Hierarchically tagged cache

A cache system comprising:

• a cache storage device to store multiple data buffers;
• and
• a cache controller to,
• manage access to the data buffers of the cache storage device, the cache controller to identify a header indicated in a data access request as being associated with one of a filesystem layer, a physical mapping layer, or an indirection layer, where each layer is indicated with an indexing structure of headers and the indexing structures are in the cache storage device,
• manage the headers hierarchically,
• manage indexes of the physical mapping layer indexing structure to map to physical addresses for data buffers,
• manage indexes of the indirection layer indexing structure each to map to an index of the physical mapping layer, and
• manage indexes of the filesystem layer indexing structure each to map to an index of the indirection layer,
• access a data buffer when one of the indexing structures includes the header, wherein the cache controller to access the data buffer comprises the cache controller to hierarchically traverse the indexes of the layers to a physical address for the data buffer, beginning at the index of the layer identified as being associated with the header, wherein the header comprises metadata when associated with either the filesystem layer or the indirection layer;
• and
• when an index does not include the header, create an entry, for the header, in the indexing structure of the layer identified as being associated with the header;
• maintain a generation count for each data buffer, wherein for each data buffer the generation count is incremented each time the data buffer is evicted from the cache or each time the data buffer is used to hold a different data block;
• and
• maintain a generation count in each index entry created that references a data buffer, wherein an index entry that has a generation count different from a generation count of the referenced data buffer is evicted.

A non-transitory computer-readable storage medium having program instructions stored thereon, the program instructions comprising program instructions to:

• identify a header of a received data access request as being associated with one of a filesystem layer, a physical mapping layer, or an indirection layer, where each layer is indicated with an indexing structure of headers and the indexing structure of each of the layers is in a cache of a computing device,
• manage headers in the cache hierarchically, manage indexes of the physical mapping layer indexing structure to map to physical addresses for data buffers, manage indexes of the indirection layer indexing structure each to map to an index of the physical mapping layer, and manage indexes of the filesystem layer indexing structure each to map to an index of the indirection layer;
• access the data buffer when an index includes the header, wherein the program instructions to access the data buffer comprise program instructions to hierarchically traverse the indexes of the layers to a physical address for the data buffer, beginning at the index of the layer identified as being associated with the header, wherein the header comprises metadata when associated with either the filesystem layer or the indirection layer;
• and
• when an index does not include the header, create an entry, for the header, in the indexing structure of the layer identified as being associated with the header;
• maintain a generation count for each data buffer, wherein for each data buffer the generation count is incremented each time the data buffer is evicted from the cache or each time the data buffer is used to hold a different data block;
• and
• maintain a generation count in each index entry created that references a data buffer, wherein an index entry that has a generation count different from a generation count of the referenced data buffer is evicted.