[RFC] About 9pfs support "O_DIRECT + aio"?

[jiangyiwen]

Hi everyone,

Currently, I found virtio-9p in VirtFS don't support "O_DIRECT + aio"
mode, both v9fs and qemu. So when user use "O_DIRECT + aio" mode and
increase iodepths, they can't get higher IOPS.

I want to know why v9fs don't implement this mode? And I will try to
implement this mode from now on.

Thanks,
Yiwen.