/*
   *  linux/fs/affs/file.c
   *
   *  (c) 1996  Hans-Joachim Widmaier - Rewritten
   *
   *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
   *
   *  (C) 1992  Eric Youngdale Modified for ISO 9660 filesystem.
   *
   *  (C) 1991  Linus Torvalds - minix filesystem
   *
   *  affs regular file handling primitives
   */
  
  #include "affs.h"
  
  #if PAGE_SIZE < 4096
  #error PAGE_SIZE must be at least 4096
  #endif
  
  static int affs_grow_extcache(struct inode *inode, u32 lc_idx);
  static struct buffer_head *affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext);
  static inline struct buffer_head *affs_get_extblock(struct inode *inode, u32 ext);
  static struct buffer_head *affs_get_extblock_slow(struct inode *inode, u32 ext);

  static int affs_file_open(struct inode *inode, struct file *filp);
  static int affs_file_release(struct inode *inode, struct file *filp);

  const struct file_operations affs_file_operations = {

  	.llseek		= generic_file_llseek,

  	.read		= do_sync_read,
  	.aio_read	= generic_file_aio_read,
  	.write		= do_sync_write,
  	.aio_write	= generic_file_aio_write,

  	.mmap		= generic_file_mmap,
  	.open		= affs_file_open,
  	.release	= affs_file_release,

  	.fsync		= affs_file_fsync,

  	.splice_read	= generic_file_splice_read,

  };

  const struct inode_operations affs_file_inode_operations = {

  	.setattr	= affs_notify_change,
  };
  
  static int
  affs_file_open(struct inode *inode, struct file *filp)
  {

  	pr_debug("AFFS: open(%lu,%d)
  ",
  		 inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
  	atomic_inc(&AFFS_I(inode)->i_opencnt);

  	return 0;
  }
  
  static int
  affs_file_release(struct inode *inode, struct file *filp)
  {

  	pr_debug("AFFS: release(%lu, %d)
  ",
  		 inode->i_ino, atomic_read(&AFFS_I(inode)->i_opencnt));
  
  	if (atomic_dec_and_test(&AFFS_I(inode)->i_opencnt)) {
  		mutex_lock(&inode->i_mutex);
  		if (inode->i_size != AFFS_I(inode)->mmu_private)
  			affs_truncate(inode);

  		affs_free_prealloc(inode);

  		mutex_unlock(&inode->i_mutex);
  	}

  
  	return 0;
  }
  
  static int
  affs_grow_extcache(struct inode *inode, u32 lc_idx)
  {
  	struct super_block	*sb = inode->i_sb;
  	struct buffer_head	*bh;
  	u32 lc_max;
  	int i, j, key;
  
  	if (!AFFS_I(inode)->i_lc) {
  		char *ptr = (char *)get_zeroed_page(GFP_NOFS);
  		if (!ptr)
  			return -ENOMEM;
  		AFFS_I(inode)->i_lc = (u32 *)ptr;
  		AFFS_I(inode)->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
  	}
  
  	lc_max = AFFS_LC_SIZE << AFFS_I(inode)->i_lc_shift;
  
  	if (AFFS_I(inode)->i_extcnt > lc_max) {
  		u32 lc_shift, lc_mask, tmp, off;
  
  		/* need to recalculate linear cache, start from old size */
  		lc_shift = AFFS_I(inode)->i_lc_shift;
  		tmp = (AFFS_I(inode)->i_extcnt / AFFS_LC_SIZE) >> lc_shift;
  		for (; tmp; tmp >>= 1)
  			lc_shift++;
  		lc_mask = (1 << lc_shift) - 1;
  
  		/* fix idx and old size to new shift */
  		lc_idx >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
  		AFFS_I(inode)->i_lc_size >>= (lc_shift - AFFS_I(inode)->i_lc_shift);
  
  		/* first shrink old cache to make more space */
  		off = 1 << (lc_shift - AFFS_I(inode)->i_lc_shift);
  		for (i = 1, j = off; j < AFFS_LC_SIZE; i++, j += off)
  			AFFS_I(inode)->i_ac[i] = AFFS_I(inode)->i_ac[j];
  
  		AFFS_I(inode)->i_lc_shift = lc_shift;
  		AFFS_I(inode)->i_lc_mask = lc_mask;
  	}
  
