linux-ext4 - Re: [PATCH v2 3/4] ext4: factor out write end code of inline file

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Date:   Fri, 16 Jul 2021 11:56:06 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <linux-ext4@...r.kernel.org>, <tytso@....edu>,
        <adilger.kernel@...ger.ca>, <yukuai3@...wei.com>
Subject: Re: [PATCH v2 3/4] ext4: factor out write end code of inline file

On 2021/7/15 20:08, Jan Kara wrote:
> On Thu 15-07-21 09:54:51, Zhang Yi wrote:
>> Now that the inline_data file write end procedure are falled into the
>> common write end functions, it is not clear. Factor them out and do
>> some cleanup. This patch also drop ext4_da_write_inline_data_end()
>> and switch to use ext4_write_inline_data_end() instead because we also
>> need to do the same error processing if we failed to write data into
>> inline entry.
>>
>> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> 
> Just two small comments below.
> 
>> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
>> index 28b666f25ac2..3d227b32b21c 100644
>> --- a/fs/ext4/inline.c
>> +++ b/fs/ext4/inline.c
> ...
>> +out:
>> +	/*
>> +	 * If we have allocated more blocks and copied less. We will have
>> +	 * blocks allocated outside inode->i_size, so truncate them.
>> +	 */
>> +	if (pos + len > inode->i_size && ext4_can_truncate(inode))
>> +		ext4_orphan_add(handle, inode);
> 
> I don't think we need this error handling here. For inline data we never
> allocate any blocks so shorter writes don't need any cleanup.
> 
>> -	return copied;
>> +	ret2 = ext4_journal_stop(handle);
>> +	if (!ret)
>> +		ret = ret2;
>> +	if (pos + len > inode->i_size) {
>> +		ext4_truncate_failed_write(inode);
>> +		/*
>> +		 * If truncate failed early the inode might still be
>> +		 * on the orphan list; we need to make sure the inode
>> +		 * is removed from the orphan list in that case.
>> +		 */
>> +		if (inode->i_nlink)
>> +			ext4_orphan_del(NULL, inode);
>> +	}
> 
> And this can go away as well...
> 

Yeah, but if we don't call ext4_truncate_failed_write()->..->
ext4_inline_data_truncate(), it will lead to incorrect larger i_inline_size
and data entry. Although it seems harmless (i_size can prevent read zero
data), I think it's better to restore the data entry(the comments need
change later), or else it will occupy more xattr space. What do you think ?

Thanks,
Yi.