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Date: Sun, 17 Oct 2021 23:25:49 +0800
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Subject: Re: [PATCH v2 1/3] erofs: get compression algorithms directly on
 mapping
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To: Gao Xiang <xiang@kernel.org>, linux-erofs@lists.ozlabs.org
References: <20211008200839.24541-1-xiang@kernel.org>
 <20211008200839.24541-2-xiang@kernel.org>
From: Chao Yu <chao@kernel.org>
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Cc: Gao Xiang <hsiangkao@linux.alibaba.com>,
 LKML <linux-kernel@vger.kernel.org>
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 <linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org>

On 2021/10/9 4:08, Gao Xiang wrote:
> From: Gao Xiang <hsiangkao@linux.alibaba.com>
> 
> Currently, z_erofs_map_blocks_iter() returns whether extents are
> compressed or not, and the decompression frontend gets the specific
> algorithms then.
> 
> It works but not quite well in many aspests, for example:
>   - The decompression frontend has to deal with whether extents are
>     compressed or not again and lookup the algorithms if compressed.
>     It's duplicated and too detailed about the on-disk mapping.
> 
>   - A new secondary compression head will be introduced later so that
>     each file can have 2 compression algorithms at most for different
>     type of data. It could increase the complexity of the decompression
>     frontend if still handled in this way;
> 
>   - A new readmore decompression strategy will be introduced to get
>     better performance for much bigger pcluster and lzma, which needs
>     the specific algorithm in advance as well.
> 
> Let's look up compression algorithms in z_erofs_map_blocks_iter()
> directly instead.
> 
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,