initial code repo

This patch creates initial code repo.

For ceph, luminous stable release will be used for base code,
and next changes and optimization for ceph will be added to it.

For opensds, currently any changes can be upstreamed into original
opensds repo (https://github.com/opensds/opensds), and so stor4nfv
will directly clone opensds code to deploy stor4nfv environment.
And the scripts for deployment based on ceph and opensds will be
put into 'ci' directory.

Change-Id: I46a32218884c75dda2936337604ff03c554648e4
Signed-off-by: Qiaowei Ren <qiaowei.ren@intel.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/src/ceph/doc/dev/versions.rst b/src/ceph/doc/dev/versions.rst
new file mode 100644
index 0000000..34ed747
--- /dev/null
+++ b/src/ceph/doc/dev/versions.rst
@@ -0,0 +1,42 @@
+==================
+Public OSD Version
+==================
+
+We maintain two versions on disk: an eversion_t pg_log.head and a
+version_t info.user_version. Each object is tagged with both the pg
+version and user_version it was last modified with.  The PG version is
+modified by manipulating OpContext::at_version and then persisting it
+to the pg log as transactions, and is incremented in all the places it
+used to be. The user_version is modified by manipulating the new
+OpContext::user_at_version and is also persisted via the pg log
+transactions.
+user_at_version is modified only in PrimaryLogPG::prepare_transaction
+when the op was a "user modify" (a non-watch write), and the durable
+user_version is updated according to the following rules:
+1) set user_at_version to the maximum of ctx->new_obs.oi.user_version+1
+and info.last_user_version+1.
+2) set user_at_version to the maximum of itself and
+ctx->at_version.version.
+3) ctx->new_obs.oi.user_version = ctx->user_at_version (to change the
+object's user_version)
+
+This set of update semantics mean that for traditional pools the
+user_version will be equal to the past reassert_version, while for
+caching pools the object and PG user-version will be able to cross
+pools without making a total mess of things.
+In order to support old clients, we keep the old reassert_version but
+rename it to "bad_replay_version"; we fill it in as before: for writes
+it is set to the at_version (and is the proper replay version); for
+watches it is set to our user version; for ENOENT replies it is set to
+the replay version's epoch but the user_version's version. We also now
+fill in the version_t portion of the bad_replay_version on read ops as
+well as write ops, which should be fine for all old clients.
+
+For new clients, we prevent them from reading bad_replay_version and
+add two proper members: user_version and replay_version; user_version
+is filled in on every operation (reads included) while replay_version
+is filled in for writes.
+
+The objclass function get_current_version() now always returns the
+pg->info.last_user_version, which means it is guaranteed to contain
+the version of the last user update in the PG (including on reads!).