Btrfs: calc file extent num_bytes correctly in file clone
[linux-2.6.git] / fs / btrfs / free-space-cache.c
index 63731a1..41ac927 100644 (file)
 #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 void recalculate_thresholds(struct btrfs_block_group_cache
-                                  *block_group);
-static int link_free_space(struct btrfs_block_group_cache *block_group,
+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)
+static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
+                                              struct btrfs_path *path,
+                                              u64 offset)
 {
        struct btrfs_key key;
        struct btrfs_key location;
@@ -46,22 +45,15 @@ struct inode *lookup_free_space_inode(struct btrfs_root *root,
        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.offset = offset;
        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);
+               btrfs_release_path(path);
                return ERR_PTR(-ENOENT);
        }
 
@@ -70,7 +62,7 @@ struct inode *lookup_free_space_inode(struct btrfs_root *root,
                                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);
+       btrfs_release_path(path);
 
        inode = btrfs_iget(root->fs_info->sb, &location, root, NULL);
        if (!inode)
@@ -84,8 +76,35 @@ struct inode *lookup_free_space_inode(struct btrfs_root *root,
 
        inode->i_mapping->flags &= ~__GFP_FS;
 
+       return inode;
+}
+
+struct inode *lookup_free_space_inode(struct btrfs_root *root,
+                                     struct btrfs_block_group_cache
+                                     *block_group, struct btrfs_path *path)
+{
+       struct inode *inode = NULL;
+
+       spin_lock(&block_group->lock);
+       if (block_group->inode)
+               inode = igrab(block_group->inode);
+       spin_unlock(&block_group->lock);
+       if (inode)
+               return inode;
+
+       inode = __lookup_free_space_inode(root, path,
+                                         block_group->key.objectid);
+       if (IS_ERR(inode))
+               return inode;
+
        spin_lock(&block_group->lock);
-       if (!root->fs_info->closing) {
+       if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) {
+               printk(KERN_INFO "Old style space inode found, converting.\n");
+               BTRFS_I(inode)->flags &= ~BTRFS_INODE_NODATASUM;
+               block_group->disk_cache_state = BTRFS_DC_CLEAR;
+       }
+
+       if (!btrfs_fs_closing(root->fs_info)) {
                block_group->inode = igrab(inode);
                block_group->iref = 1;
        }
@@ -94,24 +113,18 @@ struct inode *lookup_free_space_inode(struct btrfs_root *root,
        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)
+int __create_free_space_inode(struct btrfs_root *root,
+                             struct btrfs_trans_handle *trans,
+                             struct btrfs_path *path, u64 ino, u64 offset)
 {
        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(trans, root, 0, &objectid);
-       if (ret < 0)
-               return ret;
-
-       ret = btrfs_insert_empty_inode(trans, root, path, objectid);
+       ret = btrfs_insert_empty_inode(trans, root, path, ino);
        if (ret)
                return ret;
 
@@ -128,22 +141,21 @@ int create_free_space_inode(struct btrfs_root *root,
        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_INODE_PREALLOC);
        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_set_inode_block_group(leaf, inode_item, offset);
        btrfs_mark_buffer_dirty(leaf);
-       btrfs_release_path(root, path);
+       btrfs_release_path(path);
 
        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
-       key.offset = block_group->key.objectid;
+       key.offset = offset;
        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);
+               btrfs_release_path(path);
                return ret;
        }
        leaf = path->nodes[0];
@@ -152,19 +164,37 @@ int create_free_space_inode(struct btrfs_root *root,
        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);
+       btrfs_release_path(path);
 
        return 0;
 }
 
+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)
+{
+       int ret;
+       u64 ino;
+
+       ret = btrfs_find_free_objectid(root, &ino);
+       if (ret < 0)
+               return ret;
+
+       return __create_free_space_inode(root, trans, path, ino,
+                                        block_group->key.objectid);
+}
+
 int btrfs_truncate_free_space_cache(struct btrfs_root *root,
                                    struct btrfs_trans_handle *trans,
                                    struct btrfs_path *path,
                                    struct inode *inode)
 {
+       struct btrfs_block_rsv *rsv;
        loff_t oldsize;
        int ret = 0;
 
+       rsv = trans->block_rsv;
        trans->block_rsv = root->orphan_block_rsv;
        ret = btrfs_block_rsv_check(trans, root,
                                    root->orphan_block_rsv,
@@ -182,12 +212,15 @@ int btrfs_truncate_free_space_cache(struct btrfs_root *root,
         */
        ret = btrfs_truncate_inode_items(trans, root, inode,
                                         0, BTRFS_EXTENT_DATA_KEY);
+
+       trans->block_rsv = rsv;
        if (ret) {
                WARN_ON(1);
                return ret;
        }
 
-       return btrfs_update_inode(trans, root, inode);
+       ret = btrfs_update_inode(trans, root, inode);
+       return ret;
 }
 
 static int readahead_cache(struct inode *inode)
@@ -209,134 +242,78 @@ static int readahead_cache(struct inode *inode)
        return 0;
 }
 
-int load_free_space_cache(struct btrfs_fs_info *fs_info,
-                         struct btrfs_block_group_cache *block_group)
+int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
+                           struct btrfs_free_space_ctl *ctl,
+                           struct btrfs_path *path, u64 offset)
 {
-       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);
+       if (!i_size_read(inode))
                goto out;
-       }
 
        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
-       key.offset = block_group->key.objectid;
+       key.offset = offset;
        key.type = 0;
 
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-       if (ret) {
-               btrfs_free_path(path);
+       if (ret < 0)
+               goto out;
+       else if (ret > 0) {
+               btrfs_release_path(path);
+               ret = 0;
                goto out;
        }
 
+       ret = -1;
+
        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);
+       btrfs_release_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",
+                      " not match free space cache generation (%llu)\n",
                       (unsigned long long)BTRFS_I(inode)->generation,
-                      (unsigned long long)generation,
-                      (unsigned long long)block_group->key.objectid);
-               goto free_cache;
+                      (unsigned long long)generation);
+               goto out;
        }
 
        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;
+       if (ret)
                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;
+               page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
+               if (!page)
                        goto free_cache;
-               }
 
                if (!PageUptodate(page)) {
                        btrfs_readpage(NULL, page);
@@ -345,9 +322,7 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
                                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);
+                                      "space cache\n");
                                goto free_cache;
                        }
                }
@@ -356,41 +331,30 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
                if (index == 0) {
                        u64 *gen;
 
-                       memcpy(disk_crcs, addr, first_page_offset);
-                       gen = addr + (sizeof(u32) * num_checksums);
+                       /*
+                        * We put a bogus crc in the front of the first page in
+                        * case old kernels try to mount a fs with the new
+                        * format to make sure they discard the cache.
+                        */
+                       addr += sizeof(u64);
+                       offset += sizeof(u64);
+
+                       gen = addr;
                        if (*gen != BTRFS_I(inode)->generation) {
                                printk(KERN_ERR "btrfs: space cache generation"
-                                      " (%llu) does not match inode (%llu) "
-                                      "for block group %llu\n",
+                                      " (%llu) does not match inode (%llu)\n",
                                       (unsigned long long)*gen,
                                       (unsigned long long)
-                                      BTRFS_I(inode)->generation,
-                                      (unsigned long long)
-                                      block_group->key.objectid);
+                                      BTRFS_I(inode)->generation);
                                kunmap(page);
                                unlock_page(page);
                                page_cache_release(page);
                                goto free_cache;
                        }
-                       crc = (u32 *)disk_crcs;
+                       addr += sizeof(u64);
+                       offset += sizeof(u64);
                }
-               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++;
+               entry = addr;
 
                while (1) {
                        if (!num_entries)
@@ -417,10 +381,17 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
                        }
 
