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List:       netbsd-users
Subject:    Re: how to limit /etc/daily to local only, and cleasring bad nfs
From:       mlelstv () serpens ! de (Michael van Elst)
Date:       2022-06-18 16:29:16
Message-ID: t8kugr$c5r$1 () serpens ! de
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steve@prd.co.uk (Steve Blinkhorn) writes:

>Some off-list discussion has clarified matters.  The fundamental problem is that nfs
>mounts are not restored automatically when an nfs server is rebooted - and that
>may happen automatically so the sysadmin is unaware.

Actually that's the opposite from what NFS does. When the server comes back, the
file operations will continue. I haven't seen anything else.


>The connection with /etc/daily (etc.) is that find(1) hangs when it encounters a broken
>nfs mount point, gets stuck in tstile, and can't be killed.

Here a find gets stalled in nfscn2 when the NFS server goes down.

When mounted interruptibly (mount_nfs -i) you can kill the hanging operation, at least
the hanging find.

But interrupting is broken for other operations, e.g.:

A read will keep the client process stuck non-interruptibly in uvnfp2, waiting for
a page to become available.

A write hangs in nfsaio which can be interrupted, but the process will then hang
on exit as it waits for a synchronous close to succeed. The close operation
requires the ioflush kernel thread to complete outstanding I/Os, and ioflush will
be stuck in nfsrcv. The hanging ioflush will also impact all other I/O operations
in the system.

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