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

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

The following reply was made to PR kern/46221; it has been noted by GNATS.

From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
To: Matthias Scheler <tron%zhadum.org.uk@localhost>
Cc: gnats-bugs%NetBSD.org@localhost
Subject: Re: kern/46221: Kernel panic in NFS server code
Date: Fri, 23 Mar 2012 10:33:49 +0100

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 On Fri, Mar 23, 2012 at 12:01:16AM +0000, Matthias Scheler wrote:
 > On Wed, Mar 21, 2012 at 06:10:07PM +0000, Manuel Bouyer wrote:
 > >  The code has changed in this area; I'm not sure the same code will
 > >  work (there is a KASSERT in cleanvnode() that, I think, would
 > >  have fired if we had the same senario). There is also a KASSERT()
 > >  in vget() that we're not returning a clean vnode.
 > >  
 > >  I wonder if while we're slepping on vp->v_interlock, the vnode could
 > >  have been moved to another filesystem ...
 > >  printing the vnode when the problem happens will really help.
 > 
 > The new code in ufs_fhtovp() finally triggered.
 > Here is the output of vprint():
 > 
 > ufs_fhtovp: ip == NULL on vp %p
 > : vnode @ 0xfffffe8169463be0, flags (0x80010<MPSAFE,CLEAN>)
 >         tag VT_NON(0), type VREG(1), usecount 1, writecount 0, holdcount 0
 >         freelisthd 0x0, mount 0xfffffe8214f82000, data 0x0 lock 
 > 0xfffffe8169463cf0
 
 So it got a clean vnode. This is bad.
 I suspect ufs_ihashget() is returnning the clean vnode; otherwise it has to be
 in ffs_vget() itself.
 
 Can you run a kernel with the attached patch and see if one of the KASSERT
 fires ? You can probably turn the check to a printf if you want to
 avoid the panic.
 
 -- 
 Manuel Bouyer <bouyer%antioche.eu.org@localhost>
      NetBSD: 26 ans d'experience feront toujours la difference
 --
 
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 Index: ffs/ffs_vfsops.c
 ===================================================================
 RCS file: /cvsroot/src/sys/ufs/ffs/ffs_vfsops.c,v
 retrieving revision 1.269
 diff -u -p -u -r1.269 ffs_vfsops.c
 --- ffs/ffs_vfsops.c   7 Oct 2011 09:35:07 -0000       1.269
 +++ ffs/ffs_vfsops.c   23 Mar 2012 09:31:56 -0000
 @@ -1867,6 +1867,7 @@ ffs_vget(struct mount *mp, ino_t ino, st
        }                                                       /* XXX */
        uvm_vnp_setsize(vp, ip->i_size);
        *vpp = vp;
 +      KASSERT((vp->v_iflag & VI_CLEAN) == 0);
        return (0);
  }
  
 Index: ufs/ufs_ihash.c
 ===================================================================
 RCS file: /cvsroot/src/sys/ufs/ufs/ufs_ihash.c,v
 retrieving revision 1.31
 diff -u -p -u -r1.31 ufs_ihash.c
 --- ufs/ufs_ihash.c    12 Jun 2011 03:36:02 -0000      1.31
 +++ ufs/ufs_ihash.c    23 Mar 2012 09:31:56 -0000
 @@ -153,6 +153,7 @@ ufs_ihashget(dev_t dev, ino_t inum, int 
                                if (vget(vp, flags))
                                        goto loop;
                        }
 +                      KASSERT((vp->v_iflag & VI_CLEAN) == 0);
                        return (vp);
                }
        }
 
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