Btrfs: Cache free inode numbers in memory

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / btrfs / free-space-cache.c

/*
 * Copyright (C) 2008 Red Hat.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/pagemap.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/math64.h>
#include "ctree.h"
#include "free-space-cache.h"
#include "transaction.h"
#include "disk-io.h"
#include "extent_io.h"
#include "inode-map.h"

#define BITS_PER_BITMAP         (PAGE_CACHE_SIZE * 8)
#define MAX_CACHE_BYTES_PER_GIG (32 * 1024)

static int link_free_space(struct btrfs_free_space_ctl *ctl,
                           struct btrfs_free_space *info);

struct inode *lookup_free_space_inode(struct btrfs_root *root,
                                      struct btrfs_block_group_cache
                                      *block_group, struct btrfs_path *path)
{
        struct btrfs_key key;
        struct btrfs_key location;
        struct btrfs_disk_key disk_key;
        struct btrfs_free_space_header *header;
        struct extent_buffer *leaf;
        struct inode *inode = NULL;
        int ret;

        spin_lock(&block_group->lock);
        if (block_group->inode)
                inode = igrab(block_group->inode);
        spin_unlock(&block_group->lock);
        if (inode)
                return inode;

        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
        key.offset = block_group->key.objectid;
        key.type = 0;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                return ERR_PTR(ret);
        if (ret > 0) {
                btrfs_release_path(root, path);
                return ERR_PTR(-ENOENT);
        }

        leaf = path->nodes[0];
        header = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_free_space_header);
        btrfs_free_space_key(leaf, header, &disk_key);
        btrfs_disk_key_to_cpu(&location, &disk_key);
        btrfs_release_path(root, path);

        inode = btrfs_iget(root->fs_info->sb, &location, root, NULL);
        if (!inode)
                return ERR_PTR(-ENOENT);
        if (IS_ERR(inode))
                return inode;
        if (is_bad_inode(inode)) {
                iput(inode);
                return ERR_PTR(-ENOENT);
        }

        inode->i_mapping->flags &= ~__GFP_FS;

        spin_lock(&block_group->lock);
        if (!root->fs_info->closing) {
                block_group->inode = igrab(inode);
                block_group->iref = 1;
        }
        spin_unlock(&block_group->lock);

        return inode;
}

int create_free_space_inode(struct btrfs_root *root,
                            struct btrfs_trans_handle *trans,
                            struct btrfs_block_group_cache *block_group,
                            struct btrfs_path *path)
{
        struct btrfs_key key;
        struct btrfs_disk_key disk_key;
        struct btrfs_free_space_header *header;
        struct btrfs_inode_item *inode_item;
        struct extent_buffer *leaf;
        u64 objectid;
        int ret;

        ret = btrfs_find_free_objectid(root, &objectid);
        if (ret < 0)
                return ret;

        ret = btrfs_insert_empty_inode(trans, root, path, objectid);
        if (ret)
                return ret;

        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);
        btrfs_item_key(leaf, &disk_key, path->slots[0]);
        memset_extent_buffer(leaf, 0, (unsigned long)inode_item,
                             sizeof(*inode_item));
        btrfs_set_inode_generation(leaf, inode_item, trans->transid);
        btrfs_set_inode_size(leaf, inode_item, 0);
        btrfs_set_inode_nbytes(leaf, inode_item, 0);
        btrfs_set_inode_uid(leaf, inode_item, 0);
        btrfs_set_inode_gid(leaf, inode_item, 0);
        btrfs_set_inode_mode(leaf, inode_item, S_IFREG | 0600);
        btrfs_set_inode_flags(leaf, inode_item, BTRFS_INODE_NOCOMPRESS |
                              BTRFS_INODE_PREALLOC | BTRFS_INODE_NODATASUM);
        btrfs_set_inode_nlink(leaf, inode_item, 1);
        btrfs_set_inode_transid(leaf, inode_item, trans->transid);
        btrfs_set_inode_block_group(leaf, inode_item,
                                    block_group->key.objectid);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(root, path);

        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
        key.offset = block_group->key.objectid;
        key.type = 0;

        ret = btrfs_insert_empty_item(trans, root, path, &key,
                                      sizeof(struct btrfs_free_space_header));
        if (ret < 0) {
                btrfs_release_path(root, path);
                return ret;
        }
        leaf = path->nodes[0];
        header = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_free_space_header);
        memset_extent_buffer(leaf, 0, (unsigned long)header, sizeof(*header));
        btrfs_set_free_space_key(leaf, header, &disk_key);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(root, path);

        return 0;
}

int btrfs_truncate_free_space_cache(struct btrfs_root *root,
                                    struct btrfs_trans_handle *trans,
                                    struct btrfs_path *path,
                                    struct inode *inode)
{
        loff_t oldsize;
        int ret = 0;

        trans->block_rsv = root->orphan_block_rsv;
        ret = btrfs_block_rsv_check(trans, root,
                                    root->orphan_block_rsv,
                                    0, 5);
        if (ret)
                return ret;

        oldsize = i_size_read(inode);
        btrfs_i_size_write(inode, 0);
        truncate_pagecache(inode, oldsize, 0);

        /*
         * We don't need an orphan item because truncating the free space cache
         * will never be split across transactions.
         */
        ret = btrfs_truncate_inode_items(trans, root, inode,
                                         0, BTRFS_EXTENT_DATA_KEY);
        if (ret) {
                WARN_ON(1);
                return ret;
        }

        return btrfs_update_inode(trans, root, inode);
}

static int readahead_cache(struct inode *inode)
{
        struct file_ra_state *ra;
        unsigned long last_index;

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

        file_ra_state_init(ra, inode->i_mapping);
        last_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;

        page_cache_sync_readahead(inode->i_mapping, ra, NULL, 0, last_index);

        kfree(ra);

        return 0;
}

int load_free_space_cache(struct btrfs_fs_info *fs_info,
                          struct btrfs_block_group_cache *block_group)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_root *root = fs_info->tree_root;
        struct inode *inode;
        struct btrfs_free_space_header *header;
        struct extent_buffer *leaf;
        struct page *page;
        struct btrfs_path *path;
        u32 *checksums = NULL, *crc;
        char *disk_crcs = NULL;
        struct btrfs_key key;
        struct list_head bitmaps;
        u64 num_entries;
        u64 num_bitmaps;
        u64 generation;
        u64 used = btrfs_block_group_used(&block_group->item);
        u32 cur_crc = ~(u32)0;
        pgoff_t index = 0;
        unsigned long first_page_offset;
        int num_checksums;
        int ret = 0;

        /*
         * If we're unmounting then just return, since this does a search on the
         * normal root and not the commit root and we could deadlock.
         */
        smp_mb();
        if (fs_info->closing)
                return 0;

        /*
         * If this block group has been marked to be cleared for one reason or
         * another then we can't trust the on disk cache, so just return.
         */
        spin_lock(&block_group->lock);
        if (block_group->disk_cache_state != BTRFS_DC_WRITTEN) {
                spin_unlock(&block_group->lock);
                return 0;
        }
        spin_unlock(&block_group->lock);

        INIT_LIST_HEAD(&bitmaps);

        path = btrfs_alloc_path();
        if (!path)
                return 0;

        inode = lookup_free_space_inode(root, block_group, path);
        if (IS_ERR(inode)) {
                btrfs_free_path(path);
                return 0;
        }

        /* Nothing in the space cache, goodbye */
        if (!i_size_read(inode)) {
                btrfs_free_path(path);
                goto out;
        }

        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
        key.offset = block_group->key.objectid;
        key.type = 0;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret) {
                btrfs_free_path(path);
                goto out;
        }

        leaf = path->nodes[0];
        header = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_free_space_header);
        num_entries = btrfs_free_space_entries(leaf, header);
        num_bitmaps = btrfs_free_space_bitmaps(leaf, header);
        generation = btrfs_free_space_generation(leaf, header);
        btrfs_free_path(path);

        if (BTRFS_I(inode)->generation != generation) {
                printk(KERN_ERR "btrfs: free space inode generation (%llu) did"
                       " not match free space cache generation (%llu) for "
                       "block group %llu\n",
                       (unsigned long long)BTRFS_I(inode)->generation,
                       (unsigned long long)generation,
                       (unsigned long long)block_group->key.objectid);
                goto free_cache;
        }

        if (!num_entries)
                goto out;

