linux-kernel - Re: [PATCH] f2fs: compress: fix zstd data corruption

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Date:   Tue, 12 May 2020 09:44:27 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [PATCH] f2fs: compress: fix zstd data corruption

Hi Jaegeuk,

I think we need this patch in order to avoid writebacking incomplete data
compressed by zstd.

On 2020/5/8 9:16, Chao Yu wrote:
> During zstd compression, ZSTD_endStream() may return non-zero value
> because distination buffer is full, but there is still compressed data
> remained in intermediate buffer, it means that zstd algorithm can not
> save at last one block space, let's just writeback raw data instead of
> compressed one, this can fix data corruption when decompressing
> incomplete stored compression data.
> 

Fixes: 50cfa66f0de0 ("f2fs: compress: support zstd compress algorithm")

Thanks,


> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
>  fs/f2fs/compress.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index c22cc0d37369..5e4947250262 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -358,6 +358,13 @@ static int zstd_compress_pages(struct compress_ctx *cc)
>  		return -EIO;
>  	}
>  
> +	/*
> +	 * there is compressed data remained in intermediate buffer due to
> +	 * no more space in cbuf.cdata
> +	 */
> +	if (ret)
> +		return -EAGAIN;
> +
>  	cc->clen = outbuf.pos;
>  	return 0;
>  }
>