                        if (entry->type == BTRFS_FREE_SPACE_EXTENT) {
-                               spin_lock(&block_group->tree_lock);
-                               ret = link_free_space(block_group, e);
-                               spin_unlock(&block_group->tree_lock);
-                               BUG_ON(ret);
+                               spin_lock(&ctl->tree_lock);
+                               ret = link_free_space(ctl, e);
+                               spin_unlock(&ctl->tree_lock);
+                               if (ret) {
+                                       printk(KERN_ERR "Duplicate entries in "
+                                              "free space cache, dumping\n");
+                                       kunmap(page);
+                                       unlock_page(page);
+                                       page_cache_release(page);
+                                       goto free_cache;
+                               }
                        } else {
                                e->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
                                if (!e->bitmap) {
@@ -431,11 +402,19 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
                                        page_cache_release(page);
                                        goto free_cache;
                                }
-                               spin_lock(&block_group->tree_lock);
-                               ret = link_free_space(block_group, e);
-                               block_group->total_bitmaps++;
-                               recalculate_thresholds(block_group);
-                               spin_unlock(&block_group->tree_lock);
+                               spin_lock(&ctl->tree_lock);
+                               ret = link_free_space(ctl, e);
+                               ctl->total_bitmaps++;
+                               ctl->op->recalc_thresholds(ctl);
+                               spin_unlock(&ctl->tree_lock);
+                               if (ret) {
+                                       printk(KERN_ERR "Duplicate entries in "
+                                              "free space cache, dumping\n");
+                                       kunmap(page);
+                                       unlock_page(page);
+                                       page_cache_release(page);
+                                       goto free_cache;
+                               }
                                list_add_tail(&e->list, &bitmaps);
                        }
 
@@ -471,41 +450,94 @@ next:
                index++;
        }
 
-       spin_lock(&block_group->tree_lock);
-       if (block_group->free_space != (block_group->key.offset - used -
-                                       block_group->bytes_super)) {
-               spin_unlock(&block_group->tree_lock);
+       ret = 1;
+out:
+       return ret;
+free_cache:
+       __btrfs_remove_free_space_cache(ctl);
+       goto out;
+}
+
+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_path *path;
+       int ret;
+       bool matched;
+       u64 used = btrfs_block_group_used(&block_group->item);
+
+       /*
+        * 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.
+        */
+       if (btrfs_fs_closing(fs_info))
+               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);
+
+       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;
+       }
+
+       ret = __load_free_space_cache(fs_info->tree_root, inode, ctl,
+                                     path, block_group->key.objectid);
+       btrfs_free_path(path);
+       if (ret <= 0)
+               goto out;
+
+       spin_lock(&ctl->tree_lock);
+       matched = (ctl->free_space == (block_group->key.offset - used -
+                                      block_group->bytes_super));
+       spin_unlock(&ctl->tree_lock);
+
+       if (!matched) {
+               __btrfs_remove_free_space_cache(ctl);
                printk(KERN_ERR "block group %llu has an wrong amount of free "
                       "space\n", block_group->key.objectid);
+               ret = -1;
+       }
+out:
+       if (ret < 0) {
+               /* 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);
                ret = 0;
-               goto free_cache;
+
+               printk(KERN_ERR "btrfs: failed to load free space cache "
+                      "for block group %llu\n", block_group->key.objectid);
        }
-       spin_unlock(&block_group->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)
+int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
+                           struct btrfs_free_space_ctl *ctl,
+                           struct btrfs_block_group_cache *block_group,
+                           struct btrfs_trans_handle *trans,
+                           struct btrfs_path *path, u64 offset)
 {
        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;
@@ -517,69 +549,36 @@ int btrfs_write_out_cache(struct btrfs_root *root,
        struct btrfs_key key;
        u64 start, end, len;
        u64 bytes = 0;
-       u32 *crc, *checksums;
-       unsigned long first_page_offset;
+       u32 crc = ~(u32)0;
        int index = 0, num_pages = 0;
        int entries = 0;
        int bitmaps = 0;
-       int ret = 0;
+       int ret = -1;
        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);
+       node = rb_first(&ctl->free_space_offset);
+       if (!node)
                return 0;
-       }
 
-       node = rb_first(&block_group->free_space_offset);
-       if (!node) {
-               iput(inode);
-               return 0;
-       }
+       if (!i_size_read(inode))
+               return -1;
 
        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);
+       if (!pages)
+               return -1;
 
        /* Get the cluster for this block_group if it exists */
-       if (!list_empty(&block_group->cluster_list))
+       if (block_group && !list_empty(&block_group->cluster_list))
                cluster = list_entry(block_group->cluster_list.next,
                                     struct btrfs_free_cluster,
                                     block_group_list);
@@ -599,7 +598,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
         * know and don't freak out.
         */
        while (index < num_pages) {
-               page = grab_cache_page(inode->i_mapping, index);
+               page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
                if (!page) {
                        int i;
 
@@ -607,7 +606,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                                unlock_page(pages[i]);
                                page_cache_release(pages[i]);
                        }
-                       goto out_free;
+                       goto out;
                }
                pages[index] = page;
                index++;
@@ -621,22 +620,17 @@ int btrfs_write_out_cache(struct btrfs_root *root,
         * When searching for pinned extents, we need to start at our start
         * offset.
         */
-       start = block_group->key.objectid;
+       if (block_group)
+               start = block_group->key.objectid;
 
        /* Write out the extent entries */
        do {
                struct btrfs_free_space_entry *entry;
-               void *addr;
+               void *addr, *orig;
                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;
@@ -644,10 +638,26 @@ int btrfs_write_out_cache(struct btrfs_root *root,
 
                page = pages[index];
 
-               addr = kmap(page);
-               entry = addr + start_offset;
+               orig = addr = kmap(page);
+               if (index == 0) {
+                       u64 *gen;
 
-               memset(addr, 0, PAGE_CACHE_SIZE);
+                       /*
+                        * We're going to put in a bogus crc for this page to
+                        * make sure that old kernels who aren't aware of this
+                        * format will be sure to discard the cache.
+                        */
+                       addr += sizeof(u64);
+                       offset += sizeof(u64);
+
+                       gen = addr;
+                       *gen = trans->transid;
+                       addr += sizeof(u64);
+                       offset += sizeof(u64);
+               }
+               entry = addr;
+
+               memset(addr, 0, PAGE_CACHE_SIZE - offset);
                while (node && !next_page) {
                        struct btrfs_free_space *e;
 
