Thanks a lot! I just found it.
If we need to truncate a file to 0 bytes, we have to change i_size to
0 first, then call ext3_truncate(). Then the code makes sense.
Xin
On 2/7/07, Mingming Cao <cmm@xxxxxxxxxx> wrote:
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
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