/*
   *  linux/fs/hfs/extent.c
   *
   * Copyright (C) 1995-1997  Paul H. Hargrove
   * (C) 2003 Ardis Technologies <roman@ardistech.com>
   * This file may be distributed under the terms of the GNU General Public License.
   *
   * This file contains the functions related to the extents B-tree.
   */
  
  #include <linux/pagemap.h>
  
  #include "hfs_fs.h"
  #include "btree.h"
  
  /*================ File-local functions ================*/
  
  /*
   * build_key
   */
  static void hfs_ext_build_key(hfs_btree_key *key, u32 cnid, u16 block, u8 type)
  {
  	key->key_len = 7;
  	key->ext.FkType = type;
  	key->ext.FNum = cpu_to_be32(cnid);
  	key->ext.FABN = cpu_to_be16(block);
  }
  
  /*
   * hfs_ext_compare()
   *
   * Description:
   *   This is the comparison function used for the extents B-tree.  In
   *   comparing extent B-tree entries, the file id is the most
   *   significant field (compared as unsigned ints); the fork type is
   *   the second most significant field (compared as unsigned chars);
   *   and the allocation block number field is the least significant
   *   (compared as unsigned ints).
   * Input Variable(s):
   *   struct hfs_ext_key *key1: pointer to the first key to compare
   *   struct hfs_ext_key *key2: pointer to the second key to compare
   * Output Variable(s):
   *   NONE
   * Returns:
   *   int: negative if key1<key2, positive if key1>key2, and 0 if key1==key2
   * Preconditions:
   *   key1 and key2 point to "valid" (struct hfs_ext_key)s.
   * Postconditions:
   *   This function has no side-effects */
  int hfs_ext_keycmp(const btree_key *key1, const btree_key *key2)
  {
  	__be32 fnum1, fnum2;
  	__be16 block1, block2;
  
  	fnum1 = key1->ext.FNum;
  	fnum2 = key2->ext.FNum;
  	if (fnum1 != fnum2)
  		return be32_to_cpu(fnum1) < be32_to_cpu(fnum2) ? -1 : 1;
  	if (key1->ext.FkType != key2->ext.FkType)
  		return key1->ext.FkType < key2->ext.FkType ? -1 : 1;
  
  	block1 = key1->ext.FABN;
  	block2 = key2->ext.FABN;
  	if (block1 == block2)
  		return 0;
  	return be16_to_cpu(block1) < be16_to_cpu(block2) ? -1 : 1;
  }
  
  /*
   * hfs_ext_find_block
   *
   * Find a block within an extent record
   */
  static u16 hfs_ext_find_block(struct hfs_extent *ext, u16 off)
  {
  	int i;
  	u16 count;
  
  	for (i = 0; i < 3; ext++, i++) {
  		count = be16_to_cpu(ext->count);
  		if (off < count)
  			return be16_to_cpu(ext->block) + off;
  		off -= count;
  	}
  	/* panic? */
  	return 0;
  }
  
  static int hfs_ext_block_count(struct hfs_extent *ext)
  {
  	int i;
  	u16 count = 0;
  
  	for (i = 0; i < 3; ext++, i++)
  		count += be16_to_cpu(ext->count);
  	return count;
  }
  
  static u16 hfs_ext_lastblock(struct hfs_extent *ext)
  {
  	int i;
  
  	ext += 2;
  	for (i = 0; i < 2; ext--, i++)
  		if (ext->count)
  			break;
  	return be16_to_cpu(ext->block) + be16_to_cpu(ext->count);
  }
  
  static int __hfs_ext_write_extent(struct inode *inode, struct hfs_find_data *fd)
  {
  	int res;
  
