// 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 <linux/sched/mm.h>
#include "misc.h"
#include "delayed-inode.h"
#include "disk-io.h"
#include "transaction.h"
#include "ctree.h"
#include "qgroup.h"
#include "locking.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_create("btrfs_delayed_node",
                                        sizeof(struct btrfs_delayed_node),
                                        0,
                                        SLAB_MEM_SPREAD,
                                        NULL);
        if (!delayed_node_cache)
                return -ENOMEM;
        return 0;
}

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

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);
        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 inline int btrfs_is_continuous_delayed_item(
                                        struct btrfs_delayed_item *item1,
                                        struct btrfs_delayed_item *item2)
{
        if (item1->key.type == BTRFS_DIR_INDEX_KEY &&
            item1->key.objectid == item2->key.objectid &&
            item1->key.type == item2->key.type &&
            item1->key.offset + 1 == item2->key.offset)
                return 1;
        return 0;
}

static struct btrfs_delayed_node *btrfs_get_delayed_node(
                struct btrfs_inode *btrfs_inode)
{
        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);
                return node;
        }

        spin_lock(&root->inode_lock);
        node = radix_tree_lookup(&root->delayed_nodes_tree, ino);

        if (node) {
                if (btrfs_inode->delayed_node) {
                        refcount_inc(&node->refs);      /* can be accessed */
                        BUG_ON(btrfs_inode->delayed_node != node);
                        spin_unlock(&root->inode_lock);
                        return node;
                }

                /*
                 * It's possible that we're racing into the middle of removing
                 * this node from the radix tree.  In this case, the refcount
                 * was zero and it should never go back to one.  Just return
                 * NULL like it was never in the radix 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 radix, 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_inode->delayed_node = node;
                } else {
                        node = NULL;
                }

                spin_unlock(&root->inode_lock);
                return node;
        }
        spin_unlock(&root->inode_lock);

        return NULL;
}

/* Will return either the node or PTR_ERR(-ENOMEM) */
static struct btrfs_delayed_node *btrfs_get_or_create_delayed_node(
                struct btrfs_inode *btrfs_inode)
{
        struct btrfs_delayed_node *node;
        struct btrfs_root *root = btrfs_inode->root;
        u64 ino = btrfs_ino(btrfs_inode);
        int ret;

again:
        node = btrfs_get_delayed_node(btrfs_inode);
        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 btrfs inode and can be accessed */
        refcount_set(&node->refs, 2);

        ret = radix_tree_preload(GFP_NOFS);
        if (ret) {
                kmem_cache_free(delayed_node_cache, node);
                return ERR_PTR(ret);
        }

        spin_lock(&root->inode_lock);
        ret = radix_tree_insert(&root->delayed_nodes_tree, ino, node);
        if (ret == -EEXIST) {
                spin_unlock(&root->inode_lock);
                kmem_cache_free(delayed_node_cache, node);
                radix_tree_preload_end();
                goto again;
        }
        btrfs_inode->delayed_node = node;
        spin_unlock(&root->inode_lock);
        radix_tree_preload_end();

        return node;
}

/*
 * 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 */
                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--;
                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_delayed_root *delayed_root)
{
        struct list_head *p;
        struct btrfs_delayed_node *node = NULL;

        spin_lock(&delayed_root->lock);
        if (list_empty(&delayed_root->node_list))
                goto out;

        p = delayed_root->node_list.next;
        node = list_entry(p, struct btrfs_delayed_node, n_list);
        refcount_inc(&node->refs);
out:
        spin_unlock(&delayed_root->lock);

        return node;
}

static struct btrfs_delayed_node *btrfs_next_delayed_node(
                                                struct btrfs_delayed_node *node)
{
        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);
out:
        spin_unlock(&delayed_root->lock);

        return next;
}

static void __btrfs_release_delayed_node(
                                struct btrfs_delayed_node *delayed_node,
                                int mod)
{
        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);

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

                spin_lock(&root->inode_lock);
                /*
                 * 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);
                radix_tree_delete(&root->delayed_nodes_tree,
                                  delayed_node->inode_id);
                spin_unlock(&root->inode_lock);
                kmem_cache_free(delayed_node_cache, delayed_node);
        }
}