        /* Setup everything for doing checksumming */
        num_checksums = i_size_read(inode) / PAGE_CACHE_SIZE;
        checksums = crc = kzalloc(sizeof(u32) * num_checksums, GFP_NOFS);
        if (!checksums)
                goto out;
        first_page_offset = (sizeof(u32) * num_checksums) + sizeof(u64);
        disk_crcs = kzalloc(first_page_offset, GFP_NOFS);
        if (!disk_crcs)
                goto out;

        ret = readahead_cache(inode);
        if (ret) {
                ret = 0;
                goto out;
        }

        while (1) {
                struct btrfs_free_space_entry *entry;
                struct btrfs_free_space *e;
                void *addr;
                unsigned long offset = 0;
                unsigned long start_offset = 0;
                int need_loop = 0;

                if (!num_entries && !num_bitmaps)
                        break;

                if (index == 0) {
                        start_offset = first_page_offset;
                        offset = start_offset;
                }

                page = grab_cache_page(inode->i_mapping, index);
                if (!page) {
                        ret = 0;
                        goto free_cache;
                }

                if (!PageUptodate(page)) {
                        btrfs_readpage(NULL, page);
                        lock_page(page);
                        if (!PageUptodate(page)) {
                                unlock_page(page);
                                page_cache_release(page);
                                printk(KERN_ERR "btrfs: error reading free "
                                       "space cache: %llu\n",
                                       (unsigned long long)
                                       block_group->key.objectid);
                                goto free_cache;
                        }
                }
                addr = kmap(page);

                if (index == 0) {
                        u64 *gen;

                        memcpy(disk_crcs, addr, first_page_offset);
                        gen = addr + (sizeof(u32) * num_checksums);
                        if (*gen != BTRFS_I(inode)->generation) {
                                printk(KERN_ERR "btrfs: space cache generation"
                                       " (%llu) does not match inode (%llu) "
                                       "for block group %llu\n",
                                       (unsigned long long)*gen,
                                       (unsigned long long)
                                       BTRFS_I(inode)->generation,
                                       (unsigned long long)
                                       block_group->key.objectid);
                                kunmap(page);
                                unlock_page(page);
                                page_cache_release(page);
                                goto free_cache;
                        }
                        crc = (u32 *)disk_crcs;
                }
                entry = addr + start_offset;

                /* First lets check our crc before we do anything fun */
                cur_crc = ~(u32)0;
                cur_crc = btrfs_csum_data(root, addr + start_offset, cur_crc,
                                          PAGE_CACHE_SIZE - start_offset);
                btrfs_csum_final(cur_crc, (char *)&cur_crc);
                if (cur_crc != *crc) {
                        printk(KERN_ERR "btrfs: crc mismatch for page %lu in "
                               "block group %llu\n", index,
                               (unsigned long long)block_group->key.objectid);
                        kunmap(page);
                        unlock_page(page);
                        page_cache_release(page);
                        goto free_cache;
                }
                crc++;

                while (1) {
                        if (!num_entries)
                                break;

                        need_loop = 1;
                        e = kmem_cache_zalloc(btrfs_free_space_cachep,
                                              GFP_NOFS);
                        if (!e) {
                                kunmap(page);
                                unlock_page(page);
                                page_cache_release(page);
                                goto free_cache;
                        }

                        e->offset = le64_to_cpu(entry->offset);
                        e->bytes = le64_to_cpu(entry->bytes);
                        if (!e->bytes) {
                                kunmap(page);
                                kmem_cache_free(btrfs_free_space_cachep, e);
                                unlock_page(page);
                                page_cache_release(page);
                                goto free_cache;
                        }

                        if (entry->type == BTRFS_FREE_SPACE_EXTENT) {
                                spin_lock(&ctl->tree_lock);
                                ret = link_free_space(ctl, e);
                                spin_unlock(&ctl->tree_lock);
                                BUG_ON(ret);
                        } else {
                                e->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
                                if (!e->bitmap) {
                                        kunmap(page);
                                        kmem_cache_free(
                                                btrfs_free_space_cachep, e);
                                        unlock_page(page);
                                        page_cache_release(page);
                                        goto free_cache;
                                }
                                spin_lock(&ctl->tree_lock);
                                ret = link_free_space(ctl, e);
                                ctl->total_bitmaps++;
                                ctl->op->recalc_thresholds(ctl);
                                spin_unlock(&ctl->tree_lock);
                                list_add_tail(&e->list, &bitmaps);
                        }

                        num_entries--;
                        offset += sizeof(struct btrfs_free_space_entry);
                        if (offset + sizeof(struct btrfs_free_space_entry) >=
                            PAGE_CACHE_SIZE)
                                break;
                        entry++;
                }

                /*
                 * We read an entry out of this page, we need to move on to the
                 * next page.
                 */
                if (need_loop) {
                        kunmap(page);
                        goto next;
                }

                /*
                 * We add the bitmaps at the end of the entries in order that
                 * the bitmap entries are added to the cache.
                 */
                e = list_entry(bitmaps.next, struct btrfs_free_space, list);
                list_del_init(&e->list);
                memcpy(e->bitmap, addr, PAGE_CACHE_SIZE);
                kunmap(page);
                num_bitmaps--;
next:
                unlock_page(page);
                page_cache_release(page);
                index++;
        }

        spin_lock(&ctl->tree_lock);
        if (ctl->free_space != (block_group->key.offset - used -
                                block_group->bytes_super)) {
                spin_unlock(&ctl->tree_lock);
                printk(KERN_ERR "block group %llu has an wrong amount of free "
                       "space\n", block_group->key.objectid);
                ret = 0;
                goto free_cache;
        }
        spin_unlock(&ctl->tree_lock);

        ret = 1;
out:
        kfree(checksums);
        kfree(disk_crcs);
        iput(inode);
        return ret;

free_cache:
        /* This cache is bogus, make sure it gets cleared */
        spin_lock(&block_group->lock);
        block_group->disk_cache_state = BTRFS_DC_CLEAR;
        spin_unlock(&block_group->lock);
        btrfs_remove_free_space_cache(block_group);
        goto out;
}

int btrfs_write_out_cache(struct btrfs_root *root,
                          struct btrfs_trans_handle *trans,
                          struct btrfs_block_group_cache *block_group,
                          struct btrfs_path *path)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space_header *header;
        struct extent_buffer *leaf;
        struct inode *inode;
        struct rb_node *node;
        struct list_head *pos, *n;
        struct page **pages;
        struct page *page;
        struct extent_state *cached_state = NULL;
        struct btrfs_free_cluster *cluster = NULL;
        struct extent_io_tree *unpin = NULL;
        struct list_head bitmap_list;
        struct btrfs_key key;
        u64 start, end, len;
        u64 bytes = 0;
        u32 *crc, *checksums;
        unsigned long first_page_offset;
        int index = 0, num_pages = 0;
        int entries = 0;
        int bitmaps = 0;
        int ret = 0;
        bool next_page = false;
        bool out_of_space = false;

        root = root->fs_info->tree_root;

        INIT_LIST_HEAD(&bitmap_list);

        spin_lock(&block_group->lock);
        if (block_group->disk_cache_state < BTRFS_DC_SETUP) {
                spin_unlock(&block_group->lock);
                return 0;
        }
        spin_unlock(&block_group->lock);

        inode = lookup_free_space_inode(root, block_group, path);
        if (IS_ERR(inode))
                return 0;

        if (!i_size_read(inode)) {
                iput(inode);
                return 0;
        }

        node = rb_first(&ctl->free_space_offset);
        if (!node) {
                iput(inode);
                return 0;
        }

        num_pages = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >>
                PAGE_CACHE_SHIFT;
        filemap_write_and_wait(inode->i_mapping);
        btrfs_wait_ordered_range(inode, inode->i_size &
                                 ~(root->sectorsize - 1), (u64)-1);

        /* We need a checksum per page. */
        crc = checksums = kzalloc(sizeof(u32) * num_pages, GFP_NOFS);
        if (!crc) {
                iput(inode);
                return 0;
        }

        pages = kzalloc(sizeof(struct page *) * num_pages, GFP_NOFS);
        if (!pages) {
                kfree(crc);
                iput(inode);
                return 0;
        }

        /* Since the first page has all of our checksums and our generation we
         * need to calculate the offset into the page that we can start writing
         * our entries.
         */
        first_page_offset = (sizeof(u32) * num_pages) + sizeof(u64);

        /* Get the cluster for this block_group if it exists */
        if (!list_empty(&block_group->cluster_list))
                cluster = list_entry(block_group->cluster_list.next,
                                     struct btrfs_free_cluster,
                                     block_group_list);

