linux-kernel - Re: [PATCH v2 4/8] zram: use crypto api to check alg availability

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Message-ID: <20160601022708.GL19976@bbox>
Date:	Wed, 1 Jun 2016 11:27:09 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
CC:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/8] zram: use crypto api to check alg availability

On Wed, Jun 01, 2016 at 10:07:07AM +0900, Sergey Senozhatsky wrote:
> Hello Minchan,
> 
> On (06/01/16 09:03), Minchan Kim wrote:
> [..]
> > So, if we do 'cat /sys/block/zram0/comp_algorithm", every crypto modules
> > in the backend array are loaded in memory and not unloaded until admin
> > executes rmmod? Right?
> 
> yes, I think so.

It scares me. Common case, except one we choosed, every loaded modules
will be not used. I think it's really not good. Although the wastage
might be not big now, it will be heavy as crypto comp modules are
increased.

What do you think about it?

> 
> [..]
> > If user load out-of-tree crypto compression module, what's status of
> > comp_algorithm?
> > 
> > #> insmod foo_crypto.ko
> > #> echo foo > /sys/block/zram0/comp_algorithm
> > #> cat /sys/block/zram0/comp_algorithm
> > lzo lz4 [foo]
> > ?
> 
> yes, "lzo lz4 [out-of-tree-module-name]".

Makes sense!