/*
   * 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 (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))

  		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);

  	/*
  	 * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
  	 * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
  	 * a deadlock (attempting to write lock an already write locked leaf).
  	 */
  	path->lowest_level = 1;

  	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;
  	}

  	/*
  	 * The node at level 1 must always be locked when our path has
  	 * keep_locks set and lowest_level is 1, regardless of the value of
  	 * path->slots[1].
  	 */
  	BUG_ON(path->locks[1] == 0);

  	ret = btrfs_realloc_node(trans, root,
  				 path->nodes[1], 0,

  				 &last_ret,

  				 &root->defrag_progress);

  	if (ret) {
  		WARN_ON(ret == -EAGAIN);
  		goto out;
  	}

  	/*
  	 * Now that we reallocated the node we can find the next key. Note that
  	 * btrfs_find_next_key() can release our path and do another search
  	 * without COWing, this is because even with path->keep_locks = 1,
  	 * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
  	 * node when path->slots[node_level - 1] does not point to the last
  	 * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
  	 * we search for the next key after reallocating our node.
  	 */
  	path->slots[1] = btrfs_header_nritems(path->nodes[1]);
  	next_key_ret = btrfs_find_next_key(root, path, &key, 1,
  					   min_trans);

  	if (next_key_ret == 0) {
  		memcpy(&root->defrag_progress, &key, sizeof(key));
  		ret = -EAGAIN;

  	}

  out:

  	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;
  }