ceph/src/cls/refcount/cls_refcount_client.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3
   4 #ifndef CEPH_CLS_REFCOUNT_CLIENT_H
   5 #define CEPH_CLS_REFCOUNT_CLIENT_H
   6
   7 #include "include/rados/librados_fwd.hpp"
   8 #include "include/types.h"
   9
  10 /*
  11  * refcount objclass
  12  *
  13  * The refcount objclass implements a refcounting scheme that allows having multiple references
  14  * to a single rados object. The canonical way to use it is to add a reference and to remove a
  15  * reference using a specific tag. This way we ensure that refcounting operations are idempotent,
  16  * that is, a single client can only increase/decrease the refcount once using a single tag, so
  17  * any replay of operations (implicit or explicit) is possible.
  18  *
  19  * So, the regular usage would be to create an object, to increase the refcount. Then, when
  20  * wanting to have another reference to it, increase the refcount using a different tag. When
  21  * removing a reference it is required to drop the refcount (using the same tag that was used
  22  * for that reference). When the refcount drops to zero, the object is removed automaticfally.
  23  *
  24  * In order to maintain backwards compatibility with objects that were created without having
  25  * their refcount increased, the implicit_ref was added. Any object that was created without
  26  * having it's refcount increased (explicitly) is having an implicit refcount of 1. Since
  27  * we don't have a tag for this refcount, we consider this tag as a wildcard. So if the refcount
  28  * is being decreased by an unknown tag and we still have one wildcard tag, we'll accept it
  29  * as the relevant tag, and the refcount will be decreased.
  30  */
  31
  32 void cls_refcount_get(librados::ObjectWriteOperation& op, const std::string& tag, bool implicit_ref = false);
  33 void cls_refcount_put(librados::ObjectWriteOperation& op, const std::string& tag, bool implicit_ref = false);
  34 void cls_refcount_set(librados::ObjectWriteOperation& op, std::list<std::string>& refs);
  35 // these overloads which call io_ctx.operate() or io_ctx.exec() should not be called in the rgw.
  36 // rgw_rados_operate() should be called after the overloads w/o calls to io_ctx.operate()/exec()
  37 #ifndef CLS_CLIENT_HIDE_IOCTX
  38 int cls_refcount_read(librados::IoCtx& io_ctx, std::string& oid, std::list<std::string> *refs, bool implicit_ref = false);
  39 #endif
  40
  41 #endif