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Subject: Re: [PATCH v4 4/5] erofs-utils: zero out garbage trailing data for
 non-0padding cases
To: Gao Xiang <xiang@kernel.org>, linux-erofs@lists.ozlabs.org,
 Li Guifu <bluce.liguifu@huawei.com>
References: <20210430040345.17120-1-xiang@kernel.org>
 <20210430040345.17120-4-xiang@kernel.org>
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Date: Sat, 1 May 2021 00:17:24 +0800
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From: Li GuiFu via Linux-erofs <linux-erofs@lists.ozlabs.org>
Reply-To: Li GuiFu <bluce.lee@aliyun.com>
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 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>



On 2021/4/30 12:03, Gao Xiang wrote:
> When "-E legacy-compress" is used, lz4 0padding feature will be
> disabled by default in order to support old kernels (< Linux v5.3).
> 
> In that case, the current mkfs leaves previous garbage data after
> valid compressed data if the length becomes shorter. This doesn't
> matter for kernels >= v5.0 since LZ4_decompress_safe_partial() is used.
> 
> However, for staging erofs v4.19, it used an in-house customized
> lz4 implemention due to LZ4_decompress_safe_partial() didn't work
> as expected at that time, yet it doesn't allow trailing random
> data in practice or decompression failure could happen.
> 
> I don't think it really matters since "obsoleted_mkfs" works perfectly
> for such old staging versions (v4.19). Anyway, trailing garbage data
> sounds unreasonable, so let's zero out it now.
> 
> Fixes: 66653ef10a7f ("erofs-utils: introduce compression for regular files")
> Signed-off-by: Gao Xiang <xiang@kernel.org>
> ---
>  lib/compress.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
It looks good
Reviewed-by: Li Guifu <bluce.lee@aliyun.com>

Thanks,