Re: [PATCH 3/4] Staging: zram: allow partial page operations

[Jerome Marchand <jmarchan@redhat.com>]

On 06/10/2011 06:41 PM, Nitin Gupta wrote:
> On 06/10/2011 06:28 AM, Jerome Marchand wrote:
>> Commit 7b19b8d45b216ff3186f066b31937bdbde066f08 (zram: Prevent overflow
>> in logical block size) introduced ZRAM_LOGICAL_BLOCK_SIZE constant to
>> prevent overflow of logical block size on 64k page kernel.
>> However, the current implementation of zram only allow operation on block
>> of the same size as a page. That makes theorically legit 4k requests fail
>> on 64k page kernel.
>>
>> This patch makes zram allow operation on partial pages. Basically, it
>> means we still do operations on full pages internally, but only copy the
>> relevent segments from/to the user memory.
>>
> 
> Couldn't we just change struct queue_limits.logical_block_size type to 
> unsigned int or something so it could hold value of 64K? Then we could
> avoid making all these changes to handle partial page requests.
> 
> Thanks,
> Nitin

I believe logical_block_size is meant to be small. I don't know if it is
reasonable to set it to such a big value as 64k. I CCed Jens and Martin to
have a more valuable opinion on the matter.

Regards,
Jerome