@@ -679,8 +689,9 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                 * 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)) {
+               while (block_group && !next_page &&
+                      (start < block_group->key.objectid +
+                       block_group->key.offset)) {
                        ret = find_first_extent_bit(unpin, start, &start, &end,
                                                    EXTENT_DIRTY);
                        if (ret) {
@@ -709,13 +720,19 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                                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++;
+               /* Generate bogus crc value */
+               if (index == 0) {
+                       u32 *tmp;
+                       crc = btrfs_csum_data(root, orig + sizeof(u64), crc,
+                                             PAGE_CACHE_SIZE - sizeof(u64));
+                       btrfs_csum_final(crc, (char *)&crc);
+                       crc++;
+                       tmp = orig;
+                       *tmp = crc;
+               }
+
+               kunmap(page);
 
                bytes += PAGE_CACHE_SIZE;
 
@@ -736,11 +753,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
 
                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);
@@ -753,7 +766,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                                     i_size_read(inode) - 1, &cached_state,
                                     GFP_NOFS);
                ret = 0;
-               goto out_free;
+               goto out;
        }
 
        /* Zero out the rest of the pages just to make sure */
@@ -768,20 +781,6 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                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);
@@ -790,7 +789,7 @@ int btrfs_write_out_cache(struct btrfs_root *root,
 
        if (ret) {
                ret = 0;
-               goto out_free;
+               goto out;
        }
 
        BTRFS_I(inode)->generation = trans->transid;
@@ -798,16 +797,16 @@ int btrfs_write_out_cache(struct btrfs_root *root,
        filemap_write_and_wait(inode->i_mapping);
 
        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
-       key.offset = block_group->key.objectid;
+       key.offset = offset;
        key.type = 0;
 
        ret = btrfs_search_slot(trans, root, &key, path, 1, 1);
        if (ret < 0) {
-               ret = 0;
+               ret = -1;
                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;
+               goto out;
        }
        leaf = path->nodes[0];
        if (ret > 0) {
@@ -816,14 +815,14 @@ int btrfs_write_out_cache(struct btrfs_root *root,
                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;
+                   found_key.offset != offset) {
+                       ret = -1;
                        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;
+                       btrfs_release_path(path);
+                       goto out;
                }
        }
        header = btrfs_item_ptr(leaf, path->slots[0],
@@ -832,49 +831,82 @@ int btrfs_write_out_cache(struct btrfs_root *root,
        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);
+       btrfs_release_path(path);
 
        ret = 1;
 
-out_free:
-       if (ret == 0) {
+out:
+       kfree(pages);
+       if (ret != 1) {
                invalidate_inode_pages2_range(inode->i_mapping, 0, index);
+               BTRFS_I(inode)->generation = 0;
+       }
+       btrfs_update_inode(trans, root, inode);
+       return ret;
+}
+
+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 inode *inode;
+       int ret = 0;
+
+       root = root->fs_info->tree_root;
+
+       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;
+
+       ret = __btrfs_write_out_cache(root, inode, ctl, block_group, trans,
+                                     path, block_group->key.objectid);
+       if (ret < 0) {
                spin_lock(&block_group->lock);
                block_group->disk_cache_state = BTRFS_DC_ERROR;
                spin_unlock(&block_group->lock);
-               BTRFS_I(inode)->generation = 0;
+               ret = 0;
+
+               printk(KERN_ERR "btrfs: failed to write free space cace "
+                      "for block group %llu\n", block_group->key.objectid);
        }
-       kfree(checksums);
-       kfree(pages);
-       btrfs_update_inode(trans, root, inode);
+
        iput(inode);
        return ret;
 }
 
-static inline unsigned long offset_to_bit(u64 bitmap_start, u64 sectorsize,
+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)(div64_u64(offset, sectorsize));
+       return (unsigned long)(div_u64(offset, unit));
 }
 
-static inline unsigned long bytes_to_bits(u64 bytes, u64 sectorsize)
+static inline unsigned long bytes_to_bits(u64 bytes, u32 unit)
 {
-       return (unsigned long)(div64_u64(bytes, sectorsize));
+       return (unsigned long)(div_u64(bytes, unit));
 }
 
-static inline u64 offset_to_bitmap(struct btrfs_block_group_cache *block_group,
+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 * block_group->sectorsize;
-       bitmap_start = offset - block_group->key.objectid;
+       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 += block_group->key.objectid;
+       bitmap_start += ctl->start;
 
        return bitmap_start;
 }
@@ -909,10 +941,16 @@ static int tree_insert_offset(struct rb_root *root, u64 offset,
                         * logically.
                         */
                        if (bitmap) {
-                               WARN_ON(info->bitmap);
+                               if (info->bitmap) {
+                                       WARN_ON_ONCE(1);
+                                       return -EEXIST;
+                               }
                                p = &(*p)->rb_right;
                        } else {
-                               WARN_ON(!info->bitmap);
+                               if (!info->bitmap) {
+                                       WARN_ON_ONCE(1);
+                                       return -EEXIST;
+                               }
                                p = &(*p)->rb_left;
                        }
                }
@@ -932,10 +970,10 @@ static int tree_insert_offset(struct rb_root *root, u64 offset,
  * offset.
  */
 static struct btrfs_free_space *
-tree_search_offset(struct btrfs_block_group_cache *block_group,
+tree_search_offset(struct btrfs_free_space_ctl *ctl,
                   u64 offset, int bitmap_only, int fuzzy)
 {
-       struct rb_node *n = block_group->free_space_offset.rb_node;
+       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' */
@@ -1031,8 +1069,7 @@ tree_search_offset(struct btrfs_block_group_cache *block_group,
                                break;
                        }
                }
-               if (entry->offset + BITS_PER_BITMAP *
-                   block_group->sectorsize > offset)
+               if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
                        return entry;
        } else if (entry->offset + entry->bytes > offset)
                return entry;
@@ -1043,7 +1080,7 @@ tree_search_offset(struct btrfs_block_group_cache *block_group,
        while (1) {
                if (entry->bitmap) {
                        if (entry->offset + BITS_PER_BITMAP *
-                           block_group->sectorsize > offset)
+                           ctl->unit > offset)
                                break;
                } else {
                        if (entry->offset + entry->bytes > offset)
@@ -1059,42 +1096,47 @@ tree_search_offset(struct btrfs_block_group_cache *block_group,
 }
 
 static inline void
-__unlink_free_space(struct btrfs_block_group_cache *block_group,
+__unlink_free_space(struct btrfs_free_space_ctl *ctl,
                    struct btrfs_free_space *info)
 {
-       rb_erase(&info->offset_index, &block_group->free_space_offset);
-       block_group->free_extents--;
+       rb_erase(&info->offset_index, &ctl->free_space_offset);
+       ctl->free_extents--;
 }
 
-static void unlink_free_space(struct btrfs_block_group_cache *block_group,
+static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *info)
 {
-       __unlink_free_space(block_group, info);
-       block_group->free_space -= info->bytes;
+       __unlink_free_space(ctl, info);
+       ctl->free_space -= info->bytes;
 }
 
-static int link_free_space(struct btrfs_block_group_cache *block_group,
+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(&block_group->free_space_offset, info->offset,
+       ret = tree_insert_offset(&ctl->free_space_offset, info->offset,
                                 &info->offset_index, (info->bitmap != NULL));
        if (ret)
                return ret;
 
-       block_group->free_space += info->bytes;
-       block_group->free_extents++;
+       ctl->free_space += info->bytes;
+       ctl->free_extents++;
        return ret;
 }
 