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

static struct btrfs_delayed_node *btrfs_first_prepared_delayed_node(
                                        struct btrfs_delayed_root *delayed_root)
{
        struct list_head *p;
        struct btrfs_delayed_node *node = NULL;

        spin_lock(&delayed_root->lock);
        if (list_empty(&delayed_root->prepare_list))
                goto out;

        p = delayed_root->prepare_list.next;
        list_del_init(p);
        node = list_entry(p, struct btrfs_delayed_node, p_list);
        refcount_inc(&node->refs);
out:
        spin_unlock(&delayed_root->lock);

        return node;
}

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

static struct btrfs_delayed_item *btrfs_alloc_delayed_item(u32 data_len)
{
        struct btrfs_delayed_item *item;
        item = kmalloc(sizeof(*item) + data_len, GFP_NOFS);
        if (item) {
                item->data_len = data_len;
                item->ins_or_del = 0;
                item->bytes_reserved = 0;
                item->delayed_node = NULL;
                refcount_set(&item->refs, 1);
        }
        return item;
}

/*
 * __btrfs_lookup_delayed_item - look up the delayed item by key
 * @delayed_node: pointer to the delayed node
 * @key:          the key to look up
 * @prev:         used to store the prev item if the right item isn't found
 * @next:         used to store the next item if the right item isn't found
 *
 * 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,
                                struct btrfs_key *key,
                                struct btrfs_delayed_item **prev,
                                struct btrfs_delayed_item **next)
{
        struct rb_node *node, *prev_node = NULL;
        struct btrfs_delayed_item *delayed_item = NULL;
        int ret = 0;

        node = root->rb_node;

        while (node) {
                delayed_item = rb_entry(node, struct btrfs_delayed_item,
                                        rb_node);
                prev_node = node;
                ret = btrfs_comp_cpu_keys(&delayed_item->key, key);
                if (ret < 0)
                        node = node->rb_right;
                else if (ret > 0)
                        node = node->rb_left;
                else
                        return delayed_item;
        }

        if (prev) {
                if (!prev_node)
                        *prev = NULL;
                else if (ret < 0)
                        *prev = delayed_item;
                else if ((node = rb_prev(prev_node)) != NULL) {
                        *prev = rb_entry(node, struct btrfs_delayed_item,
                                         rb_node);
                } else
                        *prev = NULL;
        }

        if (next) {
                if (!prev_node)
                        *next = NULL;
                else if (ret > 0)
                        *next = delayed_item;
                else if ((node = rb_next(prev_node)) != NULL) {
                        *next = rb_entry(node, struct btrfs_delayed_item,
                                         rb_node);
                } else
                        *next = NULL;
        }
        return NULL;
}

static struct btrfs_delayed_item *__btrfs_lookup_delayed_insertion_item(
                                        struct btrfs_delayed_node *delayed_node,
                                        struct btrfs_key *key)
{
        return __btrfs_lookup_delayed_item(&delayed_node->ins_root.rb_root, key,
                                           NULL, NULL);
}

static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
                                    struct btrfs_delayed_item *ins,
                                    int action)
{
        struct rb_node **p, *node;
        struct rb_node *parent_node = NULL;
        struct rb_root_cached *root;
        struct btrfs_delayed_item *item;
        int cmp;
        bool leftmost = true;

        if (action == BTRFS_DELAYED_INSERTION_ITEM)
                root = &delayed_node->ins_root;
        else if (action == BTRFS_DELAYED_DELETION_ITEM)
                root = &delayed_node->del_root;
        else
                BUG();
        p = &root->rb_root.rb_node;
        node = &ins->rb_node;

        while (*p) {
                parent_node = *p;
                item = rb_entry(parent_node, struct btrfs_delayed_item,
                                 rb_node);

                cmp = btrfs_comp_cpu_keys(&item->key, &ins->key);
                if (cmp < 0) {
                        p = &(*p)->rb_right;
                        leftmost = false;
                } else if (cmp > 0) {
                        p = &(*p)->rb_left;
                } else {
                        return -EEXIST;
                }
        }

        rb_link_node(node, parent_node, p);
        rb_insert_color_cached(node, root, leftmost);
        ins->delayed_node = delayed_node;
        ins->ins_or_del = action;

        if (ins->key.type == BTRFS_DIR_INDEX_KEY &&
            action == BTRFS_DELAYED_INSERTION_ITEM &&
            ins->key.offset >= delayed_node->index_cnt)
                        delayed_node->index_cnt = ins->key.offset + 1;