  	hfs_ext_build_key(fd->search_key, inode->i_ino, HFS_I(inode)->cached_start,
  			  HFS_IS_RSRC(inode) ?  HFS_FK_RSRC : HFS_FK_DATA);
  	res = hfs_brec_find(fd);
  	if (HFS_I(inode)->flags & HFS_FLG_EXT_NEW) {
  		if (res != -ENOENT)
  			return res;
  		hfs_brec_insert(fd, HFS_I(inode)->cached_extents, sizeof(hfs_extent_rec));
  		HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
  	} else {
  		if (res)
  			return res;
  		hfs_bnode_write(fd->bnode, HFS_I(inode)->cached_extents, fd->entryoffset, fd->entrylength);
  		HFS_I(inode)->flags &= ~HFS_FLG_EXT_DIRTY;
  	}
  	return 0;
  }
  
  int hfs_ext_write_extent(struct inode *inode)
  {
  	struct hfs_find_data fd;
  	int res = 0;
  
  	if (HFS_I(inode)->flags & HFS_FLG_EXT_DIRTY) {
  		res = hfs_find_init(HFS_SB(inode->i_sb)->ext_tree, &fd);
  		if (res)
  			return res;
  		res = __hfs_ext_write_extent(inode, &fd);
  		hfs_find_exit(&fd);
  	}
  	return res;
  }
  
  static inline int __hfs_ext_read_extent(struct hfs_find_data *fd, struct hfs_extent *extent,
  					u32 cnid, u32 block, u8 type)
  {
  	int res;
  
  	hfs_ext_build_key(fd->search_key, cnid, block, type);
  	fd->key->ext.FNum = 0;
  	res = hfs_brec_find(fd);
  	if (res && res != -ENOENT)
  		return res;
  	if (fd->key->ext.FNum != fd->search_key->ext.FNum ||
  	    fd->key->ext.FkType != fd->search_key->ext.FkType)
  		return -ENOENT;
  	if (fd->entrylength != sizeof(hfs_extent_rec))
  		return -EIO;
  	hfs_bnode_read(fd->bnode, extent, fd->entryoffset, sizeof(hfs_extent_rec));
  	return 0;
  }
  
  static inline int __hfs_ext_cache_extent(struct hfs_find_data *fd, struct inode *inode, u32 block)
  {
  	int res;
  
  	if (HFS_I(inode)->flags & HFS_FLG_EXT_DIRTY) {
  		res = __hfs_ext_write_extent(inode, fd);
  		if (res)
  			return res;
  	}
  
  	res = __hfs_ext_read_extent(fd, HFS_I(inode)->cached_extents, inode->i_ino,
  				    block, HFS_IS_RSRC(inode) ? HFS_FK_RSRC : HFS_FK_DATA);
  	if (!res) {
  		HFS_I(inode)->cached_start = be16_to_cpu(fd->key->ext.FABN);
  		HFS_I(inode)->cached_blocks = hfs_ext_block_count(HFS_I(inode)->cached_extents);
  	} else {
  		HFS_I(inode)->cached_start = HFS_I(inode)->cached_blocks = 0;
  		HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
  	}
  	return res;
  }
  
  static int hfs_ext_read_extent(struct inode *inode, u16 block)
  {
  	struct hfs_find_data fd;
  	int res;
  
  	if (block >= HFS_I(inode)->cached_start &&
  	    block < HFS_I(inode)->cached_start + HFS_I(inode)->cached_blocks)
  		return 0;
  
  	res = hfs_find_init(HFS_SB(inode->i_sb)->ext_tree, &fd);
  	if (!res) {
  		res = __hfs_ext_cache_extent(&fd, inode, block);
  		hfs_find_exit(&fd);
  	}
  	return res;
  }
  
  static void hfs_dump_extent(struct hfs_extent *extent)
  {
  	int i;
  
  	hfs_dbg(EXTENT, "   ");
  	for (i = 0; i < 3; i++)
  		hfs_dbg_cont(EXTENT, " %u:%u",
  			     be16_to_cpu(extent[i].block),
  			     be16_to_cpu(extent[i].count));
  	hfs_dbg_cont(EXTENT, "
  ");
  }
  
  static int hfs_add_extent(struct hfs_extent *extent, u16 offset,
  			  u16 alloc_block, u16 block_count)
  {
  	u16 count, start;
  	int i;
  
