[PATCH 0/2] NFSD: offer write delegation for OPEN with OPEN4_SHARE_ACCESS only

[Dai Ngo <dai.ngo@oracle.com>]

RFC8881 does not explicitly state that server must grant write delegation
to OPEN with OPEN4_SHARE_ACCESS_WRITE only. However there are text in the
RFC that implies it is up to the server implementation to offer write
delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE only.

Section 9.1.2:

  "In the case of READ, the server may perform the corresponding
   check on the access mode, or it may choose to allow READ for
   OPEN4_SHARE_ACCESS_WRITE, to accommodate clients whose WRITE
   implementation may unavoidably do (e.g., due to buffer cache
   constraints)."

Also in section 10.4.1

  "Similarly, when closing a file opened for OPEN4_SHARE_ACCESS_WRITE/
   OPEN4_SHARE_ACCESS_BOTH and if an OPEN_DELEGATE_WRITE delegation
   is in effect"

This patch series offers write delegation for OPEN with OPEN4_SHARE_ACCESS_WRITE
only. When this condition is detected in nfsd4_encode_read the access mode
FMODE_READ is temporarily added to the file's f_mode and is removed when
the read is done.

 fs/nfsd/nfs4proc.c  | 15 ++++++++++++++-
 fs/nfsd/nfs4state.c | 34 +++++++++++++---------------------
 fs/nfsd/nfs4xdr.c   |  8 ++++++++
 fs/nfsd/xdr4.h      |  1 +
 4 files changed, 36 insertions(+), 22 deletions(-)