Re: pg_test_fsync problem

I wrote:
> He's complaining that it dies with EINVAL.

> I notice that (1) it's using O_DIRECT even though the printout claims
> otherwise, and (2) it's writing from a buffer that has no better than
> char alignment, which is certainly not OK for O_DIRECT.  Either one
> of those could plausibly result in EINVAL ...

Oh, scratch that: the buffer is properly aligned, it's the length that's
bogus for O_DIRECT.  I rather imagine that test_open_sync is meant to be
writing so many kilobytes, not so many bytes.
        regards, tom lane