linux-kernel - Re: [PATCH v2 08/24] ext4: support large block size in ext4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <af30cb7e-a59d-4937-8fc5-1b9c68685939@pankajraghav.com>
Date: Mon, 10 Nov 2025 13:26:14 +0100
From: Pankaj Raghav <kernel@...kajraghav.com>
To: libaokun@...weicloud.com, linux-ext4@...r.kernel.org
Cc: tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz,
 linux-kernel@...r.kernel.org, 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 08/24] ext4: support large block size in ext4_readdir()

On 11/7/25 15:42, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> In ext4_readdir(), page_cache_sync_readahead() is used to readahead mapped
> physical blocks. With LBS support, this can lead to a negative right shift.
> 
> To fix this, the page index is now calculated by first converting the
> physical block number (pblk) to a file position (pos) before converting
> it to a page index. Also, the correct number of pages to readahead is now
> passed.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
> Reviewed-by: Jan Kara <jack@...e.cz>
> ---
Minor general comments below.

Reviewed-by: Pankaj Raghav <p.raghav@...sung.com>

>  fs/ext4/dir.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
> index d4164c507a90..256fe2c1d4c1 100644
> --- a/fs/ext4/dir.c
> +++ b/fs/ext4/dir.c
> @@ -192,13 +192,13 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
>  			continue;
>  		}
>  		if (err > 0) {
> -			pgoff_t index = map.m_pblk >>
> -					(PAGE_SHIFT - inode->i_blkbits);
> +			pgoff_t index = map.m_pblk << inode->i_blkbits >>
> +					PAGE_SHIFT;

It will be nice to have some common helper for this operation. We do something
similar in filemap.c as well.

>  			if (!ra_has_index(&file->f_ra, index))
>  				page_cache_sync_readahead(
>  					sb->s_bdev->bd_mapping,
> -					&file->f_ra, file,
> -					index, 1);
> +					&file->f_ra, file, index,
> +					1 << EXT4_SB(sb)->s_min_folio_order);
Just a personal opinion but it would be nice to have some variable for this instead of doing it
inline? It could be defined along with index.

unsigned long min_nr_pages = 1UL << EXT4_SB(sb)->s_min_folio_order;


>  			file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
>  			bh = ext4_bread(NULL, inode, map.m_lblk, 0);
>  			if (IS_ERR(bh)) {