final decision about *at syscalls

[Pawel Jakub Dawidek]

On Wed, Apr 16, 2008 at 08:58:32PM +0300, Kostik Belousov wrote:
> On Wed, Apr 16, 2008 at 06:52:12PM +0100, Robert Watson wrote:
> > NDINIT() is already aware of the file descriptor array because it uses that 
> > to get the current working and root directories.  And what the *at() system 
> > calls are effectively doing is substituting another directory for the 
> > current working directory.  The exact expression of all this doesn't matter 
> > all that much to me, but I think evaluating the file descriptor array for 
> > directory stuff all in one place, rather than spread over the caller and 
> > NDINIT(), is cleaner and avoids a lot of code everywhere.  Nothing says you 
> > can't have:
> > 
> >      void
> >      NDINIT(struct nameidata *ndp, u_long op, u_long flags,
> >          enum uio_seg segflg, const char *namep, struct thread *td);
> > 
> >      void
> >      NDINIT_AT(struct nameidata *ndp, u_long op, u_long flags,
> >          enum uio_seg segflg, const char *namep, int fd, struct thread *td);
> > 
> >      NDINIT_DVP(struct nameidata *ndp, u_long op, u_long flags,
> >          enum uio_seg segflg, const char *namep, struct vnode *vp,
> >          struct thread *td);
> > 
> > However, I think I wouldn't want NDINIT_AT() to be a wrapper for 
> > NDINIT_DVP(), because I'd like all that fdp following to occur together.
> 
> I already mailed the patch implementing all the above, modulo
> s/_DVP/_ATVP/. I want to get the response from Pawel and others. If
> positive, the patch is to be tested and committed.

Back when we discussed NDINIT_AT(), I was a bit opposed, because I was
afraid that we will grow more NDINIT_<arg>() functions. I preferred to
just initialize additional arguments directly, eg.

	NDINIT(&nd, foo, bar);
	nd.ni_dirfd = fd;
	nd.ni_startvp = dvp;
	namei(&nd);

At this point I don't really care, I can use NDINIT_DVP/NDINIT_ATVP.

> I see no reason for heating the debate.

Agreed.

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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