  	/* fill cache to the needed index */
  	i = AFFS_I(inode)->i_lc_size;
  	AFFS_I(inode)->i_lc_size = lc_idx + 1;
  	for (; i <= lc_idx; i++) {
  		if (!i) {
  			AFFS_I(inode)->i_lc[0] = inode->i_ino;
  			continue;
  		}
  		key = AFFS_I(inode)->i_lc[i - 1];
  		j = AFFS_I(inode)->i_lc_mask + 1;
  		// unlock cache
  		for (; j > 0; j--) {
  			bh = affs_bread(sb, key);
  			if (!bh)
  				goto err;
  			key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
  			affs_brelse(bh);
  		}
  		// lock cache
  		AFFS_I(inode)->i_lc[i] = key;
  	}
  
  	return 0;
  
  err:
  	// lock cache
  	return -EIO;
  }
  
  static struct buffer_head *
  affs_alloc_extblock(struct inode *inode, struct buffer_head *bh, u32 ext)
  {
  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *new_bh;
  	u32 blocknr, tmp;
  
  	blocknr = affs_alloc_block(inode, bh->b_blocknr);
  	if (!blocknr)
  		return ERR_PTR(-ENOSPC);
  
  	new_bh = affs_getzeroblk(sb, blocknr);
  	if (!new_bh) {
  		affs_free_block(sb, blocknr);
  		return ERR_PTR(-EIO);
  	}
  
  	AFFS_HEAD(new_bh)->ptype = cpu_to_be32(T_LIST);
  	AFFS_HEAD(new_bh)->key = cpu_to_be32(blocknr);
  	AFFS_TAIL(sb, new_bh)->stype = cpu_to_be32(ST_FILE);
  	AFFS_TAIL(sb, new_bh)->parent = cpu_to_be32(inode->i_ino);
  	affs_fix_checksum(sb, new_bh);
  
  	mark_buffer_dirty_inode(new_bh, inode);
  
  	tmp = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
  	if (tmp)
  		affs_warning(sb, "alloc_ext", "previous extension set (%x)", tmp);
  	AFFS_TAIL(sb, bh)->extension = cpu_to_be32(blocknr);
  	affs_adjust_checksum(bh, blocknr - tmp);
  	mark_buffer_dirty_inode(bh, inode);
  
  	AFFS_I(inode)->i_extcnt++;
  	mark_inode_dirty(inode);
  
  	return new_bh;
  }
  
  static inline struct buffer_head *
  affs_get_extblock(struct inode *inode, u32 ext)
  {
  	/* inline the simplest case: same extended block as last time */
  	struct buffer_head *bh = AFFS_I(inode)->i_ext_bh;
  	if (ext == AFFS_I(inode)->i_ext_last)

  		get_bh(bh);

  	else
  		/* we have to do more (not inlined) */
  		bh = affs_get_extblock_slow(inode, ext);
  
  	return bh;
  }
  
  static struct buffer_head *
  affs_get_extblock_slow(struct inode *inode, u32 ext)
  {
  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *bh;
  	u32 ext_key;
  	u32 lc_idx, lc_off, ac_idx;
  	u32 tmp, idx;
  
  	if (ext == AFFS_I(inode)->i_ext_last + 1) {
  		/* read the next extended block from the current one */
  		bh = AFFS_I(inode)->i_ext_bh;
  		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
  		if (ext < AFFS_I(inode)->i_extcnt)
  			goto read_ext;
  		if (ext > AFFS_I(inode)->i_extcnt)
  			BUG();
  		bh = affs_alloc_extblock(inode, bh, ext);
  		if (IS_ERR(bh))
  			return bh;
  		goto store_ext;
  	}
  
  	if (ext == 0) {
  		/* we seek back to the file header block */
  		ext_key = inode->i_ino;
  		goto read_ext;
  	}
  
  	if (ext >= AFFS_I(inode)->i_extcnt) {
  		struct buffer_head *prev_bh;
  
  		/* allocate a new extended block */
  		if (ext > AFFS_I(inode)->i_extcnt)
  			BUG();
  
