#include <linux/err.h>

  #include <linux/slab.h>

  #include <linux/module.h>
  #include <linux/spinlock.h>

  #include <linux/hardirq.h>

  #include "ctree.h"

  #include "extent_map.h"

  static struct kmem_cache *extent_map_cache;

  int __init extent_map_init(void)

  {

  	extent_map_cache = kmem_cache_create("extent_map",
  			sizeof(struct extent_map), 0,
  			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);

  	if (!extent_map_cache)
  		return -ENOMEM;

  	return 0;

  }

  void extent_map_exit(void)

  {

  	if (extent_map_cache)
  		kmem_cache_destroy(extent_map_cache);

  }

  /**
   * extent_map_tree_init - initialize extent map tree
   * @tree:		tree to initialize

   *
   * Initialize the extent tree @tree.  Should be called for each new inode
   * or other user of the extent_map interface.
   */

  void extent_map_tree_init(struct extent_map_tree *tree)

  {

  	tree->map = RB_ROOT;

  	rwlock_init(&tree->lock);

  }

  /**
   * alloc_extent_map - allocate new extent map structure

   *
   * Allocate a new extent_map structure.  The new structure is
   * returned with a reference count of one and needs to be
   * freed using free_extent_map()
   */

  struct extent_map *alloc_extent_map(void)

  {
  	struct extent_map *em;

  	em = kmem_cache_alloc(extent_map_cache, GFP_NOFS);

  	if (!em)
  		return NULL;

  	em->in_tree = 0;

  	em->flags = 0;

  	em->compress_type = BTRFS_COMPRESS_NONE;

  	atomic_set(&em->refs, 1);
  	return em;
  }

  /**
   * free_extent_map - drop reference count of an extent_map
   * @em:		extent map beeing releasead
   *
   * Drops the reference out on @em by one and free the structure
   * if the reference count hits zero.
   */

  void free_extent_map(struct extent_map *em)
  {

  	if (!em)
  		return;

  	WARN_ON(atomic_read(&em->refs) == 0);

  	if (atomic_dec_and_test(&em->refs)) {
  		WARN_ON(em->in_tree);
  		kmem_cache_free(extent_map_cache, em);
  	}
  }

  static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  				   struct rb_node *node)
  {

  	struct rb_node **p = &root->rb_node;
  	struct rb_node *parent = NULL;

  	struct extent_map *entry;

  	while (*p) {

  		parent = *p;

  		entry = rb_entry(parent, struct extent_map, rb_node);
  
  		WARN_ON(!entry->in_tree);

  
  		if (offset < entry->start)
  			p = &(*p)->rb_left;

  		else if (offset >= extent_map_end(entry))

  			p = &(*p)->rb_right;
  		else
  			return parent;
  	}

  	entry = rb_entry(node, struct extent_map, rb_node);

  	entry->in_tree = 1;
  	rb_link_node(node, parent, p);
  	rb_insert_color(node, root);
  	return NULL;
  }

  /*
   * search through the tree for an extent_map with a given offset.  If
   * it can't be found, try to find some neighboring extents
   */

  static struct rb_node *__tree_search(struct rb_root *root, u64 offset,

  				     struct rb_node **prev_ret,
  				     struct rb_node **next_ret)

  {

  	struct rb_node *n = root->rb_node;

  	struct rb_node *prev = NULL;

  	struct rb_node *orig_prev = NULL;

  	struct extent_map *entry;
  	struct extent_map *prev_entry = NULL;

  	while (n) {

  		entry = rb_entry(n, struct extent_map, rb_node);

  		prev = n;
  		prev_entry = entry;

  		WARN_ON(!entry->in_tree);

  		if (offset < entry->start)
  			n = n->rb_left;

  		else if (offset >= extent_map_end(entry))

  			n = n->rb_right;
  		else
  			return n;
  	}

  
  	if (prev_ret) {
  		orig_prev = prev;

  		while (prev && offset >= extent_map_end(prev_entry)) {

  			prev = rb_next(prev);

  			prev_entry = rb_entry(prev, struct extent_map, rb_node);

  		}
  		*prev_ret = prev;
  		prev = orig_prev;
  	}
  
  	if (next_ret) {

  		prev_entry = rb_entry(prev, struct extent_map, rb_node);

  		while (prev && offset < prev_entry->start) {

  			prev = rb_prev(prev);

  			prev_entry = rb_entry(prev, struct extent_map, rb_node);

  		}
  		*next_ret = prev;

  	}

  	return NULL;
  }

  /* check to see if two extent_map structs are adjacent and safe to merge */

  static int mergable_maps(struct extent_map *prev, struct extent_map *next)

  {

  	if (test_bit(EXTENT_FLAG_PINNED, &prev->flags))
  		return 0;

  	/*
  	 * don't merge compressed extents, we need to know their
  	 * actual size
  	 */
  	if (test_bit(EXTENT_FLAG_COMPRESSED, &prev->flags))
  		return 0;

  	if (extent_map_end(prev) == next->start &&
  	    prev->flags == next->flags &&
  	    prev->bdev == next->bdev &&
  	    ((next->block_start == EXTENT_MAP_HOLE &&
  	      prev->block_start == EXTENT_MAP_HOLE) ||
  	     (next->block_start == EXTENT_MAP_INLINE &&
  	      prev->block_start == EXTENT_MAP_INLINE) ||
  	     (next->block_start == EXTENT_MAP_DELALLOC &&
  	      prev->block_start == EXTENT_MAP_DELALLOC) ||
  	     (next->block_start < EXTENT_MAP_LAST_BYTE - 1 &&
  	      next->block_start == extent_map_block_end(prev)))) {
  		return 1;
  	}

  	return 0;
  }

  static void try_merge_map(struct extent_map_tree *tree, struct extent_map *em)

