The reason why we need this ioctl is to offer the none-privileged
end-user a possibility to get filesys info gathering.
We use OCFS2_IOC_INFO to manipulate the new ioctl, userspace passes a
structure to kernel containing an array of request pointers and request
count, such as,
Get the request pointers from *info*, then handle each request one bye one.
Idea here is to make the spearated request small enough to guarantee
a better backward&forward compatibility since a small piece of request
would be less likely to be broken if filesys on raw disk get changed.
Currently, the following 7 requests are supported per the requirement from
userspace tool o2info, and I believe it will grow over time:-)