linux-kernel - Re: [PATCH 6/7] lib/lzo: implement run-length encoding

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Date:   Thu, 29 Nov 2018 12:08:40 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Dave Rodgman <dave.rodgman@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        nd <nd@....com>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Matt Sealey <Matt.Sealey@....com>,
        "nitingupta910@...il.com" <nitingupta910@...il.com>,
        "rpurdie@...nedhand.com" <rpurdie@...nedhand.com>,
        "markus@...rhumer.com" <markus@...rhumer.com>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "sergey.senozhatsky.work@...il.com" 
        <sergey.senozhatsky.work@...il.com>,
        "sonnyrao@...gle.com" <sonnyrao@...gle.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 6/7] lib/lzo: implement run-length encoding

On (11/27/18 16:19), Dave Rodgman wrote:
>
> This modifies the bitstream in a way which is backwards compatible
> (i.e., we can decompress old bitstreams, but old versions of lzo
> cannot decompress new bitstreams).
>

Hmmm... Whoa. Help me understand this:

So a btrfs filesystem, compressed with the new lzo, say I run 4.21,
won't be readable at all once I reboot under 4.19?

What about compressed net traffic between servers running different
kernel version (one with new lzo, the other one with old lzo)?
XFRM can be compressed with lzo, can't it?

	-ss