Discard
virtual ssize_t Discard(off_t offset, off_t size);
area->Discard();
void Discard();
const ssize_t discarded = VMCache::Discard(offset, size);
virtual ssize_t Discard(off_t offset, off_t size);
const ssize_t discarded = VMCache::Discard(offset, size);
virtual ssize_t Discard(off_t offset, off_t size);
cache->Discard(area->cache_offset + offset, size);