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

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

On Wed, Mar 21, 2012 at 01:35:02PM +0000, Matthias Scheler wrote:
>  >  I got a new back-trace ...
>  >  
>  >  b{1}> bt
>  >  ufs_fhtovp() at netbsd:ufs_fhtovp+0x2e
>  >  ffs_fhtovp() at netbsd:ffs_fhtovp+0x55
>  >  VFS_FHTOVP() at netbsd:VFS_FHTOVP+0x1c
>  >  dofhopen() at netbsd:dofhopen+0xda
>  >  syscall() at netbsd:syscall+0xc4
>  >  
>  >  ... and a register dump:
>  >  
>  >  db{1}> sh registers
>  >  ds          9a90
>  >  es          7480
>  >  fs          9a30
>  >  gs          a000
>  >  rdi         fffffe81c281bac0
>  >  rsi         0
>  >  rbp         fffffe810eda9a80
>  >  rbx         fffffe810eda9a90
>  >  rdx         0
>  >  rcx         7
>  >  rax         0
>  >  r8          fffffe810e9b3000
>  >  r9          0
>  >  r10         1
>  >  r11         0
>  >  r12         fffffe810eda9bc0
>  >  r13         3
>  >  r14         1c
>  >  r15         7f7ff7b4f3c0
>  >  rip         ffffffff8042b121    ufs_fhtovp+0x2e
>  >  cs          8
>  >  rflags      10246
>  >  rsp         fffffe810eda9a60
>  >  ss          10
>  >  netbsd:ufs_fhtovp+0x2e: cmpw    $0,c8(%rdx)
>  
>  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.

Looks like kern/41147. Fixed here:
http://mail-index.netbsd.org/source-changes/2009/09/20/msg001090.html
and then in a better way here:
http://mail-index.netbsd.org/source-changes/2009/11/05/msg002668.html

most of this has been removed in vfs_subr.c The commit log says that
"Now that ffs on disk inodes get freed in the reclaim routine" this is
no longer needed. 

At first glance I can't see a problem with this. But I wonder if stacked
filesystems could have a role in this; is the NFS-exported filesystem also
acceeded by layered FSes ?

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