zfs discuss - Jun 2007 - netbsd client can mount zfs snapshot dir but it never updates

My Solaris 10 box is exporting a ZFS filesystem over NFS.  I''m
accessing the data with a NetBSD 3.1 client, which only supports NFS 3. 
Everything works except when I look at the .zfs/snapshot directory.  The first
time I list out the .zfs/snapshot directory, I get a correct listing of the
contents.  An hour later, when a snapshot has been deleted and a new one
created, I still see the same listing.  If I type in the name of the new
snapshot manually, I can access it, but the contents of the .zfs/snapshot
directory as seen by the NetBSD 3.1 box never changes (well, not in the last 24
hours since I started testing this).

Some kind of cacheing problem?  Any suggestions?
 
 
This message posted from opensolaris.org

Quoth Ed Ravin on Thu, Jun 07, 2007 at 09:57:52PM -0700:
> My Solaris 10 box is exporting a ZFS filesystem over NFS.  I''m
> accessing the data with a NetBSD 3.1 client, which only supports NFS
> 3.  Everything works except when I look at the .zfs/snapshot
> directory.  The first time I list out the .zfs/snapshot directory,
> I get a correct listing of the contents.  An hour later, when
> a snapshot has been deleted and a new one created, I still see the
> same listing.  If I type in the name of the new snapshot manually,
> I can access it, but the contents of the .zfs/snapshot directory as
> seen by the NetBSD 3.1 box never changes (well, not in the last 24
> hours since I started testing this).
I''m not an NFS expert, but I do know that non-Solaris clients have had
problems accessing the snapshot directory via NFSv3 in the past.  See
http://www.opensolaris.org/jive/thread.jspa?messageID=45927&#45927 .


David

On Mon, Jun 11, 2007 at 02:03:58PM -0700, David Bustos
wrote:
> Quoth Ed Ravin on Thu, Jun 07, 2007 at 09:57:52PM -0700:
> > My Solaris 10 box is exporting a ZFS filesystem over NFS. 
I''m
> > accessing the data with a NetBSD 3.1 client, which only supports NFS
> > 3.  Everything works except when I look at the .zfs/snapshot
> > directory.  The first time I list out the .zfs/snapshot directory,
> > I get a correct listing of the contents.  An hour later, when
> > a snapshot has been deleted and a new one created, I still see the
> > same listing.  If I type in the name of the new snapshot manually,
> > I can access it, but the contents of the .zfs/snapshot directory as
> > seen by the NetBSD 3.1 box never changes (well, not in the last 24
> > hours since I started testing this).
> 
> I''m not an NFS expert, but I do know that non-Solaris clients have
had
> problems accessing the snapshot directory via NFSv3 in the past.  See
> http://www.opensolaris.org/jive/thread.jspa?messageID=45927&#45927 .
That''s a different problem - we have Netapps too and are familiar with
how
snapshots of files might have the same inode as the original files.

Back to my original problem, it seems inconsistent - after a day or
two, it''s gone, the directory listing of .zfs/snapshot shows the
correct
elements within.

However, I could have sworn that when we first started testing the
snapshots, the modtime on the snapshot directory was the time of the
snapshot, but after the cacheing problem went away, I noticed that
all the snapshot directories had the same modtime, all several days old.
And today, the most recent snapshot, taken at 4 PM, has a modtime from
five days ago, with a "last access time" of 3:36 PM today, 24 minutes
before it was created.

I did find a workaround to the original problem - I can automount the snapshot
directory elsewhere on the NetBSD 3.1 client, and if the client gets an
inconsistent listing there, it will go away when the directory is
auto-unmounted.

Any pointers on how to debug this will be appreciated.  I will start with
trying to reproduce it while the sniffer is running.