        /*
         * We shouldn't have switched the pinned extents yet so this is the
         * right one
         */
        unpin = root->fs_info->pinned_extents;

        /*
         * Lock all pages first so we can lock the extent safely.
         *
         * NOTE: Because we hold the ref the entire time we're going to write to
         * the page find_get_page should never fail, so we don't do a check
         * after find_get_page at this point.  Just putting this here so people
         * know and don't freak out.
         */
        while (index < num_pages) {
                page = grab_cache_page(inode->i_mapping, index);
                if (!page) {
                        int i;

                        for (i = 0; i < num_pages; i++) {
                                unlock_page(pages[i]);
                                page_cache_release(pages[i]);
                        }
                        goto out_free;
                }
                pages[index] = page;
                index++;
        }

        index = 0;
        lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
                         0, &cached_state, GFP_NOFS);

        /*
         * When searching for pinned extents, we need to start at our start
         * offset.
         */
        start = block_group->key.objectid;

        /* Write out the extent entries */
        do {
                struct btrfs_free_space_entry *entry;
                void *addr;
                unsigned long offset = 0;
                unsigned long start_offset = 0;

                next_page = false;

                if (index == 0) {
                        start_offset = first_page_offset;
                        offset = start_offset;
                }

                if (index >= num_pages) {
                        out_of_space = true;
                        break;
                }

                page = pages[index];

                addr = kmap(page);
                entry = addr + start_offset;

                memset(addr, 0, PAGE_CACHE_SIZE);
                while (node && !next_page) {
                        struct btrfs_free_space *e;

                        e = rb_entry(node, struct btrfs_free_space, offset_index);
                        entries++;

                        entry->offset = cpu_to_le64(e->offset);
                        entry->bytes = cpu_to_le64(e->bytes);
                        if (e->bitmap) {
                                entry->type = BTRFS_FREE_SPACE_BITMAP;
                                list_add_tail(&e->list, &bitmap_list);
                                bitmaps++;
                        } else {
                                entry->type = BTRFS_FREE_SPACE_EXTENT;
                        }
                        node = rb_next(node);
                        if (!node && cluster) {
                                node = rb_first(&cluster->root);
                                cluster = NULL;
                        }
                        offset += sizeof(struct btrfs_free_space_entry);
                        if (offset + sizeof(struct btrfs_free_space_entry) >=
                            PAGE_CACHE_SIZE)
                                next_page = true;
                        entry++;
                }

                /*
                 * We want to add any pinned extents to our free space cache
                 * so we don't leak the space
                 */
                while (!next_page && (start < block_group->key.objectid +
                                      block_group->key.offset)) {
                        ret = find_first_extent_bit(unpin, start, &start, &end,
                                                    EXTENT_DIRTY);
                        if (ret) {
                                ret = 0;
                                break;
                        }

                        /* This pinned extent is out of our range */
                        if (start >= block_group->key.objectid +
                            block_group->key.offset)
                                break;

                        len = block_group->key.objectid +
                                block_group->key.offset - start;
                        len = min(len, end + 1 - start);

                        entries++;
                        entry->offset = cpu_to_le64(start);
                        entry->bytes = cpu_to_le64(len);
                        entry->type = BTRFS_FREE_SPACE_EXTENT;

                        start = end + 1;
                        offset += sizeof(struct btrfs_free_space_entry);
                        if (offset + sizeof(struct btrfs_free_space_entry) >=
                            PAGE_CACHE_SIZE)
                                next_page = true;
                        entry++;
                }
                *crc = ~(u32)0;
                *crc = btrfs_csum_data(root, addr + start_offset, *crc,
                                       PAGE_CACHE_SIZE - start_offset);
                kunmap(page);

                btrfs_csum_final(*crc, (char *)crc);
                crc++;

                bytes += PAGE_CACHE_SIZE;

                index++;
        } while (node || next_page);

        /* Write out the bitmaps */
        list_for_each_safe(pos, n, &bitmap_list) {
                void *addr;
                struct btrfs_free_space *entry =
                        list_entry(pos, struct btrfs_free_space, list);

                if (index >= num_pages) {
                        out_of_space = true;
                        break;
                }
                page = pages[index];

                addr = kmap(page);
                memcpy(addr, entry->bitmap, PAGE_CACHE_SIZE);
                *crc = ~(u32)0;
                *crc = btrfs_csum_data(root, addr, *crc, PAGE_CACHE_SIZE);
                kunmap(page);
                btrfs_csum_final(*crc, (char *)crc);
                crc++;
                bytes += PAGE_CACHE_SIZE;

                list_del_init(&entry->list);
                index++;
        }

        if (out_of_space) {
                btrfs_drop_pages(pages, num_pages);
                unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
                                     i_size_read(inode) - 1, &cached_state,
                                     GFP_NOFS);
                ret = 0;
                goto out_free;
        }

        /* Zero out the rest of the pages just to make sure */
        while (index < num_pages) {
                void *addr;

                page = pages[index];
                addr = kmap(page);
                memset(addr, 0, PAGE_CACHE_SIZE);
                kunmap(page);
                bytes += PAGE_CACHE_SIZE;
                index++;
        }

        /* Write the checksums and trans id to the first page */
        {
                void *addr;
                u64 *gen;

                page = pages[0];

                addr = kmap(page);
                memcpy(addr, checksums, sizeof(u32) * num_pages);
                gen = addr + (sizeof(u32) * num_pages);
                *gen = trans->transid;
                kunmap(page);
        }

        ret = btrfs_dirty_pages(root, inode, pages, num_pages, 0,
                                            bytes, &cached_state);
        btrfs_drop_pages(pages, num_pages);
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, 0,
                             i_size_read(inode) - 1, &cached_state, GFP_NOFS);

        if (ret) {
                ret = 0;
                goto out_free;
        }

        BTRFS_I(inode)->generation = trans->transid;

        filemap_write_and_wait(inode->i_mapping);

        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
        key.offset = block_group->key.objectid;
        key.type = 0;

        ret = btrfs_search_slot(trans, root, &key, path, 1, 1);
        if (ret < 0) {
                ret = 0;
                clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, bytes - 1,
                                 EXTENT_DIRTY | EXTENT_DELALLOC |
                                 EXTENT_DO_ACCOUNTING, 0, 0, NULL, GFP_NOFS);
                goto out_free;
        }
        leaf = path->nodes[0];
        if (ret > 0) {
                struct btrfs_key found_key;
                BUG_ON(!path->slots[0]);
                path->slots[0]--;
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != BTRFS_FREE_SPACE_OBJECTID ||
                    found_key.offset != block_group->key.objectid) {
                        ret = 0;
                        clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, bytes - 1,
                                         EXTENT_DIRTY | EXTENT_DELALLOC |
                                         EXTENT_DO_ACCOUNTING, 0, 0, NULL,
                                         GFP_NOFS);
                        btrfs_release_path(root, path);
                        goto out_free;
                }
        }
        header = btrfs_item_ptr(leaf, path->slots[0],
                                struct btrfs_free_space_header);
        btrfs_set_free_space_entries(leaf, header, entries);
        btrfs_set_free_space_bitmaps(leaf, header, bitmaps);
        btrfs_set_free_space_generation(leaf, header, trans->transid);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_release_path(root, path);

        ret = 1;

out_free:
        if (ret == 0) {
                invalidate_inode_pages2_range(inode->i_mapping, 0, index);
                spin_lock(&block_group->lock);
                block_group->disk_cache_state = BTRFS_DC_ERROR;
                spin_unlock(&block_group->lock);
                BTRFS_I(inode)->generation = 0;
        }
        kfree(checksums);
        kfree(pages);
        btrfs_update_inode(trans, root, inode);
        iput(inode);
        return ret;
}

static inline unsigned long offset_to_bit(u64 bitmap_start, u32 unit,
                                          u64 offset)
{
        BUG_ON(offset < bitmap_start);
        offset -= bitmap_start;
        return (unsigned long)(div_u64(offset, unit));
}

static inline unsigned long bytes_to_bits(u64 bytes, u32 unit)
{
        return (unsigned long)(div_u64(bytes, unit));
}

static inline u64 offset_to_bitmap(struct btrfs_free_space_ctl *ctl,
                                   u64 offset)
{
        u64 bitmap_start;
        u64 bytes_per_bitmap;

        bytes_per_bitmap = BITS_PER_BITMAP * ctl->unit;
        bitmap_start = offset - ctl->start;
        bitmap_start = div64_u64(bitmap_start, bytes_per_bitmap);
        bitmap_start *= bytes_per_bitmap;
        bitmap_start += ctl->start;

