This commit addresses two issues in osc/rdma:
1) It is erroneous to attach regions that overlap. This was being
allowed but the standard does not allow overlapping attachments.
2) Overlapping registration regions (4k alignment of attachments)
appear to be allowed. Add attachment bases to the bookeeping
structure so we can keep better track of what can be detached.
It is possible that the standard did not intend to allow #2. If that
is the case then #2 should fail in the same way as #1. There should
be no technical reason to disallow #2 at this time.
References #7384
Signed-off-by: Nathan Hjelm <hjelmn@google.com>
6649aef8bd