Currently, rbd_dev_probe() assumes that any error returned by
rbd_dev_image_id() is most likely -ENOENT, and responds by
calling the format 1 probe routine, rbd_dev_v1_probe(). Then,
at the top of rbd_dev_v1_probe(), an empty string is allocated
for the image id.
This is sort of unbalanced. Fix this by having rbd_dev_image_id()
look for -ENOENT from its "get_id" method call. If that is seen,
have it allocate the empty string there rather than depending on
rbd_dev_v1_probe() to do it.
Given that this is effectively defining the format of the image,
set rbd_dev->image_format inside rbd_dev_image_id() rather than in
the format-specific probe routines.
Also drop a redundant hunk of code in rbd_dev_image_id().
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
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