Snapshot-enabled storage system implementing algorithm for efficient reclamation of snapshot storage space

A method comprising:

• maintaining a snapshot tree data structure having a plurality of volume nodes corresponding to respective ones of (i) a root volume and (ii) multiple snapshots related directly or indirectly to the root volume, the multiple snapshots including at least one snapshot that is a snapshot of another one of the snapshots;
• determining a set of data descriptors for a given volume offset;
• determining a set of reader volume nodes that are readers of a corresponding data item based at least in part on the set of data descriptors;
• adjusting one or more of the data descriptors in the set of data descriptors based at least in part on the set of reader volume nodes;
• and
• reclaiming storage space previously allocated to the data item responsive to the adjusting of the one or more data descriptors;
• wherein adjusting one or more of the data descriptors in the set of data descriptors based at least in part on the set of reader volume nodes comprises changing an owner volume node of at least one of the data descriptors to a new owner volume node selected from the set of reader volume nodes;
• and
• wherein the method is performed by at least one processing device comprising a processor coupled to a memory.

A computer program product comprising a non-transitory processor-readable storage medium having stored therein program code of one or more software programs, wherein the program code when executed by at least one processing device causes said at least one processing device:

• to maintain a snapshot tree data structure having a plurality of volume nodes corresponding to respective ones of (i) a root volume and (ii) multiple snapshots related directly or indirectly to the root volume, the multiple snapshots including at least one snapshot that is a snapshot of another one of the snapshots;
• to determine a set of data descriptors for a given volume offset;
• to determine a set of reader volume nodes that are readers of a corresponding data item based at least in part on the set of data descriptors;
• to adjust one or more of the data descriptors in the set of data descriptors based at least in part on the set of reader volume nodes;
• and
• to reclaim storage space previously allocated to the data item responsive to the adjusting of the one or more data descriptors;
• wherein adjusting one or more of the data descriptors in the set of data descriptors based at least in part on the set of reader volume nodes comprises changing an owner volume node of at least one of the data descriptors to a new owner volume node selected from the set of reader volume nodes.