Re: [PATCH 2/2] erofs: simplify z_erofs_transform_plain()

[Yue Hu]

On Wed, 28 Jun 2023 00:12:40 +0800
Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> wrote:

> Use memcpy_to_page() instead of open-coding them.
> 
> In addition, add a missing flush_dcache_page() even though almost all
> modern architectures clear `PG_dcache_clean` flag for new file cache
> pages so that it doesn't change anything in practice.
> 
> Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

Reviewed-by: Yue Hu <huyue2@xxxxxxxxxxx>

> ---
> preliminary tested with silesia dataset.
> 
>  fs/erofs/decompressor.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index ad53cf52d899..cfad1eac7fd9 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -328,7 +328,7 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  	const unsigned int lefthalf = rq->outputsize - righthalf;
>  	const unsigned int interlaced_offset =
>  		rq->alg == Z_EROFS_COMPRESSION_SHIFTED ? 0 : rq->pageofs_out;
> -	unsigned char *src, *dst;
> +	u8 *src;
>  
>  	if (outpages > 2 && rq->alg == Z_EROFS_COMPRESSION_SHIFTED) {
>  		DBG_BUGON(1);
> @@ -341,22 +341,19 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  	}
>  
>  	src = kmap_local_page(rq->in[inpages - 1]) + rq->pageofs_in;
> -	if (rq->out[0]) {
> -		dst = kmap_local_page(rq->out[0]);
> -		memcpy(dst + rq->pageofs_out, src + interlaced_offset,
> -		       righthalf);
> -		kunmap_local(dst);
> -	}
> +	if (rq->out[0])
> +		memcpy_to_page(rq->out[0], rq->pageofs_out,
> +			       src + interlaced_offset, righthalf);
>  
>  	if (outpages > inpages) {
>  		DBG_BUGON(!rq->out[outpages - 1]);
>  		if (rq->out[outpages - 1] != rq->in[inpages - 1]) {
> -			dst = kmap_local_page(rq->out[outpages - 1]);
> -			memcpy(dst, interlaced_offset ? src :
> -					(src + righthalf), lefthalf);
> -			kunmap_local(dst);
> +			memcpy_to_page(rq->out[outpages - 1], 0, src +
> +					(interlaced_offset ? 0 : righthalf),
> +				       lefthalf);
>  		} else if (!interlaced_offset) {
>  			memmove(src, src + righthalf, lefthalf);
> +			flush_dcache_page(rq->in[inpages - 1]);
>  		}
>  	}
>  	kunmap_local(src);