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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Richard Weinberger <richard@nod.at>
CC:     Bruce Fields <bfields@fieldses.org>,
        Steve Dickson <steved@redhat.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        david <david@sigma-star.at>,
        "luis.turcitu@appsbroker.com" <luis.turcitu@appsbroker.com>,
        "david.young@appsbroker.com" <david.young@appsbroker.com>,
        "david.oberhollenzer@sigma-star.at" 
        <david.oberhollenzer@sigma-star.at>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        "chris.chilvers@appsbroker.com" <chris.chilvers@appsbroker.com>
Subject: Re: [PATCH 0/5] nfs-utils: Improving NFS re-exports
Thread-Topic: [PATCH 0/5] nfs-utils: Improving NFS re-exports
Thread-Index: AQHYXgHepSBKAjcbhkm6tcc78z/taq0LxCaAgABs5oCAABR8AA==
Date:   Tue, 3 May 2022 00:00:19 +0000
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> On May 2, 2022, at 6:46 PM, Steve Dickson <steved@redhat.com> wrote:
>=20
>=20
>=20
> On 5/2/22 12:17 PM, J. Bruce Fields wrote:
>> On Mon, May 02, 2022 at 10:50:40AM +0200, Richard Weinberger wrote:
>>> 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.
>>>=20
>>> The core idea is adding new export option: reeport=3D
>>> Using reexport=3D 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 expor=
t option reexport=3D".
>>> 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.
>>>=20
>>> Beside of id generation this series also addresses the reboot problem.
>>> If the re-exporting NFS server reboots, uncovered NFS subvolumes are no=
t yet
>>> mounted and file handles become stale.
>>> Now mountd/exportd keeps track of uncovered subvolumes and makes sure t=
hey get
>>> uncovered while nfsd starts.
>>>=20
>>> The whole set of features is currently opt-in via --enable-reexport.
>> Can we remove that option before upstreaming?

Somehow I missed Bruce's comment, but I had the same thought.
The cover letter does not explain why someone would want to
build nfs-utils without re-export support. If there isn't a
good reason for needing this switch, IMO it can be removed.


>> For testing purposes it may makes sense to be able to turn the new code
>> on and off quickly.  But for something we're really going to support,
>> it's just another hurdle for users to jump through, and another case we
>> probably won't remember to test.  The export options themselves should
>> be enough configuration.
>> Anyway, basically sounds reasonable to me.  I'll try to give it a proper
>> review sometime, feel free to bug me if I don't get to it in a week or
>> so.
> How about --disable-reexport? So it is on by default to help testing
> but if there are issues we can turn it off...
>=20
> steved.
>=20
>> --b.
>>> I'm also not sure about the rearrangement of the reexport code,
>>> currently it is a helper library.
>>>=20
>>> A typical export entry on a re-exporting server looks like:
>>> 	/nfs *(rw,no_root_squash,no_subtree_check,crossmnt,reexport=3Dauto-fsi=
dnum)
>>> reexport=3Dauto-fsidnum will automatically assign an fsid=3D to /nfs an=
d all
>>> uncovered subvolumes.
>>>=20
>>> Richard Weinberger (5):
>>>   Implement reexport helper library
>>>   exports: Implement new export option reexport=3D
>>>   export: Implement logic behind reexport=3D
>>>   export: Avoid fsid=3D conflicts
>>>   reexport: Make state database location configurable
>>>=20
>>> [0] https://git.kernel.org/pub/scm/linux/kernel/git/rw/misc.git/log/?h=
=3Dnfs_reexport_clean
>>>=20
>>>  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
>>>=20
>>> --=20
>>> 2.31.1
>=20

--
Chuck Lever