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

static int __btrfs_add_delayed_insertion_item(struct btrfs_delayed_node *node,
                                              struct btrfs_delayed_item *item)
{
        return __btrfs_add_delayed_item(node, item,
                                        BTRFS_DELAYED_INSERTION_ITEM);
}

static int __btrfs_add_delayed_deletion_item(struct btrfs_delayed_node *node,
                                             struct btrfs_delayed_item *item)
{
        return __btrfs_add_delayed_item(node, item,
                                        BTRFS_DELAYED_DELETION_ITEM);
}

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 rb_root_cached *root;
        struct btrfs_delayed_root *delayed_root;

        /* Not associated with any delayed_node */
        if (!delayed_item->delayed_node)
                return;
        delayed_root = delayed_item->delayed_node->root->fs_info->delayed_root;

        BUG_ON(!delayed_root);
        BUG_ON(delayed_item->ins_or_del != BTRFS_DELAYED_DELETION_ITEM &&
               delayed_item->ins_or_del != BTRFS_DELAYED_INSERTION_ITEM);

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

        rb_erase_cached(&delayed_item->rb_node, root);
        delayed_item->delayed_node->count--;

        finish_one_item(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;
        struct btrfs_delayed_item *item = NULL;

        p = rb_first_cached(&delayed_node->ins_root);
        if (p)
                item = rb_entry(p, struct btrfs_delayed_item, rb_node);

        return item;
}

static struct btrfs_delayed_item *__btrfs_first_delayed_deletion_item(
                                        struct btrfs_delayed_node *delayed_node)
{
        struct rb_node *p;
        struct btrfs_delayed_item *item = NULL;

        p = rb_first_cached(&delayed_node->del_root);
        if (p)
                item = rb_entry(p, struct btrfs_delayed_item, rb_node);

        return item;
}

static struct btrfs_delayed_item *__btrfs_next_delayed_item(
                                                struct btrfs_delayed_item *item)
{
        struct rb_node *p;
        struct btrfs_delayed_item *next = NULL;

        p = rb_next(&item->rb_node);
        if (p)
                next = rb_entry(p, struct btrfs_delayed_item, rb_node);

        return next;
}

static int btrfs_delayed_item_reserve_metadata(struct btrfs_trans_handle *trans,
                                               struct btrfs_root *root,
                                               struct btrfs_delayed_item *item)
{
        struct btrfs_block_rsv *src_rsv;
        struct btrfs_block_rsv *dst_rsv;
        struct btrfs_fs_info *fs_info = root->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->key.objectid,
                                              num_bytes, 1);
                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->key.objectid, item->bytes_reserved,
                                      0);
        btrfs_block_rsv_release(fs_info, rsv, item->bytes_reserved, 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(root, 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;
}

/*
 * This helper will insert some continuous items into the same leaf according
 * to the free space of the leaf.
 */
static int btrfs_batch_insert_items(struct btrfs_root *root,
                                    struct btrfs_path *path,
                                    struct btrfs_delayed_item *item)
{
        struct btrfs_delayed_item *curr, *next;
        int free_space;
        int total_size = 0;
        struct extent_buffer *leaf;
        char *data_ptr;
        struct btrfs_key *keys;
        u32 *data_size;
        struct list_head head;
        int slot;
        int nitems;
        int i;
        int ret = 0;

        BUG_ON(!path->nodes[0]);

        leaf = path->nodes[0];
        free_space = btrfs_leaf_free_space(leaf);
        INIT_LIST_HEAD(&head);

        next = item;
        nitems = 0;

        /*
         * count the number of the continuous items that we can insert in batch
         */
        while (total_size + next->data_len + sizeof(struct btrfs_item) <=
               free_space) {
                total_size += next->data_len + sizeof(struct btrfs_item);
                list_add_tail(&next->tree_list, &head);
                nitems++;

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

                if (!btrfs_is_continuous_delayed_item(curr, next))
                        break;
        }

        if (!nitems) {
                ret = 0;
                goto out;
        }

        keys = kmalloc_array(nitems, sizeof(struct btrfs_key), GFP_NOFS);
        if (!keys) {
                ret = -ENOMEM;
                goto out;
        }

        data_size = kmalloc_array(nitems, sizeof(u32), GFP_NOFS);
        if (!data_size) {
                ret = -ENOMEM;
                goto error;
        }

        /* get keys of all the delayed items */
        i = 0;
        list_for_each_entry(next, &head, tree_list) {
                keys[i] = next->key;
                data_size[i] = next->data_len;
                i++;
        }

        /* insert the keys of the items */
        setup_items_for_insert(root, path, keys, data_size, nitems);

        /* insert the dir index items */
        slot = path->slots[0];
        list_for_each_entry_safe(curr, next, &head, tree_list) {
                data_ptr = btrfs_item_ptr(leaf, slot, char);
                write_extent_buffer(leaf, &curr->data,
                                    (unsigned long)data_ptr,
                                    curr->data_len);
                slot++;

                btrfs_delayed_item_release_metadata(root, curr);

                list_del(&curr->tree_list);
                btrfs_release_delayed_item(curr);
        }

error:
        kfree(data_size);
        kfree(keys);
out:
        return ret;
}

/*
 * This helper can just do simple insertion that needn't extend item for new
 * data, such as directory name index insertion, inode insertion.
 */
static int btrfs_insert_delayed_item(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct btrfs_path *path,
                                     struct btrfs_delayed_item *delayed_item)
{
        struct extent_buffer *leaf;
        unsigned int nofs_flag;
        char *ptr;
        int ret;

        nofs_flag = memalloc_nofs_save();
        ret = btrfs_insert_empty_item(trans, root, path, &delayed_item->key,
                                      delayed_item->data_len);
        memalloc_nofs_restore(nofs_flag);
        if (ret < 0 && ret != -EEXIST)
                return ret;

        leaf = path->nodes[0];

        ptr = btrfs_item_ptr(leaf, path->slots[0], char);

        write_extent_buffer(leaf, delayed_item->data, (unsigned long)ptr,
                            delayed_item->data_len);
        btrfs_mark_buffer_dirty(leaf);

        btrfs_delayed_item_release_metadata(root, delayed_item);
        return 0;
}

/*
 * we insert an item first, then if there are some continuous items, we try
 * to insert those items into the same leaf.
 */
static int btrfs_insert_delayed_items(struct btrfs_trans_handle *trans,
                                      struct btrfs_path *path,
                                      struct btrfs_root *root,
                                      struct btrfs_delayed_node *node)
{
        struct btrfs_delayed_item *curr, *prev;
        int ret = 0;

do_again:
        mutex_lock(&node->mutex);
        curr = __btrfs_first_delayed_insertion_item(node);
        if (!curr)
                goto insert_end;

        ret = btrfs_insert_delayed_item(trans, root, path, curr);
        if (ret < 0) {
                btrfs_release_path(path);
                goto insert_end;
        }

        prev = curr;
        curr = __btrfs_next_delayed_item(prev);
        if (curr && btrfs_is_continuous_delayed_item(prev, curr)) {
                /* insert the continuous items into the same leaf */
                path->slots[0]++;
                btrfs_batch_insert_items(root, path, curr);
        }
        btrfs_release_delayed_item(prev);
        btrfs_mark_buffer_dirty(path->nodes[0]);

        btrfs_release_path(path);
        mutex_unlock(&node->mutex);
        goto do_again;

insert_end:
        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)
{
        struct btrfs_delayed_item *curr, *next;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        struct list_head head;
        int nitems, i, last_item;
        int ret = 0;

        BUG_ON(!path->nodes[0]);

        leaf = path->nodes[0];

        i = path->slots[0];
        last_item = btrfs_header_nritems(leaf) - 1;
        if (i > last_item)
                return -ENOENT; /* FIXME: Is errno suitable? */

        next = item;
        INIT_LIST_HEAD(&head);
        btrfs_item_key_to_cpu(leaf, &key, i);
        nitems = 0;
        /*
         * count the number of the dir index items that we can delete in batch
         */
        while (btrfs_comp_cpu_keys(&next->key, &key) == 0) {
                list_add_tail(&next->tree_list, &head);
                nitems++;

