/*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/sched.h>
  #include "ctree.h"
  #include "disk-io.h"
  #include "print-tree.h"
  #include "transaction.h"
  #include "locking.h"
  
  /*
   * Defrag all the leaves in a given btree.
   * Read all the leaves and try to get key order to
   * better reflect disk order
   */
  
  int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
  			struct btrfs_root *root)
  {
  	struct btrfs_path *path = NULL;
  	struct btrfs_key key;
  	int ret = 0;
  	int wret;
  	int level;
  	int next_key_ret = 0;
  	u64 last_ret = 0;
  	u64 min_trans = 0;
  
  	if (root->fs_info->extent_root == root) {
  		/*
  		 * there's recursion here right now in the tree locking,
  		 * we can't defrag the extent root without deadlock
  		 */
  		goto out;
  	}
  
  	if (root->ref_cows == 0)
  		goto out;
  
  	if (btrfs_test_opt(root, SSD))
  		goto out;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	level = btrfs_header_level(root->node);
  
  	if (level == 0)
  		goto out;
  
  	if (root->defrag_progress.objectid == 0) {
  		struct extent_buffer *root_node;
  		u32 nritems;
  
  		root_node = btrfs_lock_root_node(root);
  		btrfs_set_lock_blocking(root_node);
  		nritems = btrfs_header_nritems(root_node);
  		root->defrag_max.objectid = 0;
  		/* from above we know this is not a leaf */
  		btrfs_node_key_to_cpu(root_node, &root->defrag_max,
  				      nritems - 1);
  		btrfs_tree_unlock(root_node);
  		free_extent_buffer(root_node);
  		memset(&key, 0, sizeof(key));
  	} else {
  		memcpy(&key, &root->defrag_progress, sizeof(key));
  	}
  
  	path->keep_locks = 1;
  
  	ret = btrfs_search_forward(root, &key, path, min_trans);
  	if (ret < 0)
  		goto out;
  	if (ret > 0) {
  		ret = 0;
  		goto out;
  	}
  	btrfs_release_path(path);
  	wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  
  	if (wret < 0) {
  		ret = wret;
  		goto out;
  	}
  	if (!path->nodes[1]) {
  		ret = 0;
  		goto out;
  	}
  	path->slots[1] = btrfs_header_nritems(path->nodes[1]);
  	next_key_ret = btrfs_find_next_key(root, path, &key, 1,
  					   min_trans);
  	ret = btrfs_realloc_node(trans, root,
  				 path->nodes[1], 0,
  				 &last_ret,
  				 &root->defrag_progress);
  	if (ret) {
  		WARN_ON(ret == -EAGAIN);
  		goto out;
  	}
  	if (next_key_ret == 0) {
  		memcpy(&root->defrag_progress, &key, sizeof(key));
  		ret = -EAGAIN;
  	}
  out:
  	if (path)
  		btrfs_free_path(path);
  	if (ret == -EAGAIN) {
  		if (root->defrag_max.objectid > root->defrag_progress.objectid)
  			goto done;
  		if (root->defrag_max.type > root->defrag_progress.type)
  			goto done;
  		if (root->defrag_max.offset > root->defrag_progress.offset)
  			goto done;
  		ret = 0;
  	}
  done:
  	if (ret != -EAGAIN) {
  		memset(&root->defrag_progress, 0,
  		       sizeof(root->defrag_progress));
  		root->defrag_trans_start = trans->transid;
  	}
  	return ret;
  }