Re: [PATCH 02/10] Remove need for explicit device initialization

Nitin Gupta
2010-08-10T03:38:07Z

On 08/10/2010 12:06 AM, Pekka Enberg wrote:
> On Mon, Aug 9, 2010 at 8:26 PM, Nitin Gupta <ngupta@vflare.org> wrote:
>> Currently, the user has to explicitly write a positive value to
>> initstate sysfs node before the device can be used. This event
>> triggers allocation of per-device metadata like memory pool,
>> table array and so on.
>>
>> We do not pre-initialize all zram devices since the 'table' array,
>> mapping disk blocks to compressed chunks, takes considerable amount
>> of memory (8 bytes per page). So, pre-initializing all devices will
>> be quite wasteful if only few or none of the devices are actually
>> used.
>>
>> This explicit device initialization from user is an odd requirement and
>> can be easily avoided. We now initialize the device when first write is
>> done to the device.
>>
>> Signed-off-by: Nitin Gupta <ngupta@vflare.org>
>
> AFAICT, most hardware block device drivers do things like this in the
> probe function. Why can't we do that for zram as well and drop the
> ->init_done and ->init_lock parts?
>

I think probe is only for PCI devices? Maybe should hook into open function
in struct block_device_operations. That way, we can also drop init_done and
init_lock parts.

Thanks,
Nitin