        return bitmap_start;
}

static int tree_insert_offset(struct rb_root *root, u64 offset,
                              struct rb_node *node, int bitmap)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent = NULL;
        struct btrfs_free_space *info;

        while (*p) {
                parent = *p;
                info = rb_entry(parent, struct btrfs_free_space, offset_index);

                if (offset < info->offset) {
                        p = &(*p)->rb_left;
                } else if (offset > info->offset) {
                        p = &(*p)->rb_right;
                } else {
                        /*
                         * we could have a bitmap entry and an extent entry
                         * share the same offset.  If this is the case, we want
                         * the extent entry to always be found first if we do a
                         * linear search through the tree, since we want to have
                         * the quickest allocation time, and allocating from an
                         * extent is faster than allocating from a bitmap.  So
                         * if we're inserting a bitmap and we find an entry at
                         * this offset, we want to go right, or after this entry
                         * logically.  If we are inserting an extent and we've
                         * found a bitmap, we want to go left, or before
                         * logically.
                         */
                        if (bitmap) {
                                WARN_ON(info->bitmap);
                                p = &(*p)->rb_right;
                        } else {
                                WARN_ON(!info->bitmap);
                                p = &(*p)->rb_left;
                        }
                }
        }

        rb_link_node(node, parent, p);
        rb_insert_color(node, root);

        return 0;
}

/*
 * searches the tree for the given offset.
 *
 * fuzzy - If this is set, then we are trying to make an allocation, and we just
 * want a section that has at least bytes size and comes at or after the given
 * offset.
 */
static struct btrfs_free_space *
tree_search_offset(struct btrfs_free_space_ctl *ctl,
                   u64 offset, int bitmap_only, int fuzzy)
{
        struct rb_node *n = ctl->free_space_offset.rb_node;
        struct btrfs_free_space *entry, *prev = NULL;

        /* find entry that is closest to the 'offset' */
        while (1) {
                if (!n) {
                        entry = NULL;
                        break;
                }

                entry = rb_entry(n, struct btrfs_free_space, offset_index);
                prev = entry;

                if (offset < entry->offset)
                        n = n->rb_left;
                else if (offset > entry->offset)
                        n = n->rb_right;
                else
                        break;
        }

        if (bitmap_only) {
                if (!entry)
                        return NULL;
                if (entry->bitmap)
                        return entry;

                /*
                 * bitmap entry and extent entry may share same offset,
                 * in that case, bitmap entry comes after extent entry.
                 */
                n = rb_next(n);
                if (!n)
                        return NULL;
                entry = rb_entry(n, struct btrfs_free_space, offset_index);
                if (entry->offset != offset)
                        return NULL;

                WARN_ON(!entry->bitmap);
                return entry;
        } else if (entry) {
                if (entry->bitmap) {
                        /*
                         * if previous extent entry covers the offset,
                         * we should return it instead of the bitmap entry
                         */
                        n = &entry->offset_index;
                        while (1) {
                                n = rb_prev(n);
                                if (!n)
                                        break;
                                prev = rb_entry(n, struct btrfs_free_space,
                                                offset_index);
                                if (!prev->bitmap) {
                                        if (prev->offset + prev->bytes > offset)
                                                entry = prev;
                                        break;
                                }
                        }
                }
                return entry;
        }

        if (!prev)
                return NULL;

        /* find last entry before the 'offset' */
        entry = prev;
        if (entry->offset > offset) {
                n = rb_prev(&entry->offset_index);
                if (n) {
                        entry = rb_entry(n, struct btrfs_free_space,
                                        offset_index);
                        BUG_ON(entry->offset > offset);
                } else {
                        if (fuzzy)
                                return entry;
                        else
                                return NULL;
                }
        }

        if (entry->bitmap) {
                n = &entry->offset_index;
                while (1) {
                        n = rb_prev(n);
                        if (!n)
                                break;
                        prev = rb_entry(n, struct btrfs_free_space,
                                        offset_index);
                        if (!prev->bitmap) {
                                if (prev->offset + prev->bytes > offset)
                                        return prev;
                                break;
                        }
                }
                if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
                        return entry;
        } else if (entry->offset + entry->bytes > offset)
                return entry;

        if (!fuzzy)
                return NULL;

        while (1) {
                if (entry->bitmap) {
                        if (entry->offset + BITS_PER_BITMAP *
                            ctl->unit > offset)
                                break;
                } else {
                        if (entry->offset + entry->bytes > offset)
                                break;
                }

                n = rb_next(&entry->offset_index);
                if (!n)
                        return NULL;
                entry = rb_entry(n, struct btrfs_free_space, offset_index);
        }
        return entry;
}

static inline void
__unlink_free_space(struct btrfs_free_space_ctl *ctl,
                    struct btrfs_free_space *info)
{
        rb_erase(&info->offset_index, &ctl->free_space_offset);
        ctl->free_extents--;
}

static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *info)
{
        __unlink_free_space(ctl, info);
        ctl->free_space -= info->bytes;
}

static int link_free_space(struct btrfs_free_space_ctl *ctl,
                           struct btrfs_free_space *info)
{
        int ret = 0;

        BUG_ON(!info->bitmap && !info->bytes);
        ret = tree_insert_offset(&ctl->free_space_offset, info->offset,
                                 &info->offset_index, (info->bitmap != NULL));
        if (ret)
                return ret;

        ctl->free_space += info->bytes;
        ctl->free_extents++;
        return ret;
}

static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
{
        struct btrfs_block_group_cache *block_group = ctl->private;
        u64 max_bytes;
        u64 bitmap_bytes;
        u64 extent_bytes;
        u64 size = block_group->key.offset;
        u64 bytes_per_bg = BITS_PER_BITMAP * block_group->sectorsize;
        int max_bitmaps = div64_u64(size + bytes_per_bg - 1, bytes_per_bg);

        BUG_ON(ctl->total_bitmaps > max_bitmaps);

        /*
         * The goal is to keep the total amount of memory used per 1gb of space
         * at or below 32k, so we need to adjust how much memory we allow to be
         * used by extent based free space tracking
         */
        if (size < 1024 * 1024 * 1024)
                max_bytes = MAX_CACHE_BYTES_PER_GIG;
        else
                max_bytes = MAX_CACHE_BYTES_PER_GIG *
                        div64_u64(size, 1024 * 1024 * 1024);

        /*
         * we want to account for 1 more bitmap than what we have so we can make
         * sure we don't go over our overall goal of MAX_CACHE_BYTES_PER_GIG as
         * we add more bitmaps.
         */
        bitmap_bytes = (ctl->total_bitmaps + 1) * PAGE_CACHE_SIZE;

        if (bitmap_bytes >= max_bytes) {
                ctl->extents_thresh = 0;
                return;
        }

        /*
         * we want the extent entry threshold to always be at most 1/2 the maxw
         * bytes we can have, or whatever is less than that.
         */
        extent_bytes = max_bytes - bitmap_bytes;
        extent_bytes = min_t(u64, extent_bytes, div64_u64(max_bytes, 2));

        ctl->extents_thresh =
                div64_u64(extent_bytes, (sizeof(struct btrfs_free_space)));
}

static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *info, u64 offset,
                              u64 bytes)
{
        unsigned long start, count;

        start = offset_to_bit(info->offset, ctl->unit, offset);
        count = bytes_to_bits(bytes, ctl->unit);
        BUG_ON(start + count > BITS_PER_BITMAP);

        bitmap_clear(info->bitmap, start, count);

        info->bytes -= bytes;
        ctl->free_space -= bytes;
}

static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
                            struct btrfs_free_space *info, u64 offset,
                            u64 bytes)
{
        unsigned long start, count;

        start = offset_to_bit(info->offset, ctl->unit, offset);
        count = bytes_to_bits(bytes, ctl->unit);
        BUG_ON(start + count > BITS_PER_BITMAP);

        bitmap_set(info->bitmap, start, count);

        info->bytes += bytes;
        ctl->free_space += bytes;
}

static int search_bitmap(struct btrfs_free_space_ctl *ctl,
                         struct btrfs_free_space *bitmap_info, u64 *offset,
                         u64 *bytes)
{
        unsigned long found_bits = 0;
        unsigned long bits, i;
        unsigned long next_zero;

        i = offset_to_bit(bitmap_info->offset, ctl->unit,
                          max_t(u64, *offset, bitmap_info->offset));
        bits = bytes_to_bits(*bytes, ctl->unit);

