This has 2 effects:
1) OSD sets aren't added into PG history until actual write attempts anymore
which removes unneeded extra osd_sets in PG history
2) New OSD sets are reported synchronously and can't be lost on PG restarts
happening at the same time with reconfiguration
Build problems fixed:
- void* pointer arithmetic which is a GNU extension (works as byte*)
- "variable size object may not be initialized" which is OK under GCC
- nullptr_t related error in json11 (it lacks 'operator <' in clang)
Warnings fixed:
- empty nested struct initializer { 0 } replaced by {}
- removed several unused lambda captures
From now on, reads will return the server-side object version numbers
and writes and deletes will have an additional "version" parameter
which, if set to a non-zero value, will be atomically compared with
the current version of the object plus 1 and the modification will
fail if it doesn't match.
This feature opens the road to correct online flattening of snapshot
layers and other interesting things.
Vitaliy Filippov