Coalescing transactional same-block writes for virtual block maps

A storage system for preserving metadata changes in a transaction log, the storage system comprising:

• a storage device;
• and
• a storage processor, the storage processor including:
• memory;
• and
• a set of processors coupled to the memory to form control circuitry, the control circuitry constructed and arranged to:
• in response to a request to perform a file system operation on a file stored in the storage device, identify a set of metadata change instructions that accompany the file system operation on the file;
• arrange the set of metadata change instructions in multiple nodes of a searchable data structure, each of the multiple nodes accumulating metadata changes specified in metadata change instructions to be recorded in a respective block of storage in the storage device, such that each node of the searchable data structure accumulates metadata change information for a different block of the storage device;
• and
• for each node of the set of nodes, write the accumulated metadata change information to the transaction log,
• wherein each respective block of storage in which metadata change information is to be recorded stores multiple elements of metadata, such that each node of the searchable data structure corresponds to a respective block of storage and to respective metadata elements,
• wherein, when arranging the metadata change information, the control circuitry accumulating metadata change information to be recorded in a respective block of storage is constructed and arranged to accumulate changes in greater than one of the metadata elements stored in that block of storage, and
• wherein accumulating the metadata change information in each node of the searchable data structure, the control circuitry is constructed and arranged to accumulate elements of metadata in respective bits of a bitmap, the bitmap providing a respective bit for each of the elements of metadata.

A computer program product having a non-transitory, computer-readable storage medium which stores instructions which, when executed by a computer, cause the computer to perform a method of preserving metadata changes in a transaction log, the method comprising:

• in response to a request to perform a file system operation on a file stored in the storage device, identifying a set of metadata change instructions that accompany the file system operation on the file;
• arranging metadata change information specified in the set of metadata change instructions among multiple nodes of a searchable data structure, each of the multiple nodes accumulating metadata change information to be recorded in a respective block of storage in the storage device, such that each node of the searchable data structure accumulates metadata change information for a different block of the storage device;
• and
• for each node of the set of nodes, writing the accumulated metadata change information to the transaction log,
• wherein each respective block of storage in which metadata change information is to be recorded stores multiple elements of metadata, such that each node of the searchable data structure corresponds to a respective block of storage and to respective metadata elements,
• wherein, when arranging the metadata change information, accumulating metadata change information to be recorded in a respective block of storage includes (i) accumulating changes in greater than one of the metadata elements stored in that block of storage, and (ii) accumulating elements of metadata in respective bits of a bitmap, the bitmap providing a respective bit for each of the elements of metadata.