balloc.c

这是Linux系统下的对UDF文件系统新增的功能

			{
				elen = (etype << 30) |
					(elen + (count << sb->s_blocksize_bits));
				start += count;
				count = 0;
			}
			udf_write_aext(table, obloc, &oextoffset, eloc, elen, obh, 1);
		}
		else if (eloc.logicalBlockNum == (end + 1))
		{
			if ((0x3FFFFFFF - elen) < (count << sb->s_blocksize_bits))
			{
				count -= ((0x3FFFFFFF - elen) >> sb->s_blocksize_bits);
				end -= ((0x3FFFFFFF - elen) >> sb->s_blocksize_bits);
				eloc.logicalBlockNum -=
					((0x3FFFFFFF - elen) >> sb->s_blocksize_bits);
				elen = (etype << 30) | (0x40000000 - sb->s_blocksize);
			}
			else
			{
				eloc.logicalBlockNum = start;
				elen = (etype << 30) |
					(elen + (count << sb->s_blocksize_bits));
				end -= count;
				count = 0;
			}
			udf_write_aext(table, obloc, &oextoffset, eloc, elen, obh, 1);
		}

		if (nbh != obh)
		{
			i = -1;
			obloc = nbloc;
			udf_release_data(obh);
			atomic_inc(&nbh->b_count);
			obh = nbh;
			oextoffset = 0;
		}
		else
			oextoffset = nextoffset;
	}

	if (count)
	{
		/* NOTE: we CANNOT use udf_add_aext here, as it can try to allocate
				 a new block, and since we hold the super block lock already
				 very bad things would happen :)

				 We copy the behavior of udf_add_aext, but instead of
				 trying to allocate a new block close to the existing one,
				 we just steal a block from the extent we are trying to add.

				 It would be nice if the blocks were close together, but it
				 isn't required.
		*/

		int adsize;
		short_ad *sad = NULL;
		long_ad *lad = NULL;
		struct allocExtDesc *aed;

		eloc.logicalBlockNum = start;
		elen = EXT_RECORDED_ALLOCATED |
			(count << sb->s_blocksize_bits);

		if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_SHORT)
			adsize = sizeof(short_ad);
		else if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_LONG)
			adsize = sizeof(long_ad);
		else
		{
			udf_release_data(obh);
			udf_release_data(nbh);
			goto error_return;
		}

		if (nextoffset + (2 * adsize) > sb->s_blocksize)
		{
			char *sptr, *dptr;
			int loffset;
	
			udf_release_data(obh);
			obh = nbh;
			obloc = nbloc;
			oextoffset = nextoffset;

			/* Steal a block from the extent being free'd */
			nbloc.logicalBlockNum = eloc.logicalBlockNum;
			eloc.logicalBlockNum ++;
			elen -= sb->s_blocksize;

			if (!(nbh = udf_tread(sb,
				udf_get_lb_pblock(sb, nbloc, 0))))
			{
				udf_release_data(obh);
				goto error_return;
			}
			aed = (struct allocExtDesc *)(nbh->b_data);
			aed->previousAllocExtLocation = cpu_to_le32(obloc.logicalBlockNum);
			if (nextoffset + adsize > sb->s_blocksize)
			{
				loffset = nextoffset;
				aed->lengthAllocDescs = cpu_to_le32(adsize);
				if (obh)
					sptr = UDF_I_DATA(inode) + nextoffset -  udf_file_entry_alloc_offset(inode) + UDF_I_LENEATTR(inode) - adsize;
				else
					sptr = obh->b_data + nextoffset - adsize;
				dptr = nbh->b_data + sizeof(struct allocExtDesc);
				memcpy(dptr, sptr, adsize);
				nextoffset = sizeof(struct allocExtDesc) + adsize;
			}
			else
			{
				loffset = nextoffset + adsize;
				aed->lengthAllocDescs = cpu_to_le32(0);
				sptr = (obh)->b_data + nextoffset;
				nextoffset = sizeof(struct allocExtDesc);

				if (obh)
				{
					aed = (struct allocExtDesc *)(obh)->b_data;
					aed->lengthAllocDescs =
						cpu_to_le32(le32_to_cpu(aed->lengthAllocDescs) + adsize);
				}
				else
				{
					UDF_I_LENALLOC(table) += adsize;
					mark_inode_dirty(table);
				}
			}
			if (UDF_SB_UDFREV(sb) >= 0x0200)
				udf_new_tag(nbh->b_data, TAG_IDENT_AED, 3, 1,
					nbloc.logicalBlockNum, sizeof(tag));
			else
				udf_new_tag(nbh->b_data, TAG_IDENT_AED, 2, 1,
					nbloc.logicalBlockNum, sizeof(tag));
			switch (UDF_I_ALLOCTYPE(table))
			{
				case ICBTAG_FLAG_AD_SHORT:
				{
					sad = (short_ad *)sptr;
					sad->extLength = cpu_to_le32(
						EXT_NEXT_EXTENT_ALLOCDECS |
						sb->s_blocksize);
					sad->extPosition = cpu_to_le32(nbloc.logicalBlockNum);
					break;
				}
				case ICBTAG_FLAG_AD_LONG:
				{
					lad = (long_ad *)sptr;
					lad->extLength = cpu_to_le32(
						EXT_NEXT_EXTENT_ALLOCDECS |
						sb->s_blocksize);
					lad->extLocation = cpu_to_lelb(nbloc);
					break;
				}
			}
			if (obh)
			{
				udf_update_tag(obh->b_data, loffset);
				mark_buffer_dirty(obh);
			}
			else
				mark_inode_dirty(table);
		}

