linux-kernel - Re: [PATCH] loop: export module parameters

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Date:	Fri, 27 May 2011 07:59:41 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Namhyung Kim <namhyung@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Laurent Vivier <Laurent.Vivier@...l.net>
Subject: Re: [PATCH] loop: export module parameters

On 2011-05-27 06:57, Namhyung Kim wrote:
> 2011-05-25 (수), 14:44 +0900, Namhyung Kim:
>> Export 'max_loop' and 'max_part' parameters to sysfs so user can know
>> that how many devices are allowed and how many partitions are supported.
>>
>> If 'max_loop' is 0, there is no restriction on the number of loop devices.
>> User can create/use the devices as many as minor numbers available. If
>> 'max_part' is 0, it means simply the device doesn't support partitioning.
>>
>> Also note that 'max_part' can be adjusted to power of 2 minus 1 form if
>> needed. User should check this value after the module loading if he/she
>> want to use that number correctly (i.e. fdisk, mknod, etc.).
>>
>> Signed-off-by: Namhyung Kim <namhyung@...il.com>
>> Cc: Laurent Vivier <Laurent.Vivier@...l.net>
>> ---
>>  drivers/block/loop.c |   17 ++++++++++++++---
>>  1 files changed, 14 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>> index c59a672a3de0..76c8da78212b 100644
>> --- a/drivers/block/loop.c
>> +++ b/drivers/block/loop.c
>> @@ -1540,9 +1540,9 @@ static const struct block_device_operations lo_fops = {
>>   * And now the modules code and kernel interface.
>>   */
>>  static int max_loop;
>> -module_param(max_loop, int, 0);
>> +module_param(max_loop, int, S_IRUGO);
>>  MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
>> -module_param(max_part, int, 0);
>> +module_param(max_part, int, S_IRUGO);
>>  MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
>>  MODULE_LICENSE("GPL");
>>  MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
>> @@ -1688,9 +1688,20 @@ static int __init loop_init(void)
>>  	 */
>>  
>>  	part_shift = 0;
>> -	if (max_part > 0)
>> +	if (max_part > 0) {
>>  		part_shift = fls(max_part);
>>  
>> +		/*
>> +		 * Adjust max_part according to part_shift as it is exported
>> +		 * to user space so that user can decide correct minor number
>> +		 * if [s]he want to create more devices.
>> +		 *
>> +		 * Note that -1 is required because partition 0 is reserved
>> +		 * for the whole disk.
>> +		 */
>> +		max_part = (1UL << part_shift) - 1;
>> +	}
>> +
>>  	if ((1UL << part_shift) > DISK_MAX_PARTS)
>>  		return -EINVAL;
>>  
> 
> Hi Jens,
> 
> Could you please consider applying this in your tree too? It's exactly
> the same thing what I did for brd series.

Applied now, missed it yesterday. Thanks!

-- 
Jens Axboe

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