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

                if (!btrfs_is_continuous_delayed_item(curr, next))
                        break;

                i++;
                if (i > last_item)
                        break;
                btrfs_item_key_to_cpu(leaf, &key, i);
        }

        if (!nitems)
                return 0;

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

        list_for_each_entry_safe(curr, next, &head, tree_list) {
                btrfs_delayed_item_release_metadata(root, curr);
                list_del(&curr->tree_list);
                btrfs_release_delayed_item(curr);
        }

out:
        return ret;
}

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_delayed_item *curr, *prev;
        unsigned int nofs_flag;
        int ret = 0;

do_again:
        mutex_lock(&node->mutex);
        curr = __btrfs_first_delayed_deletion_item(node);
        if (!curr)
                goto delete_fail;

        nofs_flag = memalloc_nofs_save();
        ret = btrfs_search_slot(trans, root, &curr->key, path, -1, 1);
        memalloc_nofs_restore(nofs_flag);
        if (ret < 0)
                goto delete_fail;
        else if (ret > 0) {
                /*
                 * can't find the item which the node points to, so this node
                 * is invalid, just drop it.
                 */
                prev = curr;
                curr = __btrfs_next_delayed_item(prev);
                btrfs_release_delayed_item(prev);
                ret = 0;
                btrfs_release_path(path);
                if (curr) {
                        mutex_unlock(&node->mutex);
                        goto do_again;
                } else
                        goto delete_fail;
        }

        btrfs_batch_delete_items(trans, root, path, curr);
        btrfs_release_path(path);
        mutex_unlock(&node->mutex);
        goto do_again;

delete_fail:
        btrfs_release_path(path);
        mutex_unlock(&node->mutex);
        return ret;
}

static void btrfs_release_delayed_inode(struct btrfs_delayed_node *delayed_node)
{
        struct btrfs_delayed_root *delayed_root;

        if (delayed_node &&
            test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                BUG_ON(!delayed_node->root);
                clear_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags);
                delayed_node->count--;

                delayed_root = delayed_node->root->fs_info->delayed_root;
                finish_one_item(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)) {
                struct btrfs_delayed_root *delayed_root;

                ASSERT(delayed_node->root);
                delayed_node->count--;

                delayed_root = delayed_node->root->fs_info->delayed_root;
                finish_one_item(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;
        unsigned int nofs_flag;
        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;

        nofs_flag = memalloc_nofs_save();
        ret = btrfs_lookup_inode(trans, root, path, &key, mod);
        memalloc_nofs_restore(nofs_flag);
        if (ret > 0)
                ret = -ENOENT;
        if (ret < 0)
                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));
        btrfs_mark_buffer_dirty(leaf);

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

        path->slots[0]++;
        if (path->slots[0] >= btrfs_header_nritems(leaf))
                goto search;
again:
        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.
         */
        btrfs_del_item(trans, root, path);
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);

        /*
         * 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 (ret && ret != -ENOENT)
                btrfs_abort_transaction(trans, ret);

        return ret;

search:
        btrfs_release_path(path);

        key.type = BTRFS_INODE_EXTREF_KEY;
        key.offset = -1;

        nofs_flag = memalloc_nofs_save();
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        memalloc_nofs_restore(nofs_flag);
        if (ret < 0)
                goto err_out;
        ASSERT(ret);

        ret = 0;
        leaf = path->nodes[0];
        path->slots[0]--;
        goto again;
}

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

/*
 * 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_root *delayed_root;
        struct btrfs_delayed_node *curr_node, *prev_node;
        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;

        delayed_root = fs_info->delayed_root;

        curr_node = btrfs_first_delayed_node(delayed_root);
        while (curr_node && (!count || nr--)) {
                ret = __btrfs_commit_inode_delayed_items(trans, path,
                                                         curr_node);
                if (ret) {
                        btrfs_release_delayed_node(curr_node);
                        curr_node = NULL;
                        btrfs_abort_transaction(trans, ret);
                        break;
                }

                prev_node = curr_node;
                curr_node = btrfs_next_delayed_node(curr_node);
                btrfs_release_delayed_node(prev_node);
        }

        if (curr_node)
                btrfs_release_delayed_node(curr_node);
        btrfs_free_path(path);
        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_delayed_node *delayed_node = btrfs_get_delayed_node(inode);
        struct btrfs_path *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);
                return 0;
        }
        mutex_unlock(&delayed_node->mutex);

        path = btrfs_alloc_path();
        if (!path) {
                btrfs_release_delayed_node(delayed_node);
                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);
        btrfs_free_path(path);
        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_delayed_node *delayed_node = btrfs_get_delayed_node(inode);
        struct btrfs_path *path;
        struct btrfs_block_rsv *block_rsv;
        int ret;