        for (i = find_next_bit(bitmap_info->bitmap, BITS_PER_BITMAP, i);
             i < BITS_PER_BITMAP;
             i = find_next_bit(bitmap_info->bitmap, BITS_PER_BITMAP, i + 1)) {
                next_zero = find_next_zero_bit(bitmap_info->bitmap,
                                               BITS_PER_BITMAP, i);
                if ((next_zero - i) >= bits) {
                        found_bits = next_zero - i;
                        break;
                }
                i = next_zero;
        }

        if (found_bits) {
                *offset = (u64)(i * ctl->unit) + bitmap_info->offset;
                *bytes = (u64)(found_bits) * ctl->unit;
                return 0;
        }

        return -1;
}

static struct btrfs_free_space *
find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes)
{
        struct btrfs_free_space *entry;
        struct rb_node *node;
        int ret;

        if (!ctl->free_space_offset.rb_node)
                return NULL;

        entry = tree_search_offset(ctl, offset_to_bitmap(ctl, *offset), 0, 1);
        if (!entry)
                return NULL;

        for (node = &entry->offset_index; node; node = rb_next(node)) {
                entry = rb_entry(node, struct btrfs_free_space, offset_index);
                if (entry->bytes < *bytes)
                        continue;

                if (entry->bitmap) {
                        ret = search_bitmap(ctl, entry, offset, bytes);
                        if (!ret)
                                return entry;
                        continue;
                }

                *offset = entry->offset;
                *bytes = entry->bytes;
                return entry;
        }

        return NULL;
}

static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
                           struct btrfs_free_space *info, u64 offset)
{
        info->offset = offset_to_bitmap(ctl, offset);
        info->bytes = 0;
        link_free_space(ctl, info);
        ctl->total_bitmaps++;

        ctl->op->recalc_thresholds(ctl);
}

static void free_bitmap(struct btrfs_free_space_ctl *ctl,
                        struct btrfs_free_space *bitmap_info)
{
        unlink_free_space(ctl, bitmap_info);
        kfree(bitmap_info->bitmap);
        kmem_cache_free(btrfs_free_space_cachep, bitmap_info);
        ctl->total_bitmaps--;
        ctl->op->recalc_thresholds(ctl);
}

static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *bitmap_info,
                              u64 *offset, u64 *bytes)
{
        u64 end;
        u64 search_start, search_bytes;
        int ret;

again:
        end = bitmap_info->offset + (u64)(BITS_PER_BITMAP * ctl->unit) - 1;

        /*
         * XXX - this can go away after a few releases.
         *
         * since the only user of btrfs_remove_free_space is the tree logging
         * stuff, and the only way to test that is under crash conditions, we
         * want to have this debug stuff here just in case somethings not
         * working.  Search the bitmap for the space we are trying to use to
         * make sure its actually there.  If its not there then we need to stop
         * because something has gone wrong.
         */
        search_start = *offset;
        search_bytes = *bytes;
        search_bytes = min(search_bytes, end - search_start + 1);
        ret = search_bitmap(ctl, bitmap_info, &search_start, &search_bytes);
        BUG_ON(ret < 0 || search_start != *offset);

        if (*offset > bitmap_info->offset && *offset + *bytes > end) {
                bitmap_clear_bits(ctl, bitmap_info, *offset, end - *offset + 1);
                *bytes -= end - *offset + 1;
                *offset = end + 1;
        } else if (*offset >= bitmap_info->offset && *offset + *bytes <= end) {
                bitmap_clear_bits(ctl, bitmap_info, *offset, *bytes);
                *bytes = 0;
        }

        if (*bytes) {
                struct rb_node *next = rb_next(&bitmap_info->offset_index);
                if (!bitmap_info->bytes)
                        free_bitmap(ctl, bitmap_info);

                /*
                 * no entry after this bitmap, but we still have bytes to
                 * remove, so something has gone wrong.
                 */
                if (!next)
                        return -EINVAL;

                bitmap_info = rb_entry(next, struct btrfs_free_space,
                                       offset_index);

                /*
                 * if the next entry isn't a bitmap we need to return to let the
                 * extent stuff do its work.
                 */
                if (!bitmap_info->bitmap)
                        return -EAGAIN;

                /*
                 * Ok the next item is a bitmap, but it may not actually hold
                 * the information for the rest of this free space stuff, so
                 * look for it, and if we don't find it return so we can try
                 * everything over again.
                 */
                search_start = *offset;
                search_bytes = *bytes;
                ret = search_bitmap(ctl, bitmap_info, &search_start,
                                    &search_bytes);
                if (ret < 0 || search_start != *offset)
                        return -EAGAIN;

                goto again;
        } else if (!bitmap_info->bytes)
                free_bitmap(ctl, bitmap_info);

        return 0;
}

static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
                      struct btrfs_free_space *info)
{
        struct btrfs_block_group_cache *block_group = ctl->private;

        /*
         * If we are below the extents threshold then we can add this as an
         * extent, and don't have to deal with the bitmap
         */
        if (ctl->free_extents < ctl->extents_thresh) {
                /*
                 * If this block group has some small extents we don't want to
                 * use up all of our free slots in the cache with them, we want
                 * to reserve them to larger extents, however if we have plent
                 * of cache left then go ahead an dadd them, no sense in adding
                 * the overhead of a bitmap if we don't have to.
                 */
                if (info->bytes <= block_group->sectorsize * 4) {
                        if (ctl->free_extents * 2 <= ctl->extents_thresh)
                                return false;
                } else {
                        return false;
                }
        }

        /*
         * some block groups are so tiny they can't be enveloped by a bitmap, so
         * don't even bother to create a bitmap for this
         */
        if (BITS_PER_BITMAP * block_group->sectorsize >
            block_group->key.offset)
                return false;

        return true;
}

static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *info)
{
        struct btrfs_free_space *bitmap_info;
        int added = 0;
        u64 bytes, offset, end;
        int ret;

        bytes = info->bytes;
        offset = info->offset;

        if (!ctl->op->use_bitmap(ctl, info))
                return 0;

again:
        bitmap_info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
                                         1, 0);
        if (!bitmap_info) {
                BUG_ON(added);
                goto new_bitmap;
        }

        end = bitmap_info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);

        if (offset >= bitmap_info->offset && offset + bytes > end) {
                bitmap_set_bits(ctl, bitmap_info, offset, end - offset);
                bytes -= end - offset;
                offset = end;
                added = 0;
        } else if (offset >= bitmap_info->offset && offset + bytes <= end) {
                bitmap_set_bits(ctl, bitmap_info, offset, bytes);
                bytes = 0;
        } else {
                BUG();
        }

        if (!bytes) {
                ret = 1;
                goto out;
        } else
                goto again;

new_bitmap:
        if (info && info->bitmap) {
                add_new_bitmap(ctl, info, offset);
                added = 1;
                info = NULL;
                goto again;
        } else {
                spin_unlock(&ctl->tree_lock);

                /* no pre-allocated info, allocate a new one */
                if (!info) {
                        info = kmem_cache_zalloc(btrfs_free_space_cachep,
                                                 GFP_NOFS);
                        if (!info) {
                                spin_lock(&ctl->tree_lock);
                                ret = -ENOMEM;
                                goto out;
                        }
                }

                /* allocate the bitmap */
                info->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
                spin_lock(&ctl->tree_lock);
                if (!info->bitmap) {
                        ret = -ENOMEM;
                        goto out;
                }
                goto again;
        }

out:
        if (info) {
                if (info->bitmap)
                        kfree(info->bitmap);
                kmem_cache_free(btrfs_free_space_cachep, info);
        }

        return ret;
}

bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
                          struct btrfs_free_space *info, bool update_stat)
{
        struct btrfs_free_space *left_info;
        struct btrfs_free_space *right_info;
        bool merged = false;
        u64 offset = info->offset;
        u64 bytes = info->bytes;

