/*
   * 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/delay.h>
  #include <linux/kthread.h>
  #include <linux/pagemap.h>

  #include "ctree.h"
  #include "disk-io.h"

  #include "free-space-cache.h"
  #include "inode-map.h"

  #include "transaction.h"

  static int caching_kthread(void *data)
  {
  	struct btrfs_root *root = data;
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
  	struct btrfs_key key;
  	struct btrfs_path *path;
  	struct extent_buffer *leaf;
  	u64 last = (u64)-1;
  	int slot;
  	int ret;

  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return 0;

  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	/* Since the commit root is read-only, we can safely skip locking. */
  	path->skip_locking = 1;
  	path->search_commit_root = 1;
  	path->reada = 2;
  
  	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
  	key.offset = 0;
  	key.type = BTRFS_INODE_ITEM_KEY;
  again:
  	/* need to make sure the commit_root doesn't disappear */
  	mutex_lock(&root->fs_commit_mutex);
  
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0)
  		goto out;
  
  	while (1) {

  		if (btrfs_fs_closing(fs_info))

  			goto out;
  
  		leaf = path->nodes[0];
  		slot = path->slots[0];

  		if (slot >= btrfs_header_nritems(leaf)) {

  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				goto out;
  			else if (ret > 0)
  				break;
  
  			if (need_resched() ||
  			    btrfs_transaction_in_commit(fs_info)) {
  				leaf = path->nodes[0];
  
  				if (btrfs_header_nritems(leaf) == 0) {
  					WARN_ON(1);
  					break;
  				}
  
  				/*
  				 * Save the key so we can advances forward
  				 * in the next search.
  				 */
  				btrfs_item_key_to_cpu(leaf, &key, 0);

  				btrfs_release_path(path);

  				root->cache_progress = last;
  				mutex_unlock(&root->fs_commit_mutex);
  				schedule_timeout(1);
  				goto again;
  			} else
  				continue;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, slot);
  
  		if (key.type != BTRFS_INODE_ITEM_KEY)
  			goto next;

  		if (key.objectid >= root->highest_objectid)

  			break;
  
  		if (last != (u64)-1 && last + 1 != key.objectid) {
  			__btrfs_add_free_space(ctl, last + 1,
  					       key.objectid - last - 1);
  			wake_up(&root->cache_wait);
  		}
  
  		last = key.objectid;
  next:
  		path->slots[0]++;
  	}

  	if (last < root->highest_objectid - 1) {

  		__btrfs_add_free_space(ctl, last + 1,

  				       root->highest_objectid - last - 1);

  	}
  
  	spin_lock(&root->cache_lock);
  	root->cached = BTRFS_CACHE_FINISHED;
  	spin_unlock(&root->cache_lock);
  
  	root->cache_progress = (u64)-1;
  	btrfs_unpin_free_ino(root);
  out:
  	wake_up(&root->cache_wait);
  	mutex_unlock(&root->fs_commit_mutex);
  
  	btrfs_free_path(path);
  
  	return ret;
  }
  
  static void start_caching(struct btrfs_root *root)
  {

  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;

  	struct task_struct *tsk;

  	int ret;

  	u64 objectid;

  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return;

  	spin_lock(&root->cache_lock);
  	if (root->cached != BTRFS_CACHE_NO) {
  		spin_unlock(&root->cache_lock);
  		return;
  	}
  
  	root->cached = BTRFS_CACHE_STARTED;
  	spin_unlock(&root->cache_lock);

  	ret = load_free_ino_cache(root->fs_info, root);
  	if (ret == 1) {
  		spin_lock(&root->cache_lock);
  		root->cached = BTRFS_CACHE_FINISHED;
  		spin_unlock(&root->cache_lock);
  		return;
  	}