        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);
                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);

        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);
}

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_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);
                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);
                        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);
                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(sizeof(*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,
                        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)
{
        WARN_ON(btrfs_first_delayed_node(fs_info->delayed_root));
}

static int 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 1;

        if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND)
                return 1;

        return 0;
}

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);
}

/* Will return 0 or -ENOMEM */
int btrfs_insert_delayed_dir_index(struct btrfs_trans_handle *trans,
                                   const char *name, int name_len,
                                   struct btrfs_inode *dir,
                                   struct btrfs_disk_key *disk_key, u8 type,
                                   u64 index)
{
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_delayed_item *delayed_item;
        struct btrfs_dir_item *dir_item;
        int ret;

        delayed_node = btrfs_get_or_create_delayed_node(dir);
        if (IS_ERR(delayed_node))
                return PTR_ERR(delayed_node);

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

        delayed_item->key.objectid = btrfs_ino(dir);
        delayed_item->key.type = BTRFS_DIR_INDEX_KEY;
        delayed_item->key.offset = 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_type(dir_item, type);
        memcpy((char *)(dir_item + 1), name, name_len);

        ret = btrfs_delayed_item_reserve_metadata(trans, dir->root, delayed_item);
        /*
         * we have reserved enough space when we start a new transaction,
         * so reserving metadata failure is impossible
         */
        BUG_ON(ret);

        mutex_lock(&delayed_node->mutex);
        ret = __btrfs_add_delayed_insertion_item(delayed_node, delayed_item);
        if (unlikely(ret)) {
                btrfs_err(trans->fs_info,
                          "err add delayed dir index item(name: %.*s) into the insertion tree of the delayed node(root id: %llu, inode id: %llu, errno: %d)",
                          name_len, name, delayed_node->root->root_key.objectid,
                          delayed_node->inode_id, ret);
                BUG();
        }
        mutex_unlock(&delayed_node->mutex);

release_node:
        btrfs_release_delayed_node(delayed_node);
        return ret;
}

static int btrfs_delete_delayed_insertion_item(struct btrfs_fs_info *fs_info,
                                               struct btrfs_delayed_node *node,
                                               struct btrfs_key *key)
{
        struct btrfs_delayed_item *item;

        mutex_lock(&node->mutex);
        item = __btrfs_lookup_delayed_insertion_item(node, key);
        if (!item) {
                mutex_unlock(&node->mutex);
                return 1;
        }

        btrfs_delayed_item_release_metadata(node->root, item);
        btrfs_release_delayed_item(item);
        mutex_unlock(&node->mutex);
        return 0;
}

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

        node = btrfs_get_or_create_delayed_node(dir);
        if (IS_ERR(node))
                return PTR_ERR(node);

        item_key.objectid = btrfs_ino(dir);
        item_key.type = BTRFS_DIR_INDEX_KEY;
        item_key.offset = index;

        ret = btrfs_delete_delayed_insertion_item(trans->fs_info, node,
                                                  &item_key);
        if (!ret)
                goto end;

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

        item->key = item_key;

        ret = btrfs_delayed_item_reserve_metadata(trans, dir->root, 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 deltiona, should have been reserved");
                btrfs_release_delayed_item(item);
                goto end;
        }

        mutex_lock(&node->mutex);
        ret = __btrfs_add_delayed_deletion_item(node, item);
        if (unlikely(ret)) {
                btrfs_err(trans->fs_info,
                          "err add delayed dir index item(index: %llu) into the deletion tree of the delayed node(root id: %llu, inode id: %llu, errno: %d)",
                          index, node->root->root_key.objectid,
                          node->inode_id, ret);
                btrfs_delayed_item_release_metadata(dir->root, item);
                btrfs_release_delayed_item(item);
        }
        mutex_unlock(&node->mutex);
end:
        btrfs_release_delayed_node(node);
        return ret;
}

int btrfs_inode_delayed_dir_index_count(struct btrfs_inode *inode)
{
        struct btrfs_delayed_node *delayed_node = btrfs_get_delayed_node(inode);

