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

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Message-ID: <vkbarfyd6ozrrljhvwhmy2cq23mby6mxl2kxlsxp2wqgmvxvgi@6sgmqhhdnmru>
Date: Wed, 5 Nov 2025 10:50:26 +0100
From: Jan Kara <jack@...e.cz>
To: libaokun@...weicloud.com
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, 
	jack@...e.cz, 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
Subject: Re: [PATCH 21/25] ext4: make online defragmentation support large
 block size

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'.

								Honza

>  	/* 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
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR