Posted Mar 16, 2009 22:42 UTC (Mon) by quotemstr
In reply to: Wishful thinking
Parent article: Garrett: ext4, application expectations and power management
there is no need for a write barrier anywhere in this case.
You don't need a write barrier for a completely unmodified file either. But a write barrier hurts neither case.
adding the ability to selectivly mask this, so that you can have some programs (say your word processor) go ahead and wake up the drive to save it's data, but keep other non-critical things from doing so (even if those things _think_ that they are critical) would be a very good thing.
That's a nightmare API that makes it very difficult to determine whether you're actually
writing to the disk or not. If an application's data aren't critical, it shouldn't be calling fsync in the first place. And if the property of whether the data are critical can change, the application itself should provide a knob to control that. A process-level flub is both coarse and crude as a means of controlling that.
to post comments)