linux-kernel - Re: [PATCH 21/25] ext4: make online defragmentation support large block size

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Message-ID: <adbcac4d-e1fc-47a0-ad36-4672ff3c71f5@huawei.com>
Date: Wed, 5 Nov 2025 19:28:00 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Jan Kara <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, <tytso@....edu>, <adilger.kernel@...ger.ca>,
	<linux-kernel@...r.kernel.org>, <kernel@...kajraghav.com>,
	<mcgrof@...nel.org>, <linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
	<yi.zhang@...wei.com>, <yangerkun@...wei.com>, <chengzhihao1@...wei.com>,
	<libaokun1@...wei.com>, Baokun Li <libaokun@...weicloud.com>
Subject: Re: [PATCH 21/25] ext4: make online defragmentation support large
 block size

On 2025-11-05 17:50, Jan Kara wrote:
> On Sat 25-10-25 11:22:17, libaokun@...weicloud.com wrote:
>> From: Zhihao Cheng <chengzhihao1@...wei.com>
>>
>> There are several places assuming that block size <= PAGE_SIZE, modify
>> them to support large block size (bs > ps).
>>
>> Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
>> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> ...
>
>> @@ -565,7 +564,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  	struct inode *orig_inode = file_inode(o_filp);
>>  	struct inode *donor_inode = file_inode(d_filp);
>>  	struct ext4_ext_path *path = NULL;
>> -	int blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
>> +	int blocks_per_page = 1;
>>  	ext4_lblk_t o_end, o_start = orig_blk;
>>  	ext4_lblk_t d_start = donor_blk;
>>  	int ret;
>> @@ -608,6 +607,9 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  		return -EOPNOTSUPP;
>>  	}
>>  
>> +	if (i_blocksize(orig_inode) < PAGE_SIZE)
>> +		blocks_per_page = PAGE_SIZE >> orig_inode->i_blkbits;
>> +
> I think these are strange and the only reason for this is that
> ext4_move_extents() tries to make life easier to move_extent_per_page() and
> that doesn't really work with larger folios anymore. I think
> ext4_move_extents() just shouldn't care about pages / folios at all and
> pass 'cur_len' as the length to the end of extent / moved range and
> move_extent_per_page() will trim the length based on the folios it has got.
>
> Also then we can rename some of the variables and functions from 'page' to
> 'folio'.

Yes, the code here doesn’t really support folios. YI mentioned earlier
that he would make online defragmentation support large folios. So in
this patch I only avoided shifting negative values, without doing a
deeper conversion.

YI’s conversion work looks nearly complete, so in the next version I will
rebase on top of his patches. Since his patch already removes the
function modified here, the next version will likely drop this patch or
adapt it accordingly.

Thanks for your review!


Cheers,
Baokun

>>  	/* Protect orig and donor inodes against a truncate */
>>  	lock_two_nondirectories(orig_inode, donor_inode);
>>  
>> @@ -665,10 +667,8 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  		if (o_end - o_start < cur_len)
>>  			cur_len = o_end - o_start;
>>  
>> -		orig_page_index = o_start >> (PAGE_SHIFT -
>> -					       orig_inode->i_blkbits);
>> -		donor_page_index = d_start >> (PAGE_SHIFT -
>> -					       donor_inode->i_blkbits);
>> +		orig_page_index = EXT4_LBLK_TO_P(orig_inode, o_start);
>> +		donor_page_index = EXT4_LBLK_TO_P(donor_inode, d_start);
>>  		offset_in_page = o_start % blocks_per_page;
>>  		if (cur_len > blocks_per_page - offset_in_page)
>>  			cur_len = blocks_per_page - offset_in_page;
>> -- 
>> 2.46.1
>>