linux-kernel - Re: [PATCH -next 6/7] ext4: simply the mapping query logic in ext4_iomap

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Message-ID: <rixkslnrchbru4bx3jzox5qxctabams37idsxtexenculvivhy@u2ywm4ojxycg>
Date: Fri, 19 Dec 2025 17:44:04 +0100
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, 
	ojaswin@...ux.ibm.com, ritesh.list@...il.com, yi.zhang@...wei.com, yizhang089@...il.com, 
	libaokun1@...wei.com, yangerkun@...wei.com, yukuai@...as.com
Subject: Re: [PATCH -next 6/7] ext4: simply the mapping query logic in
 ext4_iomap_begin()

On Sat 13-12-25 10:20:07, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> In the write path mapping check of ext4_iomap_begin(), the return value
> 'ret' should never greater than orig_mlen. If 'ret' equals 'orig_mlen',
> it can be returned directly without checking IOMAP_ATOMIC.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

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

								Honza

> ---
>  fs/ext4/inode.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 88144e2ce3e2..39348ee46e5c 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3815,15 +3815,15 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>  		 */
>  		if (offset + length <= i_size_read(inode)) {
>  			ret = ext4_map_blocks(NULL, inode, &map, 0);
> -			/*
> -			 * For atomic writes the entire requested length should
> -			 * be mapped.
> -			 */
>  			if ((map.m_flags & EXT4_MAP_MAPPED) ||
>  			    (!(flags & IOMAP_DAX) &&
>  			     (map.m_flags & EXT4_MAP_UNWRITTEN))) {
> -				if ((!(flags & IOMAP_ATOMIC) && ret > 0) ||
> -				   (flags & IOMAP_ATOMIC && ret >= orig_mlen))
> +				/*
> +				 * For atomic writes the entire requested
> +				 * length should be mapped.
> +				 */
> +				if (ret == orig_mlen ||
> +				    (!(flags & IOMAP_ATOMIC) && ret > 0))
>  					goto out;
>  			}
>  			map.m_len = orig_mlen;
> -- 
> 2.46.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR