Re: [PATCH 6/6] ext4: skip ext4_update_disksize_before_punch() in WRITE_ZEROES

[Zhang Yi <yizhang089@gmail.com>]

On 7/2/2026 6:19 PM, Jan Kara wrote:
> On Wed 01-07-26 22:20:09, yizhang089@gmail.com wrote:
>> From: Zhang Yi <yi.zhang@huawei.com>
>>
>> FALLOC_FL_WRITE_ZEROES is mutually exclusive with FALLOC_FL_KEEP_SIZE.
>> In ext4_zero_range(), when end > i_disksize, new_size is always set to
>> end for WRITE_ZEROES, so the i_disksize update should not be lost.
>>
>> The ext4_update_disksize_before_punch() call is only needed for the
>> ZERO_RANGE path in ext4_zero_range(), as it handles the case where
>> KEEP_SIZE may preserve the original disk size. Skip it for WRITE_ZEROES
>> to avoid unnecessary work and potential confusion.
>>
>> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
> 
> Hum, but suppose i_disksize is before the start of our zeroed range, i_size
> is beyond the end of the zeroed range. Now
> ext4_alloc_file_blocks(EXT4_GET_BLOCKS_CREATE_ZERO) will create some zeroed
> written extents beyond i_disksize and if we crash before
> ext4_update_inode_size() runs, we have inconsistent filesystem with
> written extents beyond i_disksize... Hum, actually that could have been the
> case even before, just now there are more cases where this can happen. So I
> think FALLOC_FL_WRITE_ZEROES mode needs to add the inode to the orphan list
> to truncate the inode properly in case of crash.
> 
> 								Honza

Yes, indeed. I overlooked this case previously. I will address it in the
next version.

Thanks,
Yi.

> 
>> ---
>>   fs/ext4/extents.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index c083703bf704..38753c2ef910 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -4748,9 +4748,11 @@ static long ext4_zero_range(struct file *file, loff_t offset,
>>   			return ret;
>>   	}
>>   
>> -	ret = ext4_update_disksize_before_punch(inode, offset, len);
>> -	if (ret)
>> -		return ret;
>> +	if (mode & FALLOC_FL_ZERO_RANGE) {
>> +		ret = ext4_update_disksize_before_punch(inode, offset, len);
>> +		if (ret)
>> +			return ret;
>> +	}
>>   
>>   	/* Now release the pages and zero block aligned part of pages */
>>   	ret = ext4_truncate_page_cache_block_range(inode, offset, end);
>> -- 
>> 2.53.0
>>