Re: a question regarding Ext3 file truncate

[Mingming Cao <cmm@us.ibm.com>]

On Wed, 2007-02-07 at 12:16 -0500, Xin Zhao wrote:
> Hi,
> 
> Please forgive me if the question is dumb.
> 
> I am modifying ext3 to add some new features, but was confused by the
> implementation of ext3_truncate().
> 
> In ext3_truncate():
> 
> we first use
> 	n = ext3_block_to_path(inode, last_block, offsets, NULL);
> to get the path of the last block.
> 
> If the number of blocks is smaller than 12,  all blocks are then
> direct blocks. We then need to clear them.
> 
> But the interesting thing happens:
> 	if (n == 1)									  /* direct blocks */
> 	{
> 		ext3_free_data(handle, inode, NULL, i_data+offsets[0],
> 			i_data + EXT3_NDIR_BLOCKS);
> 		goto do_indirects;
> 	}
> This code seems to free data blocks right after the blocks used by the
> file. I think it should be
> ext3_free_data(handle, inode, NULL, i_data, i_data+offsets[0]);

Last_block is the last logical block after the truncate, so
ext3_truncate() free data blocks after this point.

Mingming