        /*
         * first we want to see if there is free space adjacent to the range we
         * are adding, if there is remove that struct and add a new one to
         * cover the entire range
         */
        right_info = tree_search_offset(ctl, offset + bytes, 0, 0);
        if (right_info && rb_prev(&right_info->offset_index))
                left_info = rb_entry(rb_prev(&right_info->offset_index),
                                     struct btrfs_free_space, offset_index);
        else
                left_info = tree_search_offset(ctl, offset - 1, 0, 0);

        if (right_info && !right_info->bitmap) {
                if (update_stat)
                        unlink_free_space(ctl, right_info);
                else
                        __unlink_free_space(ctl, right_info);
                info->bytes += right_info->bytes;
                kmem_cache_free(btrfs_free_space_cachep, right_info);
                merged = true;
        }

        if (left_info && !left_info->bitmap &&
            left_info->offset + left_info->bytes == offset) {
                if (update_stat)
                        unlink_free_space(ctl, left_info);
                else
                        __unlink_free_space(ctl, left_info);
                info->offset = left_info->offset;
                info->bytes += left_info->bytes;
                kmem_cache_free(btrfs_free_space_cachep, left_info);
                merged = true;
        }

        return merged;
}

int __btrfs_add_free_space(struct btrfs_free_space_ctl *ctl,
                           u64 offset, u64 bytes)
{
        struct btrfs_free_space *info;
        int ret = 0;

        info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
        if (!info)
                return -ENOMEM;

        info->offset = offset;
        info->bytes = bytes;

        spin_lock(&ctl->tree_lock);

        if (try_merge_free_space(ctl, info, true))
                goto link;

        /*
         * There was no extent directly to the left or right of this new
         * extent then we know we're going to have to allocate a new extent, so
         * before we do that see if we need to drop this into a bitmap
         */
        ret = insert_into_bitmap(ctl, info);
        if (ret < 0) {
                goto out;
        } else if (ret) {
                ret = 0;
                goto out;
        }
link:
        ret = link_free_space(ctl, info);
        if (ret)
                kmem_cache_free(btrfs_free_space_cachep, info);
out:
        spin_unlock(&ctl->tree_lock);

        if (ret) {
                printk(KERN_CRIT "btrfs: unable to add free space :%d\n", ret);
                BUG_ON(ret == -EEXIST);
        }

        return ret;
}

int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
                            u64 offset, u64 bytes)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *info;
        struct btrfs_free_space *next_info = NULL;
        int ret = 0;

        spin_lock(&ctl->tree_lock);

again:
        info = tree_search_offset(ctl, offset, 0, 0);
        if (!info) {
                /*
                 * oops didn't find an extent that matched the space we wanted
                 * to remove, look for a bitmap instead
                 */
                info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
                                          1, 0);
                if (!info) {
                        WARN_ON(1);
                        goto out_lock;
                }
        }

        if (info->bytes < bytes && rb_next(&info->offset_index)) {
                u64 end;
                next_info = rb_entry(rb_next(&info->offset_index),
                                             struct btrfs_free_space,
                                             offset_index);

                if (next_info->bitmap)
                        end = next_info->offset +
                              BITS_PER_BITMAP * ctl->unit - 1;
                else
                        end = next_info->offset + next_info->bytes;

                if (next_info->bytes < bytes ||
                    next_info->offset > offset || offset > end) {
                        printk(KERN_CRIT "Found free space at %llu, size %llu,"
                              " trying to use %llu\n",
                              (unsigned long long)info->offset,
                              (unsigned long long)info->bytes,
                              (unsigned long long)bytes);
                        WARN_ON(1);
                        ret = -EINVAL;
                        goto out_lock;
                }

                info = next_info;
        }

        if (info->bytes == bytes) {
                unlink_free_space(ctl, info);
                if (info->bitmap) {
                        kfree(info->bitmap);
                        ctl->total_bitmaps--;
                }
                kmem_cache_free(btrfs_free_space_cachep, info);
                goto out_lock;
        }

        if (!info->bitmap && info->offset == offset) {
                unlink_free_space(ctl, info);
                info->offset += bytes;
                info->bytes -= bytes;
                link_free_space(ctl, info);
                goto out_lock;
        }

        if (!info->bitmap && info->offset <= offset &&
            info->offset + info->bytes >= offset + bytes) {
                u64 old_start = info->offset;
                /*
                 * we're freeing space in the middle of the info,
                 * this can happen during tree log replay
                 *
                 * first unlink the old info and then
                 * insert it again after the hole we're creating
                 */
                unlink_free_space(ctl, info);
                if (offset + bytes < info->offset + info->bytes) {
                        u64 old_end = info->offset + info->bytes;

                        info->offset = offset + bytes;
                        info->bytes = old_end - info->offset;
                        ret = link_free_space(ctl, info);
                        WARN_ON(ret);
                        if (ret)
                                goto out_lock;
                } else {
                        /* the hole we're creating ends at the end
                         * of the info struct, just free the info
                         */
                        kmem_cache_free(btrfs_free_space_cachep, info);
                }
                spin_unlock(&ctl->tree_lock);

                /* step two, insert a new info struct to cover
                 * anything before the hole
                 */
                ret = btrfs_add_free_space(block_group, old_start,
                                           offset - old_start);
                WARN_ON(ret);
                goto out;
        }

        ret = remove_from_bitmap(ctl, info, &offset, &bytes);
        if (ret == -EAGAIN)
                goto again;
        BUG_ON(ret);
out_lock:
        spin_unlock(&ctl->tree_lock);
out:
        return ret;
}

void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
                           u64 bytes)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *info;
        struct rb_node *n;
        int count = 0;

        for (n = rb_first(&ctl->free_space_offset); n; n = rb_next(n)) {
                info = rb_entry(n, struct btrfs_free_space, offset_index);
                if (info->bytes >= bytes)
                        count++;
                printk(KERN_CRIT "entry offset %llu, bytes %llu, bitmap %s\n",
                       (unsigned long long)info->offset,
                       (unsigned long long)info->bytes,
                       (info->bitmap) ? "yes" : "no");
        }
        printk(KERN_INFO "block group has cluster?: %s\n",
               list_empty(&block_group->cluster_list) ? "no" : "yes");
        printk(KERN_INFO "%d blocks of free space at or bigger than bytes is"
               "\n", count);
}

static struct btrfs_free_space_op free_space_op = {
        .recalc_thresholds      = recalculate_thresholds,
        .use_bitmap             = use_bitmap,
};

void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;

        spin_lock_init(&ctl->tree_lock);
        ctl->unit = block_group->sectorsize;
        ctl->start = block_group->key.objectid;
        ctl->private = block_group;
        ctl->op = &free_space_op;

        /*
         * we only want to have 32k of ram per block group for keeping
         * track of free space, and if we pass 1/2 of that we want to
         * start converting things over to using bitmaps
         */
        ctl->extents_thresh = ((1024 * 32) / 2) /
                                sizeof(struct btrfs_free_space);
}

/*
 * for a given cluster, put all of its extents back into the free
 * space cache.  If the block group passed doesn't match the block group
 * pointed to by the cluster, someone else raced in and freed the
 * cluster already.  In that case, we just return without changing anything
 */
static int
__btrfs_return_cluster_to_free_space(
                             struct btrfs_block_group_cache *block_group,
                             struct btrfs_free_cluster *cluster)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry;
        struct rb_node *node;

        spin_lock(&cluster->lock);
        if (cluster->block_group != block_group)
                goto out;

        cluster->block_group = NULL;
        cluster->window_start = 0;
        list_del_init(&cluster->block_group_list);

        node = rb_first(&cluster->root);
        while (node) {
                bool bitmap;

                entry = rb_entry(node, struct btrfs_free_space, offset_index);
                node = rb_next(&entry->offset_index);
                rb_erase(&entry->offset_index, &cluster->root);

                bitmap = (entry->bitmap != NULL);
                if (!bitmap)
                        try_merge_free_space(ctl, entry, false);
                tree_insert_offset(&ctl->free_space_offset,
                                   entry->offset, &entry->offset_index, bitmap);
        }
        cluster->root = RB_ROOT;

out:
        spin_unlock(&cluster->lock);
        btrfs_put_block_group(block_group);
        return 0;
}

void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl)
{
        struct btrfs_free_space *info;
        struct rb_node *node;

        spin_lock(&ctl->tree_lock);
        while ((node = rb_last(&ctl->free_space_offset)) != NULL) {
                info = rb_entry(node, struct btrfs_free_space, offset_index);
                unlink_free_space(ctl, info);
                kfree(info->bitmap);
                kmem_cache_free(btrfs_free_space_cachep, info);
                if (need_resched()) {
                        spin_unlock(&ctl->tree_lock);
                        cond_resched();
                        spin_lock(&ctl->tree_lock);
                }
        }
        spin_unlock(&ctl->tree_lock);
}

void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_cluster *cluster;
        struct list_head *head;

        spin_lock(&ctl->tree_lock);
        while ((head = block_group->cluster_list.next) !=
               &block_group->cluster_list) {
                cluster = list_entry(head, struct btrfs_free_cluster,
                                     block_group_list);

