Re: kern/46221: Kernel panic in NFS server code

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Mar 21, 2012 at 03:10:10PM +0000, Matthias Scheler wrote:
> The following reply was made to PR kern/46221; it has been noted by GNATS.
> 
> From: Matthias Scheler <tron%zhadum.org.uk@localhost>
> To: "J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>
> Cc: NetBSD GNATS <gnats-bugs%NetBSD.org@localhost>
> Subject: Re: kern/46221: Kernel panic in NFS server code
> Date: Wed, 21 Mar 2012 15:08:27 +0000
> 
>  On Wed, Mar 21, 2012 at 03:44:28PM +0100, J. Hannken-Illjes wrote:
>  > <snip>
>  > > 
>  > > Manual Bouyer has looked at this crash. The kernel paniced here:
>  > > 
>  > >         ip = VTOI(nvp);
>  > > -->     if (ip->i_mode == 0 || ip->i_gen != ufhp->ufid_gen) {
>  > >                 vput(nvp);
>  > >                 *vpp = NULLVP;
>  > >                 return (ESTALE);
>  > >         }
>  > > 
>  > > I guess that an extra check whether "ip" is NULL would prevent the
>  > > panic. But I'm not sure whether that is the correct fix.
>  > 
>  > Please change this to
>  > 
>  >    ip = VTOI(nvp);
>  > +  if (ip == NULL) {
>  > +          vprintf("NULL IP", nvp);
>  > +          panic("NULL IP");
>  > +  }
>  >    if (...
>  > 
>  > so on the next crash we know more about the state of the vnode/inode.
>  
>  I've already changed it like this:
>  
>  Index: sys/ufs/ufs/ufs_vfsops.c
>  ===================================================================
>  RCS file: /cvsroot/src/sys/ufs/ufs/ufs_vfsops.c,v
>  retrieving revision 1.50
>  diff -u -r1.50 ufs_vfsops.c
>  --- sys/ufs/ufs/ufs_vfsops.c 1 Feb 2012 05:34:43 -0000       1.50
>  +++ sys/ufs/ufs/ufs_vfsops.c 21 Mar 2012 15:07:49 -0000
>  @@ -223,7 +223,11 @@
>               return (error);
>       }
>       ip = VTOI(nvp);
>  -    if (ip->i_mode == 0 || ip->i_gen != ufhp->ufid_gen) {
>  +    if (ip == NULL || ip->i_mode == 0 || ip->i_gen != ufhp->ufid_gen) {
>  +            if (ip == NULL) {
>  +                    aprint_normal("ufs_fhtovp: ip == NULL on vp %p\n",
>  +                        nvp);
>  +            }
>               vput(nvp);
>               *vpp = NULLVP;
>               return (ESTALE);
>  
>  I'll check whether I get some of these kernel messages.
>  
>  > If you are able to debug the core dump you could `print *nvp' here.
>  
>  Kernel core dumps have never worked for me under NetBSD/amd64.

But I think, once you have the vnode address, you can do a
show vnode <addr>
from ddb.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--