  		/* get previous extended block */
  		prev_bh = affs_get_extblock(inode, ext - 1);
  		if (IS_ERR(prev_bh))
  			return prev_bh;
  		bh = affs_alloc_extblock(inode, prev_bh, ext);
  		affs_brelse(prev_bh);
  		if (IS_ERR(bh))
  			return bh;
  		goto store_ext;
  	}
  
  again:
  	/* check if there is an extended cache and whether it's large enough */
  	lc_idx = ext >> AFFS_I(inode)->i_lc_shift;
  	lc_off = ext & AFFS_I(inode)->i_lc_mask;
  
  	if (lc_idx >= AFFS_I(inode)->i_lc_size) {
  		int err;
  
  		err = affs_grow_extcache(inode, lc_idx);
  		if (err)
  			return ERR_PTR(err);
  		goto again;
  	}
  
  	/* every n'th key we find in the linear cache */
  	if (!lc_off) {
  		ext_key = AFFS_I(inode)->i_lc[lc_idx];
  		goto read_ext;
  	}
  
  	/* maybe it's still in the associative cache */
  	ac_idx = (ext - lc_idx - 1) & AFFS_AC_MASK;
  	if (AFFS_I(inode)->i_ac[ac_idx].ext == ext) {
  		ext_key = AFFS_I(inode)->i_ac[ac_idx].key;
  		goto read_ext;
  	}
  
  	/* try to find one of the previous extended blocks */
  	tmp = ext;
  	idx = ac_idx;
  	while (--tmp, --lc_off > 0) {
  		idx = (idx - 1) & AFFS_AC_MASK;
  		if (AFFS_I(inode)->i_ac[idx].ext == tmp) {
  			ext_key = AFFS_I(inode)->i_ac[idx].key;
  			goto find_ext;
  		}
  	}
  
  	/* fall back to the linear cache */
  	ext_key = AFFS_I(inode)->i_lc[lc_idx];
  find_ext:
  	/* read all extended blocks until we find the one we need */
  	//unlock cache
  	do {
  		bh = affs_bread(sb, ext_key);
  		if (!bh)
  			goto err_bread;
  		ext_key = be32_to_cpu(AFFS_TAIL(sb, bh)->extension);
  		affs_brelse(bh);
  		tmp++;
  	} while (tmp < ext);
  	//lock cache
  
  	/* store it in the associative cache */
  	// recalculate ac_idx?
  	AFFS_I(inode)->i_ac[ac_idx].ext = ext;
  	AFFS_I(inode)->i_ac[ac_idx].key = ext_key;
  
  read_ext:
  	/* finally read the right extended block */
  	//unlock cache
  	bh = affs_bread(sb, ext_key);
  	if (!bh)
  		goto err_bread;
  	//lock cache
  
  store_ext:
  	/* release old cached extended block and store the new one */
  	affs_brelse(AFFS_I(inode)->i_ext_bh);
  	AFFS_I(inode)->i_ext_last = ext;
  	AFFS_I(inode)->i_ext_bh = bh;

  	get_bh(bh);

  
  	return bh;
  
  err_bread:
  	affs_brelse(bh);
  	return ERR_PTR(-EIO);
  }
  
  static int
  affs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh_result, int create)
  {
  	struct super_block	*sb = inode->i_sb;
  	struct buffer_head	*ext_bh;
  	u32			 ext;
  
  	pr_debug("AFFS: get_block(%u, %lu)
  ", (u32)inode->i_ino, (unsigned long)block);

  	BUG_ON(block > (sector_t)0x7fffffffUL);

  
  	if (block >= AFFS_I(inode)->i_blkcnt) {
  		if (block > AFFS_I(inode)->i_blkcnt || !create)
  			goto err_big;
  	} else
  		create = 0;
  
  	//lock cache
  	affs_lock_ext(inode);
  
  	ext = (u32)block / AFFS_SB(sb)->s_hashsize;
  	block -= ext * AFFS_SB(sb)->s_hashsize;
  	ext_bh = affs_get_extblock(inode, ext);
  	if (IS_ERR(ext_bh))
  		goto err_ext;
  	map_bh(bh_result, sb, (sector_t)be32_to_cpu(AFFS_BLOCK(sb, ext_bh, block)));
  
  	if (create) {
  		u32 blocknr = affs_alloc_block(inode, ext_bh->b_blocknr);
  		if (!blocknr)
  			goto err_alloc;
  		set_buffer_new(bh_result);
  		AFFS_I(inode)->mmu_private += AFFS_SB(sb)->s_data_blksize;
  		AFFS_I(inode)->i_blkcnt++;
  