                WARN_ON(cluster->block_group != block_group);
                __btrfs_return_cluster_to_free_space(block_group, cluster);
                if (need_resched()) {
                        spin_unlock(&ctl->tree_lock);
                        cond_resched();
                        spin_lock(&ctl->tree_lock);
                }
        }
        spin_unlock(&ctl->tree_lock);

        __btrfs_remove_free_space_cache(ctl);
}

u64 btrfs_find_space_for_alloc(struct btrfs_block_group_cache *block_group,
                               u64 offset, u64 bytes, u64 empty_size)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry = NULL;
        u64 bytes_search = bytes + empty_size;
        u64 ret = 0;

        spin_lock(&ctl->tree_lock);
        entry = find_free_space(ctl, &offset, &bytes_search);
        if (!entry)
                goto out;

        ret = offset;
        if (entry->bitmap) {
                bitmap_clear_bits(ctl, entry, offset, bytes);
                if (!entry->bytes)
                        free_bitmap(ctl, entry);
        } else {
                unlink_free_space(ctl, entry);
                entry->offset += bytes;
                entry->bytes -= bytes;
                if (!entry->bytes)
                        kmem_cache_free(btrfs_free_space_cachep, entry);
                else
                        link_free_space(ctl, entry);
        }

out:
        spin_unlock(&ctl->tree_lock);

        return ret;
}

/*
 * given a cluster, put all of its extents back into the free space
 * cache.  If a block group is passed, this function will only free
 * a cluster that belongs to the passed block group.
 *
 * Otherwise, it'll get a reference on the block group pointed to by the
 * cluster and remove the cluster from it.
 */
int btrfs_return_cluster_to_free_space(
                               struct btrfs_block_group_cache *block_group,
                               struct btrfs_free_cluster *cluster)
{
        struct btrfs_free_space_ctl *ctl;
        int ret;

        /* first, get a safe pointer to the block group */
        spin_lock(&cluster->lock);
        if (!block_group) {
                block_group = cluster->block_group;
                if (!block_group) {
                        spin_unlock(&cluster->lock);
                        return 0;
                }
        } else if (cluster->block_group != block_group) {
                /* someone else has already freed it don't redo their work */
                spin_unlock(&cluster->lock);
                return 0;
        }
        atomic_inc(&block_group->count);
        spin_unlock(&cluster->lock);

        ctl = block_group->free_space_ctl;

        /* now return any extents the cluster had on it */
        spin_lock(&ctl->tree_lock);
        ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
        spin_unlock(&ctl->tree_lock);

        /* finally drop our ref */
        btrfs_put_block_group(block_group);
        return ret;
}

static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
                                   struct btrfs_free_cluster *cluster,
                                   struct btrfs_free_space *entry,
                                   u64 bytes, u64 min_start)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        int err;
        u64 search_start = cluster->window_start;
        u64 search_bytes = bytes;
        u64 ret = 0;

        search_start = min_start;
        search_bytes = bytes;

        err = search_bitmap(ctl, entry, &search_start, &search_bytes);
        if (err)
                return 0;

        ret = search_start;
        bitmap_clear_bits(ctl, entry, ret, bytes);

        return ret;
}

/*
 * given a cluster, try to allocate 'bytes' from it, returns 0
 * if it couldn't find anything suitably large, or a logical disk offset
 * if things worked out
 */
u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
                             struct btrfs_free_cluster *cluster, u64 bytes,
                             u64 min_start)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry = NULL;
        struct rb_node *node;
        u64 ret = 0;

        spin_lock(&cluster->lock);
        if (bytes > cluster->max_size)
                goto out;

        if (cluster->block_group != block_group)
                goto out;

        node = rb_first(&cluster->root);
        if (!node)
                goto out;

        entry = rb_entry(node, struct btrfs_free_space, offset_index);
        while(1) {
                if (entry->bytes < bytes ||
                    (!entry->bitmap && entry->offset < min_start)) {
                        struct rb_node *node;

                        node = rb_next(&entry->offset_index);
                        if (!node)
                                break;
                        entry = rb_entry(node, struct btrfs_free_space,
                                         offset_index);
                        continue;
                }

                if (entry->bitmap) {
                        ret = btrfs_alloc_from_bitmap(block_group,
                                                      cluster, entry, bytes,
                                                      min_start);
                        if (ret == 0) {
                                struct rb_node *node;
                                node = rb_next(&entry->offset_index);
                                if (!node)
                                        break;
                                entry = rb_entry(node, struct btrfs_free_space,
                                                 offset_index);
                                continue;
                        }
                } else {

                        ret = entry->offset;

                        entry->offset += bytes;
                        entry->bytes -= bytes;
                }

                if (entry->bytes == 0)
                        rb_erase(&entry->offset_index, &cluster->root);
                break;
        }
out:
        spin_unlock(&cluster->lock);

        if (!ret)
                return 0;

        spin_lock(&ctl->tree_lock);

        ctl->free_space -= bytes;
        if (entry->bytes == 0) {
                ctl->free_extents--;
                if (entry->bitmap) {
                        kfree(entry->bitmap);
                        ctl->total_bitmaps--;
                        ctl->op->recalc_thresholds(ctl);
                }
                kmem_cache_free(btrfs_free_space_cachep, entry);
        }

        spin_unlock(&ctl->tree_lock);

        return ret;
}

static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
                                struct btrfs_free_space *entry,
                                struct btrfs_free_cluster *cluster,
                                u64 offset, u64 bytes, u64 min_bytes)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        unsigned long next_zero;
        unsigned long i;
        unsigned long search_bits;
        unsigned long total_bits;
        unsigned long found_bits;
        unsigned long start = 0;
        unsigned long total_found = 0;
        int ret;
        bool found = false;

        i = offset_to_bit(entry->offset, block_group->sectorsize,
                          max_t(u64, offset, entry->offset));
        search_bits = bytes_to_bits(bytes, block_group->sectorsize);
        total_bits = bytes_to_bits(min_bytes, block_group->sectorsize);

again:
        found_bits = 0;
        for (i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, i);
             i < BITS_PER_BITMAP;
             i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, i + 1)) {
                next_zero = find_next_zero_bit(entry->bitmap,
                                               BITS_PER_BITMAP, i);
                if (next_zero - i >= search_bits) {
                        found_bits = next_zero - i;
                        break;
                }
                i = next_zero;
        }

        if (!found_bits)
                return -ENOSPC;

        if (!found) {
                start = i;
                found = true;
        }

        total_found += found_bits;

        if (cluster->max_size < found_bits * block_group->sectorsize)
                cluster->max_size = found_bits * block_group->sectorsize;

        if (total_found < total_bits) {
                i = find_next_bit(entry->bitmap, BITS_PER_BITMAP, next_zero);
                if (i - start > total_bits * 2) {
                        total_found = 0;
                        cluster->max_size = 0;
                        found = false;
                }
                goto again;
        }

        cluster->window_start = start * block_group->sectorsize +
                entry->offset;
        rb_erase(&entry->offset_index, &ctl->free_space_offset);
        ret = tree_insert_offset(&cluster->root, entry->offset,
                                 &entry->offset_index, 1);
        BUG_ON(ret);

        return 0;
}

/*
 * This searches the block group for just extents to fill the cluster with.
 */
static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
                                   struct btrfs_free_cluster *cluster,
                                   u64 offset, u64 bytes, u64 min_bytes)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *first = NULL;
        struct btrfs_free_space *entry = NULL;
        struct btrfs_free_space *prev = NULL;
        struct btrfs_free_space *last;
        struct rb_node *node;
        u64 window_start;
        u64 window_free;
        u64 max_extent;
        u64 max_gap = 128 * 1024;

        entry = tree_search_offset(ctl, offset, 0, 1);
        if (!entry)
                return -ENOSPC;

