Re: [Libguestfs] [PATCH nbdkit v5 FINAL 00/19] Implement extents.
On Thu, Mar 28, 2019 at 09:15:17PM -0500, Eric Blake wrote:
On 3/28/19 11:18 AM, Richard W.M. Jones wrote:
> This has already been pushed upstream. I am simply posting these here
> so we have a reference in the mailing list in case we find bugs later
> (as I'm sure we will - it's a complex patch series).
>
> Great thanks to Eric Blake for tireless review on this one. It also
> seems to have identified a few minor bugs in qemu along the way.
>
Should nbdkit-rate-filter.pod mention that extents is considered
effectively free (same as zeroing and trimming)?
I guess it's covered by the existing docs. Extents aren't quite as
"free" as zeroing and trimming but the structured reply message is
still quite small.
I know that I want the nbd plugin to do extents passthrough, but I
have
some work to do to teach it do to NBD_OPT_GO/structured replies first.
The full and null plugins should probably have a trivial .extents that
reports completely sparse, all of the time :)
I think it would be wrong for full wouldn't it? It could mean that
the client would skip the read, thus not getting the intended ENOSPC
error. For null I agree.
Various plugins like partitioning and linuxdisk might be interesting
to
support extents on (particularly since we know we pad in between files);
but it may be trickier to write.
Can curl or ssh access extents information?
Not sure about curl, but I checked ssh (sftp) and it cannot. However
at some point I intend to submit an extension to the sftp protocol
(similar to my "fsync(a)openssh.com" extension) to support it. We will
need it for efficient ssh access in virt-v2v one day.
Language bindings will also be an interesting exercise ;)
Yes, the language bindings lag behind what's available because they
aren't generated ...
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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