		if (elen) /* It's possible that stealing the block emptied the extent */
		{
			udf_write_aext(table, nbloc, &nextoffset, eloc, elen, nbh, 1);

			if (!nbh)
			{
				UDF_I_LENALLOC(table) += adsize;
				mark_inode_dirty(table);
			}
			else
			{
				aed = (struct allocExtDesc *)nbh->b_data;
				aed->lengthAllocDescs =
					cpu_to_le32(le32_to_cpu(aed->lengthAllocDescs) + adsize);
				udf_update_tag(nbh->b_data, nextoffset);
				mark_buffer_dirty(nbh);
			}
		}
	}

	udf_release_data(nbh);
	udf_release_data(obh);

error_return:
	sb->s_dirt = 1;
	unlock_kernel();
	return;
}

static int udf_table_prealloc_blocks(struct super_block * sb,
	struct inode * inode,
	struct inode *table, uint16_t partition, uint32_t first_block,
	uint32_t block_count)
{
	int alloc_count = 0;
	uint32_t extoffset, elen, adsize;
	lb_addr bloc, eloc;
	struct buffer_head *bh;
	int8_t etype = -1;

	if (first_block < 0 || first_block >= UDF_SB_PARTLEN(sb, partition))
		return 0;

	if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_SHORT)
		adsize = sizeof(short_ad);
	else if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_LONG)
		adsize = sizeof(long_ad);
	else
		return 0;

	lock_kernel();

	extoffset = sizeof(struct unallocSpaceEntry);
	bloc = UDF_I_LOCATION(table);

	bh = NULL;
	eloc.logicalBlockNum = 0xFFFFFFFF;

	while (first_block != eloc.logicalBlockNum && (etype =
		udf_next_aext(table, &bloc, &extoffset, &eloc, &elen, &bh, 1)) != -1)
	{
		udf_debug("eloc=%d, elen=%d, first_block=%d\n",
			eloc.logicalBlockNum, elen, first_block);
		; /* empty loop body */
	}

	if (first_block == eloc.logicalBlockNum)
	{
		extoffset -= adsize;

		alloc_count = (elen >> sb->s_blocksize_bits);
		if (inode && DQUOT_PREALLOC_BLOCK(inode, alloc_count > block_count ? block_count : alloc_count))
			alloc_count = 0;
		else if (alloc_count > block_count)
		{
			alloc_count = block_count;
			eloc.logicalBlockNum += alloc_count;
			elen -= (alloc_count << sb->s_blocksize_bits);
			udf_write_aext(table, bloc, &extoffset, eloc, (etype << 30) | elen, bh, 1);
		}
		else
			udf_delete_aext(table, bloc, extoffset, eloc, (etype << 30) | elen, bh);
	}
	else
		alloc_count = 0;

	udf_release_data(bh);

	if (alloc_count && UDF_SB_LVIDBH(sb))
	{
		UDF_SB_LVID(sb)->freeSpaceTable[partition] =
			cpu_to_le32(le32_to_cpu(UDF_SB_LVID(sb)->freeSpaceTable[partition])-alloc_count);
		mark_buffer_dirty(UDF_SB_LVIDBH(sb));
		sb->s_dirt = 1;
	}
	unlock_kernel();
	return alloc_count;
}

static int udf_table_new_block(struct super_block * sb,
	struct inode * inode,
	struct inode *table, uint16_t partition, uint32_t goal, int *err)
{
	uint32_t spread = 0xFFFFFFFF, nspread = 0xFFFFFFFF;
	uint32_t newblock = 0, adsize;
	uint32_t extoffset, goal_extoffset, elen, goal_elen = 0;
	lb_addr bloc, goal_bloc, eloc, goal_eloc;
	struct buffer_head *bh, *goal_bh;
	int8_t etype;

	*err = -ENOSPC;

	if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_SHORT)
		adsize = sizeof(short_ad);
	else if (UDF_I_ALLOCTYPE(table) == ICBTAG_FLAG_AD_LONG)
		adsize = sizeof(long_ad);
	else
		return newblock;

	lock_kernel();

	if (goal < 0 || goal >= UDF_SB_PARTLEN(sb, partition))
		goal = 0;

