[PATCH 0/5] nfs-utils: Improving NFS re-exports

From: Richard Weinberger <richard@nod.at>
To: linux-nfs@vger.kernel.org
Cc: david@sigma-star.at, bfields@fieldses.org,
	luis.turcitu@appsbroker.com, david.young@appsbroker.com,
	david.oberhollenzer@sigma-star.at,
	trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
	steved@redhat.com, chris.chilvers@appsbroker.com,
	Richard Weinberger <richard@nod.at>
Subject: [PATCH 0/5] nfs-utils: Improving NFS re-exports
Date: Mon,  2 May 2022 10:50:40 +0200	[thread overview]
Message-ID: <20220502085045.13038-1-richard@nod.at> (raw)

This is the first non-RFC iteration of the NFS re-export
improvement series for nfs-utils.
While the kernel side[0] didn't change at all and is still small,
the userspace side saw much more changes.

The core idea is adding new export option: reeport=
Using reexport= it is possible to mark an export entry in the exports
file explicitly as NFS re-export and select a strategy how unique
identifiers should be provided.
Currently two strategies are supported, "auto-fsidnum" and
"predefined-fsidnum", both use a SQLite database as backend to keep
track of generated ids.
For a more detailed description see patch "exports: Implement new export option reexport=".
I choose SQLite because nfs-utils already uses it and using SQL ids can nicely
generated and maintained. It will also scale for large setups where the amount
of subvolumes is high.

Beside of id generation this series also addresses the reboot problem.
If the re-exporting NFS server reboots, uncovered NFS subvolumes are not yet
mounted and file handles become stale.
Now mountd/exportd keeps track of uncovered subvolumes and makes sure they get
uncovered while nfsd starts.

The whole set of features is currently opt-in via --enable-reexport.
I'm also not sure about the rearrangement of the reexport code,
currently it is a helper library.

A typical export entry on a re-exporting server looks like:
	/nfs *(rw,no_root_squash,no_subtree_check,crossmnt,reexport=auto-fsidnum)
reexport=auto-fsidnum will automatically assign an fsid= to /nfs and all
uncovered subvolumes.

Richard Weinberger (5):
  Implement reexport helper library
  exports: Implement new export option reexport=
  export: Implement logic behind reexport=
  export: Avoid fsid= conflicts
  reexport: Make state database location configurable

[0] https://git.kernel.org/pub/scm/linux/kernel/git/rw/misc.git/log/?h=nfs_reexport_clean

 configure.ac                   |  12 ++
 nfs.conf                       |   3 +
 support/Makefile.am            |   4 +
 support/export/Makefile.am     |   2 +
 support/export/cache.c         |  71 ++++++-
 support/export/export.c        |  27 ++-
 support/include/nfslib.h       |   1 +
 support/nfs/Makefile.am        |   1 +
 support/nfs/exports.c          |  68 +++++++
 support/reexport/Makefile.am   |   6 +
 support/reexport/reexport.c    | 354 +++++++++++++++++++++++++++++++++
 support/reexport/reexport.h    |  39 ++++
 systemd/Makefile.am            |   4 +
 systemd/nfs-server-generator.c |  14 +-
 systemd/nfs.conf.man           |   6 +
 utils/exportd/Makefile.am      |   8 +-
 utils/exportd/exportd.c        |   5 +
 utils/exportfs/Makefile.am     |   6 +
 utils/exportfs/exportfs.c      |  21 +-
 utils/exportfs/exports.man     |  31 +++
 utils/mount/Makefile.am        |   7 +
 utils/mountd/Makefile.am       |   6 +
 utils/mountd/mountd.c          |   1 +
 utils/mountd/svc_run.c         |   6 +
 24 files changed, 690 insertions(+), 13 deletions(-)
 create mode 100644 support/reexport/Makefile.am
 create mode 100644 support/reexport/reexport.c
 create mode 100644 support/reexport/reexport.h

-- 
2.31.1