  	hfs_dump_extent(extent);
  	for (i = 0; i < 3; extent++, i++) {
  		count = be16_to_cpu(extent->count);
  		if (offset == count) {
  			start = be16_to_cpu(extent->block);
  			if (alloc_block != start + count) {
  				if (++i >= 3)
  					return -ENOSPC;
  				extent++;
  				extent->block = cpu_to_be16(alloc_block);
  			} else
  				block_count += count;
  			extent->count = cpu_to_be16(block_count);
  			return 0;
  		} else if (offset < count)
  			break;
  		offset -= count;
  	}
  	/* panic? */
  	return -EIO;
  }
  
  static int hfs_free_extents(struct super_block *sb, struct hfs_extent *extent,
  			    u16 offset, u16 block_nr)
  {
  	u16 count, start;
  	int i;
  
  	hfs_dump_extent(extent);
  	for (i = 0; i < 3; extent++, i++) {
  		count = be16_to_cpu(extent->count);
  		if (offset == count)
  			goto found;
  		else if (offset < count)
  			break;
  		offset -= count;
  	}
  	/* panic? */
  	return -EIO;
  found:
  	for (;;) {
  		start = be16_to_cpu(extent->block);
  		if (count <= block_nr) {
  			hfs_clear_vbm_bits(sb, start, count);
  			extent->block = 0;
  			extent->count = 0;
  			block_nr -= count;
  		} else {
  			count -= block_nr;
  			hfs_clear_vbm_bits(sb, start + count, block_nr);
  			extent->count = cpu_to_be16(count);
  			block_nr = 0;
  		}
  		if (!block_nr || !i)
  			return 0;
  		i--;
  		extent--;
  		count = be16_to_cpu(extent->count);
  	}
  }
  
  int hfs_free_fork(struct super_block *sb, struct hfs_cat_file *file, int type)
  {
  	struct hfs_find_data fd;
  	u32 total_blocks, blocks, start;
  	u32 cnid = be32_to_cpu(file->FlNum);
  	struct hfs_extent *extent;
  	int res, i;
  
  	if (type == HFS_FK_DATA) {
  		total_blocks = be32_to_cpu(file->PyLen);
  		extent = file->ExtRec;
  	} else {
  		total_blocks = be32_to_cpu(file->RPyLen);
  		extent = file->RExtRec;
  	}
  	total_blocks /= HFS_SB(sb)->alloc_blksz;
  	if (!total_blocks)
  		return 0;
  
  	blocks = 0;
  	for (i = 0; i < 3; extent++, i++)
  		blocks += be16_to_cpu(extent[i].count);
  
  	res = hfs_free_extents(sb, extent, blocks, blocks);
  	if (res)
  		return res;
  	if (total_blocks == blocks)
  		return 0;
  
  	res = hfs_find_init(HFS_SB(sb)->ext_tree, &fd);
  	if (res)
  		return res;
  	do {
  		res = __hfs_ext_read_extent(&fd, extent, cnid, total_blocks, type);
  		if (res)
  			break;
  		start = be16_to_cpu(fd.key->ext.FABN);
  		hfs_free_extents(sb, extent, total_blocks - start, total_blocks);
  		hfs_brec_remove(&fd);
  		total_blocks = start;
  	} while (total_blocks > blocks);
  	hfs_find_exit(&fd);
  
  	return res;
  }
  
  /*
   * hfs_get_block
   */
  int hfs_get_block(struct inode *inode, sector_t block,
  		  struct buffer_head *bh_result, int create)
  {
  	struct super_block *sb;
  	u16 dblock, ablock;
  	int res;
  
  	sb = inode->i_sb;
  	/* Convert inode block to disk allocation block */
  	ablock = (u32)block / HFS_SB(sb)->fs_div;
  
  	if (block >= HFS_I(inode)->fs_blocks) {
  		if (block > HFS_I(inode)->fs_blocks || !create)
  			return -EIO;
  		if (ablock >= HFS_I(inode)->alloc_blocks) {
  			res = hfs_extend_file(inode);
  			if (res)
  				return res;
  		}
  	} else
  		create = 0;
  
