again:
        em = lookup_extent_mapping(em_tree, start, end);
        if (em) {
+               if (em->start > start) {
+                       printk("get_extent start %Lu em start %Lu\n",
+                              start, em->start);
+                       WARN_ON(1);
+               }
                goto out;
        }
        if (!em) {
        return extent_bmap(mapping, iblock, btrfs_get_extent);
 }
 
-static int btrfs_prepare_write(struct file *file, struct page *page,
-                              unsigned from, unsigned to)
-{
-       struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-       int err;
-
-       mutex_lock(&root->fs_info->fs_mutex);
-       err = btrfs_check_free_space(root, PAGE_CACHE_SIZE, 0);
-       mutex_unlock(&root->fs_info->fs_mutex);
-       if (err)
-               return -ENOSPC;
-
-       return extent_prepare_write(&BTRFS_I(page->mapping->host)->extent_tree,
-                                   page->mapping->host, page, from, to,
-                                   btrfs_get_extent);
-}
-
 int btrfs_readpage(struct file *file, struct page *page)
 {
        struct extent_map_tree *tree;
        btrfs_btree_balance_dirty(root, nr);
 }
 
-int btrfs_commit_write(struct file *file, struct page *page,
-                      unsigned from, unsigned to)
-{
-       loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
-       struct inode *inode = page->mapping->host;
-
-       btrfs_cow_one_page(inode, page, PAGE_CACHE_SIZE);
-
-       if (pos > inode->i_size) {
-               i_size_write(inode, pos);
-               mark_inode_dirty(inode);
-       }
-       return 0;
-}
-
 static int create_subvol(struct btrfs_root *root, char *name, int namelen)
 {
        struct btrfs_trans_handle *trans;
        .writepages     = btrfs_writepages,
        .readpages      = btrfs_readpages,
        .sync_page      = block_sync_page,
-       .prepare_write  = btrfs_prepare_write,
-       .commit_write   = btrfs_commit_write,
        .bmap           = btrfs_bmap,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,