-static void recalculate_thresholds(struct btrfs_block_group_cache *block_group)
+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
@@ -1112,10 +1154,10 @@ static void recalculate_thresholds(struct btrfs_block_group_cache *block_group)
         * sure we don't go over our overall goal of MAX_CACHE_BYTES_PER_GIG as
         * we add more bitmaps.
         */
-       bitmap_bytes = (block_group->total_bitmaps + 1) * PAGE_CACHE_SIZE;
+       bitmap_bytes = (ctl->total_bitmaps + 1) * PAGE_CACHE_SIZE;
 
        if (bitmap_bytes >= max_bytes) {
-               block_group->extents_thresh = 0;
+               ctl->extents_thresh = 0;
                return;
        }
 
@@ -1126,47 +1168,50 @@ static void recalculate_thresholds(struct btrfs_block_group_cache *block_group)
        extent_bytes = max_bytes - bitmap_bytes;
        extent_bytes = min_t(u64, extent_bytes, div64_u64(max_bytes, 2));
 
-       block_group->extents_thresh =
+       ctl->extents_thresh =
                div64_u64(extent_bytes, (sizeof(struct btrfs_free_space)));
 }
 
-static void bitmap_clear_bits(struct btrfs_block_group_cache *block_group,
-                             struct btrfs_free_space *info, u64 offset,
-                             u64 bytes)
+static inline void __bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
+                                      struct btrfs_free_space *info,
+                                      u64 offset, u64 bytes)
 {
-       unsigned long start, end;
-       unsigned long i;
+       unsigned long start, count;
 
-       start = offset_to_bit(info->offset, block_group->sectorsize, offset);
-       end = start + bytes_to_bits(bytes, block_group->sectorsize);
-       BUG_ON(end > BITS_PER_BITMAP);
+       start = offset_to_bit(info->offset, ctl->unit, offset);
+       count = bytes_to_bits(bytes, ctl->unit);
+       BUG_ON(start + count > BITS_PER_BITMAP);
 
-       for (i = start; i < end; i++)
-               clear_bit(i, info->bitmap);
+       bitmap_clear(info->bitmap, start, count);
 
        info->bytes -= bytes;
-       block_group->free_space -= bytes;
 }
 
-static void bitmap_set_bits(struct btrfs_block_group_cache *block_group,
+static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
+                             struct btrfs_free_space *info, u64 offset,
+                             u64 bytes)
+{
+       __bitmap_clear_bits(ctl, info, offset, 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, end;
-       unsigned long i;
+       unsigned long start, count;
 
-       start = offset_to_bit(info->offset, block_group->sectorsize, offset);
-       end = start + bytes_to_bits(bytes, block_group->sectorsize);
-       BUG_ON(end > BITS_PER_BITMAP);
+       start = offset_to_bit(info->offset, ctl->unit, offset);
+       count = bytes_to_bits(bytes, ctl->unit);
+       BUG_ON(start + count > BITS_PER_BITMAP);
 
-       for (i = start; i < end; i++)
-               set_bit(i, info->bitmap);
+       bitmap_set(info->bitmap, start, count);
 
        info->bytes += bytes;
-       block_group->free_space += bytes;
+       ctl->free_space += bytes;
 }
 
-static int search_bitmap(struct btrfs_block_group_cache *block_group,
+static int search_bitmap(struct btrfs_free_space_ctl *ctl,
                         struct btrfs_free_space *bitmap_info, u64 *offset,
                         u64 *bytes)
 {
@@ -1174,9 +1219,9 @@ static int search_bitmap(struct btrfs_block_group_cache *block_group,
        unsigned long bits, i;
        unsigned long next_zero;
 
-       i = offset_to_bit(bitmap_info->offset, block_group->sectorsize,
+       i = offset_to_bit(bitmap_info->offset, ctl->unit,
                          max_t(u64, *offset, bitmap_info->offset));
-       bits = bytes_to_bits(*bytes, block_group->sectorsize);
+       bits = bytes_to_bits(*bytes, ctl->unit);
 
        for (i = find_next_bit(bitmap_info->bitmap, BITS_PER_BITMAP, i);
             i < BITS_PER_BITMAP;
@@ -1191,29 +1236,25 @@ static int search_bitmap(struct btrfs_block_group_cache *block_group,
        }
 
        if (found_bits) {
-               *offset = (u64)(i * block_group->sectorsize) +
-                       bitmap_info->offset;
-               *bytes = (u64)(found_bits) * block_group->sectorsize;
+               *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_block_group_cache
-                                               *block_group, u64 *offset,
-                                               u64 *bytes, int debug)
+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 (!block_group->free_space_offset.rb_node)
+       if (!ctl->free_space_offset.rb_node)
                return NULL;
 
-       entry = tree_search_offset(block_group,
-                                  offset_to_bitmap(block_group, *offset),
-                                  0, 1);
+       entry = tree_search_offset(ctl, offset_to_bitmap(ctl, *offset), 0, 1);
        if (!entry)
                return NULL;
 
@@ -1223,7 +1264,7 @@ static struct btrfs_free_space *find_free_space(struct btrfs_block_group_cache
                        continue;
 
                if (entry->bitmap) {
-                       ret = search_bitmap(block_group, entry, offset, bytes);
+                       ret = search_bitmap(ctl, entry, offset, bytes);
                        if (!ret)
                                return entry;
                        continue;
@@ -1237,33 +1278,28 @@ static struct btrfs_free_space *find_free_space(struct btrfs_block_group_cache
        return NULL;
 }
 
-static void add_new_bitmap(struct btrfs_block_group_cache *block_group,
+static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
                           struct btrfs_free_space *info, u64 offset)
 {
-       u64 bytes_per_bg = BITS_PER_BITMAP * block_group->sectorsize;
-       int max_bitmaps = (int)div64_u64(block_group->key.offset +
-                                        bytes_per_bg - 1, bytes_per_bg);
-       BUG_ON(block_group->total_bitmaps >= max_bitmaps);
-
-       info->offset = offset_to_bitmap(block_group, offset);
+       info->offset = offset_to_bitmap(ctl, offset);
        info->bytes = 0;
-       link_free_space(block_group, info);
-       block_group->total_bitmaps++;
+       link_free_space(ctl, info);
+       ctl->total_bitmaps++;
 
-       recalculate_thresholds(block_group);
+       ctl->op->recalc_thresholds(ctl);
 }
 
-static void free_bitmap(struct btrfs_block_group_cache *block_group,
+static void free_bitmap(struct btrfs_free_space_ctl *ctl,
                        struct btrfs_free_space *bitmap_info)
 {
-       unlink_free_space(block_group, bitmap_info);
+       unlink_free_space(ctl, bitmap_info);
        kfree(bitmap_info->bitmap);
        kmem_cache_free(btrfs_free_space_cachep, bitmap_info);
-       block_group->total_bitmaps--;
-       recalculate_thresholds(block_group);
+       ctl->total_bitmaps--;
+       ctl->op->recalc_thresholds(ctl);
 }
 
-static noinline int remove_from_bitmap(struct btrfs_block_group_cache *block_group,
+static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
                              struct btrfs_free_space *bitmap_info,
                              u64 *offset, u64 *bytes)
 {
@@ -1272,8 +1308,7 @@ static noinline int remove_from_bitmap(struct btrfs_block_group_cache *block_gro
        int ret;
 
 again:
-       end = bitmap_info->offset +
-               (u64)(BITS_PER_BITMAP * block_group->sectorsize) - 1;
+       end = bitmap_info->offset + (u64)(BITS_PER_BITMAP * ctl->unit) - 1;
 