  		/* store new block */
  		if (bh_result->b_blocknr)
  			affs_warning(sb, "get_block", "block already set (%x)", bh_result->b_blocknr);
  		AFFS_BLOCK(sb, ext_bh, block) = cpu_to_be32(blocknr);
  		AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(block + 1);
  		affs_adjust_checksum(ext_bh, blocknr - bh_result->b_blocknr + 1);
  		bh_result->b_blocknr = blocknr;
  
  		if (!block) {
  			/* insert first block into header block */
  			u32 tmp = be32_to_cpu(AFFS_HEAD(ext_bh)->first_data);
  			if (tmp)
  				affs_warning(sb, "get_block", "first block already set (%d)", tmp);
  			AFFS_HEAD(ext_bh)->first_data = cpu_to_be32(blocknr);
  			affs_adjust_checksum(ext_bh, blocknr - tmp);
  		}
  	}
  
  	affs_brelse(ext_bh);
  	//unlock cache
  	affs_unlock_ext(inode);
  	return 0;
  
  err_big:
  	affs_error(inode->i_sb,"get_block","strange block request %d", block);
  	return -EIO;
  err_ext:
  	// unlock cache
  	affs_unlock_ext(inode);
  	return PTR_ERR(ext_bh);
  err_alloc:
  	brelse(ext_bh);
  	clear_buffer_mapped(bh_result);
  	bh_result->b_bdev = NULL;
  	// unlock cache
  	affs_unlock_ext(inode);
  	return -ENOSPC;
  }
  
  static int affs_writepage(struct page *page, struct writeback_control *wbc)
  {
  	return block_write_full_page(page, affs_get_block, wbc);
  }

  static int affs_readpage(struct file *file, struct page *page)
  {
  	return block_read_full_page(page, affs_get_block);
  }

  static void affs_write_failed(struct address_space *mapping, loff_t to)
  {
  	struct inode *inode = mapping->host;
  
  	if (to > inode->i_size) {

  		truncate_pagecache(inode, inode->i_size);

  		affs_truncate(inode);
  	}
  }

  static int affs_write_begin(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned flags,
  			struct page **pagep, void **fsdata)

  {

  	int ret;

  	*pagep = NULL;

  	ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,

  				affs_get_block,
  				&AFFS_I(mapping->host)->mmu_private);

  	if (unlikely(ret))
  		affs_write_failed(mapping, pos + len);

  
  	return ret;

  }

  static sector_t _affs_bmap(struct address_space *mapping, sector_t block)
  {
  	return generic_block_bmap(mapping,block,affs_get_block);
  }

  const struct address_space_operations affs_aops = {

  	.readpage = affs_readpage,
  	.writepage = affs_writepage,

  	.write_begin = affs_write_begin,
  	.write_end = generic_write_end,

  	.bmap = _affs_bmap
  };
  
  static inline struct buffer_head *
  affs_bread_ino(struct inode *inode, int block, int create)
  {
  	struct buffer_head *bh, tmp_bh;
  	int err;
  
  	tmp_bh.b_state = 0;
  	err = affs_get_block(inode, block, &tmp_bh, create);
  	if (!err) {
  		bh = affs_bread(inode->i_sb, tmp_bh.b_blocknr);
  		if (bh) {
  			bh->b_state |= tmp_bh.b_state;
  			return bh;
  		}
  		err = -EIO;
  	}
  	return ERR_PTR(err);
  }
  
  static inline struct buffer_head *
  affs_getzeroblk_ino(struct inode *inode, int block)
  {
  	struct buffer_head *bh, tmp_bh;
  	int err;
  
  	tmp_bh.b_state = 0;
  	err = affs_get_block(inode, block, &tmp_bh, 1);
  	if (!err) {
  		bh = affs_getzeroblk(inode->i_sb, tmp_bh.b_blocknr);
  		if (bh) {
  			bh->b_state |= tmp_bh.b_state;
  			return bh;
  		}
  		err = -EIO;
  	}
  	return ERR_PTR(err);
  }
  
  static inline struct buffer_head *
  affs_getemptyblk_ino(struct inode *inode, int block)
  {
  	struct buffer_head *bh, tmp_bh;
  	int err;
  