  	/*
  	 * It can be quite time-consuming to fill the cache by searching
  	 * through the extent tree, and this can keep ino allocation path
  	 * waiting. Therefore at start we quickly find out the highest
  	 * inode number and we know we can use inode numbers which fall in
  	 * [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID].
  	 */
  	ret = btrfs_find_free_objectid(root, &objectid);
  	if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
  		__btrfs_add_free_space(ctl, objectid,
  				       BTRFS_LAST_FREE_OBJECTID - objectid + 1);
  	}

  	tsk = kthread_run(caching_kthread, root, "btrfs-ino-cache-%llu
  ",
  			  root->root_key.objectid);
  	BUG_ON(IS_ERR(tsk));
  }
  
  int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid)
  {

  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return btrfs_find_free_objectid(root, objectid);

  again:
  	*objectid = btrfs_find_ino_for_alloc(root);
  
  	if (*objectid != 0)
  		return 0;
  
  	start_caching(root);
  
  	wait_event(root->cache_wait,
  		   root->cached == BTRFS_CACHE_FINISHED ||
  		   root->free_ino_ctl->free_space > 0);
  
  	if (root->cached == BTRFS_CACHE_FINISHED &&
  	    root->free_ino_ctl->free_space == 0)
  		return -ENOSPC;
  	else
  		goto again;
  }
  
  void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
  {
  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
  	struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;

  
  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return;

  again:
  	if (root->cached == BTRFS_CACHE_FINISHED) {
  		__btrfs_add_free_space(ctl, objectid, 1);
  	} else {
  		/*
  		 * If we are in the process of caching free ino chunks,
  		 * to avoid adding the same inode number to the free_ino
  		 * tree twice due to cross transaction, we'll leave it
  		 * in the pinned tree until a transaction is committed
  		 * or the caching work is done.
  		 */
  
  		mutex_lock(&root->fs_commit_mutex);
  		spin_lock(&root->cache_lock);
  		if (root->cached == BTRFS_CACHE_FINISHED) {
  			spin_unlock(&root->cache_lock);
  			mutex_unlock(&root->fs_commit_mutex);
  			goto again;
  		}
  		spin_unlock(&root->cache_lock);
  
  		start_caching(root);

  		if (objectid <= root->cache_progress ||
  		    objectid > root->highest_objectid)

  			__btrfs_add_free_space(ctl, objectid, 1);
  		else
  			__btrfs_add_free_space(pinned, objectid, 1);
  
  		mutex_unlock(&root->fs_commit_mutex);
  	}
  }
  
  /*
   * When a transaction is committed, we'll move those inode numbers which
   * are smaller than root->cache_progress from pinned tree to free_ino tree,
   * and others will just be dropped, because the commit root we were
   * searching has changed.
   *
   * Must be called with root->fs_commit_mutex held
   */
  void btrfs_unpin_free_ino(struct btrfs_root *root)
  {
  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
  	struct rb_root *rbroot = &root->free_ino_pinned->free_space_offset;
  	struct btrfs_free_space *info;
  	struct rb_node *n;
  	u64 count;

  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return;

  	while (1) {
  		n = rb_first(rbroot);
  		if (!n)
  			break;
  
  		info = rb_entry(n, struct btrfs_free_space, offset_index);
  		BUG_ON(info->bitmap);
  
  		if (info->offset > root->cache_progress)
  			goto free;
  		else if (info->offset + info->bytes > root->cache_progress)
  			count = root->cache_progress - info->offset + 1;
  		else
  			count = info->bytes;
  
  		__btrfs_add_free_space(ctl, info->offset, count);
  free:
  		rb_erase(&info->offset_index, rbroot);
  		kfree(info);
  	}
  }
  
  #define INIT_THRESHOLD	(((1024 * 32) / 2) / sizeof(struct btrfs_free_space))
  #define INODES_PER_BITMAP (PAGE_CACHE_SIZE * 8)
  
  /*
   * The goal is to keep the memory used by the free_ino tree won't
   * exceed the memory if we use bitmaps only.
   */
  static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
  {
  	struct btrfs_free_space *info;
  	struct rb_node *n;
  	int max_ino;
  	int max_bitmaps;
  
  	n = rb_last(&ctl->free_space_offset);
  	if (!n) {
  		ctl->extents_thresh = INIT_THRESHOLD;
  		return;
  	}
  	info = rb_entry(n, struct btrfs_free_space, offset_index);
  
  	/*
  	 * Find the maximum inode number in the filesystem. Note we
  	 * ignore the fact that this can be a bitmap, because we are
  	 * not doing precise calculation.
  	 */
  	max_ino = info->bytes - 1;
  
  	max_bitmaps = ALIGN(max_ino, INODES_PER_BITMAP) / INODES_PER_BITMAP;
  	if (max_bitmaps <= ctl->total_bitmaps) {
  		ctl->extents_thresh = 0;
  		return;
  	}
  
  	ctl->extents_thresh = (max_bitmaps - ctl->total_bitmaps) *
  				PAGE_CACHE_SIZE / sizeof(*info);
  }
  
  /*
   * We don't fall back to bitmap, if we are below the extents threshold
   * or this chunk of inode numbers is a big one.
   */
  static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
  		       struct btrfs_free_space *info)
  {
  	if (ctl->free_extents < ctl->extents_thresh ||
  	    info->bytes > INODES_PER_BITMAP / 10)
  		return false;
  
  	return true;
  }
  
  static struct btrfs_free_space_op free_ino_op = {
  	.recalc_thresholds	= recalculate_thresholds,
  	.use_bitmap		= use_bitmap,
  };
  
  static void pinned_recalc_thresholds(struct btrfs_free_space_ctl *ctl)
  {
  }
  
  static bool pinned_use_bitmap(struct btrfs_free_space_ctl *ctl,
  			      struct btrfs_free_space *info)
  {
  	/*
  	 * We always use extents for two reasons:
  	 *
  	 * - The pinned tree is only used during the process of caching
  	 *   work.
  	 * - Make code simpler. See btrfs_unpin_free_ino().
  	 */
  	return false;
  }
  
  static struct btrfs_free_space_op pinned_free_ino_op = {
  	.recalc_thresholds	= pinned_recalc_thresholds,
  	.use_bitmap		= pinned_use_bitmap,
  };
  
  void btrfs_init_free_ino_ctl(struct btrfs_root *root)
  {
  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
  	struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
  
  	spin_lock_init(&ctl->tree_lock);
  	ctl->unit = 1;
  	ctl->start = 0;
  	ctl->private = NULL;
  	ctl->op = &free_ino_op;
  
  	/*
  	 * Initially we allow to use 16K of ram to cache chunks of
  	 * inode numbers before we resort to bitmaps. This is somewhat
  	 * arbitrary, but it will be adjusted in runtime.
  	 */
  	ctl->extents_thresh = INIT_THRESHOLD;
  
  	spin_lock_init(&pinned->tree_lock);
  	pinned->unit = 1;
  	pinned->start = 0;
  	pinned->private = NULL;
  	pinned->extents_thresh = 0;
  	pinned->op = &pinned_free_ino_op;
  }

  int btrfs_save_ino_cache(struct btrfs_root *root,
  			 struct btrfs_trans_handle *trans)
  {
  	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
  	struct btrfs_path *path;
  	struct inode *inode;

  	struct btrfs_block_rsv *rsv;
  	u64 num_bytes;

  	u64 alloc_hint = 0;
  	int ret;
  	int prealloc;
  	bool retry = false;

  	/* only fs tree and subvol/snap needs ino cache */
  	if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID &&
  	    (root->root_key.objectid < BTRFS_FIRST_FREE_OBJECTID ||
  	     root->root_key.objectid > BTRFS_LAST_FREE_OBJECTID))
  		return 0;

  	/* Don't save inode cache if we are deleting this root */
  	if (btrfs_root_refs(&root->root_item) == 0 &&
  	    root != root->fs_info->tree_root)
  		return 0;

  	if (!btrfs_test_opt(root, INODE_MAP_CACHE))
  		return 0;

  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;

  	rsv = trans->block_rsv;
  	trans->block_rsv = &root->fs_info->trans_block_rsv;
  
  	num_bytes = trans->bytes_reserved;
  	/*
  	 * 1 item for inode item insertion if need
  	 * 3 items for inode item update (in the worst case)
  	 * 1 item for free space object
  	 * 3 items for pre-allocation
  	 */
  	trans->bytes_reserved = btrfs_calc_trans_metadata_size(root, 8);
  	ret = btrfs_block_rsv_add_noflush(root, trans->block_rsv,
  					  trans->bytes_reserved);
  	if (ret)
  		goto out;

  again:
  	inode = lookup_free_ino_inode(root, path);
  	if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
  		ret = PTR_ERR(inode);

  		goto out_release;