        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);
                return -EINVAL;
        }

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

bool btrfs_readdir_get_delayed_items(struct inode *inode,
                                     struct list_head *ins_list,
                                     struct list_head *del_list)
{
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_delayed_item *item;

        delayed_node = btrfs_get_delayed_node(BTRFS_I(inode));
        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) {
                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) {
                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.
         */
        refcount_dec(&delayed_node->refs);

        return true;
}

void btrfs_readdir_put_delayed_items(struct 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->i_rwsem);
}

int btrfs_should_delete_dir_index(struct list_head *del_list,
                                  u64 index)
{
        struct btrfs_delayed_item *curr;
        int ret = 0;

        list_for_each_entry(curr, del_list, readdir_list) {
                if (curr->key.offset > index)
                        break;
                if (curr->key.offset == index) {
                        ret = 1;
                        break;
                }
        }
        return ret;
}

/*
 * btrfs_readdir_delayed_dir_index - read dir info stored in the delayed tree
 *
 */
int btrfs_readdir_delayed_dir_index(struct dir_context *ctx,
                                    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;
        int over = 0;
        unsigned char d_type;

        if (list_empty(ins_list))
                return 0;

        /*
         * 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) {
                list_del(&curr->readdir_list);

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

                ctx->pos = curr->key.offset;

                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(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 1;
                ctx->pos++;
        }
        return 0;
}

static void fill_stack_inode_item(struct btrfs_trans_handle *trans,
                                  struct btrfs_inode_item *inode_item,
                                  struct inode *inode)
{
        btrfs_set_stack_inode_uid(inode_item, i_uid_read(inode));
        btrfs_set_stack_inode_gid(inode_item, i_gid_read(inode));
        btrfs_set_stack_inode_size(inode_item, BTRFS_I(inode)->disk_i_size);
        btrfs_set_stack_inode_mode(inode_item, inode->i_mode);
        btrfs_set_stack_inode_nlink(inode_item, inode->i_nlink);
        btrfs_set_stack_inode_nbytes(inode_item, inode_get_bytes(inode));
        btrfs_set_stack_inode_generation(inode_item,
                                         BTRFS_I(inode)->generation);
        btrfs_set_stack_inode_sequence(inode_item,
                                       inode_peek_iversion(inode));
        btrfs_set_stack_inode_transid(inode_item, trans->transid);
        btrfs_set_stack_inode_rdev(inode_item, inode->i_rdev);
        btrfs_set_stack_inode_flags(inode_item, BTRFS_I(inode)->flags);
        btrfs_set_stack_inode_block_group(inode_item, 0);

        btrfs_set_stack_timespec_sec(&inode_item->atime,
                                     inode->i_atime.tv_sec);
        btrfs_set_stack_timespec_nsec(&inode_item->atime,
                                      inode->i_atime.tv_nsec);

        btrfs_set_stack_timespec_sec(&inode_item->mtime,
                                     inode->i_mtime.tv_sec);
        btrfs_set_stack_timespec_nsec(&inode_item->mtime,
                                      inode->i_mtime.tv_nsec);

        btrfs_set_stack_timespec_sec(&inode_item->ctime,
                                     inode->i_ctime.tv_sec);
        btrfs_set_stack_timespec_nsec(&inode_item->ctime,
                                      inode->i_ctime.tv_nsec);

        btrfs_set_stack_timespec_sec(&inode_item->otime,
                                     BTRFS_I(inode)->i_otime.tv_sec);
        btrfs_set_stack_timespec_nsec(&inode_item->otime,
                                     BTRFS_I(inode)->i_otime.tv_nsec);
}

int btrfs_fill_inode(struct inode *inode, u32 *rdev)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct btrfs_delayed_node *delayed_node;
        struct btrfs_inode_item *inode_item;

        delayed_node = btrfs_get_delayed_node(BTRFS_I(inode));
        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);
                return -ENOENT;
        }

        inode_item = &delayed_node->inode_item;

