[OpenAFS] Disconnected OpenAFS

Jeffrey Altman jaltman@secure-endpoints.com
Tue, 25 Sep 2007 00:57:31 -0400

Jim Rees wrote:
> Jeffrey Altman wrote:
>   You do not need to have all of the callbacks at once.  You can perform
>   your check and mark files/directories disconnected a bit at a time.
> I don't understand that.  If you don't snapshot the state of your file
> system at one particular instant, won't you have an inconsistent view of the
> file system?  What do you mean by "mark files/directories disconnected?"

For each vnode in the cache, you keep track of the
connected/disconnected state.  While you are in the transition from
connected -> disconnected you sync files into the cache and mark them
disconnected.  When a request comes in for a file marked disconnected,
you treat it as if disconnected mode was active.

For disconnected -> connected transitions you do the same in reverse.
You sync the files back to the file server and then remove the
disconnected flag.  Files/directories that are in a conflict state
remain disconnected until the end user deals with the conflict and
decides what should be done.

We can't give a user a perfectly consistent view of the entire afs file
system space.  What we can do is provide a mostly consistent view of the
portions of the file system space that the user cares about.  Note that
a user can only care about as many files as fit in the cache.

Jeffrey Altman