linux-kernel - Re: [PATCH 2/7] zram: Prevent overflow in logical block size

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Message-ID: <20110126190908.GE17383@linux.vnet.ibm.com>
Date:	Wed, 26 Jan 2011 13:09:08 -0600
From:	Robert Jennings <rcj@...ux.vnet.ibm.com>
To:	Pekka Enberg <penberg@...nel.org>
Cc:	Nitin Gupta <ngupta@...are.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] zram: Prevent overflow in logical block size

Pekka Enberg <penberg@...nel.org> wrote:
> On Wed, Jan 26, 2011 at 7:23 PM, Robert Jennings <rcj@...ux.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@...ux.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.
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