issue_comments: 259202265

A few other thoughts on thread safety with the LRU approach: 1. We need to a global lock ensure internal consistency of the LRU cache, and so that we don't overwrite files without closing them. It probably makes sense to put this in memoize function. 2. We need separate, per file locks, to ensure that we don't evict files in the process of reading or writing data from them (which would cause segfaults). As a stop-gap measure, we could simply refuse to evict files until we can acquire a lock, but more broadly this suggests that strict LRU is not quite right. Instead, we want to evict the least-recently-used unlocked item.