_inode *inode,
                                     u64 last_index,
                                     struct list_head *ins_list,
                                     struct list_head *del_list)
{
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_delayed_item *item;
        struct btrfs_ref_tracker delayed_node_tracker;

        delayed_node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!delayed_node)
                return false;

        /*
         * We can only do one readdir with delayed items at a time because of
         * item->readdir_list.
         */
        btrfs_inode_unlock(inode, BTRFS_ILOCK_SHARED);
        btrfs_inode_lock(inode, 0);

        mutex_lock(&delayed_node->mutex);
        item = __btrfs_first_delayed_insertion_item(delayed_node);
        while (item && item->index <= last_index) {
                refcount_inc(&item->refs);
                list_add_tail(&item->readdir_list, ins_list);
                item = __btrfs_next_delayed_item(item);
        }

        item = __btrfs_first_delayed_deletion_item(delayed_node);
        while (item && item->index <= last_index) {
                refcount_inc(&item->refs);
                list_add_tail(&item->readdir_list, del_list);
                item = __btrfs_next_delayed_item(item);
        }
        mutex_unlock(&delayed_node->mutex);
        /*
         * This delayed node is still cached in the btrfs inode, so refs
         * must be > 1 now, and we needn't check it is going to be freed
         * or not.
         *
         * Besides that, this function is used to read dir, we do not
         * insert/delete delayed items in this period. So we also needn't
         * requeue or dequeue this delayed node.
         */
        btrfs_delayed_node_ref_tracker_free(delayed_node, &delayed_node_tracker);
        refcount_dec(&delayed_node->refs);

        return true;
}

void btrfs_readdir_put_delayed_items(struct btrfs_inode *inode,
                                     struct list_head *ins_list,
                                     struct list_head *del_list)
{
        struct btrfs_delayed_item *curr, *next;

        list_for_each_entry_safe(curr, next, ins_list, readdir_list) {
                list_del(&curr->readdir_list);
                if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
        }

        list_for_each_entry_safe(curr, next, del_list, readdir_list) {
                list_del(&curr->readdir_list);
                if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);
        }

        /*
         * The VFS is going to do up_read(), so we need to downgrade back to a
         * read lock.
         */
        downgrade_write(&inode->vfs_inode.i_rwsem);
}

bool btrfs_should_delete_dir_index(const struct list_head *del_list, u64 index)
{
        struct btrfs_delayed_item *curr;
        bool ret = false;

        list_for_each_entry(curr, del_list, readdir_list) {
                if (curr->index > index)
                        break;
                if (curr->index == index) {
                        ret = true;
                        break;
                }
        }
        return ret;
}

/*
 * Read dir info stored in the delayed tree.
 */
bool btrfs_readdir_delayed_dir_index(struct dir_context *ctx,
                                     const struct list_head *ins_list)
{
        struct btrfs_dir_item *di;
        struct btrfs_delayed_item *curr, *next;
        struct btrfs_key location;
        char *name;
        int name_len;
        unsigned char d_type;

        /*
         * Changing the data of the delayed item is impossible. So
         * we needn't lock them. And we have held i_mutex of the
         * directory, nobody can delete any directory indexes now.
         */
        list_for_each_entry_safe(curr, next, ins_list, readdir_list) {
                bool over;

                list_del(&curr->readdir_list);

                if (curr->index < ctx->pos) {
                        if (refcount_dec_and_test(&curr->refs))
                                kfree(curr);
                        continue;
                }

                ctx->pos = curr->index;

                di = (struct btrfs_dir_item *)curr->data;
                name = (char *)(di + 1);
                name_len = btrfs_stack_dir_name_len(di);

                d_type = fs_ftype_to_dtype(btrfs_dir_flags_to_ftype(di->type));
                btrfs_disk_key_to_cpu(&location, &di->location);

                over = !dir_emit(ctx, name, name_len, location.objectid, d_type);

