[PATCH 32/32] kbase: Add document outlining internals of incremental backup in qemu

[Peter Krempa]

On Fri, Jun 19, 2020 at 10:10:36 -0500, Eric Blake wrote:
> On 6/15/20 12:10 PM, Peter Krempa wrote:
> > Outline the basics and how to integrate with externally created
> > overlays. Other topics will continue later.
> > 
> > Signed-off-by: Peter Krempa <pkrempa at redhat.com>
> > ---
> >   docs/kbase.html.in                        |   3 +
> >   docs/kbase/incrementalbackupinternals.rst | 210 ++++++++++++++++++++++
> >   2 files changed, 213 insertions(+)
> >   create mode 100644 docs/kbase/incrementalbackupinternals.rst

[...]

> > +Snapshot
> > +
> > +    Similarly to a checkpoint it's a point in time in the lifecycle of the VM
> > +    but the state of the VM including memory is captured at that point allowing
> > +    returning to the state later.
> 
> Hmm. We have disk-only snapshots which do not save the state of memory. Does
> this paragraph need adjustment to mention the difference between a disk-only
> snapshot and a full state capture?  Are we redefining any of the terms in
> domainstatecapture.rst, and/or should those two documents have
> cross-references?

Good idea! I'll keep this as is, but I'll link to the
domainstatecapture.rst document at the beginning of the glossary.


[...]

> > +  fi
> > +
> > +  for BACKING_BITMAP_ in $(jq -c '.[]' <<< "$BACKING_BITMAPS"); do
> > +      BITMAP_FLAGS=$(jq -c -r '.flags[]' <<< "$BACKING_BITMAP_")
> > +      BITMAP_NAME=$(jq -r '.name' <<< "$BACKING_BITMAP_")
> > +
> > +      if grep 'in-use' <<< "$BITMAP_FLAGS" ||
> > +         grep -v 'auto' <<< "$BITMAP_FLAGS"; then
> > +         continue
> > +      fi
> > +
> > +      qemu-img bitmap -f "$SNAP_FMT" "$SNAP_IMG" --add "$BITMAP_NAME"
> 
> Do you want to also copy the --granularity of the bitmaps being
> added?

Hmm, yeah, that's what libvirt does.