Deadlock (?) with ZFS, NFS

[Peter Maloney]

On 03/08/2012 07:02 AM, Garrett Wollman wrote:
> This is a 9.0-RELEASE system with the mps driver backported from
> 9-stable.  Hourly and daily snapshots were enabled.  It had been
> working extremely well up to this point, and we were looking at
> possibly replacing our existing NFS servers with this architecture.
On one system, (haven't tried it lately), it will hang a single dataset 
if a Linux *client* mounts the zfs dataset and does:

cd /mount/point
ls .zfs/snapshot

So try that and see if it reproduces the problem.

Setting snapdir=hidden doesn't prevent accessing it, only hides it from 
"ls -a" output.

The problem did not occur back when I had few or no snapshots. It also 
doesn't happen on the replicated backup server, with all the same 
software, data and snapshots.

So far, my hack solution is to mount /var/empty on top of every .zfs 
directory on the client side. Another idea is to never export a whole 
dataset from the root of it, because that is the only place that 
contains the .zfs directory, other than if you have subdatasets inside 
that one.



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Peter Maloney
Brockmann Consult
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E-mail: peter.maloney at brockmann-consult.de
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