  	if (ablock < HFS_I(inode)->first_blocks) {
  		dblock = hfs_ext_find_block(HFS_I(inode)->first_extents, ablock);
  		goto done;
  	}
  
  	mutex_lock(&HFS_I(inode)->extents_lock);
  	res = hfs_ext_read_extent(inode, ablock);
  	if (!res)
  		dblock = hfs_ext_find_block(HFS_I(inode)->cached_extents,
  					    ablock - HFS_I(inode)->cached_start);
  	else {
  		mutex_unlock(&HFS_I(inode)->extents_lock);
  		return -EIO;
  	}
  	mutex_unlock(&HFS_I(inode)->extents_lock);
  
  done:
  	map_bh(bh_result, sb, HFS_SB(sb)->fs_start +
  	       dblock * HFS_SB(sb)->fs_div +
  	       (u32)block % HFS_SB(sb)->fs_div);
  
  	if (create) {
  		set_buffer_new(bh_result);
  		HFS_I(inode)->phys_size += sb->s_blocksize;
  		HFS_I(inode)->fs_blocks++;
  		inode_add_bytes(inode, sb->s_blocksize);
  		mark_inode_dirty(inode);
  	}
  	return 0;
  }
  
  int hfs_extend_file(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  	u32 start, len, goal;
  	int res;
  
  	mutex_lock(&HFS_I(inode)->extents_lock);
  	if (HFS_I(inode)->alloc_blocks == HFS_I(inode)->first_blocks)
  		goal = hfs_ext_lastblock(HFS_I(inode)->first_extents);
  	else {
  		res = hfs_ext_read_extent(inode, HFS_I(inode)->alloc_blocks);
  		if (res)
  			goto out;
  		goal = hfs_ext_lastblock(HFS_I(inode)->cached_extents);
  	}
  
  	len = HFS_I(inode)->clump_blocks;
  	start = hfs_vbm_search_free(sb, goal, &len);
  	if (!len) {
  		res = -ENOSPC;
  		goto out;
  	}
  
  	hfs_dbg(EXTENT, "extend %lu: %u,%u
  ", inode->i_ino, start, len);
  	if (HFS_I(inode)->alloc_blocks == HFS_I(inode)->first_blocks) {
  		if (!HFS_I(inode)->first_blocks) {
  			hfs_dbg(EXTENT, "first extents
  ");
  			/* no extents yet */
  			HFS_I(inode)->first_extents[0].block = cpu_to_be16(start);
  			HFS_I(inode)->first_extents[0].count = cpu_to_be16(len);
  			res = 0;
  		} else {
  			/* try to append to extents in inode */
  			res = hfs_add_extent(HFS_I(inode)->first_extents,
  					     HFS_I(inode)->alloc_blocks,
  					     start, len);
  			if (res == -ENOSPC)
  				goto insert_extent;
  		}
  		if (!res) {
  			hfs_dump_extent(HFS_I(inode)->first_extents);
  			HFS_I(inode)->first_blocks += len;
  		}
  	} else {
  		res = hfs_add_extent(HFS_I(inode)->cached_extents,
  				     HFS_I(inode)->alloc_blocks -
  				     HFS_I(inode)->cached_start,
  				     start, len);
  		if (!res) {
  			hfs_dump_extent(HFS_I(inode)->cached_extents);
  			HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY;
  			HFS_I(inode)->cached_blocks += len;
  		} else if (res == -ENOSPC)
  			goto insert_extent;
  	}
  out:
  	mutex_unlock(&HFS_I(inode)->extents_lock);
  	if (!res) {
  		HFS_I(inode)->alloc_blocks += len;
  		mark_inode_dirty(inode);
  		if (inode->i_ino < HFS_FIRSTUSER_CNID)
  			set_bit(HFS_FLG_ALT_MDB_DIRTY, &HFS_SB(sb)->flags);
  		set_bit(HFS_FLG_MDB_DIRTY, &HFS_SB(sb)->flags);
  		hfs_mark_mdb_dirty(sb);
  	}
  	return res;
  
  insert_extent:
  	hfs_dbg(EXTENT, "insert new extent
  ");
  	res = hfs_ext_write_extent(inode);
  	if (res)
  		goto out;
  
