2011/4/3 Amir Goldstein <amir73il@xxxxxxxxx>:
> On Sat, Apr 2, 2011 at 1:05 AM, Ding Dinghua <dingdinghua85@xxxxxxxxx> wrote:
>> When truncate files and free blocks, the following codes make me puzzled:
>>
>> void ext4_free_blocks(handle_t *handle, struct inode *inode,
>> struct buffer_head *bh, ext4_fsblk_t block,
>> unsigned long count, int flags)
>> {
>> if (flags & EXT4_FREE_BLOCKS_FORGET) {
>> struct buffer_head *tbh = bh;
>> int i;
>>
>> BUG_ON(bh && (count > 1));
>>
>> for (i = 0; i < count; i++) {
>> if (!bh)
>> tbh = sb_find_get_block(inode->i_sb,
>> block + i);
>> if (unlikely(!tbh))
>> continue;
>> ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
>> inode, tbh, block + i);
>> }
>> }
>> }
>>
>> I notice that ext4_forget mainly do two things:
>> a) call jbd2_journa_forget to forget the modification of some buffer head
>> b) or deal with the revoke issue
>> however, if we are freeing data blocks && ext4_forget get into branch a),
>
> Simple. we don't pass the FORGET flag when freeing data blocks,
> only when freeing metadata blocks, which may have been journalled
> already.
> I am not sure about the journal=data case through.
Thanks for reply. The reason for me to dip into this issue is journal=data mode.
>
>> tbh is not the buffer_head which journal took care of in ext4_write_begin,
>> so i'm puzzled with this.
>>
>> Could anyone explain it to me? Thanks.
>>
>> --
>> Ding Dinghua
>> --
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>
--
Ding Dinghua
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