  	tmp_bh.b_state = 0;
  	err = affs_get_block(inode, block, &tmp_bh, 1);
  	if (!err) {
  		bh = affs_getemptyblk(inode->i_sb, tmp_bh.b_blocknr);
  		if (bh) {
  			bh->b_state |= tmp_bh.b_state;
  			return bh;
  		}
  		err = -EIO;
  	}
  	return ERR_PTR(err);
  }

  static int
  affs_do_readpage_ofs(struct file *file, struct page *page, unsigned from, unsigned to)
  {
  	struct inode *inode = page->mapping->host;
  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *bh;
  	char *data;
  	u32 bidx, boff, bsize;
  	u32 tmp;
  
  	pr_debug("AFFS: read_page(%u, %ld, %d, %d)
  ", (u32)inode->i_ino, page->index, from, to);

  	BUG_ON(from > to || to > PAGE_CACHE_SIZE);

  	kmap(page);
  	data = page_address(page);
  	bsize = AFFS_SB(sb)->s_data_blksize;
  	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
  	bidx = tmp / bsize;
  	boff = tmp % bsize;
  
  	while (from < to) {
  		bh = affs_bread_ino(inode, bidx, 0);
  		if (IS_ERR(bh))
  			return PTR_ERR(bh);
  		tmp = min(bsize - boff, to - from);

  		BUG_ON(from + tmp > to || tmp > bsize);

  		memcpy(data + from, AFFS_DATA(bh) + boff, tmp);
  		affs_brelse(bh);
  		bidx++;
  		from += tmp;
  		boff = 0;
  	}
  	flush_dcache_page(page);
  	kunmap(page);
  	return 0;
  }
  
  static int
  affs_extent_file_ofs(struct inode *inode, u32 newsize)
  {
  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *bh, *prev_bh;
  	u32 bidx, boff;
  	u32 size, bsize;
  	u32 tmp;
  
  	pr_debug("AFFS: extent_file(%u, %d)
  ", (u32)inode->i_ino, newsize);
  	bsize = AFFS_SB(sb)->s_data_blksize;
  	bh = NULL;
  	size = AFFS_I(inode)->mmu_private;
  	bidx = size / bsize;
  	boff = size % bsize;
  	if (boff) {
  		bh = affs_bread_ino(inode, bidx, 0);
  		if (IS_ERR(bh))
  			return PTR_ERR(bh);
  		tmp = min(bsize - boff, newsize - size);

  		BUG_ON(boff + tmp > bsize || tmp > bsize);

  		memset(AFFS_DATA(bh) + boff, 0, tmp);

  		be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);

  		affs_fix_checksum(sb, bh);
  		mark_buffer_dirty_inode(bh, inode);
  		size += tmp;
  		bidx++;
  	} else if (bidx) {
  		bh = affs_bread_ino(inode, bidx - 1, 0);
  		if (IS_ERR(bh))
  			return PTR_ERR(bh);
  	}
  
  	while (size < newsize) {
  		prev_bh = bh;
  		bh = affs_getzeroblk_ino(inode, bidx);
  		if (IS_ERR(bh))
  			goto out;
  		tmp = min(bsize, newsize - size);

  		BUG_ON(tmp > bsize);

  		AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
  		AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
  		AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
  		AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
  		affs_fix_checksum(sb, bh);
  		bh->b_state &= ~(1UL << BH_New);
  		mark_buffer_dirty_inode(bh, inode);
  		if (prev_bh) {
  			u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
  			if (tmp)
  				affs_warning(sb, "extent_file_ofs", "next block already set for %d (%d)", bidx, tmp);
  			AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
  			affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
  			mark_buffer_dirty_inode(prev_bh, inode);
  			affs_brelse(prev_bh);
  		}
  		size += bsize;
  		bidx++;
  	}
  	affs_brelse(bh);
  	inode->i_size = AFFS_I(inode)->mmu_private = newsize;
  	return 0;
  
  out:
  	inode->i_size = AFFS_I(inode)->mmu_private = newsize;
  	return PTR_ERR(bh);
  }
  
  static int
  affs_readpage_ofs(struct file *file, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	u32 to;
  	int err;
  
  	pr_debug("AFFS: read_page(%u, %ld)
  ", (u32)inode->i_ino, page->index);
  	to = PAGE_CACHE_SIZE;
  	if (((page->index + 1) << PAGE_CACHE_SHIFT) > inode->i_size) {
  		to = inode->i_size & ~PAGE_CACHE_MASK;
  		memset(page_address(page) + to, 0, PAGE_CACHE_SIZE - to);
  	}
  
  	err = affs_do_readpage_ofs(file, page, 0, to);
  	if (!err)
  		SetPageUptodate(page);
  	unlock_page(page);
  	return err;
  }

  static int affs_write_begin_ofs(struct file *file, struct address_space *mapping,
  				loff_t pos, unsigned len, unsigned flags,
  				struct page **pagep, void **fsdata)