                if (refcount_dec_and_test(&curr->refs))
                        kfree(curr);

                if (over)
                        return true;
                ctx->pos++;
        }
        return false;
}

static void fill_stack_inode_item(struct btrfs_trans_handle *trans,
                                  struct btrfs_inode_item *inode_item,
                                  struct btrfs_inode *inode)
{
        struct inode *vfs_inode = &inode->vfs_inode;
        u64 flags;

        btrfs_set_stack_inode_uid(inode_item, i_uid_read(vfs_inode));
        btrfs_set_stack_inode_gid(inode_item, i_gid_read(vfs_inode));
        btrfs_set_stack_inode_size(inode_item, inode->disk_i_size);
        btrfs_set_stack_inode_mode(inode_item, vfs_inode->i_mode);
        btrfs_set_stack_inode_nlink(inode_item, vfs_inode->i_nlink);
        btrfs_set_stack_inode_nbytes(inode_item, inode_get_bytes(vfs_inode));
        btrfs_set_stack_inode_generation(inode_item, inode->generation);
        btrfs_set_stack_inode_sequence(inode_item,
                                       inode_peek_iversion(vfs_inode));
        btrfs_set_stack_inode_transid(inode_item, trans->transid);
        btrfs_set_stack_inode_rdev(inode_item, vfs_inode->i_rdev);
        flags = btrfs_inode_combine_flags(inode->flags, inode->ro_flags);
        btrfs_set_stack_inode_flags(inode_item, flags);
        btrfs_set_stack_inode_block_group(inode_item, 0);

        btrfs_set_stack_timespec_sec(&inode_item->atime,
                                     inode_get_atime_sec(vfs_inode));
        btrfs_set_stack_timespec_nsec(&inode_item->atime,
                                      inode_get_atime_nsec(vfs_inode));

        btrfs_set_stack_timespec_sec(&inode_item->mtime,
                                     inode_get_mtime_sec(vfs_inode));
        btrfs_set_stack_timespec_nsec(&inode_item->mtime,
                                      inode_get_mtime_nsec(vfs_inode));

        btrfs_set_stack_timespec_sec(&inode_item->ctime,
                                     inode_get_ctime_sec(vfs_inode));
        btrfs_set_stack_timespec_nsec(&inode_item->ctime,
                                      inode_get_ctime_nsec(vfs_inode));

        btrfs_set_stack_timespec_sec(&inode_item->otime, inode->i_otime_sec);
        btrfs_set_stack_timespec_nsec(&inode_item->otime, inode->i_otime_nsec);
}

int btrfs_fill_inode(struct btrfs_inode *inode, u32 *rdev)
{
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_ref_tracker delayed_node_tracker;
        struct btrfs_inode_item *inode_item;
        struct inode *vfs_inode = &inode->vfs_inode;

        delayed_node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!delayed_node)
                return -ENOENT;

        mutex_lock(&delayed_node->mutex);
        if (!test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                mutex_unlock(&delayed_node->mutex);
                btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
                return -ENOENT;
        }

        inode_item = &delayed_node->inode_item;

        i_uid_write(vfs_inode, btrfs_stack_inode_uid(inode_item));
        i_gid_write(vfs_inode, btrfs_stack_inode_gid(inode_item));
        btrfs_i_size_write(inode, btrfs_stack_inode_size(inode_item));
        vfs_inode->i_mode = btrfs_stack_inode_mode(inode_item);
        set_nlink(vfs_inode, btrfs_stack_inode_nlink(inode_item));
        inode_set_bytes(vfs_inode, btrfs_stack_inode_nbytes(inode_item));
        inode->generation = btrfs_stack_inode_generation(inode_item);
        inode->last_trans = btrfs_stack_inode_transid(inode_item);

