osd: fix PG::copy_after vs backlog
osd: fix PG::copy_after vs backlog

If you call copy_after(..., 0) on a log with a backlog, you get all the
backlog entries, but no backlog flag.  That's invalid.  You either need
the _complete_ backlog + the flag, or no backlog entries; getting only
some of them is useless information.

Make copy_after stop when it hits the tail.  Callers who need the backlog
are already checking for that and copying the whole log as appropriate.

Signed-off-by: Sage Weil <c5b6ff1fd4f0bde10db63d7a3e07166cf6c4229f@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph