initial code repo

[stor4nfv.git] / src / ceph / src / cls / refcount / cls_refcount_client.h

diff --git a/src/ceph/src/cls/refcount/cls_refcount_client.h b/src/ceph/src/cls/refcount/cls_refcount_client.h
new file mode 100644 (file)
index 0000000..654cc00
--- /dev/null
+++ b/src/ceph/src/cls/refcount/cls_refcount_client.h
@@ -0,0 +1,38 @@
+#ifndef CEPH_CLS_REFCOUNT_CLIENT_H
+#define CEPH_CLS_REFCOUNT_CLIENT_H
+
+#include "include/types.h"
+
+namespace librados {
+  class ObjectWriteOperation;
+  class IoCtx;
+}
+
+/*
+ * refcount objclass
+ *
+ * The refcount objclass implements a refcounting scheme that allows having multiple references
+ * to a single rados object. The canonical way to use it is to add a reference and to remove a
+ * reference using a specific tag. This way we ensure that refcounting operations are idempotent,
+ * that is, a single client can only increase/decrease the refcount once using a single tag, so
+ * any replay of operations (implicit or explicit) is possible.
+ *
+ * So, the regular usage would be to create an object, to increase the refcount. Then, when
+ * wanting to have another reference to it, increase the refcount using a different tag. When
+ * removing a reference it is required to drop the refcount (using the same tag that was used
+ * for that reference). When the refcount drops to zero, the object is removed automaticfally.
+ *
+ * In order to maintain backwards compatibility with objects that were created without having
+ * their refcount increased, the implicit_ref was added. Any object that was created without
+ * having it's refcount increased (explicitly) is having an implicit refcount of 1. Since
+ * we don't have a tag for this refcount, we consider this tag as a wildcard. So if the refcount
+ * is being decreased by an unknown tag and we still have one wildcard tag, we'll accept it
+ * as the relevant tag, and the refcount will be decreased.
+ */
+
+void cls_refcount_get(librados::ObjectWriteOperation& op, const string& tag, bool implicit_ref = false);
+void cls_refcount_put(librados::ObjectWriteOperation& op, const string& tag, bool implicit_ref = false);
+void cls_refcount_set(librados::ObjectWriteOperation& op, list<string>& refs);
+int cls_refcount_read(librados::IoCtx& io_ctx, string& oid, list<string> *refs, bool implicit_ref = false);
+
+#endif