        i_uid_write(inode, btrfs_stack_inode_uid(inode_item));
        i_gid_write(inode, btrfs_stack_inode_gid(inode_item));
        btrfs_i_size_write(BTRFS_I(inode), btrfs_stack_inode_size(inode_item));
        btrfs_inode_set_file_extent_range(BTRFS_I(inode), 0,
                        round_up(i_size_read(inode), fs_info->sectorsize));
        inode->i_mode = btrfs_stack_inode_mode(inode_item);
        set_nlink(inode, btrfs_stack_inode_nlink(inode_item));
        inode_set_bytes(inode, btrfs_stack_inode_nbytes(inode_item));
        BTRFS_I(inode)->generation = btrfs_stack_inode_generation(inode_item);
        BTRFS_I(inode)->last_trans = btrfs_stack_inode_transid(inode_item);

        inode_set_iversion_queried(inode,
                                   btrfs_stack_inode_sequence(inode_item));
        inode->i_rdev = 0;
        *rdev = btrfs_stack_inode_rdev(inode_item);
        BTRFS_I(inode)->flags = btrfs_stack_inode_flags(inode_item);

        inode->i_atime.tv_sec = btrfs_stack_timespec_sec(&inode_item->atime);
        inode->i_atime.tv_nsec = btrfs_stack_timespec_nsec(&inode_item->atime);

        inode->i_mtime.tv_sec = btrfs_stack_timespec_sec(&inode_item->mtime);
        inode->i_mtime.tv_nsec = btrfs_stack_timespec_nsec(&inode_item->mtime);

        inode->i_ctime.tv_sec = btrfs_stack_timespec_sec(&inode_item->ctime);
        inode->i_ctime.tv_nsec = btrfs_stack_timespec_nsec(&inode_item->ctime);

        BTRFS_I(inode)->i_otime.tv_sec =
                btrfs_stack_timespec_sec(&inode_item->otime);
        BTRFS_I(inode)->i_otime.tv_nsec =
                btrfs_stack_timespec_nsec(&inode_item->otime);

        inode->i_generation = BTRFS_I(inode)->generation;
        BTRFS_I(inode)->index_cnt = (u64)-1;

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

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

        delayed_node = btrfs_get_or_create_delayed_node(inode);
        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->vfs_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->vfs_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);
        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;

        /*
         * 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);
        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_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags))
                goto release_node;

        set_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags);
        delayed_node->count++;
        atomic_inc(&fs_info->delayed_root->items);
release_node:
        mutex_unlock(&delayed_node->mutex);
        btrfs_release_delayed_node(delayed_node);
        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) {
                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);
        }

        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;

        delayed_node = btrfs_get_delayed_node(inode);
        if (!delayed_node)
                return;

        __btrfs_kill_delayed_node(delayed_node);
        btrfs_release_delayed_node(delayed_node);
}

void btrfs_kill_all_delayed_nodes(struct btrfs_root *root)
{
        u64 inode_id = 0;
        struct btrfs_delayed_node *delayed_nodes[8];
        int i, n;

        while (1) {
                spin_lock(&root->inode_lock);
                n = radix_tree_gang_lookup(&root->delayed_nodes_tree,
                                           (void **)delayed_nodes, inode_id,
                                           ARRAY_SIZE(delayed_nodes));
                if (!n) {
                        spin_unlock(&root->inode_lock);
                        break;
                }

                inode_id = delayed_nodes[n - 1]->inode_id + 1;
                for (i = 0; i < n; i++) {
                        /*
                         * 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(&delayed_nodes[i]->refs))
                                delayed_nodes[i] = NULL;
                }
                spin_unlock(&root->inode_lock);

                for (i = 0; i < n; i++) {
                        if (!delayed_nodes[i])
                                continue;
                        __btrfs_kill_delayed_node(delayed_nodes[i]);
                        btrfs_release_delayed_node(delayed_nodes[i]);
                }
        }
}

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

        curr_node = btrfs_first_delayed_node(fs_info->delayed_root);
        while (curr_node) {
                __btrfs_kill_delayed_node(curr_node);

                prev_node = curr_node;
                curr_node = btrfs_next_delayed_node(curr_node);
                btrfs_release_delayed_node(prev_node);
        }
}