linux-kernel - Re: [PATCH 01/10] Replace ioctls with sysfs interface

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Date:	Tue, 31 Aug 2010 16:06:23 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Nitin Gupta <ngupta@...are.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Minchan Kim <minchan.kim@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Linux Driver Project <devel@...uxdriverproject.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/10] Replace ioctls with sysfs interface

On Mon, 2010-08-09 at 22:56 +0530, Nitin Gupta wrote:
> Creates per-device sysfs nodes in /sys/block/zram<id>/
> Currently following stats are exported:
>  - disksize
>  - num_reads
>  - num_writes
>  - invalid_io
>  - zero_pages
>  - orig_data_size
>  - compr_data_size
>  - mem_used_total
> 
> By default, disksize is set to 0. So, to start using
> a zram device, fist write a disksize value and then
> initialize device by writing any positive value to
> initstate. For example:
> 
>         # initialize /dev/zram0 with 50MB disksize
>         echo 50*1024*1024 | bc > /sys/block/zram0/disksize
>         echo 1 > /sys/block/zram0/initstate
> 
> When done using a disk, issue reset to free its memory
> by writing any positive value to reset node:
> 
>         echo 1 > /sys/block/zram0/reset

Maybe I'm just a weirdo, but I don't really use modules much.  That
effectively means that I'm stuck at boot with one zram device.

Making it a read-only module param also means that someone can't add a
second at runtime while the first is still in use.

It doesn't seem to be used very pervasively, but there is a
module_param_cb() function so you can register callbacks when the param
gets updated.  Might come in handy for this.

-- Dave

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