Re: [dm-devel] [RFC][PATCH] dm-mirror: fix data corruption

[Takahiro Yasui <tyasui redhat com>]

Hi Nomura-san,

On 07/10/09 07:16, Jun'ichi Nomura wrote:
> Hi Yasui-san,
> 
> Takahiro Yasui wrote:
>> This is a prototype patch to fix data corruption issue on dm-raid1.
>> It is just a draft patch and is not tested well, but let me post it
>> to review and discuss this in-kernel superblock approach.
>>
>> I appreciate your comments and suggestions.
> <snip>
>>   * Introduce superblock area
>>
>>     A superblock area is related to a mirror leg on a one-to-one basis and
>>     keeps a sequential number to decide the default mirror when the mirror
>>     is resumed.
> 
> If you are to introduce kernel-managed RAID1 superblock,
> isn't it possible to use the on-disk format compatible to md's?
> Then the kernel code to handle the superblock may be shared between
> md and dm in future, which I think is even better and would help
> dm/md convergence.

Thank you for the comment. You are right and sharing the kernel code to
handle superblock between md and dm would be better toward merging dm/md.
I would like to introduce this in-kernel superblock approach, but userspace
approach handled by dmeventd seems to be preferred. I try to check the
possibility to reduce overhead of error handling in userspace.

Thanks,
Taka