Re: [PATCH] erofs-utils: add clusterofs zero check to write_uncompressed_extent()

[Gao Xiang <hsiangkao@linux.alibaba.com>]

Hi Yue,

On Tue, Aug 17, 2021 at 12:06:04PM +0800, Yue Hu wrote:
> From: Yue Hu <huyue2@yulong.com>
> 
> No need to reset clusterofs to 0 if it's already 0. Acturally, we also
> observed that case frequently. Let's avoid it.
> 
> Signed-off-by: Yue Hu <huyue2@yulong.com>
> ---
>  lib/compress.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/compress.c b/lib/compress.c
> index 40723a1..a8ebbc1 100644
> --- a/lib/compress.c
> +++ b/lib/compress.c
> @@ -130,7 +130,7 @@ static int write_uncompressed_extent(struct z_erofs_vle_compress_ctx *ctx,
>  	unsigned int count;
>  
>  	/* reset clusterofs to 0 if permitted */
> -	if (!erofs_sb_has_lz4_0padding() &&
> +	if (!erofs_sb_has_lz4_0padding() && ctx->clusterofs &&

Also out of curiosity, which means erofs is used without lz4 0padding?
That way is not recommended now anyway, since it forbids erofs in-place
decompression (only inplace I/O works instead.)

Actually we could make clusterofs aligned with 0 for 0padding cases as
well, but in that cases, we need to recompress the previous pcluster
with new trimmed size rather than just like this.

Thanks,
Gao Xiang

>  	    ctx->head >= ctx->clusterofs) {
>  		ctx->head -= ctx->clusterofs;
>  		*len += ctx->clusterofs;
> -- 
> 1.9.1