[PATCH v2 0/6] nfsd: add new export options for controlling read/write iomode

[Jeff Layton <jlayton@kernel.org>]

This version has the changes that Chuck requested. Most of it is minor
logic tweaks for saner handling of splice reads, and renaming the
options to read_io=/write_io=. I'll also be sending a v2 of the nfs-utils
patchset. Original cover letter follows:

When we originally added support for the dontcache and direct iomodes to
nfsd, we added global debugfs switches to control them. That was fine for
experimentation but the goal was always to move these controls to
something more permanent.

This patch series adds a new set of read_io= and write_io= export
options. With this, we can set the read and write iomode on a per-export
basis to either buffered, direct or dontcache.

The debugfs knobs will still stick around for now, and govern the
default iomode when it's not set on the export. Eventually these
controls should also be moved to something more permanent, but I've left
that as a future change for now.

The last patch adds new documentation that attempts to give the admin
some guidance on choosing read_io/write_io settings.

A companion nfs-utils patchset will follow that adds support for these
options to exportfs/mountd, and adds a new script to help users choose
iomode settings.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Changes in v2:
- Rename riomode=/wiomode= to read_io=/write_io=, and the netlink
  attributes to read-io/write-io (Chuck)
- io_cache_read=dontcache/direct no longer sets disable-splice-read, so
  read_io=buffered exports can still splice (Chuck)
- disable-splice-read=0 no longer resets io_cache_read to buffered
- Update the docs to match
- Rebase onto nfsd-testing
- Link to v1: https://lore.kernel.org/r/20261027-export-iomode-v1-0-262ed932a036@kernel.org

---
Jeff Layton (6):
      NFSD: Add per-export read/write I/O mode settings
      NFSD: Apply per-export I/O modes to READ and WRITE
      NFSD: Document per-export read_io= and write_io= options
      NFSD: Keep per-export statistics across export cache updates
      NFSD: Count the storage reads of each export's READs
      NFSD: Document how to choose an IO mode

 Documentation/filesystems/nfs/nfsd-io-modes.rst | 196 +++++++++++++++++
 Documentation/netlink/specs/nfsd.yaml           |  24 +++
 fs/nfsd/debugfs.c                               |  23 +-
 fs/nfsd/export.c                                | 268 +++++++++++++++++++++---
 fs/nfsd/export.h                                |  19 ++
 fs/nfsd/netlink.c                               |   4 +-
 fs/nfsd/netlink.h                               |   2 +-
 fs/nfsd/netns.h                                 |   6 +
 fs/nfsd/nfs4xdr.c                               |   6 +-
 fs/nfsd/nfsd.h                                  |  17 +-
 fs/nfsd/stats.h                                 |  33 +++
 fs/nfsd/vfs.c                                   |  59 +++++-
 fs/nfsd/vfs.h                                   |   2 +
 include/uapi/linux/nfsd_netlink.h               |  12 ++
 14 files changed, 605 insertions(+), 66 deletions(-)
---
base-commit: 19bbac00ad1cfa28e9127488f161ffc2ac03fad4
change-id: 20261013-export-iomode-1b56e9d89821

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>