  {

  	struct inode *inode = mapping->host;
  	struct page *page;
  	pgoff_t index;

  	int err = 0;

  	pr_debug("AFFS: write_begin(%u, %llu, %llu)
  ", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);
  	if (pos > AFFS_I(inode)->mmu_private) {
  		/* XXX: this probably leaves a too-big i_size in case of
  		 * failure. Should really be updating i_size at write_end time
  		 */
  		err = affs_extent_file_ofs(inode, pos);

  		if (err)
  			return err;
  	}

  
  	index = pos >> PAGE_CACHE_SHIFT;

  	page = grab_cache_page_write_begin(mapping, index, flags);

  	if (!page)
  		return -ENOMEM;
  	*pagep = page;

  
  	if (PageUptodate(page))
  		return 0;

  	/* XXX: inefficient but safe in the face of short writes */
  	err = affs_do_readpage_ofs(file, page, 0, PAGE_CACHE_SIZE);
  	if (err) {
  		unlock_page(page);
  		page_cache_release(page);

  	}
  	return err;
  }

  static int affs_write_end_ofs(struct file *file, struct address_space *mapping,
  				loff_t pos, unsigned len, unsigned copied,
  				struct page *page, void *fsdata)

  {

  	struct inode *inode = mapping->host;

  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *bh, *prev_bh;
  	char *data;
  	u32 bidx, boff, bsize;

  	unsigned from, to;

  	u32 tmp;
  	int written;

  	from = pos & (PAGE_CACHE_SIZE - 1);
  	to = pos + len;
  	/*
  	 * XXX: not sure if this can handle short copies (len < copied), but
  	 * we don't have to, because the page should always be uptodate here,
  	 * due to write_begin.
  	 */
  
  	pr_debug("AFFS: write_begin(%u, %llu, %llu)
  ", (u32)inode->i_ino, (unsigned long long)pos, (unsigned long long)pos + len);

  	bsize = AFFS_SB(sb)->s_data_blksize;
  	data = page_address(page);
  
  	bh = NULL;
  	written = 0;
  	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
  	bidx = tmp / bsize;
  	boff = tmp % bsize;
  	if (boff) {
  		bh = affs_bread_ino(inode, bidx, 0);
  		if (IS_ERR(bh))
  			return PTR_ERR(bh);
  		tmp = min(bsize - boff, to - from);

  		BUG_ON(boff + tmp > bsize || tmp > bsize);

  		memcpy(AFFS_DATA(bh) + boff, data + from, tmp);

  		be32_add_cpu(&AFFS_DATA_HEAD(bh)->size, tmp);

  		affs_fix_checksum(sb, bh);
  		mark_buffer_dirty_inode(bh, inode);
  		written += tmp;
  		from += tmp;
  		bidx++;
  	} else if (bidx) {
  		bh = affs_bread_ino(inode, bidx - 1, 0);
  		if (IS_ERR(bh))
  			return PTR_ERR(bh);
  	}
  	while (from + bsize <= to) {
  		prev_bh = bh;
  		bh = affs_getemptyblk_ino(inode, bidx);
  		if (IS_ERR(bh))
  			goto out;
  		memcpy(AFFS_DATA(bh), data + from, bsize);
  		if (buffer_new(bh)) {
  			AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
  			AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
  			AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
  			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(bsize);
  			AFFS_DATA_HEAD(bh)->next = 0;
  			bh->b_state &= ~(1UL << BH_New);
  			if (prev_bh) {
  				u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
  				if (tmp)
  					affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
  				AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
  				affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
  				mark_buffer_dirty_inode(prev_bh, inode);
  			}
  		}
  		affs_brelse(prev_bh);
  		affs_fix_checksum(sb, bh);
  		mark_buffer_dirty_inode(bh, inode);
  		written += bsize;
  		from += bsize;
  		bidx++;
  	}
  	if (from < to) {
  		prev_bh = bh;
  		bh = affs_bread_ino(inode, bidx, 1);
  		if (IS_ERR(bh))
  			goto out;
  		tmp = min(bsize, to - from);

  		BUG_ON(tmp > bsize);

  		memcpy(AFFS_DATA(bh), data + from, tmp);
  		if (buffer_new(bh)) {
  			AFFS_DATA_HEAD(bh)->ptype = cpu_to_be32(T_DATA);
  			AFFS_DATA_HEAD(bh)->key = cpu_to_be32(inode->i_ino);
  			AFFS_DATA_HEAD(bh)->sequence = cpu_to_be32(bidx);
  			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
  			AFFS_DATA_HEAD(bh)->next = 0;
  			bh->b_state &= ~(1UL << BH_New);
  			if (prev_bh) {
  				u32 tmp = be32_to_cpu(AFFS_DATA_HEAD(prev_bh)->next);
  				if (tmp)
  					affs_warning(sb, "commit_write_ofs", "next block already set for %d (%d)", bidx, tmp);
  				AFFS_DATA_HEAD(prev_bh)->next = cpu_to_be32(bh->b_blocknr);
  				affs_adjust_checksum(prev_bh, bh->b_blocknr - tmp);
  				mark_buffer_dirty_inode(prev_bh, inode);
  			}
  		} else if (be32_to_cpu(AFFS_DATA_HEAD(bh)->size) < tmp)
  			AFFS_DATA_HEAD(bh)->size = cpu_to_be32(tmp);
  		affs_brelse(prev_bh);
  		affs_fix_checksum(sb, bh);
  		mark_buffer_dirty_inode(bh, inode);
  		written += tmp;
  		from += tmp;
  		bidx++;
  	}
  	SetPageUptodate(page);
  
  done:
  	affs_brelse(bh);
  	tmp = (page->index << PAGE_CACHE_SHIFT) + from;
  	if (tmp > inode->i_size)
  		inode->i_size = AFFS_I(inode)->mmu_private = tmp;

  	unlock_page(page);
  	page_cache_release(page);

  	return written;
  
  out:
  	bh = prev_bh;
  	if (!written)
  		written = PTR_ERR(bh);
  	goto done;
  }

  const struct address_space_operations affs_aops_ofs = {

  	.readpage = affs_readpage_ofs,
  	//.writepage = affs_writepage_ofs,

  	.write_begin = affs_write_begin_ofs,
  	.write_end = affs_write_end_ofs

  };
  
  /* Free any preallocated blocks. */
  
  void
  affs_free_prealloc(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  
  	pr_debug("AFFS: free_prealloc(ino=%lu)
  ", inode->i_ino);
  
  	while (AFFS_I(inode)->i_pa_cnt) {
  		AFFS_I(inode)->i_pa_cnt--;
  		affs_free_block(sb, ++AFFS_I(inode)->i_lastalloc);
  	}
  }
  
  /* Truncate (or enlarge) a file to the requested size. */
  
  void
  affs_truncate(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  	u32 ext, ext_key;
  	u32 last_blk, blkcnt, blk;
  	u32 size;
  	struct buffer_head *ext_bh;
  	int i;
  
  	pr_debug("AFFS: truncate(inode=%d, oldsize=%u, newsize=%u)
  ",
  		 (u32)inode->i_ino, (u32)AFFS_I(inode)->mmu_private, (u32)inode->i_size);
  
  	last_blk = 0;
  	ext = 0;
  	if (inode->i_size) {
  		last_blk = ((u32)inode->i_size - 1) / AFFS_SB(sb)->s_data_blksize;
  		ext = last_blk / AFFS_SB(sb)->s_hashsize;
  	}
  
  	if (inode->i_size > AFFS_I(inode)->mmu_private) {
  		struct address_space *mapping = inode->i_mapping;
  		struct page *page;

  		void *fsdata;

  		loff_t size = inode->i_size;

  		int res;

  		res = mapping->a_ops->write_begin(NULL, mapping, size, 0, 0, &page, &fsdata);

  		if (!res)

  			res = mapping->a_ops->write_end(NULL, mapping, size, 0, 0, page, fsdata);

  		else
  			inode->i_size = AFFS_I(inode)->mmu_private;

  		mark_inode_dirty(inode);
  		return;
  	} else if (inode->i_size == AFFS_I(inode)->mmu_private)
  		return;
  
