Re: O_DIRECT, ext3fs, kernel 2.4.32... again

[DervishD <lkml@dervishd.net>]

    Hi Nathan :)

 * Nathan Scott <nathans@sgi.com> dixit:
> On Mon, May 01, 2006 at 01:23:03PM +0200, DervishD wrote:
> >  * Marcelo Tosatti <marcelo@kvack.org> dixit:
> > > >     Shouldn't ext3fs return an error when the O_DIRECT flag is
> > > > used in the open call? Is the open call userspace only and thus
> > > > only libc can return such error? Am I misunderstanding the entire
> > > > issue and this is a perfectly legal behaviour (allowing the open,
> > > > failing in the read operation)?
> > > 
> > > Your interpretation is correct. It would be nicer for open() to
> > > fail on fs'es which don't support O_DIRECT, but v2.4 makes such
> > > check later at read/write unfortunately ;(
> > 
> >     Oops :(
> 
> Nothing else really make sense due to fcntl...
> 	fcntl(fd, F_SETFL, O_DIRECT);
> ...can happen at any time, to enable/disable direct I/O.

    I know, but that fcntl call should fail just like the open() one.
I mean, I don't find this very different, it's just another point
where the flag can be activated and so it should fail if the
underlying filesystem doesn't support it (and doesn't ignore it in
read()/write()).

    Raúl Núñez de Arenas Coronado

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