	/* We search for the closest matching block to goal. If we find a exact hit,
	   we stop. Otherwise we keep going till we run out of extents.
	   We store the buffer_head, bloc, and extoffset of the current closest
	   match and use that when we are done.
	*/

	extoffset = sizeof(struct unallocSpaceEntry);
	bloc = UDF_I_LOCATION(table);

	goal_bh = bh = NULL;

	while (spread && (etype =
		udf_next_aext(table, &bloc, &extoffset, &eloc, &elen, &bh, 1)) != -1)
	{
		if (goal >= eloc.logicalBlockNum)
		{
			if (goal < eloc.logicalBlockNum + (elen >> sb->s_blocksize_bits))
				nspread = 0;
			else
				nspread = goal - eloc.logicalBlockNum -
					(elen >> sb->s_blocksize_bits);
		}
		else
			nspread = eloc.logicalBlockNum - goal;

		if (nspread < spread)
		{
			spread = nspread;
			if (goal_bh != bh)
			{
				udf_release_data(goal_bh);
				goal_bh = bh;
				atomic_inc(&goal_bh->b_count);
			}
			goal_bloc = bloc;
			goal_extoffset = extoffset - adsize;
			goal_eloc = eloc;
			goal_elen = (etype << 30) | elen;
		}
	}

	udf_release_data(bh);

	if (spread == 0xFFFFFFFF)
	{
		udf_release_data(goal_bh);
		unlock_kernel();
		return 0;
	}

	/* Only allocate blocks from the beginning of the extent.
	   That way, we only delete (empty) extents, never have to insert an
	   extent because of splitting */
	/* This works, but very poorly.... */

	newblock = goal_eloc.logicalBlockNum;
	goal_eloc.logicalBlockNum ++;
	goal_elen -= sb->s_blocksize;

	if (inode && DQUOT_ALLOC_BLOCK(inode, 1))
	{
		udf_release_data(goal_bh);
		unlock_kernel();
		*err = -EDQUOT;
		return 0;
	}

	if (goal_elen)
		udf_write_aext(table, goal_bloc, &goal_extoffset, goal_eloc, goal_elen, goal_bh, 1);
	else
		udf_delete_aext(table, goal_bloc, goal_extoffset, goal_eloc, goal_elen, goal_bh);
	udf_release_data(goal_bh);

	if (UDF_SB_LVIDBH(sb))
	{
		UDF_SB_LVID(sb)->freeSpaceTable[partition] =
			cpu_to_le32(le32_to_cpu(UDF_SB_LVID(sb)->freeSpaceTable[partition])-1);
		mark_buffer_dirty(UDF_SB_LVIDBH(sb));
	}

	sb->s_dirt = 1;
	unlock_kernel();
	*err = 0;
	return newblock;
}

inline void udf_free_blocks(struct super_block * sb,
	struct inode * inode,
	lb_addr bloc, uint32_t offset, uint32_t count)
{
	uint16_t partition = bloc.partitionReferenceNum;

	if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_BITMAP)
	{
		return udf_bitmap_free_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_bitmap,
			bloc, offset, count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_TABLE)
	{
		return udf_table_free_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_table,
			bloc, offset, count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_BITMAP)
	{
		return udf_bitmap_free_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_bitmap,
			bloc, offset, count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_TABLE)
	{
		return udf_table_free_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_table,
			bloc, offset, count);
	}
	else
		return;
}

inline int udf_prealloc_blocks(struct super_block * sb,
	struct inode * inode,
	uint16_t partition, uint32_t first_block, uint32_t block_count)
{
	if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_BITMAP)
	{
		return udf_bitmap_prealloc_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_bitmap,
			partition, first_block, block_count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_TABLE)
	{
		return udf_table_prealloc_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_table,
			partition, first_block, block_count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_BITMAP)
	{
		return udf_bitmap_prealloc_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_bitmap,
			partition, first_block, block_count);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_TABLE)
	{
		return udf_table_prealloc_blocks(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_table,
			partition, first_block, block_count);
	}
	else
		return 0;
}

inline int udf_new_block(struct super_block * sb,
	struct inode * inode,
	uint16_t partition, uint32_t goal, int *err)
{
	if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_BITMAP)
	{
		return udf_bitmap_new_block(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_bitmap,
			partition, goal, err);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_UNALLOC_TABLE)
	{
		return udf_table_new_block(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_uspace.s_table,
			partition, goal, err);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_BITMAP)
	{
		return udf_bitmap_new_block(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_bitmap,
			partition, goal, err);
	}
	else if (UDF_SB_PARTFLAGS(sb, partition) & UDF_PART_FLAG_FREED_TABLE)
	{
		return udf_table_new_block(sb, inode,
			UDF_SB_PARTMAPS(sb)[partition].s_fspace.s_table,
			partition, goal, err);
	}
	else
	{
		*err = -EIO;
		return 0;
	}
}