linux-kernel - Re: [PATCH 14/25] ext4: prepare buddy cache inode for BS

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Message-ID: <6beewixhvz3kfu33gz7silaiceywhuftyuplfnqsusrzwlsq6l@b75fxyfcmrkg>
Date: Wed, 5 Nov 2025 10:19:27 +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 14/25] ext4: prepare buddy cache inode for BS > PS with
 large folios

On Sat 25-10-25 11:22:10, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> We use EXT4_BAD_INO for the buddy cache inode number. This inode is not
> accessed via __ext4_new_inode() or __ext4_iget(), meaning
> ext4_set_inode_mapping_order() is not called to set its folio order range.
> 
> However, future block size greater than page size support requires this
> inode to support large folios, and the buddy cache code already handles
> BS > PS. Therefore, ext4_set_inode_mapping_order() is now explicitly
> called for this specific inode to set its folio order range.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/mballoc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 31f4c7d65eb4..155c43ff2bc2 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -3493,6 +3493,8 @@ static int ext4_mb_init_backend(struct super_block *sb)
>  	 * this will avoid confusion if it ever shows up during debugging. */
>  	sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;
>  	EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
> +	ext4_set_inode_mapping_order(sbi->s_buddy_cache);
> +
>  	for (i = 0; i < ngroups; i++) {
>  		cond_resched();
>  		desc = ext4_get_group_desc(sb, i, NULL);
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR