Re: RFC: Patch for mountd to handle a database for exports

>> I did try to fix that but the code quickly got hairy so I didn’t like it. If we really want/need that I’m thinking of creating a special case for the V4: handling, sort of like prefixing the database key with a NUL byte or something (so that it will be sorted first).
>> 
> Does the ZFS share property generate a V4: line?
> I doubt anyone will convert a non-ZFS /etc/exports file to a DB file,
> so support of that does not seem to be needed.
> 
> I see this as useful for the ZFS share property case,
> so if that works correctly, I do not see the above as a concern.

No, the ZFS share property stuff never generates the V4: line(s) so it’s not a problem for the /etc/zfs/exports.db case.

And converting /etc/exports to /etc/exports.db is not really necessary from a performance point since I doubt it ever will be very long. 
However I bet some enthusiastic fellow is bound to try to do it sometime in the future just because it can be done :-)


>> 
>> Multiline options - well, the current ZFS code doesn’t support it either so no change from the current setup but it would be nice to have.
>>  Ie, support for things like:
>>     /export -sec=krb5
>>     /export -sec=sys ro
>> 
> Yes. There is at least one PR that requests that the ZFS share property
> be enhanced to do this. Part of the reason for getting this patch in main
> is so that this can be pursued.
> 
> Again, I only see this as a ZFS share property issue because I do not
> see any reason to convert /etc/exports flat files to db files?
> 

I agree that the need probably isn’t there.

The current DB code will generate a syslog(LOG_ERR) warning if it detects anything not starting with / in the keys (and ignores it).

Perhaps there should be a warning in the manual for mountd about not trying to convert /etc/exports into a DB (if it uses NFSv4 / the “V4:” line(s)). 
Or should we just special-case /etc/exports and forbid the check for /etc/exports.db? 

- Peter

> rick
> 
>> 
>> 
>> 
>> 
>> 
>> (I also agree that the USE_SHAREDB probably should be removed, I just have that here for now so that I can quickly disable the code)
>> 
>> Regarding the patch to the zfs part - I’m not sure which way to go there - the current patch switches to always use the DB. But one could argue that the code could check for an existing /etc/zfs/exports.db and only use the DB-writing code if that already exists. That way it will support both the old way and the new way, but it requires an empty /etc/zfs/exports.db to be pre-created at initial boot time for it to start using it.
>> 
>> - Peter
>> 
>> 
>>> On 21 Jul 2023, at 00:50, Rick Macklem <rick.macklem@gmail.com> wrote:
>>> 
>>> Hi,
>>> 
>>> Peter Eriksson has submitted an interesting patch that adds support
>>> for a database file for exports.  My understanding is that this improves
>>> performance when used with the ZFS share property for exporting a
>>> large number of file systems.
>>> 
>>> There are a couple of user visible issues that I'd like feedback from
>>> others. (Hopefully Peter can correct me if I get any of these wrong.)
>>> 
>>> - The patch uses a single database file and a new "-D" option to
>>> specify it on the command line.
>>> --> I think it might be less confusing to just put the database file(s)
>>>       in the exports list and identify them via a ".db" filename suffix.
>>> What do others think?
>>> 
>>> The changes are #ifdef'd on USE_SHAREDB. I'm thinking that this
>>> change will be always built, so maybe USE_SHAREDB is not needed?
>>> (Obviously mountd(8)'s semantics will only changed if/when database
>>> file(s) are provided.)
>>> 
>>> Once I have feedback on the above, I will put a patch up on
>>> phabricator.
>>> 
>>> rick
>>> ps: I believe kevans@ has volunteered to shepperd the ZFS share
>>>     property changes.