Notice

This document is for a development version of Ceph.

Refcount

Introduction

Dedupliation, as described in ../deduplication.rst, needs a way to maintain a target pool of deduplicated chunks with atomic ref refcounting. To that end, there exists an osd object class refcount responsible for using the object class machinery to maintain refcounts on deduped chunks and ultimately remove them as the refcount hits 0.

Class Interface

See cls/refcount/cls_refcount_client*

  • cls_refcount_get

    Atomically increments the refcount with specified tag

    void cls_refcount_get(librados::ObjectWriteOperation& op, const string& tag, bool implicit_ref = false);
    
  • cls_refcount_put

    Atomically decrements the refcount specified by passed tag

    void cls_refcount_put(librados::ObjectWriteOperation& op, const string& tag, bool implicit_ref = false);
    
  • cls_refcount_Set

    Atomically sets the set of refcounts with passed list of tags

    void cls_refcount_set(librados::ObjectWriteOperation& op, list<string>& refs);
    
  • cls_refcount_read

    Dumps the current set of ref tags for the object

    int cls_refcount_read(librados::IoCtx& io_ctx, string& oid, list<string> *refs, bool implicit_ref = false);