/*
   * Copyright (C) 2011 Red Hat, Inc.
   *
   * This file is released under the GPL.
   */
  
  #include "dm-btree-internal.h"
  #include "dm-transaction-manager.h"
  
  #include <linux/device-mapper.h>
  
  #define DM_MSG_PREFIX "btree spine"
  
  /*----------------------------------------------------------------*/
  
  #define BTREE_CSUM_XOR 121107
  
  static int node_check(struct dm_block_validator *v,
  		      struct dm_block *b,
  		      size_t block_size);
  
  static void node_prepare_for_write(struct dm_block_validator *v,
  				   struct dm_block *b,
  				   size_t block_size)
  {
  	struct btree_node *n = dm_block_data(b);
  	struct node_header *h = &n->header;
  
  	h->blocknr = cpu_to_le64(dm_block_location(b));
  	h->csum = cpu_to_le32(dm_bm_checksum(&h->flags,
  					     block_size - sizeof(__le32),
  					     BTREE_CSUM_XOR));
  
  	BUG_ON(node_check(v, b, 4096));
  }
  
  static int node_check(struct dm_block_validator *v,
  		      struct dm_block *b,
  		      size_t block_size)
  {
  	struct btree_node *n = dm_block_data(b);
  	struct node_header *h = &n->header;
  	size_t value_size;
  	__le32 csum_disk;
  	uint32_t flags;
  
  	if (dm_block_location(b) != le64_to_cpu(h->blocknr)) {
  		DMERR_LIMIT("node_check failed: blocknr %llu != wanted %llu",
  			    le64_to_cpu(h->blocknr), dm_block_location(b));
  		return -ENOTBLK;
  	}
  
  	csum_disk = cpu_to_le32(dm_bm_checksum(&h->flags,
  					       block_size - sizeof(__le32),
  					       BTREE_CSUM_XOR));
  	if (csum_disk != h->csum) {
  		DMERR_LIMIT("node_check failed: csum %u != wanted %u",
  			    le32_to_cpu(csum_disk), le32_to_cpu(h->csum));
  		return -EILSEQ;
  	}
  
  	value_size = le32_to_cpu(h->value_size);
  
  	if (sizeof(struct node_header) +
  	    (sizeof(__le64) + value_size) * le32_to_cpu(h->max_entries) > block_size) {
  		DMERR_LIMIT("node_check failed: max_entries too large");
  		return -EILSEQ;
  	}
  
  	if (le32_to_cpu(h->nr_entries) > le32_to_cpu(h->max_entries)) {
  		DMERR_LIMIT("node_check failed: too many entries");
  		return -EILSEQ;
  	}
  
  	/*
  	 * The node must be either INTERNAL or LEAF.
  	 */
  	flags = le32_to_cpu(h->flags);
  	if (!(flags & INTERNAL_NODE) && !(flags & LEAF_NODE)) {
  		DMERR_LIMIT("node_check failed: node is neither INTERNAL or LEAF");
  		return -EILSEQ;
  	}
  
  	return 0;
  }
  
  struct dm_block_validator btree_node_validator = {
  	.name = "btree_node",
  	.prepare_for_write = node_prepare_for_write,
  	.check = node_check
  };
  
  /*----------------------------------------------------------------*/
  
  int bn_read_lock(struct dm_btree_info *info, dm_block_t b,
  		 struct dm_block **result)
  {
  	return dm_tm_read_lock(info->tm, b, &btree_node_validator, result);
  }
  
  static int bn_shadow(struct dm_btree_info *info, dm_block_t orig,
  	      struct dm_btree_value_type *vt,
  	      struct dm_block **result)
  {
  	int r, inc;
  
  	r = dm_tm_shadow_block(info->tm, orig, &btree_node_validator,
  			       result, &inc);
  	if (!r && inc)
  		inc_children(info->tm, dm_block_data(*result), vt);
  
  	return r;
  }
  
  int new_block(struct dm_btree_info *info, struct dm_block **result)
  {
  	return dm_tm_new_block(info->tm, &btree_node_validator, result);
  }
  
  int unlock_block(struct dm_btree_info *info, struct dm_block *b)
  {
  	return dm_tm_unlock(info->tm, b);
  }
  
  /*----------------------------------------------------------------*/
  
  void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info)
  {
  	s->info = info;
  	s->count = 0;
  	s->nodes[0] = NULL;
  	s->nodes[1] = NULL;
  }
  
  int exit_ro_spine(struct ro_spine *s)
  {
  	int r = 0, i;
  
  	for (i = 0; i < s->count; i++) {
  		int r2 = unlock_block(s->info, s->nodes[i]);
  		if (r2 < 0)
  			r = r2;
  	}
  
  	return r;
  }
  
  int ro_step(struct ro_spine *s, dm_block_t new_child)
  {
  	int r;
  
  	if (s->count == 2) {
  		r = unlock_block(s->info, s->nodes[0]);
  		if (r < 0)
  			return r;
  		s->nodes[0] = s->nodes[1];
  		s->count--;
  	}
  
  	r = bn_read_lock(s->info, new_child, s->nodes + s->count);
  	if (!r)
  		s->count++;
  
  	return r;
  }
  
  void ro_pop(struct ro_spine *s)
  {
  	BUG_ON(!s->count);
  	--s->count;
  	unlock_block(s->info, s->nodes[s->count]);
  }
  
  struct btree_node *ro_node(struct ro_spine *s)
  {
  	struct dm_block *block;
  
  	BUG_ON(!s->count);
  	block = s->nodes[s->count - 1];
  
  	return dm_block_data(block);
  }
  
  /*----------------------------------------------------------------*/
  
  void init_shadow_spine(struct shadow_spine *s, struct dm_btree_info *info)
  {
  	s->info = info;
  	s->count = 0;
  }
  
  int exit_shadow_spine(struct shadow_spine *s)
  {
  	int r = 0, i;
  
  	for (i = 0; i < s->count; i++) {
  		int r2 = unlock_block(s->info, s->nodes[i]);
  		if (r2 < 0)
  			r = r2;
  	}
  
  	return r;
  }
  
  int shadow_step(struct shadow_spine *s, dm_block_t b,
  		struct dm_btree_value_type *vt)
  {
  	int r;
  
  	if (s->count == 2) {
  		r = unlock_block(s->info, s->nodes[0]);
  		if (r < 0)
  			return r;
  		s->nodes[0] = s->nodes[1];
  		s->count--;
  	}
  
  	r = bn_shadow(s->info, b, vt, s->nodes + s->count);
  	if (!r) {
  		if (!s->count)
  			s->root = dm_block_location(s->nodes[0]);
  
  		s->count++;
  	}
  
  	return r;
  }
  
  struct dm_block *shadow_current(struct shadow_spine *s)
  {
  	BUG_ON(!s->count);
  
  	return s->nodes[s->count - 1];
  }
  
  struct dm_block *shadow_parent(struct shadow_spine *s)
  {
  	BUG_ON(s->count != 2);
  
  	return s->count == 2 ? s->nodes[0] : NULL;
  }
  
  int shadow_has_parent(struct shadow_spine *s)
  {
  	return s->count >= 2;
  }
  
  int shadow_root(struct shadow_spine *s)
  {
  	return s->root;
  }