        inode_set_iversion_queried(vfs_inode, btrfs_stack_inode_sequence(inode_item));
        vfs_inode->i_rdev = 0;
        *rdev = btrfs_stack_inode_rdev(inode_item);
        btrfs_inode_split_flags(btrfs_stack_inode_flags(inode_item),
                                &inode->flags, &inode->ro_flags);

        inode_set_atime(vfs_inode, btrfs_stack_timespec_sec(&inode_item->atime),
                        btrfs_stack_timespec_nsec(&inode_item->atime));

        inode_set_mtime(vfs_inode, btrfs_stack_timespec_sec(&inode_item->mtime),
                        btrfs_stack_timespec_nsec(&inode_item->mtime));

        inode_set_ctime(vfs_inode, btrfs_stack_timespec_sec(&inode_item->ctime),
                        btrfs_stack_timespec_nsec(&inode_item->ctime));

        inode->i_otime_sec = btrfs_stack_timespec_sec(&inode_item->otime);
        inode->i_otime_nsec = btrfs_stack_timespec_nsec(&inode_item->otime);

        vfs_inode->i_generation = inode->generation;
        if (S_ISDIR(vfs_inode->i_mode))
                inode->index_cnt = (u64)-1;

        mutex_unlock(&delayed_node->mutex);
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        return 0;
}

int btrfs_delayed_update_inode(struct btrfs_trans_handle *trans,
                               struct btrfs_inode *inode)
{
        struct btrfs_root *root = inode->root;
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_ref_tracker delayed_node_tracker;
        int ret = 0;

        delayed_node = btrfs_get_or_create_delayed_node(inode, &delayed_node_tracker);
        if (IS_ERR(delayed_node))
                return PTR_ERR(delayed_node);

        mutex_lock(&delayed_node->mutex);
        if (test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                fill_stack_inode_item(trans, &delayed_node->inode_item, inode);
                goto release_node;
        }

        ret = btrfs_delayed_inode_reserve_metadata(trans, root, delayed_node);
        if (ret)
                goto release_node;

        fill_stack_inode_item(trans, &delayed_node->inode_item, inode);
        set_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags);
        delayed_node->count++;
        atomic_inc(&root->fs_info->delayed_root.items);
release_node:
        mutex_unlock(&delayed_node->mutex);
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        return ret;
}

int btrfs_delayed_delete_inode_ref(struct btrfs_inode *inode)
{
        struct btrfs_fs_info *fs_info = inode->root->fs_info;
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_ref_tracker delayed_node_tracker;

        /*
         * we don't do delayed inode updates during log recovery because it
         * leads to enospc problems.  This means we also can't do
         * delayed inode refs
         */
        if (test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags))
                return -EAGAIN;

        delayed_node = btrfs_get_or_create_delayed_node(inode, &delayed_node_tracker);
        if (IS_ERR(delayed_node))
                return PTR_ERR(delayed_node);

        /*
         * We don't reserve space for inode ref deletion is because:
         * - We ONLY do async inode ref deletion for the inode who has only
         *   one link(i_nlink == 1), it means there is only one inode ref.
         *   And in most case, the inode ref and the inode item are in the
         *   same leaf, and we will deal with them at the same time.
         *   Since we are sure we will reserve the space for the inode item,
         *   it is unnecessary to reserve space for inode ref deletion.
         * - If the inode ref and the inode item are not in the same leaf,
         *   We also needn't worry about enospc problem, because we reserve
         *   much more space for the inode update than it needs.
         * - At the worst, we can steal some space from the global reservation.
         *   It is very rare.
         */
        mutex_lock(&delayed_node->mutex);
        if (!test_and_set_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags)) {
                delayed_node->count++;
                atomic_inc(&fs_info->delayed_root.items);
        }
        mutex_unlock(&delayed_node->mutex);
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
        return 0;
}

static void __btrfs_kill_delayed_node(struct btrfs_delayed_node *delayed_node)
{
        struct btrfs_root *root = delayed_node->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct btrfs_delayed_item *curr_item, *prev_item;

