linux-kernel - Re: [PATCH v2 1/3] erofs: get compression algorithms directly on mapping

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Message-ID: <c56a53cc-3c63-4b87-7d32-2a5a36b48008@kernel.org>
Date:   Sun, 17 Oct 2021 23:25:49 +0800
From:   Chao Yu <chao@...nel.org>
To:     Gao Xiang <xiang@...nel.org>, linux-erofs@...ts.ozlabs.org
Cc:     LKML <linux-kernel@...r.kernel.org>, Yue Hu <zbestahu@...il.com>,
        Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: Re: [PATCH v2 1/3] erofs: get compression algorithms directly on
 mapping

On 2021/10/9 4:08, Gao Xiang wrote:
> From: Gao Xiang <hsiangkao@...ux.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@...ux.alibaba.com>

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

Thanks,