Re: panic: LK_RETRY set with incompatible flags

Sergey Kandaurov wrote:
> On 5 February 2013 04:13, Rick Macklem <rmacklem_at_uoguelph.ca> wrote:
> > Sergey Kandaurov wrote:
> >> On 4 February 2013 06:32, Rick Macklem <rmacklem_at_uoguelph.ca>
> >> wrote:
> >> > Konstantin Belousov wrote:
> >> >> On Sat, Feb 02, 2013 at 09:30:39PM -0500, Rick Macklem wrote:
> >> >> > Andriy Gapon wrote:
> >> >> > > on 31/01/2013 15:29 Sergey Kandaurov said the following:
> >> >> > > > Hi.
> >> >> > > >
> >> >> > > > Got this assertion on idle NFS server while `ls -la
> >> >> > > > /.zfs/shares/'
> >> >> > > > issued on NFS client.
> >> > Ok, here's a snippet of zfs_dirlook() from zfs_dir.c:
> >> > 388 } else if (name[0] == '.' && name[1] == '.' && name[2] == 0)
> >> > {
> >> > 389 zfsvfs_t *zfsvfs = dzp->z_zfsvfs;
> >> > 390
> >> > 391 /*
> >> > 392 * If we are a snapshot mounted under .zfs, return
> >> > 393 * the vp for the snapshot directory.
> >> > 394 */
> >> > 395 if ((error = sa_lookup(dzp->z_sa_hdl,
> >> > 396 SA_ZPL_PARENT(zfsvfs), &parent, sizeof (parent))) != 0)
> >> > 397 return (error);
> >> > 398 if (parent == dzp->z_id && zfsvfs->z_parent != zfsvfs) {
> >> > 399 error = zfsctl_root_lookup(zfsvfs->z_parent->z_ctldir,
> >> > 400 "snapshot", vpp, NULL, 0, NULL, kcred,
> >> > 401 NULL, NULL, NULL);
> >> > 402 return (error);
> >> > 403 }
> >> >
> >> > Just reading the comment, I don't know what it is referring to by
> >> > "snapshot directory". Would that be "shares" for Sergey's case?
> >> >
> >> > It seems too obvious, but maybe the lookup of ".." is returning
> >> > the
> >> > vnode for /.zfs/shares for this case?
> >> >
> >> > I don't know why this wouldn't have shown up before, but maybe it
> >> > usually
> >> > replies from its cache (I think zfs_lookup() calls it a "fast
> >> > path").
> >> >
> >> > It might still be interesting to replace zfs_vnops.c line# 1451
> >> > with:
> >> >       if ((cnp->cn_flags & ISDOTDOT) && *vpp != dvp)
> >> > and see what happens?
> >> >
> >>
> >> With this change `ls /home/user1001/.zfs/shares/' lists empty
> >> directory
> >> (although the relevant dataset has snapshot, but that's a different
> >> story :)).
> >> Great!
> >> Nothing panics/asserts/etc, just seemingly unrelated LOR
> >>
> > Yes, I think the patch is relatively safe, since lookup() checks for
> > same vnode and does a vrele() instead of a vput() when they are the
> > same,
> > at least for a plain lookup without wantparent.
> >
> > So, since I've never used ZFS, what does a "ls -la
> > /home/user1001/.zfs/shares/"
> > give you when done locally one the server?
> 
> On server (with unmodified kernel):
> # ls -la /pool1/user1001/.zfs/share
> total 2
> dr-xr-xr-x 2 root wheel 2 Feb 2 20:06 .
> dr-xr-xr-x 4 root wheel 4 Feb 2 20:06 ..
> 
> It crashes only when .zfs/share is accessed via NFS
> (with and without snapshots), and not when accessed locally.
> 
I'm not surprised. If it crashed for local accesses, I would
suspect people would have reported it much sooner.

I also suspect it only happens for NFSv4 mounts, since those
try and cross server mount points.

Since I don't understand ZFS, I have just posted a query on
freebsd-fs_at_, which I hope will get noticed by people who
may know why ZFS is doing this.

rick

> --
> wbr,
> pluknet
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