On 30/12/2020 17:06, John Stoffel wrote:
Danny> "Provide a way for stacking block device to re-submit Danny> the bio which should be handled first." Danny> I will fix it. Great, though my second question is*why* it needs to be handled first? What is the difference between stacked and un-stacked devices and how could it be done in a way that doesn't require a seperate function like this?
Is this anything to do with what's on my mind as a database guy? I've heard that things like RAID and LVM have difficulty providing write barriers.
I want to be confident that, at EVERY level of the stack, I can put a barrier in that guarantees that everything written by user-space BEFORE the barrier is handled before anything written AFTER the barrier. That way, I can be confident that, after a problem, I know whether I can safely roll the log forward or back.
Cheers, Wol
