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NFSD support for backchannel session "cachethis" flag #37

Closed chucklever closed 6 months ago

chucklever commented 7 months ago

From RFC 8881 Section 20.9.3:

If csa_cachethis is TRUE, then the server is requesting that the client cache the reply in the callback reply cache. The client MUST cache the reply (see Section 2.10.6.1.3).

A to-do comment in fs/nfsd/nfs4callback.c suggests NFSD's callback client should support this boolean flag. However, it does not mention use cases. Other comments suggest that all callback operations that NFSD supports are idempotent, so there likely is no need to set this flag for any operation NFSD uses. It's also not known if any clients have support for caching in their backchannel implementations.

chucklever commented 6 months ago

There are no non-idempotent callback operations, so there is no need for "cachethis" support in the backchannel at this time. Marking it WONTFIX.