  	memset(HFS_I(inode)->cached_extents, 0, sizeof(hfs_extent_rec));
  	HFS_I(inode)->cached_extents[0].block = cpu_to_be16(start);
  	HFS_I(inode)->cached_extents[0].count = cpu_to_be16(len);
  	hfs_dump_extent(HFS_I(inode)->cached_extents);
  	HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW;
  	HFS_I(inode)->cached_start = HFS_I(inode)->alloc_blocks;
  	HFS_I(inode)->cached_blocks = len;
  
  	res = 0;
  	goto out;
  }
  
  void hfs_file_truncate(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  	struct hfs_find_data fd;
  	u16 blk_cnt, alloc_cnt, start;
  	u32 size;
  	int res;
  
  	hfs_dbg(INODE, "truncate: %lu, %Lu -> %Lu
  ",
  		inode->i_ino, (long long)HFS_I(inode)->phys_size,
  		inode->i_size);
  	if (inode->i_size > HFS_I(inode)->phys_size) {
  		struct address_space *mapping = inode->i_mapping;
  		void *fsdata;
  		struct page *page;
  
  		/* XXX: Can use generic_cont_expand? */
  		size = inode->i_size - 1;
  		res = pagecache_write_begin(NULL, mapping, size+1, 0,
  				AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
  		if (!res) {
  			res = pagecache_write_end(NULL, mapping, size+1, 0, 0,
  					page, fsdata);
  		}
  		if (res)
  			inode->i_size = HFS_I(inode)->phys_size;
  		return;
  	} else if (inode->i_size == HFS_I(inode)->phys_size)
  		return;
  	size = inode->i_size + HFS_SB(sb)->alloc_blksz - 1;
  	blk_cnt = size / HFS_SB(sb)->alloc_blksz;
  	alloc_cnt = HFS_I(inode)->alloc_blocks;
  	if (blk_cnt == alloc_cnt)
  		goto out;
  
  	mutex_lock(&HFS_I(inode)->extents_lock);
  	res = hfs_find_init(HFS_SB(sb)->ext_tree, &fd);
  	if (res) {
  		mutex_unlock(&HFS_I(inode)->extents_lock);
  		/* XXX: We lack error handling of hfs_file_truncate() */
  		return;
  	}
  	while (1) {
  		if (alloc_cnt == HFS_I(inode)->first_blocks) {
  			hfs_free_extents(sb, HFS_I(inode)->first_extents,
  					 alloc_cnt, alloc_cnt - blk_cnt);
  			hfs_dump_extent(HFS_I(inode)->first_extents);
  			HFS_I(inode)->first_blocks = blk_cnt;
  			break;
  		}
  		res = __hfs_ext_cache_extent(&fd, inode, alloc_cnt);
  		if (res)
  			break;
  		start = HFS_I(inode)->cached_start;
  		hfs_free_extents(sb, HFS_I(inode)->cached_extents,
  				 alloc_cnt - start, alloc_cnt - blk_cnt);
  		hfs_dump_extent(HFS_I(inode)->cached_extents);
  		if (blk_cnt > start) {
  			HFS_I(inode)->flags |= HFS_FLG_EXT_DIRTY;
  			break;
  		}
  		alloc_cnt = start;
  		HFS_I(inode)->cached_start = HFS_I(inode)->cached_blocks = 0;
  		HFS_I(inode)->flags &= ~(HFS_FLG_EXT_DIRTY|HFS_FLG_EXT_NEW);
  		hfs_brec_remove(&fd);
  	}
  	hfs_find_exit(&fd);
  	mutex_unlock(&HFS_I(inode)->extents_lock);
  
  	HFS_I(inode)->alloc_blocks = blk_cnt;
  out:
  	HFS_I(inode)->phys_size = inode->i_size;
  	HFS_I(inode)->fs_blocks = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
  	inode_set_bytes(inode, HFS_I(inode)->fs_blocks << sb->s_blocksize_bits);
  	mark_inode_dirty(inode);
  }