        mutex_lock(&delayed_node->mutex);
        curr_item = __btrfs_first_delayed_insertion_item(delayed_node);
        while (curr_item) {
                prev_item = curr_item;
                curr_item = __btrfs_next_delayed_item(prev_item);
                btrfs_release_delayed_item(prev_item);
        }

        if (delayed_node->index_item_leaves > 0) {
                btrfs_delayed_item_release_leaves(delayed_node,
                                          delayed_node->index_item_leaves);
                delayed_node->index_item_leaves = 0;
        }

        curr_item = __btrfs_first_delayed_deletion_item(delayed_node);
        while (curr_item) {
                btrfs_delayed_item_release_metadata(root, curr_item);
                prev_item = curr_item;
                curr_item = __btrfs_next_delayed_item(prev_item);
                btrfs_release_delayed_item(prev_item);
        }

        btrfs_release_delayed_iref(delayed_node);

        if (test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                btrfs_delayed_inode_release_metadata(fs_info, delayed_node, false);
                btrfs_release_delayed_inode(delayed_node);
        }
        mutex_unlock(&delayed_node->mutex);
}

void btrfs_kill_delayed_inode_items(struct btrfs_inode *inode)
{
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_ref_tracker delayed_node_tracker;

        delayed_node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!delayed_node)
                return;

        __btrfs_kill_delayed_node(delayed_node);
        btrfs_release_delayed_node(delayed_node, &delayed_node_tracker);
}

void btrfs_kill_all_delayed_nodes(struct btrfs_root *root)
{
        unsigned long index = 0;
        struct btrfs_delayed_node *delayed_nodes[8];
        struct btrfs_ref_tracker delayed_node_trackers[8];

        while (1) {
                struct btrfs_delayed_node *node;
                int count;

                xa_lock(&root->delayed_nodes);
                if (xa_empty(&root->delayed_nodes)) {
                        xa_unlock(&root->delayed_nodes);
                        return;
                }

                count = 0;
                xa_for_each_start(&root->delayed_nodes, index, node, index) {
                        /*
                         * Don't increase refs in case the node is dead and
                         * about to be removed from the tree in the loop below
                         */
                        if (refcount_inc_not_zero(&node->refs)) {
                                btrfs_delayed_node_ref_tracker_alloc(node,
                                                     &delayed_node_trackers[count],
                                                     GFP_ATOMIC);
                                delayed_nodes[count] = node;
                                count++;
                        }
                        if (count >= ARRAY_SIZE(delayed_nodes))
                                break;
                }
                xa_unlock(&root->delayed_nodes);
                index++;

                for (int i = 0; i < count; i++) {
                        __btrfs_kill_delayed_node(delayed_nodes[i]);
                        btrfs_delayed_node_ref_tracker_dir_print(delayed_nodes[i]);
                        btrfs_release_delayed_node(delayed_nodes[i],
                                                   &delayed_node_trackers[i]);
                }
        }
}

void btrfs_destroy_delayed_inodes(struct btrfs_fs_info *fs_info)
{
        struct btrfs_delayed_node *curr_node, *prev_node;
        struct btrfs_ref_tracker curr_delayed_node_tracker, prev_delayed_node_tracker;

        curr_node = btrfs_first_delayed_node(fs_info, &curr_delayed_node_tracker);
        while (curr_node) {
                __btrfs_kill_delayed_node(curr_node);

                prev_node = curr_node;
                prev_delayed_node_tracker = curr_delayed_node_tracker;
                curr_node = btrfs_next_delayed_node(curr_node, &curr_delayed_node_tracker);
                btrfs_release_delayed_node(prev_node, &prev_delayed_node_tracker);
        }
}

void btrfs_log_get_delayed_items(struct btrfs_inode *inode,
                                 struct list_head *ins_list,
                                 struct list_head *del_list)
{
        struct btrfs_delayed_node *node;
        struct btrfs_delayed_item *item;
        struct btrfs_ref_tracker delayed_node_tracker;

