Re: Possible error in nfs_nfsdserv.c?

On Fri, 26 Mar 2010, Petr Lampa wrote:

>
> I've got several "panic: nfsrelpath", see attached photo. I've found
> one place where it could probably happen, please, can you look at this?
>
> First name buffer is initialized in nfsrvd_link() with:
>       	NFSNAMEICNDSET(&named.ni_cnd, nd->nd_cred, CREATE, LOCKPARENT);
>
> Then:
> 	nd->nd_repstat = nfsvno_namei(nd, &named, dp, 0, &tnes,
> 	                             p, &dirp);
>
> and
> 	nd->nd_repstat = nfsvno_link(&named, vp, nd->nd_cred, p, exp);
>
> is called. The nfsvno_link() calls nfsvno_relpathbuf() unconditionally,
> this is the place where the panic happened. The only place where buffer can
> be released in no error case is in the nfsvno_namei(). There is a call
>
> 	  if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0)
>                                  nfsvno_relpathbuf(ndp);
>
> there and no SAVENAME|SAVESTART is set in NFSNAMEICNDSET(). But if
> buffer is alwyas released at this place, then link would be panicing also
> always (and it isn't). So probably I'm missing something here. Other

For ufs, ufs_lookup() sets SAVENAME for the CREATE case, which is why
I don't see such a panic. I had thought that all file systems would do
this for VOP_LOOKUP() for CREATE. It sounds like you've found a case
where that isn't happening. Could you please tell us what file system
type is being accessed when this panic occurs?

I've cc'd freebsd-current, so that anyone conversant with the FreeBSD
VFS can jump in here. Am I right to assume that VOP_LOOKUP() for CREATE
will set SAVENAME when returning error == 0?

> functions where nfsvno_namei() is called without SAVENAME|SAVESTART flags
> also don't call nfsvno_relpathbuf(). Perhaps buffer should be initialized
> with
>
> NFSNAMEICNDSET(&named.ni_cnd, nd->nd_cred, CREATE, LOCKPARENT | SAVENAME);
>

Yes, please try this. I think it will fix the problem, since my server
code assumes that VOP_LOOKUP() will have set SAVENAME for the non-error
case. (I don't think setting it is harmful and it will help isolate the
problem further.)

Please let us know how things go with SAVENAME set, as above.

rick