  	// lock cache
  	ext_bh = affs_get_extblock(inode, ext);
  	if (IS_ERR(ext_bh)) {
  		affs_warning(sb, "truncate", "unexpected read error for ext block %u (%d)",
  			     ext, PTR_ERR(ext_bh));
  		return;
  	}
  	if (AFFS_I(inode)->i_lc) {
  		/* clear linear cache */
  		i = (ext + 1) >> AFFS_I(inode)->i_lc_shift;
  		if (AFFS_I(inode)->i_lc_size > i) {
  			AFFS_I(inode)->i_lc_size = i;
  			for (; i < AFFS_LC_SIZE; i++)
  				AFFS_I(inode)->i_lc[i] = 0;
  		}
  		/* clear associative cache */
  		for (i = 0; i < AFFS_AC_SIZE; i++)
  			if (AFFS_I(inode)->i_ac[i].ext >= ext)
  				AFFS_I(inode)->i_ac[i].ext = 0;
  	}
  	ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
  
  	blkcnt = AFFS_I(inode)->i_blkcnt;
  	i = 0;
  	blk = last_blk;
  	if (inode->i_size) {
  		i = last_blk % AFFS_SB(sb)->s_hashsize + 1;
  		blk++;
  	} else
  		AFFS_HEAD(ext_bh)->first_data = 0;

  	AFFS_HEAD(ext_bh)->block_count = cpu_to_be32(i);

  	size = AFFS_SB(sb)->s_hashsize;
  	if (size > blkcnt - blk + i)
  		size = blkcnt - blk + i;
  	for (; i < size; i++, blk++) {
  		affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
  		AFFS_BLOCK(sb, ext_bh, i) = 0;
  	}
  	AFFS_TAIL(sb, ext_bh)->extension = 0;
  	affs_fix_checksum(sb, ext_bh);
  	mark_buffer_dirty_inode(ext_bh, inode);
  	affs_brelse(ext_bh);
  
  	if (inode->i_size) {
  		AFFS_I(inode)->i_blkcnt = last_blk + 1;
  		AFFS_I(inode)->i_extcnt = ext + 1;
  		if (AFFS_SB(sb)->s_flags & SF_OFS) {
  			struct buffer_head *bh = affs_bread_ino(inode, last_blk, 0);
  			u32 tmp;

  			if (IS_ERR(bh)) {

  				affs_warning(sb, "truncate", "unexpected read error for last block %u (%d)",

  					     ext, PTR_ERR(bh));

  				return;
  			}
  			tmp = be32_to_cpu(AFFS_DATA_HEAD(bh)->next);
  			AFFS_DATA_HEAD(bh)->next = 0;
  			affs_adjust_checksum(bh, -tmp);
  			affs_brelse(bh);
  		}
  	} else {
  		AFFS_I(inode)->i_blkcnt = 0;
  		AFFS_I(inode)->i_extcnt = 1;
  	}
  	AFFS_I(inode)->mmu_private = inode->i_size;
  	// unlock cache
  
  	while (ext_key) {
  		ext_bh = affs_bread(sb, ext_key);
  		size = AFFS_SB(sb)->s_hashsize;
  		if (size > blkcnt - blk)
  			size = blkcnt - blk;
  		for (i = 0; i < size; i++, blk++)
  			affs_free_block(sb, be32_to_cpu(AFFS_BLOCK(sb, ext_bh, i)));
  		affs_free_block(sb, ext_key);
  		ext_key = be32_to_cpu(AFFS_TAIL(sb, ext_bh)->extension);
  		affs_brelse(ext_bh);
  	}
  	affs_free_prealloc(inode);
  }

  int affs_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)

  {

  	struct inode *inode = filp->f_mapping->host;

  	int ret, err;

  	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (err)
  		return err;
  
  	mutex_lock(&inode->i_mutex);

  	ret = write_inode_now(inode, 0);
  	err = sync_blockdev(inode->i_sb->s_bdev);
  	if (!ret)
  		ret = err;

  	mutex_unlock(&inode->i_mutex);

  	return ret;
  }