        node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!node)
                return;

        mutex_lock(&node->mutex);
        item = __btrfs_first_delayed_insertion_item(node);
        while (item) {
                /*
                 * It's possible that the item is already in a log list. This
                 * can happen in case two tasks are trying to log the same
                 * directory. For example if we have tasks A and task B:
                 *
                 * Task A collected the delayed items into a log list while
                 * under the inode's log_mutex (at btrfs_log_inode()), but it
                 * only releases the items after logging the inodes they point
                 * to (if they are new inodes), which happens after unlocking
                 * the log mutex;
                 *
                 * Task B enters btrfs_log_inode() and acquires the log_mutex
                 * of the same directory inode, before task B releases the
                 * delayed items. This can happen for example when logging some
                 * inode we need to trigger logging of its parent directory, so
                 * logging two files that have the same parent directory can
                 * lead to this.
                 *
                 * If this happens, just ignore delayed items already in a log
                 * list. All the tasks logging the directory are under a log
                 * transaction and whichever finishes first can not sync the log
                 * before the other completes and leaves the log transaction.
                 */
                if (!item->logged && list_empty(&item->log_list)) {
                        refcount_inc(&item->refs);
                        list_add_tail(&item->log_list, ins_list);
                }
                item = __btrfs_next_delayed_item(item);
        }

        item = __btrfs_first_delayed_deletion_item(node);
        while (item) {
                /* It may be non-empty, for the same reason mentioned above. */
                if (!item->logged && list_empty(&item->log_list)) {
                        refcount_inc(&item->refs);
                        list_add_tail(&item->log_list, del_list);
                }
                item = __btrfs_next_delayed_item(item);
        }
        mutex_unlock(&node->mutex);

        /*
         * We are called during inode logging, which means the inode is in use
         * and can not be evicted before we finish logging the inode. So we never
         * have the last reference on the delayed inode.
         * Also, we don't use btrfs_release_delayed_node() because that would
         * requeue the delayed inode (change its order in the list of prepared
         * nodes) and we don't want to do such change because we don't create or
         * delete delayed items.
         */
        ASSERT(refcount_read(&node->refs) > 1);
        btrfs_delayed_node_ref_tracker_free(node, &delayed_node_tracker);
        refcount_dec(&node->refs);
}

void btrfs_log_put_delayed_items(struct btrfs_inode *inode,
                                 struct list_head *ins_list,
                                 struct list_head *del_list)
{
        struct btrfs_delayed_node *node;
        struct btrfs_delayed_item *item;
        struct btrfs_delayed_item *next;
        struct btrfs_ref_tracker delayed_node_tracker;

        node = btrfs_get_delayed_node(inode, &delayed_node_tracker);
        if (!node)
                return;

        mutex_lock(&node->mutex);

        list_for_each_entry_safe(item, next, ins_list, log_list) {
                item->logged = true;
                list_del_init(&item->log_list);
                if (refcount_dec_and_test(&item->refs))
                        kfree(item);
        }

        list_for_each_entry_safe(item, next, del_list, log_list) {
                item->logged = true;
                list_del_init(&item->log_list);
                if (refcount_dec_and_test(&item->refs))
                        kfree(item);
        }

        mutex_unlock(&node->mutex);

        /*
         * We are called during inode logging, which means the inode is in use
         * and can not be evicted before we finish logging the inode. So we never
         * have the last reference on the delayed inode.
         * Also, we don't use btrfs_release_delayed_node() because that would
         * requeue the delayed inode (change its order in the list of prepared
         * nodes) and we don't want to do such change because we don't create or
         * delete delayed items.
         */
        ASSERT(refcount_read(&node->refs) > 1);
        btrfs_delayed_node_ref_tracker_free(node, &delayed_node_tracker);
        refcount_dec(&node->refs);
}