        /*
         * XXX - this can go away after a few releases.
@@ -1288,24 +1323,22 @@ again:
        search_start = *offset;
        search_bytes = *bytes;
        search_bytes = min(search_bytes, end - search_start + 1);
-       ret = search_bitmap(block_group, bitmap_info, &search_start,
-                           &search_bytes);
+       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(block_group, bitmap_info, *offset,
-                                 end - *offset + 1);
+               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(block_group, bitmap_info, *offset, *bytes);
+               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(block_group, bitmap_info);
+                       free_bitmap(ctl, bitmap_info);
 
                /*
                 * no entry after this bitmap, but we still have bytes to
@@ -1332,31 +1365,45 @@ again:
                 */
                search_start = *offset;
                search_bytes = *bytes;
-               ret = search_bitmap(block_group, bitmap_info, &search_start,
+               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(block_group, bitmap_info);
+               free_bitmap(ctl, bitmap_info);
 
        return 0;
 }
 
-static int insert_into_bitmap(struct btrfs_block_group_cache *block_group,
-                             struct btrfs_free_space *info)
+static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
+                              struct btrfs_free_space *info, u64 offset,
+                              u64 bytes)
 {
-       struct btrfs_free_space *bitmap_info;
-       int added = 0;
-       u64 bytes, offset, end;
-       int ret;
+       u64 bytes_to_set = 0;
+       u64 end;
+
+       end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
+
+       bytes_to_set = min(end - offset, bytes);
+
+       bitmap_set_bits(ctl, info, offset, bytes_to_set);
+
+       return bytes_to_set;
+
+}
+
+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 (block_group->free_extents < block_group->extents_thresh) {
+       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
@@ -1365,11 +1412,10 @@ static int insert_into_bitmap(struct btrfs_block_group_cache *block_group,
                 * the overhead of a bitmap if we don't have to.
                 */
                if (info->bytes <= block_group->sectorsize * 4) {
-                       if (block_group->free_extents * 2 <=
-                           block_group->extents_thresh)
-                               return 0;
+                       if (ctl->free_extents * 2 <= ctl->extents_thresh)
+                               return false;
                } else {
-                       return 0;
+                       return false;
                }
        }
 
@@ -1379,35 +1425,85 @@ static int insert_into_bitmap(struct btrfs_block_group_cache *block_group,
         */
        if (BITS_PER_BITMAP * block_group->sectorsize >
            block_group->key.offset)
-               return 0;
+               return false;
+
+       return true;
+}
+
+static struct btrfs_free_space_op free_space_op = {
+       .recalc_thresholds      = recalculate_thresholds,
+       .use_bitmap             = use_bitmap,
+};
+
+static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
+                             struct btrfs_free_space *info)
+{
+       struct btrfs_free_space *bitmap_info;
+       struct btrfs_block_group_cache *block_group = NULL;
+       int added = 0;
+       u64 bytes, offset, bytes_added;
+       int ret;
 
        bytes = info->bytes;
        offset = info->offset;
 
+       if (!ctl->op->use_bitmap(ctl, info))
+               return 0;
+
+       if (ctl->op == &free_space_op)
+               block_group = ctl->private;
 again:
-       bitmap_info = tree_search_offset(block_group,
-                                        offset_to_bitmap(block_group, offset),
+       /*
+        * Since we link bitmaps right into the cluster we need to see if we
+        * have a cluster here, and if so and it has our bitmap we need to add
+        * the free space to that bitmap.
+        */
+       if (block_group && !list_empty(&block_group->cluster_list)) {
+               struct btrfs_free_cluster *cluster;
+               struct rb_node *node;
+               struct btrfs_free_space *entry;
+
+               cluster = list_entry(block_group->cluster_list.next,
+                                    struct btrfs_free_cluster,
+                                    block_group_list);
+               spin_lock(&cluster->lock);
+               node = rb_first(&cluster->root);
+               if (!node) {
+                       spin_unlock(&cluster->lock);
+                       goto no_cluster_bitmap;
+               }
+
+               entry = rb_entry(node, struct btrfs_free_space, offset_index);
+               if (!entry->bitmap) {
+                       spin_unlock(&cluster->lock);
+                       goto no_cluster_bitmap;
+               }
+
+               if (entry->offset == offset_to_bitmap(ctl, offset)) {
+                       bytes_added = add_bytes_to_bitmap(ctl, entry,
+                                                         offset, bytes);
+                       bytes -= bytes_added;
+                       offset += bytes_added;
+               }
+               spin_unlock(&cluster->lock);
+               if (!bytes) {
+                       ret = 1;
+                       goto out;
+               }
+       }
+
+no_cluster_bitmap:
+       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 * block_group->sectorsize);
-
-       if (offset >= bitmap_info->offset && offset + bytes > end) {
-               bitmap_set_bits(block_group, bitmap_info, offset,
-                               end - offset);
-               bytes -= end - offset;
-               offset = end;
-               added = 0;
-       } else if (offset >= bitmap_info->offset && offset + bytes <= end) {
-               bitmap_set_bits(block_group, bitmap_info, offset, bytes);
-               bytes = 0;
-       } else {
-               BUG();
-       }
+       bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+       bytes -= bytes_added;
+       offset += bytes_added;
+       added = 0;
 
        if (!bytes) {
                ret = 1;
@@ -1417,19 +1513,19 @@ again:
 
 new_bitmap:
        if (info && info->bitmap) {
-               add_new_bitmap(block_group, info, offset);
+               add_new_bitmap(ctl, info, offset);
                added = 1;
                info = NULL;
                goto again;
        } else {
-               spin_unlock(&block_group->tree_lock);
+               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(&block_group->tree_lock);
+                               spin_lock(&ctl->tree_lock);
                                ret = -ENOMEM;
                                goto out;
                        }
@@ -1437,7 +1533,7 @@ new_bitmap:
 
                /* allocate the bitmap */
                info->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
-               spin_lock(&block_group->tree_lock);
+               spin_lock(&ctl->tree_lock);
                if (!info->bitmap) {
                        ret = -ENOMEM;
                        goto out;
@@ -1455,7 +1551,7 @@ out:
        return ret;
 }
 
-bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
+static 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;
@@ -1469,18 +1565,18 @@ bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
         * are adding, if there is remove that struct and add a new one to
         * cover the entire range
         */
-       right_info = tree_search_offset(block_group, offset + bytes, 0, 0);
+       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(block_group, offset - 1, 0, 0);
+               left_info = tree_search_offset(ctl, offset - 1, 0, 0);
 
        if (right_info && !right_info->bitmap) {
                if (update_stat)
-                       unlink_free_space(block_group, right_info);
+                       unlink_free_space(ctl, right_info);
                else
-                       __unlink_free_space(block_group, right_info);
+                       __unlink_free_space(ctl, right_info);
                info->bytes += right_info->bytes;
                kmem_cache_free(btrfs_free_space_cachep, right_info);
                merged = true;
@@ -1489,9 +1585,9 @@ bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
        if (left_info && !left_info->bitmap &&
            left_info->offset + left_info->bytes == offset) {
                if (update_stat)
-                       unlink_free_space(block_group, left_info);
+                       unlink_free_space(ctl, left_info);
                else
-                       __unlink_free_space(block_group, left_info);
+                       __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);
@@ -1501,8 +1597,8 @@ bool try_merge_free_space(struct btrfs_block_group_cache *block_group,
        return merged;
 }
 
