linux-kernel - Re: [PATCH V2] f2fs: fix to adjust appropriate length for fiemap

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Message-ID: <ab9f63b2-8d02-411b-8d2f-bc1b5b748ffe@kernel.org>
Date: Tue, 5 Nov 2024 15:04:20 +0800
From: Chao Yu <chao@...nel.org>
To: Zhiguo Niu <zhiguo.niu@...soc.com>, jaegeuk@...nel.org
Cc: Chao Yu <chao@...nel.org>, linux-f2fs-devel@...ts.sourceforge.net,
 linux-kernel@...r.kernel.org, niuzhiguo84@...il.com, ke.wang@...soc.com,
 Hao_hao.Wang@...soc.com
Subject: Re: [PATCH V2] f2fs: fix to adjust appropriate length for fiemap

On 2024/11/4 9:56, Zhiguo Niu wrote:
> If user give a file size as "length" parameter for fiemap
> operations, but if this size is non-block size aligned,
> it will show 2 segments fiemap results even this whole file
> is contiguous on disk, such as the following results:
> 
>   ./f2fs_io fiemap 0 19034 ylog/analyzer.py
> Fiemap: offset = 0 len = 19034
>          logical addr.    physical addr.   length           flags
> 0       0000000000000000 0000000020baa000 0000000000004000 00001000
> 1       0000000000004000 0000000020bae000 0000000000001000 00001001
> 
> after this patch:
> ./f2fs_io fiemap 0 19034 ylog/analyzer.py
> Fiemap: offset = 0 len = 19034
>      logical addr.    physical addr.   length           flags
> 0    0000000000000000 00000000315f3000 0000000000005000 00001001
> 
> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> ---
> V2: correct commit msg according to Chao's questions
> f2fs_io has been modified for testing, the length for fiemap is
> real file size, not block number
> ---
>   fs/f2fs/data.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 306b86b0..9fc229d 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1966,8 +1966,8 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   			goto out;
>   	}
>   
> -	if (bytes_to_blks(inode, len) == 0)
> -		len = blks_to_bytes(inode, 1);
> +	if (len & (blks_to_bytes(inode, 1) - 1))
> +		len = round_up(len, blks_to_bytes(inode, 1));

How do you think of getting rid of above alignment for len?

>   
>   	start_blk = bytes_to_blks(inode, start);
>   	last_blk = bytes_to_blks(inode, start + len - 1);

And round up end position w/:

last_blk = bytes_to_blks(inode, round_up(start + len - 1, F2FS_BLKSIZE));

Thanks,