Re: remounting hard -> soft

[NeilBrown <neilb@suse.de>]

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On Wed, Oct 02 2019, Chuck Lever wrote:

> Hi Trond-
>
> We (Oracle) had another (fairly rare) instance of a weekend maintenance
> window where an NFS server's IP address changed while there were mounted
> clients. It brought up the issue again of how we (the Linux NFS community)
> would like to deal with cases where a client administrator has to deal
> with a moribund mount (like that alliteration :-).

What exactly is the problem that this caused?

As I understand it, a moribund mount can still be unmounted with "-l"
and processes accessing it can still be killed ... except....
There are some waits the VFS/MM which are not TASK_KILLABLE and
probably should be.  I think that "we" definitely want "someone" to
track them down and fix them.

>
> Does remounting with "soft" work today? That seems like the most direct
> way to deal with this particular situation.

I don't think this does work, and it would be non-trivial (but maybe not
impossible) to mark all the outstanding RPCs as also "soft".
If we wanted to follow a path like this (and I suspect we don't), I
would hope that we could expose the server connection (shared among
multiple mounts) in sysfs somewhere, and could then set "soft" (or
"dead") on that connection, rather than having to do it on every mount
from the particular server.

NeilBrown

>
>
> --
> Chuck Lever

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