[OpenAFS] switching to DAFS and -showmounts

[Jeffrey Altman]

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On 5/31/2013 10:28 AM, Mark Vitale wrote:
> We look to provide a patch after we've discussed the best way to fix th=
is.
>
> So far some ideas I've come up with are to either:=20
>=20
> 1. have the running salvageserver only obtain salvage.lock when it is "=
doing something",
>    and relinquish it during idle periods.

I think it is important that the salvageserver be the only entity able
to obtain the salvage.lock.  Otherwise, another tool can be run that
would block the ability to demand salvage.

> or=20
>=20
> 2. allow -showmounts (and maybe some other options as well) tor run
> from the command line without obtaining the lock (or locking on a diffe=
rent range,
> perhaps).

If -showmounts remains in 'salvager', my preferred solution would be for
-showmounts to:

 1. generate a temporary COW clone

 2. perform a readonly scan of the clone without locking

 3. remove the COW clone

Although I question whether this functionality should be part of
salvaging at all.  Operations that scan a volume for the purpose of
extracting data or statistics is what "volscan" does.  Removing
-showmounts from salvager and modifying "volscan" (or something similar)
so that it can safely be run in conjunction with "salvageserver" might
be the better direction.

Jeffrey Altman



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