On 2013-05-30 06:55:16 -0400, Greg Smith wrote: > On 5/30/13 6:49 AM, Robert Haas wrote: > >On Wed, May 29, 2013 at 10:42 AM, Andres Freund <and...@2ndquadrant.com> > >wrote: > >>So we don't even know whether we can read. I think that means we need to > >>zero the file anyway... > > > >Surely this is undue pessimism. > > There have been many occasions where I've found the Linux kernel defining > support for POSIX behavior with a NOP stub that basically says "we should > make this work one day". I don't know whether the fallocate code is one of > those or a fully implemented call. Based on that history, until I see a > reader that validates the resulting files are good I have to assume they're > not.
That argument in contrast I find not very convincing though. What was the last incidence of such a system call that did not just error out with ENOTSUPP or such? The linux fallocate call is fully specified for this behaviour and got added 2.6.23, there wasn't a stub before, so I am far less worried about it than about the underspecifiedness of posix_fallocate(). Also, if some system call doesn't follow its documented specifications it's not fully our problem anymore. If we rely on undocumented behaviour though... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers