Re: [PATCH] fsdax: dedupe should compare the min of two iters' length

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Mar 22, 2023 at 07:25:58AM +0000, Shiyang Ruan wrote:
> In an dedupe corporation iter loop, the length of iomap_iter decreases
> because it implies the remaining length after each iteration.  The
> compare function should use the min length of the current iters, not the
> total length.
> 
> Fixes: 0e79e3736d54 ("fsdax: dedupe: iter two files at the same time")
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>

Makese sense,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/dax.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 3e457a16c7d1..9800b93ee14d 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -2022,8 +2022,8 @@ int dax_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
>  
>  	while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
>  	       (ret = iomap_iter(&dst_iter, ops)) > 0) {
> -		compared = dax_range_compare_iter(&src_iter, &dst_iter, len,
> -						  same);
> +		compared = dax_range_compare_iter(&src_iter, &dst_iter,
> +				min(src_iter.len, dst_iter.len), same);
>  		if (compared < 0)
>  			return ret;
>  		src_iter.processed = dst_iter.processed = compared;
> -- 
> 2.39.2
>