[Libguestfs] [libnbd PATCH 0/3] opt_list_meta_context

[Richard W.M. Jones]

On Tue, Sep 29, 2020 at 06:51:06AM -0500, Eric Blake wrote:
> On 9/29/20 6:23 AM, Richard W.M. Jones wrote:
> >This is not related to the current patch, but generally for libnbd:
> >
> >(1) Should we be testing interop separately for qemu-storage-daemon
> >(qsd), or is qsd basically qemu-nbd in a new wrapper so it's not worth
> >doing it?

Any thoughts on this one?

> >(2) I found a bug in the new nbdinfo behaviour:
> >
> >$ nbdkit -fv file dir=/scratch
> >
> >(where /scratch is a directory with a lot of files in it)
> >
> >$ nbdinfo --version
> >libnbd 1.5.3
> >$ nbdinfo --list nbd://localhost
> >[... lots of files shown ...]
> >nbd_opt_info: recv: Connection reset by peer
> >
> >nbdkit gives this error:
> >
> >nbdkit: file[1]: error: client exceeded maximum number of options (32)
> 
> Yeah, we really ought to raise nbdkit's limits when .list_exports
> returns a large list.  We haven't yet released nbdkit 1.24 where the
> file driver actually has a large .list_exports; but it may also be a
> reason to figure out if libnbd should go to the effort of
> re-connecting for the later portion of a list on servers like older
> nbdkit that limit the length of the negotiation phase.

It raises the question about what the limit needs to be.  If I point
nbdkit-file-plugin at a directory, the number of exports could be
pretty much unlimited.  But at the smae time the options limit is
there for a fairly good reason.  Should we change the client to
request info in groups of <N> (presumably requiring reconnection)?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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