Andriy Gapon wrote:
> on 14/02/2014 21:18 Jeremie Le Hen said the following:
> > I've just got another occurence of the exact same panic. Any clue
> > how
> > to debug this?
>
> Could you please obtain *vp from frame 12 ?
>
> The problem seems to be happening in this piece of ZFS code:
> if (cnp->cn_flags & ISDOTDOT) {
> ltype = VOP_ISLOCKED(dvp);
> VOP_UNLOCK(dvp, 0);
> }
> ZFS_EXIT(zfsvfs);
> error = vn_lock(*vpp, cnp->cn_lkflags);
> if (cnp->cn_flags & ISDOTDOT)
> vn_lock(dvp, ltype | LK_RETRY);
>
> ltype is apparently LK_SHARED and the assertion is apparently
> triggered by
> EDEADLK error. The error can occur only if a thread tries to obtain
> a lock in a
> shared mode when it already has the lock exclusively.
> My only explanation of how this could happen is that dvp == *vpp and
> cn_lkflags
> is LK_EXCLUSIVE. In other words, this is a dot-dot lookup that
> results in the
> same vnode. I think that this is only possible if dvp is the root
> vnode.
> I am not sure if my theory is correct though.
> Also, I am not sure if zfs_lookup() should be prepared to handle such
> a lookup
> or if this kind of lookup should be handled by upper/other layers.
> In this case
> these would be VFS lookup code and nullfs code.
>
I don't know if it ever occurs, but the NFS client has a check for
if (vp != dvp)
vn_lock(dvp...); /* roughly what the code looks like. */
in the ISDOTDOT section of nfs_lookup().
I don't think this check would be harmful?
rick
> --
> Andriy Gapon
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