ZFS deadlock

[Rafi Rubin]

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I have a small server with a mirrored pair of hard drives that handles
generally light loads for a number of linux machines over nfs v3.

I've been seeing some deadlocks (and possibly worse) lately.  I've narrowed
down the freezing to a simple test run simultaneously on a number of the
client machines:

mount host:/food/bar
ls bar/.zfs/snapshot

When I do that, all the client machines hang on any access to the server.  On
the server, only the volume "bar" hangs, the rest are fine.

This occurs even when there is no other load on the server.  Also, after
rebooting the server, the client machines eventually complete the ls and
behave normally.


I think this doesn't happen if the directory is cached, either in memory or on
an L2 ssd, but I need to rerun some tests.

For now the machine seems to be stable with nfsd limited to a single thread.


Any help debugging would be appreciated,
Rafi
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