  {

  	struct extent_map *merge = NULL;
  	struct rb_node *rb;

  
  	if (em->start != 0) {
  		rb = rb_prev(&em->rb_node);
  		if (rb)
  			merge = rb_entry(rb, struct extent_map, rb_node);
  		if (rb && mergable_maps(merge, em)) {
  			em->start = merge->start;
  			em->len += merge->len;
  			em->block_len += merge->block_len;
  			em->block_start = merge->block_start;
  			merge->in_tree = 0;
  			rb_erase(&merge->rb_node, &tree->map);
  			free_extent_map(merge);
  		}
  	}
  
  	rb = rb_next(&em->rb_node);
  	if (rb)
  		merge = rb_entry(rb, struct extent_map, rb_node);
  	if (rb && mergable_maps(em, merge)) {
  		em->len += merge->len;
  		em->block_len += merge->len;
  		rb_erase(&merge->rb_node, &tree->map);
  		merge->in_tree = 0;
  		free_extent_map(merge);
  	}

  }
  
  int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
  {
  	int ret = 0;
  	struct extent_map *em;
  
  	write_lock(&tree->lock);
  	em = lookup_extent_mapping(tree, start, len);
  
  	WARN_ON(!em || em->start != start);
  
  	if (!em)
  		goto out;
  
  	clear_bit(EXTENT_FLAG_PINNED, &em->flags);
  
  	try_merge_map(tree, em);

  
  	free_extent_map(em);
  out:
  	write_unlock(&tree->lock);
  	return ret;
  
  }

  /**
   * add_extent_mapping - add new extent map to the extent tree
   * @tree:	tree to insert new map in
   * @em:		map to insert
   *
   * Insert @em into @tree or perform a simple forward/backward merge with
   * existing mappings.  The extent_map struct passed in will be inserted
   * into the tree directly, with an additional reference taken, or a

   * reference dropped if the merge attempt was successful.

   */
  int add_extent_mapping(struct extent_map_tree *tree,
  		       struct extent_map *em)
  {
  	int ret = 0;

  	struct rb_node *rb;

  	struct extent_map *exist;

  	exist = lookup_extent_mapping(tree, em->start, em->len);
  	if (exist) {
  		free_extent_map(exist);
  		ret = -EEXIST;
  		goto out;
  	}

  	rb = tree_insert(&tree->map, em->start, &em->rb_node);

  	if (rb) {

  		ret = -EEXIST;
  		goto out;
  	}
  	atomic_inc(&em->refs);

  
  	try_merge_map(tree, em);

  out:

  	return ret;
  }

  /* simple helper to do math around the end of an extent, handling wrap */

  static u64 range_end(u64 start, u64 len)
  {
  	if (start + len < start)
  		return (u64)-1;
  	return start + len;
  }

  struct extent_map *__lookup_extent_mapping(struct extent_map_tree *tree,
  					   u64 start, u64 len, int strict)

  {
  	struct extent_map *em;
  	struct rb_node *rb_node;

  	struct rb_node *prev = NULL;
  	struct rb_node *next = NULL;
  	u64 end = range_end(start, len);

  	rb_node = __tree_search(&tree->map, start, &prev, &next);

  	if (!rb_node) {

  		if (prev)
  			rb_node = prev;
  		else if (next)
  			rb_node = next;
  		else
  			return NULL;

  	}

  	em = rb_entry(rb_node, struct extent_map, rb_node);

  	if (strict && !(end > em->start && start < extent_map_end(em)))
  		return NULL;

  	atomic_inc(&em->refs);

  	return em;
  }

  /**

   * lookup_extent_mapping - lookup extent_map
   * @tree:	tree to lookup in
   * @start:	byte offset to start the search
   * @len:	length of the lookup range
   *
   * Find and return the first extent_map struct in @tree that intersects the
   * [start, len] range.  There may be additional objects in the tree that
   * intersect, so check the object returned carefully to make sure that no
   * additional lookups are needed.
   */
  struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
  					 u64 start, u64 len)
  {
  	return __lookup_extent_mapping(tree, start, len, 1);
  }
  
  /**

   * search_extent_mapping - find a nearby extent map
   * @tree:	tree to lookup in
   * @start:	byte offset to start the search
   * @len:	length of the lookup range
   *
   * Find and return the first extent_map struct in @tree that intersects the
   * [start, len] range.
   *
   * If one can't be found, any nearby extent may be returned
   */
  struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
  					 u64 start, u64 len)
  {

  	return __lookup_extent_mapping(tree, start, len, 0);

  }
  
  /**

   * remove_extent_mapping - removes an extent_map from the extent tree
   * @tree:	extent tree to remove from
   * @em:		extent map beeing removed
   *
   * Removes @em from @tree.  No reference counts are dropped, and no checks
   * are done to see if the range is in use

   */
  int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
  {

  	int ret = 0;

  	WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags));

  	rb_erase(&em->rb_node, &tree->map);
  	em->in_tree = 0;

  	return ret;
  }