linux-kernel - Re: [PATCH v2 24/24] ext4: enable block size larger than page size

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Message-ID: <uhztqnoan3lnkp6tb7jtdludunzhjdrfb2ejn7ujpos6z5jalg@42yrgqimodd3>
Date: Mon, 10 Nov 2025 11:00:13 +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, ebiggers@...nel.org, willy@...radead.org, yi.zhang@...wei.com, 
	yangerkun@...wei.com, chengzhihao1@...wei.com, libaokun1@...wei.com
Subject: Re: [PATCH v2 24/24] ext4: enable block size larger than page size

On Fri 07-11-25 22:42:49, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> Since block device (See commit 3c20917120ce ("block/bdev: enable large
> folio support for large logical block sizes")) and page cache (See commit
> ab95d23bab220ef8 ("filemap: allocate mapping_min_order folios in the page
> cache")) has the ability to have a minimum order when allocating folio,
> and ext4 has supported large folio in commit 7ac67301e82f ("ext4: enable
> large folio for regular file"), now add support for block_size > PAGE_SIZE
> in ext4.
> 
> set_blocksize() -> bdev_validate_blocksize() already validates the block
> size, so ext4_load_super() does not need to perform additional checks.
> 
> Here we only need to add the FS_LBS bit to fs_flags.
> 
> In addition, allocation failures for large folios may trigger warn_alloc()
> warnings. Therefore, as with XFS, mark this feature as experimental.
> 
> 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/super.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 6735152dd219..1fbbae5a0426 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5074,6 +5074,9 @@ static int ext4_check_large_folio(struct super_block *sb)
>  		return -EINVAL;
>  	}
>  
> +	if (sb->s_blocksize > PAGE_SIZE)
> +		ext4_msg(sb, KERN_NOTICE, "EXPERIMENTAL bs(%lu) > ps(%lu) enabled.",
> +			 sb->s_blocksize, PAGE_SIZE);
>  	return 0;
>  }
>  
> @@ -7453,7 +7456,8 @@ static struct file_system_type ext4_fs_type = {
>  	.init_fs_context	= ext4_init_fs_context,
>  	.parameters		= ext4_param_specs,
>  	.kill_sb		= ext4_kill_sb,
> -	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME,
> +	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME |
> +				  FS_LBS,
>  };
>  MODULE_ALIAS_FS("ext4");
>  
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR