[Libguestfs] [PATCH libnbd v2 0/2] copy: Preserve the host page cache when reading local files.

Previously: https://listman.redhat.com/archives/libguestfs/2021-February/msg00087.html Version 1 had a rather serious bug where it under-evicted pages (because of shadowing of the variable 'n'). This fixes that problem. Also I cleaned up the code by putting the cache work into separate inline functions. Rich.