linux-kernel - Re: [PATCH] ext4: disambiguate the return value of ext4_dio_write_end

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Message-ID: <9de82d23-902f-cb18-7688-f5e687e86d14@huaweicloud.com>
Date: Fri, 16 Aug 2024 20:21:22 +0800
From: yangerkun <yangerkun@...weicloud.com>
To: alexjlzheng@...il.com, tytso@....edu, adilger.kernel@...ger.ca
Cc: linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jinliang Zheng <alexjlzheng@...cent.com>
Subject: Re: [PATCH] ext4: disambiguate the return value of
 ext4_dio_write_end_io()



在 2024/8/15 19:27, alexjlzheng@...il.com 写道:
> From: Jinliang Zheng <alexjlzheng@...cent.com>
> 
> The commit 91562895f803 ("ext4: properly sync file size update after O_SYNC
> direct IO") causes confusion about the meaning of the return value of
> ext4_dio_write_end_io().
> 
> Specifically, when the ext4_handle_inode_extension() operation succeeds,
> ext4_dio_write_end_io() directly returns count instead of 0.
> 
> This does not cause a bug in the current kernel, but the semantics of the
> return value of the ext4_dio_write_end_io() function are wrong, which is
> likely to introduce bugs in the future code evolution.
> 
> Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
> ---
>   fs/ext4/file.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index c89e434db6b7..6df5a92cec2b 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -392,8 +392,9 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
>   	 */
>   	if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize) &&
>   	    pos + size <= i_size_read(inode))
> -		return size;
> -	return ext4_handle_inode_extension(inode, pos, size);
> +		return 0;
> +	error = ext4_handle_inode_extension(inode, pos, size);
> +	return error < 0 ? error : 0;

Why?

iomap_dio_complete can use the return value directly without any bug. 
And I think the code now seems more clearly...

>   }
>   
>   static const struct iomap_dio_ops ext4_dio_write_ops = {