-int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
-                        u64 offset, u64 bytes)
+int __btrfs_add_free_space(struct btrfs_free_space_ctl *ctl,
+                          u64 offset, u64 bytes)
 {
        struct btrfs_free_space *info;
        int ret = 0;
@@ -1514,9 +1610,9 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
        info->offset = offset;
        info->bytes = bytes;
 
-       spin_lock(&block_group->tree_lock);
+       spin_lock(&ctl->tree_lock);
 
-       if (try_merge_free_space(block_group, info, true))
+       if (try_merge_free_space(ctl, info, true))
                goto link;
 
        /*
@@ -1524,7 +1620,7 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
         * 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(block_group, info);
+       ret = insert_into_bitmap(ctl, info);
        if (ret < 0) {
                goto out;
        } else if (ret) {
@@ -1532,11 +1628,11 @@ int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
                goto out;
        }
 link:
-       ret = link_free_space(block_group, info);
+       ret = link_free_space(ctl, info);
        if (ret)
                kmem_cache_free(btrfs_free_space_cachep, info);
 out:
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 
        if (ret) {
                printk(KERN_CRIT "btrfs: unable to add free space :%d\n", ret);
@@ -1549,21 +1645,21 @@ out:
 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(&block_group->tree_lock);
+       spin_lock(&ctl->tree_lock);
 
 again:
-       info = tree_search_offset(block_group, offset, 0, 0);
+       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(block_group,
-                                         offset_to_bitmap(block_group, offset),
+               info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
                                          1, 0);
                if (!info) {
                        WARN_ON(1);
@@ -1578,8 +1674,8 @@ again:
                                             offset_index);
 
                if (next_info->bitmap)
-                       end = next_info->offset + BITS_PER_BITMAP *
-                               block_group->sectorsize - 1;
+                       end = next_info->offset +
+                             BITS_PER_BITMAP * ctl->unit - 1;
                else
                        end = next_info->offset + next_info->bytes;
 
@@ -1599,20 +1695,20 @@ again:
        }
 
        if (info->bytes == bytes) {
-               unlink_free_space(block_group, info);
+               unlink_free_space(ctl, info);
                if (info->bitmap) {
                        kfree(info->bitmap);
-                       block_group->total_bitmaps--;
+                       ctl->total_bitmaps--;
                }
                kmem_cache_free(btrfs_free_space_cachep, info);
                goto out_lock;
        }
 
        if (!info->bitmap && info->offset == offset) {
-               unlink_free_space(block_group, info);
+               unlink_free_space(ctl, info);
                info->offset += bytes;
                info->bytes -= bytes;
-               link_free_space(block_group, info);
+               link_free_space(ctl, info);
                goto out_lock;
        }
 
@@ -1626,13 +1722,13 @@ again:
                 * first unlink the old info and then
                 * insert it again after the hole we're creating
                 */
-               unlink_free_space(block_group, info);
+               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(block_group, info);
+                       ret = link_free_space(ctl, info);
                        WARN_ON(ret);
                        if (ret)
                                goto out_lock;
@@ -1642,7 +1738,7 @@ again:
                         */
                        kmem_cache_free(btrfs_free_space_cachep, info);
                }
-               spin_unlock(&block_group->tree_lock);
+               spin_unlock(&ctl->tree_lock);
 
                /* step two, insert a new info struct to cover
                 * anything before the hole
@@ -1653,12 +1749,12 @@ again:
                goto out;
        }
 
-       ret = remove_from_bitmap(block_group, info, &offset, &bytes);
+       ret = remove_from_bitmap(ctl, info, &offset, &bytes);
        if (ret == -EAGAIN)
                goto again;
        BUG_ON(ret);
 out_lock:
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 out:
        return ret;
 }
@@ -1666,11 +1762,12 @@ out:
 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(&block_group->free_space_offset); n; n = rb_next(n)) {
+       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++;
@@ -1685,19 +1782,23 @@ void btrfs_dump_free_space(struct btrfs_block_group_cache *block_group,
               "\n", count);
 }
 
-u64 btrfs_block_group_free_space(struct btrfs_block_group_cache *block_group)
+void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group)
 {
-       struct btrfs_free_space *info;
-       struct rb_node *n;
-       u64 ret = 0;
+       struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 
-       for (n = rb_first(&block_group->free_space_offset); n;
-            n = rb_next(n)) {
-               info = rb_entry(n, struct btrfs_free_space, offset_index);
-               ret += info->bytes;
-       }
+       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;
 
-       return ret;
+       /*
+        * 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);
 }
 
 /*
@@ -1711,6 +1812,7 @@ __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;
 
@@ -1732,8 +1834,8 @@ __btrfs_return_cluster_to_free_space(
 
                bitmap = (entry->bitmap != NULL);
                if (!bitmap)
-                       try_merge_free_space(block_group, entry, false);
-               tree_insert_offset(&block_group->free_space_offset,
+                       try_merge_free_space(ctl, entry, false);
+               tree_insert_offset(&ctl->free_space_offset,
                                   entry->offset, &entry->offset_index, bitmap);
        }
        cluster->root = RB_ROOT;
@@ -1744,14 +1846,41 @@ out:
        return 0;
 }
 
-void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
+void __btrfs_remove_free_space_cache_locked(struct btrfs_free_space_ctl *ctl)
 {
        struct btrfs_free_space *info;
        struct rb_node *node;
+
+       while ((node = rb_last(&ctl->free_space_offset)) != NULL) {
+               info = rb_entry(node, struct btrfs_free_space, offset_index);
+               if (!info->bitmap) {
+                       unlink_free_space(ctl, info);
+                       kmem_cache_free(btrfs_free_space_cachep, info);
+               } else {
+                       free_bitmap(ctl, info);
+               }
+               if (need_resched()) {
+                       spin_unlock(&ctl->tree_lock);
+                       cond_resched();
+                       spin_lock(&ctl->tree_lock);
+               }
+       }
+}
+
+void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl)
+{
+       spin_lock(&ctl->tree_lock);
+       __btrfs_remove_free_space_cache_locked(ctl);
+       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(&block_group->tree_lock);
+       spin_lock(&ctl->tree_lock);
        while ((head = block_group->cluster_list.next) !=
               &block_group->cluster_list) {
                cluster = list_entry(head, struct btrfs_free_cluster,
@@ -1760,60 +1889,46 @@ void btrfs_remove_free_space_cache(struct btrfs_block_group_cache *block_group)
                WARN_ON(cluster->block_group != block_group);
                __btrfs_return_cluster_to_free_space(block_group, cluster);
                if (need_resched()) {
-                       spin_unlock(&block_group->tree_lock);
+                       spin_unlock(&ctl->tree_lock);
                        cond_resched();
-                       spin_lock(&block_group->tree_lock);
+                       spin_lock(&ctl->tree_lock);
                }
        }
+       __btrfs_remove_free_space_cache_locked(ctl);
+       spin_unlock(&ctl->tree_lock);
 
