[PATCH v9 00/12] NFSD: Implement NFSD_IO_DIRECT for NFS WRITE

[Chuck Lever <cel@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

Following on https://lore.kernel.org/linux-nfs/aPAci7O_XK1ljaum@kernel.org/
this series includes the patches needed to make NFSD Direct WRITE
operational.

The Documentation update is taken verbatim from Mike's Sep 3 series.
The document refers to NFSD_IO_DIRECT as working in an "uncached"
mode, but it doesn't explain how UNSTABLE works with NFSD_IO_DIRECT
(why a subsequent COMMIT is still required for durability). And IMO,
it needs a more thorough explanation of "Linux memory management's
page reclaim scalability problems". I prefer a brief root-cause
analysis here rather than a reference to a video or a benchmark
result.

I think the functional code changes come pretty close to what we've
agreed to so far, however. I dropped one R-b due to significant
mechanical changes in that patch.

Changes since v8:
* Drop "NFSD: Handle both offset and memory alignment for direct I/O"
* Include the Sep 3 version of the Documentation update

Changes since v7:
* Rebase the series on Mike's original v3 patch
* Address more review comments
* Optimize the "when can NFSD use IOCB_DIRECT" logic
* Revert the "always promote to FILE_SYNC" logic

Changes since v6:
* Patches to address review comments have been split out
* Refactored the iter initialization code

Changes since v5:
* Add a patch to make FILE_SYNC WRITEs persist timestamps
* Address some of Christoph's review comments
* The svcrdma patch has been dropped until we actually need it

Changes since v4:
* Split out refactoring nfsd_buffered_write() into a separate patch
* Expand patch description of 1/4
* Don't set IOCB_SYNC flag

Changes since v3:
* Address checkpatch.pl nits in 2/3
* Add an untested patch to mark ingress RDMA Read chunks

Chuck Lever (10):
  NFSD: Make FILE_SYNC WRITEs comply with spec
  NFSD: Enable return of an updated stable_how to NFS clients
  NFSD: Remove specific error handling
  NFSD: Remove alignment size checking
  NFSD: Clean up struct nfsd_write_dio
  NFSD: Introduce struct nfsd_write_dio_seg
  NFSD: Simplify nfsd_iov_iter_aligned_bvec()
  NFSD: Combine direct I/O feasibility check with iterator setup
  NFSD: Handle kiocb->ki_flags correctly
  NFSD: Refactor nfsd_vfs_write

Mike Snitzer (2):
  NFSD: Implement NFSD_IO_DIRECT for NFS WRITE
  NFSD: add Documentation/filesystems/nfs/nfsd-io-modes.rst

 .../filesystems/nfs/nfsd-io-modes.rst         | 144 +++++++++++++
 fs/nfsd/debugfs.c                             |   1 +
 fs/nfsd/nfs3proc.c                            |   2 +-
 fs/nfsd/nfs4proc.c                            |   2 +-
 fs/nfsd/nfsproc.c                             |   3 +-
 fs/nfsd/trace.h                               |   1 +
 fs/nfsd/vfs.c                                 | 199 +++++++++++++++++-
 fs/nfsd/vfs.h                                 |   6 +-
 fs/nfsd/xdr3.h                                |   2 +-
 9 files changed, 343 insertions(+), 17 deletions(-)
 create mode 100644 Documentation/filesystems/nfs/nfsd-io-modes.rst

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2.51.0