[PATCH 2/7] zram: Prevent overflow in logical block size

[Robert Jennings]

Pekka Enberg <penberg at kernel.org> wrote:
> On Wed, Jan 26, 2011 at 7:23 PM, Robert Jennings <rcj at linux.vnet.ibm.com> wrote:
>> On a 64K page kernel, the value PAGE_SIZE passed to
>> blk_queue_logical_block_size would overflow the logical block size
>> argument (resulting in setting it to 0).
>> 
>> Take the minimum of PAGE_SIZE or 4096 and use this for the block device
>> logical block size.
>> 
>> Signed-off-by: Robert Jennings <rcj at linux.vnet.ibm.com>
>> ---
>>  drivers/staging/zram/zram_drv.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>> 
>> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
>> index d0e9e02..d5e0275 100644
>> --- a/drivers/staging/zram/zram_drv.c
>> +++ b/drivers/staging/zram/zram_drv.c
>> @@ -621,7 +621,8 @@ static int create_device(struct zram *zram, int device_id)
>>  	 * and n*PAGE_SIZED sized I/O requests.
>>  	 */
>>  	blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
>> -	blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
>> +	blk_queue_logical_block_size(zram->disk->queue,
>> +			(unsigned short) min_t(unsigned int, PAGE_SIZE, 4096));
> 
> I don't get it. No architecture supports PAGE_SIZE less than 4K so
> that expression always ends up being 4096, no?

Yes, I will cut out the min_t and just hard-code this to 4096.