Define a new function rbd_dev_v2_refresh() to update/refresh the
snapshot context for a format version 2 rbd image. This function
will update anything that is not fixed for the life of an rbd
image--at the moment this is mainly the snapshot context and (for
a base mapping) the size.
Update rbd_refresh_header() so it selects which function to use
based on the image format.
Rename __rbd_refresh_header() to be rbd_dev_v1_refresh()
to be consistent with the naming of its version 2 counterpart.
Similarly rename rbd_refresh_header() to be rbd_dev_refresh().
Unrelated--we use rbd_image_format_valid() here. Delete the other
use of it, which was primarily put in place to ensure that function
was referenced at the time it was defined.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
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