-       while ((node = rb_last(&block_group->free_space_offset)) != NULL) {
-               info = rb_entry(node, struct btrfs_free_space, offset_index);
-               if (!info->bitmap) {
-                       unlink_free_space(block_group, info);
-                       kmem_cache_free(btrfs_free_space_cachep, info);
-               } else {
-                       free_bitmap(block_group, info);
-               }
-
-               if (need_resched()) {
-                       spin_unlock(&block_group->tree_lock);
-                       cond_resched();
-                       spin_lock(&block_group->tree_lock);
-               }
-       }
-
-       spin_unlock(&block_group->tree_lock);
 }
 
 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(&block_group->tree_lock);
-       entry = find_free_space(block_group, &offset, &bytes_search, 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(block_group, entry, offset, bytes);
+               bitmap_clear_bits(ctl, entry, offset, bytes);
                if (!entry->bytes)
-                       free_bitmap(block_group, entry);
+                       free_bitmap(ctl, entry);
        } else {
-               unlink_free_space(block_group, entry);
+               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(block_group, entry);
+                       link_free_space(ctl, entry);
        }
 
 out:
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 
        return ret;
 }
@@ -1830,6 +1945,7 @@ 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 */
@@ -1848,10 +1964,12 @@ int btrfs_return_cluster_to_free_space(
        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(&block_group->tree_lock);
+       spin_lock(&ctl->tree_lock);
        ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 
        /* finally drop our ref */
        btrfs_put_block_group(block_group);
@@ -1863,6 +1981,7 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
                                   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;
@@ -1871,13 +1990,12 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
        search_start = min_start;
        search_bytes = bytes;
 
-       err = search_bitmap(block_group, entry, &search_start,
-                           &search_bytes);
+       err = search_bitmap(ctl, entry, &search_start, &search_bytes);
        if (err)
                return 0;
 
        ret = search_start;
-       bitmap_clear_bits(block_group, entry, ret, bytes);
+       __bitmap_clear_bits(ctl, entry, ret, bytes);
 
        return ret;
 }
@@ -1891,6 +2009,7 @@ 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;
@@ -1910,8 +2029,6 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
        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;
@@ -1925,7 +2042,6 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
                                                      cluster, entry, bytes,
                                                      min_start);
                        if (ret == 0) {
-                               struct rb_node *node;
                                node = rb_next(&entry->offset_index);
                                if (!node)
                                        break;
@@ -1934,7 +2050,6 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group_cache *block_group,
                                continue;
                        }
                } else {
-
                        ret = entry->offset;
 
                        entry->offset += bytes;
@@ -1951,20 +2066,20 @@ out:
        if (!ret)
                return 0;
 
-       spin_lock(&block_group->tree_lock);
+       spin_lock(&ctl->tree_lock);
 
-       block_group->free_space -= bytes;
+       ctl->free_space -= bytes;
        if (entry->bytes == 0) {
-               block_group->free_extents--;
+               ctl->free_extents--;
                if (entry->bitmap) {
                        kfree(entry->bitmap);
-                       block_group->total_bitmaps--;
-                       recalculate_thresholds(block_group);
+                       ctl->total_bitmaps--;
+                       ctl->op->recalc_thresholds(ctl);
                }
                kmem_cache_free(btrfs_free_space_cachep, entry);
        }
 
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 
        return ret;
 }
@@ -1974,6 +2089,7 @@ static int btrfs_bitmap_cluster(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;
        unsigned long next_zero;
        unsigned long i;
        unsigned long search_bits;
@@ -2028,7 +2144,7 @@ again:
 
        cluster->window_start = start * block_group->sectorsize +
                entry->offset;
-       rb_erase(&entry->offset_index, &block_group->free_space_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);
@@ -2039,10 +2155,13 @@ again:
 /*
  * 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)
+static noinline int
+setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
+                       struct btrfs_free_cluster *cluster,
+                       struct list_head *bitmaps, 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;
@@ -2053,7 +2172,7 @@ static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
        u64 max_extent;
        u64 max_gap = 128 * 1024;
 
-       entry = tree_search_offset(block_group, offset, 0, 1);
+       entry = tree_search_offset(ctl, offset, 0, 1);
        if (!entry)
                return -ENOSPC;
 
@@ -2062,6 +2181,8 @@ static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
         * extent entry.
         */
        while (entry->bitmap) {
+               if (list_empty(&entry->list))
+                       list_add_tail(&entry->list, bitmaps);
                node = rb_next(&entry->offset_index);
                if (!node)
                        return -ENOSPC;
@@ -2081,8 +2202,12 @@ static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
                        return -ENOSPC;
                entry = rb_entry(node, struct btrfs_free_space, offset_index);
 
-               if (entry->bitmap)
+               if (entry->bitmap) {
+                       if (list_empty(&entry->list))
+                               list_add_tail(&entry->list, bitmaps);
                        continue;
+               }
+
                /*
                 * we haven't filled the empty size and the window is
                 * very large.  reset and try again
@@ -2119,7 +2244,7 @@ static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
                if (entry->bitmap)
                        continue;
 
-               rb_erase(&entry->offset_index, &block_group->free_space_offset);
+               rb_erase(&entry->offset_index, &ctl->free_space_offset);
                ret = tree_insert_offset(&cluster->root, entry->offset,
                                         &entry->offset_index, 0);
                BUG_ON(ret);
@@ -2134,23 +2259,53 @@ static int setup_cluster_no_bitmap(struct btrfs_block_group_cache *block_group,
  * 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)
+static noinline int
+setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
+                    struct btrfs_free_cluster *cluster,
+                    struct list_head *bitmaps, 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 (block_group->total_bitmaps == 0)
+       if (ctl->total_bitmaps == 0)
                return -ENOSPC;
 
-       entry = tree_search_offset(block_group,
-                                  offset_to_bitmap(block_group, offset),
-                                  0, 1);
+       /*
+        * First check our cached list of bitmaps and see if there is an entry
+        * here that will work.
+        */
+       list_for_each_entry(entry, bitmaps, list) {
+               if (entry->bytes < min_bytes)
+                       continue;
+               ret = btrfs_bitmap_cluster(block_group, entry, cluster, offset,
+                                          bytes, min_bytes);
+               if (!ret)
+                       return 0;
+       }
+
+       /*
+        * If we do have entries on our list and we are here then we didn't find
+        * anything, so go ahead and get the next entry after the last entry in
+        * this list and start the search from there.
+        */
+       if (!list_empty(bitmaps)) {
+               entry = list_entry(bitmaps->prev, struct btrfs_free_space,
+                                  list);
+               node = rb_next(&entry->offset_index);
+               if (!node)
+                       return -ENOSPC;
+               entry = rb_entry(node, struct btrfs_free_space, offset_index);
+               goto search;
+       }
+
+       entry = tree_search_offset(ctl, offset_to_bitmap(ctl, offset), 0, 1);
        if (!entry)
                return -ENOSPC;
 
+search:
        node = &entry->offset_index;
        do {
                entry = rb_entry(node, struct btrfs_free_space, offset_index);
@@ -2180,6 +2335,9 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
                             struct btrfs_free_cluster *cluster,
                             u64 offset, u64 bytes, u64 empty_size)
 {
+       struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+       struct list_head bitmaps;
+       struct btrfs_free_space *entry, *tmp;
        u64 min_bytes;
        int ret;
 
@@ -2199,14 +2357,14 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
        } else
                min_bytes = max(bytes, (bytes + empty_size) >> 2);
 
-       spin_lock(&block_group->tree_lock);
+       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 (block_group->free_space < min_bytes) {
-               spin_unlock(&block_group->tree_lock);
+       if (ctl->free_space < min_bytes) {
+               spin_unlock(&ctl->tree_lock);
                return -ENOSPC;
        }
 
@@ -2218,11 +2376,16 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
                goto out;
        }
 
-       ret = setup_cluster_no_bitmap(block_group, cluster, offset, bytes,
-                                     min_bytes);
+       INIT_LIST_HEAD(&bitmaps);
+       ret = setup_cluster_no_bitmap(block_group, cluster, &bitmaps, offset,
+                                     bytes, min_bytes);
        if (ret)
-               ret = setup_cluster_bitmap(block_group, cluster, offset,
-                                          bytes, min_bytes);
+               ret = setup_cluster_bitmap(block_group, cluster, &bitmaps,
+                                          offset, bytes, min_bytes);
+
+       /* Clear our temporary list */
+       list_for_each_entry_safe(entry, tmp, &bitmaps, list)
+               list_del_init(&entry->list);
 
        if (!ret) {
                atomic_inc(&block_group->count);
@@ -2232,7 +2395,7 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
        }
 out:
        spin_unlock(&cluster->lock);
-       spin_unlock(&block_group->tree_lock);
+       spin_unlock(&ctl->tree_lock);
 
        return ret;
 }
@@ -2253,6 +2416,7 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 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;
@@ -2262,52 +2426,50 @@ int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
        *trimmed = 0;
 
        while (start < end) {
-               spin_lock(&block_group->tree_lock);
+               spin_lock(&ctl->tree_lock);
 
-               if (block_group->free_space < minlen) {
-                       spin_unlock(&block_group->tree_lock);
+               if (ctl->free_space < minlen) {
+                       spin_unlock(&ctl->tree_lock);
                        break;
                }
 
-               entry = tree_search_offset(block_group, start, 0, 1);
+               entry = tree_search_offset(ctl, start, 0, 1);
                if (!entry)
-                       entry = tree_search_offset(block_group,
-                                                  offset_to_bitmap(block_group,
-                                                                   start),
+                       entry = tree_search_offset(ctl,
+                                                  offset_to_bitmap(ctl, start),
                                                   1, 1);
 
                if (!entry || entry->offset >= end) {
-                       spin_unlock(&block_group->tree_lock);
+                       spin_unlock(&ctl->tree_lock);
                        break;
                }
 
                if (entry->bitmap) {
-                       ret = search_bitmap(block_group, entry, &start, &bytes);
+                       ret = search_bitmap(ctl, entry, &start, &bytes);
                        if (!ret) {
                                if (start >= end) {
-                                       spin_unlock(&block_group->tree_lock);
+                                       spin_unlock(&ctl->tree_lock);
                                        break;
                                }
                                bytes = min(bytes, end - start);
-                               bitmap_clear_bits(block_group, entry,
-                                                 start, bytes);
+                               bitmap_clear_bits(ctl, entry, start, bytes);
                                if (entry->bytes == 0)
-                                       free_bitmap(block_group, entry);
+                                       free_bitmap(ctl, entry);
                        } else {
                                start = entry->offset + BITS_PER_BITMAP *
                                        block_group->sectorsize;
-                               spin_unlock(&block_group->tree_lock);
+                               spin_unlock(&ctl->tree_lock);
                                ret = 0;
                                continue;
                        }
                } else {
                        start = entry->offset;
                        bytes = min(entry->bytes, end - start);
-                       unlink_free_space(block_group, entry);
+                       unlink_free_space(ctl, entry);
                        kmem_cache_free(btrfs_free_space_cachep, entry);
                }
 
-               spin_unlock(&block_group->tree_lock);
+               spin_unlock(&ctl->tree_lock);
 
                if (bytes >= minlen) {
                        int update_ret;
@@ -2319,8 +2481,7 @@ int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
                                                         bytes,
                                                         &actually_trimmed);
 
-                       btrfs_add_free_space(block_group,
-                                            start, bytes);
+                       btrfs_add_free_space(block_group, start, bytes);
                        if (!update_ret)
                                btrfs_update_reserved_bytes(block_group,
                                                            bytes, 0, 1);
@@ -2342,3 +2503,150 @@ int btrfs_trim_block_group(struct btrfs_block_group_cache *block_group,
 
        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;
+}
+
+struct inode *lookup_free_ino_inode(struct btrfs_root *root,
+                                   struct btrfs_path *path)
+{
+       struct inode *inode = NULL;
+
+       spin_lock(&root->cache_lock);
+       if (root->cache_inode)
+               inode = igrab(root->cache_inode);
+       spin_unlock(&root->cache_lock);
+       if (inode)
+               return inode;
+
+       inode = __lookup_free_space_inode(root, path, 0);
+       if (IS_ERR(inode))
+               return inode;
+
+       spin_lock(&root->cache_lock);
+       if (!btrfs_fs_closing(root->fs_info))
+               root->cache_inode = igrab(inode);
+       spin_unlock(&root->cache_lock);
+
+       return inode;
+}
+
+int create_free_ino_inode(struct btrfs_root *root,
+                         struct btrfs_trans_handle *trans,
+                         struct btrfs_path *path)
+{
+       return __create_free_space_inode(root, trans, path,
+                                        BTRFS_FREE_INO_OBJECTID, 0);
+}
+
+int load_free_ino_cache(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
+{
+       struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
+       struct btrfs_path *path;
+       struct inode *inode;
+       int ret = 0;
+       u64 root_gen = btrfs_root_generation(&root->root_item);
+
+       if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+               return 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.
+        */
+       if (btrfs_fs_closing(fs_info))
+               return 0;
+
+       path = btrfs_alloc_path();
+       if (!path)
+               return 0;
+
+       inode = lookup_free_ino_inode(root, path);
+       if (IS_ERR(inode))
+               goto out;
+
+       if (root_gen != BTRFS_I(inode)->generation)
+               goto out_put;
+
+       ret = __load_free_space_cache(root, inode, ctl, path, 0);
+
+       if (ret < 0)
+               printk(KERN_ERR "btrfs: failed to load free ino cache for "
+                      "root %llu\n", root->root_key.objectid);
+out_put:
+       iput(inode);
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
+int btrfs_write_out_ino_cache(struct btrfs_root *root,
+                             struct btrfs_trans_handle *trans,
+                             struct btrfs_path *path)
+{
+       struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
+       struct inode *inode;
+       int ret;
+
+       if (!btrfs_test_opt(root, INODE_MAP_CACHE))
+               return 0;
+
+       inode = lookup_free_ino_inode(root, path);
+       if (IS_ERR(inode))
+               return 0;
+
+       ret = __btrfs_write_out_cache(root, inode, ctl, NULL, trans, path, 0);
+       if (ret < 0)
+               printk(KERN_ERR "btrfs: failed to write free ino cache "
+                      "for root %llu\n", root->root_key.objectid);
+
+       iput(inode);
+       return ret;
+}