Hi, On 2018-11-13 12:04:23 -0500, Robert Haas wrote: > I still feel like this whole pass-the-fds-to-the-checkpointer thing is > a bit of a fool's errand, though. I mean, there's no guarantee that > the first FD that gets passed to the checkpointer is the first one > opened, or even the first one written, is there?
I'm not sure I understand the danger you're seeing here. It doesn't have to be the first fd opened, it has to be an fd that's older than all the writes that we need to ensure made it to disk. And that ought to be guaranteed by the logic? Between the FileWrite() and the register_dirty_segment() (and other relevant paths) the FD cannot be closed. > It seems like if you wanted to make this work reliably, you'd need to > do it the other way around: have the checkpointer (or some other > background process) open all the FDs, and anybody else who wants to > have one open get it from the checkpointer. That'd require a process context switch for each FD opened, which seems clearly like a no-go? Greetings, Andres Freund
