linux-kernel - Re: [PATCHv4 00/10] add on-demand device creation

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Date:	Wed, 6 May 2015 14:01:15 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCHv4 00/10] add on-demand device creation

Hello Sergey,

On Mon, May 04, 2015 at 09:38:52PM +0900, Sergey Senozhatsky wrote:
> We currently don't support zram on-demand device creation.  The only way
> to have N zram devices is to specify num_devices module parameter (default
> value 1).  That means that if, for some reason, at some point, user wants
> to have N + 1 devies he/she must umount all the existing devices, unload
> the module, load the module passing num_devices equals to N + 1.
> 
> This patchset introduces zram-control sysfs class, which has two sysfs
> attrs:
> 
>  - zram_add     -- add a new zram device
>  - zram_remove  -- remove a specific (device_id) zram device
> 
>     Usage example:
>         # add a new specific zram device
>         cat /sys/class/zram-control/zram_add
>         1
> 
>         # remove a specific zram device
>         echo 4 > /sys/class/zram-control/zram_remove

I just reported bug. Please handle it.

Other nits:

1) How about inserting a step to reset before zram_remove?
IOW, user should echo "1" > /sys/block/zram[0-9]*/reset before
echo zram_id > /sys/class/zram-control/zram_remove.

Actually, I can't think any benefit other than consistency of
zram interface but you might have.

2) How about using hot_add/hot_remove?

/class/zram-control includes prefix zram meaning so I think
we don't need zram prefix of the knobs. Instead, let's add
*hot* which is more straightforward for representing *dynamic*.

What do you think about it?

-- 
Kind regards,
Minchan Kim
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