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Subject: [PATCH v2 0/3] Wait for DELEGRETURN before returning NFS4ERR_DELAY
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Cc:     imammedo@redhat.com
Date:   Wed, 03 Aug 2022 10:37:26 -0400
Message-ID: <165953688893.1658.15242150042289528147.stgit@manet.1015granger.net>
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This RFC series adds logic to the Linux NFS server to make it wait a
few moments for clients to return a delegation before replying with
NFS4ERR_DELAY. There are two main benefits:

- This improves responsiveness when a delegated file is accessed
  from another client
- This removes an unnecessary latency if a client has neglected to
  return a delegation before attempting a RENAME or SETATTR

This series is incomplete:
- There are likely other operations that can benefit (eg. OPEN)
- The wait is a fixed 30ms delay; it would be better if the server
  could match an incoming CB_RECALL reply with waiters so they can
  proceed immediately, but I am still figuring out how that can be
  done

Changes since RFC:
- Eliminate spurious console messages on the server
- Wait for DELEGRETURN for RENAME operations
- Add CB done tracepoints
- Rework the retry loop

---

Chuck Lever (3):
      NFSD: Add tracepoints to report NFSv4 callback completions
      NFSD: Make nfsd4_setattr() wait before returning NFS4ERR_DELAY
      NFSD: Make nfsd4_rename() wait before returning NFS4ERR_DELAY


 fs/nfsd/nfs4layouts.c |  2 +-
 fs/nfsd/nfs4proc.c    | 52 ++++++++++++++++++++++++++++++--------
 fs/nfsd/nfs4state.c   | 21 ++++++++++++++++
 fs/nfsd/nfsd.h        |  1 +
 fs/nfsd/trace.h       | 58 +++++++++++++++++++++++++++++++++++++++++++
 fs/nfsd/xdr4.h        |  2 ++
 6 files changed, 124 insertions(+), 12 deletions(-)

--
Chuck Lever