Re: May close() return any error code?

[Al Viro <viro@ZenIV.linux.org.uk>]

On Wed, Jul 29, 2015 at 07:45:11AM -0700, Dmitry Torokhov wrote:
> > This seems coming from evdev_flush().  As there is no fd leak, it's no
> > big problem per se.  But, now the question is whether returning such
> > an error code is correct behavior at all.  At least, it doesn't seem
> > defined in POSIX:
> >   http://pubs.opengroup.org/onlinepubs/009695399/functions/close.html
> 
> Hmm, if I checked the right version of the code close_nointr_nofail()
> expects only 0 as the return code so even if we change the kernel to
> use more conforming -EIO instead of -ENODEV systemd will still die...
> 
> The question is whether we really need to propagate return value from
> f_op->flush() up to userspace in filp_close(). Why don't we ask Al?

That's the whole damn point of having ->flush().  And yes, we do need that -
things like NFS (not to mention tapes, etc.) do rely on that.

Whether it makes sense to do this kind of "do something that might have
a failure to report on each close()" for evdev is up to driver, obviously.