[Lustre-devel] Sub Tree lock ideas.

[Nikita Danilov]

Oleg Drokin writes:
 > Hello!
 > 
 > On Feb 3, 2009, at 10:01 AM, Nikita Danilov wrote:
 > >>    For the case of a different client stepping into area covered by
 > >> STL lock, this client would get STL lock's cookie and will start
 > >> present it for all subsequent
 > >>    operations (also a special flag meaning that the client is not
 > >> operating within STL).
 > > How is it determined that a given point in a namespace is covered by  
 > > an
 > > STL lock? E.g., client A holds an STL on /a, and client B accesses
 > > /a/b/c/f (where /a/b/c is a working directory of some process on B)?
 > > This looks especially problematic in the CMD case.
 > 
 > When client B looks up /a during its path traversal, it will get a  
 > lock cookie
 > of the STL lock and will start presenting it with further lookups.
 > If /a/b/c became a working dir of process B before STL on /a was  
 > granted, then
 > /a/b/c has a normal lock for client B and STL does not cover that  
 > subtree.

Yes, this is the case I meant. So we have to track (and recover) current
directories for all client processes.

 > Also see other discussion on this topic here, since in the end we  
 > might end up
 > not implementing entire STL idea.
 > 
 > Bye,
 >      Oleg

Nikita.