When caching rather than reading from the upstream we should allow the users to read the data as it stands in cache (filling gaps with 0's) rather than writing to the upstream. This can allow basically any upstream to be read to sparsely (and possibly written to).
When caching rather than reading from the upstream we should allow the users to read the data as it stands in cache (filling gaps with 0's) rather than writing to the upstream. This can allow basically any upstream to be read to sparsely (and possibly written to).