        /*
         * We don't want bitmaps, so just move along until we find a normal
         * extent entry.
         */
        while (entry->bitmap) {
                node = rb_next(&entry->offset_index);
                if (!node)
                        return -ENOSPC;
                entry = rb_entry(node, struct btrfs_free_space, offset_index);
        }

        window_start = entry->offset;
        window_free = entry->bytes;
        max_extent = entry->bytes;
        first = entry;
        last = entry;
        prev = entry;

        while (window_free <= min_bytes) {
                node = rb_next(&entry->offset_index);
                if (!node)
                        return -ENOSPC;
                entry = rb_entry(node, struct btrfs_free_space, offset_index);

                if (entry->bitmap)
                        continue;
                /*
                 * we haven't filled the empty size and the window is
                 * very large.  reset and try again
                 */
                if (entry->offset - (prev->offset + prev->bytes) > max_gap ||
                    entry->offset - window_start > (min_bytes * 2)) {
                        first = entry;
                        window_start = entry->offset;
                        window_free = entry->bytes;
                        last = entry;
                        max_extent = entry->bytes;
                } else {
                        last = entry;
                        window_free += entry->bytes;
                        if (entry->bytes > max_extent)
                                max_extent = entry->bytes;
                }
                prev = entry;
        }

        cluster->window_start = first->offset;

        node = &first->offset_index;

        /*
         * now we've found our entries, pull them out of the free space
         * cache and put them into the cluster rbtree
         */
        do {
                int ret;

                entry = rb_entry(node, struct btrfs_free_space, offset_index);
                node = rb_next(&entry->offset_index);
                if (entry->bitmap)
                        continue;

                rb_erase(&entry->offset_index, &ctl->free_space_offset);
                ret = tree_insert_offset(&cluster->root, entry->offset,
                                         &entry->offset_index, 0);
                BUG_ON(ret);
        } while (node && entry != last);

        cluster->max_size = max_extent;

        return 0;
}

/*
 * This specifically looks for bitmaps that may work in the cluster, we assume
 * that we have already failed to find extents that will work.
 */
static int setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
                                struct btrfs_free_cluster *cluster,
                                u64 offset, u64 bytes, u64 min_bytes)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry;
        struct rb_node *node;
        int ret = -ENOSPC;

        if (ctl->total_bitmaps == 0)
                return -ENOSPC;

        entry = tree_search_offset(ctl, offset_to_bitmap(ctl, offset), 0, 1);
        if (!entry)
                return -ENOSPC;

        node = &entry->offset_index;
        do {
                entry = rb_entry(node, struct btrfs_free_space, offset_index);
                node = rb_next(&entry->offset_index);
                if (!entry->bitmap)
                        continue;
                if (entry->bytes < min_bytes)
                        continue;
                ret = btrfs_bitmap_cluster(block_group, entry, cluster, offset,
                                           bytes, min_bytes);
        } while (ret && node);

        return ret;
}

/*
 * here we try to find a cluster of blocks in a block group.  The goal
 * is to find at least bytes free and up to empty_size + bytes free.
 * We might not find them all in one contiguous area.
 *
 * returns zero and sets up cluster if things worked out, otherwise
 * it returns -enospc
 */
int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root,
                             struct btrfs_block_group_cache *block_group,
                             struct btrfs_free_cluster *cluster,
                             u64 offset, u64 bytes, u64 empty_size)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        u64 min_bytes;
        int ret;

        /* for metadata, allow allocates with more holes */
        if (btrfs_test_opt(root, SSD_SPREAD)) {
                min_bytes = bytes + empty_size;
        } else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
                /*
                 * we want to do larger allocations when we are
                 * flushing out the delayed refs, it helps prevent
                 * making more work as we go along.
                 */
                if (trans->transaction->delayed_refs.flushing)
                        min_bytes = max(bytes, (bytes + empty_size) >> 1);
                else
                        min_bytes = max(bytes, (bytes + empty_size) >> 4);
        } else
                min_bytes = max(bytes, (bytes + empty_size) >> 2);

        spin_lock(&ctl->tree_lock);

        /*
         * If we know we don't have enough space to make a cluster don't even
         * bother doing all the work to try and find one.
         */
        if (ctl->free_space < min_bytes) {
                spin_unlock(&ctl->tree_lock);
                return -ENOSPC;
        }

        spin_lock(&cluster->lock);

        /* someone already found a cluster, hooray */
        if (cluster->block_group) {
                ret = 0;
                goto out;
        }

        ret = setup_cluster_no_bitmap(block_group, cluster, offset, bytes,
                                      min_bytes);
        if (ret)
                ret = setup_cluster_bitmap(block_group, cluster, offset,
                                           bytes, min_bytes);

        if (!ret) {
                atomic_inc(&block_group->count);
                list_add_tail(&cluster->block_group_list,
                              &block_group->cluster_list);
                cluster->block_group = block_group;
        }
out:
        spin_unlock(&cluster->lock);
        spin_unlock(&ctl->tree_lock);

        return ret;
}

/*
 * simple code to zero out a cluster
 */
void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
{
        spin_lock_init(&cluster->lock);
        spin_lock_init(&cluster->refill_lock);
        cluster->root = RB_ROOT;
        cluster->max_size = 0;
        INIT_LIST_HEAD(&cluster->block_group_list);
        cluster->block_group = NULL;
}

int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
                           u64 *trimmed, u64 start, u64 end, u64 minlen)
{
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
        struct btrfs_free_space *entry = NULL;
        struct btrfs_fs_info *fs_info = block_group->fs_info;
        u64 bytes = 0;
        u64 actually_trimmed;
        int ret = 0;

        *trimmed = 0;

        while (start < end) {
                spin_lock(&ctl->tree_lock);

                if (ctl->free_space < minlen) {
                        spin_unlock(&ctl->tree_lock);
                        break;
                }

                entry = tree_search_offset(ctl, start, 0, 1);
                if (!entry)
                        entry = tree_search_offset(ctl,
                                                   offset_to_bitmap(ctl, start),
                                                   1, 1);

                if (!entry || entry->offset >= end) {
                        spin_unlock(&ctl->tree_lock);
                        break;
                }

                if (entry->bitmap) {
                        ret = search_bitmap(ctl, entry, &start, &bytes);
                        if (!ret) {
                                if (start >= end) {
                                        spin_unlock(&ctl->tree_lock);
                                        break;
                                }
                                bytes = min(bytes, end - start);
                                bitmap_clear_bits(ctl, entry, start, bytes);
                                if (entry->bytes == 0)
                                        free_bitmap(ctl, entry);
                        } else {
                                start = entry->offset + BITS_PER_BITMAP *
                                        block_group->sectorsize;
                                spin_unlock(&ctl->tree_lock);
                                ret = 0;
                                continue;
                        }
                } else {
                        start = entry->offset;
                        bytes = min(entry->bytes, end - start);
                        unlink_free_space(ctl, entry);
                        kfree(entry);
                }

                spin_unlock(&ctl->tree_lock);

                if (bytes >= minlen) {
                        int update_ret;
                        update_ret = btrfs_update_reserved_bytes(block_group,
                                                                 bytes, 1, 1);

                        ret = btrfs_error_discard_extent(fs_info->extent_root,
                                                         start,
                                                         bytes,
                                                         &actually_trimmed);

                        btrfs_add_free_space(block_group, start, bytes);
                        if (!update_ret)
                                btrfs_update_reserved_bytes(block_group,
                                                            bytes, 0, 1);

                        if (ret)
                                break;
                        *trimmed += actually_trimmed;
                }
                start += bytes;
                bytes = 0;

                if (fatal_signal_pending(current)) {
                        ret = -ERESTARTSYS;
                        break;
                }

                cond_resched();
        }

        return ret;
}

/*
 * Find the left-most item in the cache tree, and then return the
 * smallest inode number in the item.
 *
 * Note: the returned inode number may not be the smallest one in
 * the tree, if the left-most item is a bitmap.
 */
u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root)
{
        struct btrfs_free_space_ctl *ctl = fs_root->free_ino_ctl;
        struct btrfs_free_space *entry = NULL;
        u64 ino = 0;

        spin_lock(&ctl->tree_lock);

        if (RB_EMPTY_ROOT(&ctl->free_space_offset))
                goto out;

        entry = rb_entry(rb_first(&ctl->free_space_offset),
                         struct btrfs_free_space, offset_index);

        if (!entry->bitmap) {
                ino = entry->offset;

                unlink_free_space(ctl, entry);
                entry->offset++;
                entry->bytes--;
                if (!entry->bytes)
                        kmem_cache_free(btrfs_free_space_cachep, entry);
                else
                        link_free_space(ctl, entry);
        } else {
                u64 offset = 0;
                u64 count = 1;
                int ret;

                ret = search_bitmap(ctl, entry, &offset, &count);
                BUG_ON(ret);

                ino = offset;
                bitmap_clear_bits(ctl, entry, offset, 1);
                if (entry->bytes == 0)
                        free_bitmap(ctl, entry);
        }
out:
        spin_unlock(&ctl->tree_lock);

        return ino;
}