[Libguestfs] [PATCH nbdkit v4 05/15] cow: Disable extents information in this filter.

[Eric Blake]

On 3/26/19 4:17 PM, Richard W.M. Jones wrote:
> The cow filter doesn't support trimming and we should assume the
> underlying plugin is fully allocated too.  Note that both of these
> limitations might be lifted with a more advanced filter
> implementation.
> 
> However we ought to support this in future because xz files contain
> sparseness information, so add a note.

Stale copy-and-paste comment?

Also, since the series is mostly alphabetical, I suspect you're missing
4.5/15 for filters/cache/cache.c (blindly passing through .extents to
the underlying plugin); easiest is probably forcing .can_extents false,
but nicer would be remembering status of portions that we have cached
locally to avoid repeated callouts to the plugin.

ACK for the cow filter.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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