  	}
  
  	if (IS_ERR(inode)) {
  		BUG_ON(retry);
  		retry = true;
  
  		ret = create_free_ino_inode(root, trans, path);
  		if (ret)

  			goto out_release;

  		goto again;
  	}
  
  	BTRFS_I(inode)->generation = 0;
  	ret = btrfs_update_inode(trans, root, inode);
  	WARN_ON(ret);
  
  	if (i_size_read(inode) > 0) {
  		ret = btrfs_truncate_free_space_cache(root, trans, path, inode);
  		if (ret)
  			goto out_put;
  	}
  
  	spin_lock(&root->cache_lock);
  	if (root->cached != BTRFS_CACHE_FINISHED) {
  		ret = -1;
  		spin_unlock(&root->cache_lock);
  		goto out_put;
  	}
  	spin_unlock(&root->cache_lock);
  
  	spin_lock(&ctl->tree_lock);
  	prealloc = sizeof(struct btrfs_free_space) * ctl->free_extents;
  	prealloc = ALIGN(prealloc, PAGE_CACHE_SIZE);
  	prealloc += ctl->total_bitmaps * PAGE_CACHE_SIZE;
  	spin_unlock(&ctl->tree_lock);
  
  	/* Just to make sure we have enough space */
  	prealloc += 8 * PAGE_CACHE_SIZE;

  	ret = btrfs_delalloc_reserve_space(inode, prealloc);

  	if (ret)
  		goto out_put;
  
  	ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc,
  					      prealloc, prealloc, &alloc_hint);

  	if (ret) {
  		btrfs_delalloc_release_space(inode, prealloc);

  		goto out_put;

  	}

  	btrfs_free_reserved_data_space(inode, prealloc);

  	ret = btrfs_write_out_ino_cache(root, trans, path);

  out_put:
  	iput(inode);

  out_release:
  	btrfs_block_rsv_release(root, trans->block_rsv, trans->bytes_reserved);

  out:

  	trans->block_rsv = rsv;
  	trans->bytes_reserved = num_bytes;

  
  	btrfs_free_path(path);
  	return ret;
  }

  static int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid)

  {
  	struct btrfs_path *path;
  	int ret;

  	struct extent_buffer *l;

  	struct btrfs_key search_key;

  	struct btrfs_key found_key;

  	int slot;
  
  	path = btrfs_alloc_path();

  	if (!path)
  		return -ENOMEM;

  	search_key.objectid = BTRFS_LAST_FREE_OBJECTID;
  	search_key.type = -1;

  	search_key.offset = (u64)-1;
  	ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
  	if (ret < 0)
  		goto error;
  	BUG_ON(ret == 0);
  	if (path->slots[0] > 0) {
  		slot = path->slots[0] - 1;

  		l = path->nodes[0];
  		btrfs_item_key_to_cpu(l, &found_key, slot);

  		*objectid = max_t(u64, found_key.objectid,
  				  BTRFS_FIRST_FREE_OBJECTID - 1);

  	} else {

  		*objectid = BTRFS_FIRST_FREE_OBJECTID - 1;

  	}
  	ret = 0;
  error:
  	btrfs_free_path(path);
  	return ret;
  }

  int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid)

  {

  	int ret;

  	mutex_lock(&root->objectid_mutex);

  	if (unlikely(root->highest_objectid < BTRFS_FIRST_FREE_OBJECTID)) {

  		ret = btrfs_find_highest_objectid(root,
  						  &root->highest_objectid);

  		if (ret)
  			goto out;
  	}

  	if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
  		ret = -ENOSPC;
  		goto out;

  	}

  
  	*objectid = ++root->highest_objectid;
  	ret = 0;
  out:

  	mutex_unlock(&root->objectid_mutex);

  	return ret;
  }